Tag Archive : John Green

/ John Green

Why Male Mammoths Lost the Game (w/ TierZoo!)

November 28, 2019 | Articles, Blog | 100 Comments

Why Male Mammoths Lost the Game (w/ TierZoo!)


Hey everyone, we have an exciting announcement! Just in time for the holidays, you can now
get your own cozy, Eons socks! Now you can stay warm while showcasing the
layers of rock and fossils that help reveal the history of life on Earth. Get yours at DFTBA.com!! About 140,000 years ago in what’s now South
Dakota, a mammoth approached a sinkhole filled with steaming water. Lured by vegetation, the mammoth ventured
into the water. But with its flat, heavy feet, it had little
hope of scaling the steep, muddy sides of the pond to climb out. With no hope of escape, it either starved or drowned,
eventually being covered by silt and preserved. And it wasn’t the only one. To date, the remains of 61 mammoths have been
excavated from the Mammoth Site of Hot Springs, South Dakota, all victims of an ancient sinkhole. And one of the most intriguing things about
these dead mammoths is that the vast majority of them are male. Woolly mammoths roamed Eurasia and North America
for millions of years. They foraged mainly on grasses, along with
some shrubs, mosses, and herbs. They fended off wolves, cave hyenas, and big
cats with their large bodies, huge, curved tusks and powerful trunks. The life of a mammoth was probably a lot like
the life of their distant cousins, the elephants. But what caused the extinction of the mammoths
is still a matter of debate. They disappeared from Europe and North America
at the end of the last ice age, about 10,000 years ago, though some small groups hung on
for much longer by hiding out in remote areas. The very last mammoths died out on a small
island in the Arctic Ocean about 4000 years ago – around the same time that the ancient
Egyptians were constructing the Great Pyramid of Giza. Experts blame the mammoths’ extinction mostly
on a rapidly changing climate, with maybe a little hunting by, well, us. And today, we’ve teamed up with TierZoo
to solve one of the mysteries about these charismatic megafauna, gamer-style. As TierZoo put it, the mammoth’s
top tier gear and high HP dominated the Pleistocene meta. But climate change doesn’t explain the nagging
mystery about our favorite ice age proboscidean: Why do most remains of mammoths found in the
fossil record turn out to be male? Even without humans hunting them or the ice
sheets melting, mammoth life was dangerous. The Ice Age tundra could be an unforgiving
place to live. Dry, dusty winds. Bitter cold. Frozen earth. Not swampy, like our modern tundra, but still
no picnic. And even if the cold or wind didn’t get
you, the tundra was full of deadly traps that sent unsuspecting inhabitants to an early
grave. In 1901, a group of scientists from St. Petersburg
ventured into the Siberian tundra. After several months of chasing tips from
locals, they saw, or rather smelled, something extraordinary. It was a woolly mammoth, embedded in the frozen
banks of the Berezovka River. Its head and neck had thawed enough to rot,
attracting scavengers. These scanvengers were eating meat that was thousands of years old! I just want to emphasize that. After they slowly dug the carcass out from
the bank, the team’s paleontologist examined it closely. Its leg bones and pelvis were broken. Its blood vessels had torn open, causing blood
to pool around its muscles. He said this creature fell from a cliff
along the river, and was smothered by the ensuing landslide of half-frozen mud. Game over. The Berezovka mammoth would turn out to be
a famous, early example of this kind of accidental preservation. Fast-forward to 2007. A reindeer herder found another carcass along
a frozen Siberian river, this time on the Yamal Peninsula. It was a small woolly mammoth calf, only about
a month old. Fermenting bacteria had taken over the remains,
pickling the carcass and thwarting scavengers. Lyuba, as she was named, was fat and healthy
when she died. But her skull was full of nodules of iron
phosphate, a sign that a lot of blood had flowed to her brain just before she died. This was clear evidence of the mammalian diving
reflex that activates when a mammal’s face is submerged in cold water and it has to hold
its breath. She also had sediment in her trunk, trachea,
and lungs. Poor Lyuba seems to have face-planted into
some soupy mud and suffocated while trying to clear it from her trunk. Like the Berezovka mammoth and Lyuba, many
mammoths’ lives were claimed by the treacherous landscape of the tundra. But for paleontologists, dramatic deaths like
these are a goldmine. Since these specimens were buried quickly,
they were shielded from scavengers like wolves, so their bodies had a much better chance of
being preserved. And these accident victims can reveal incredible
details about how mammoths lived. The Berezovka mammoth had half-chewed leaves
and grasses between its teeth. Lyuba still had her mother’s milk in her
stomach. But a freak accident like falling into mud
and suffocating could happen to anyone, right? The fact is, even if they stayed far away
from environmental hazards, mammoth life was still not easy. In the Little Badlands of Nebraska in 1962, a couple of workers discovered a large thighbone
while surveying for a dam. Paleontologists quickly descended on the scene
and unearthed the remains of not one but two Columbian mammoths, the larger, southern cousin
of the woolly mammoth. And the tusks of the two males were locked
together in mortal combat. They each had a broken tusk, and one had run
its tusk through the eye of his opponent. Brutal! These bull mammoths, later named Benny and
George, met about 10,000 years ago and died fighting over…you guessed it…. sex. And we think is what happened, because modern
bull elephants also get into aggressive confrontations and fight each other with their tusks, often
for access to females. They go pretty wild during the breeding season
because of raging hormones during a phase called musth. Researchers were able to confirm that these
animals died during the spring — which was their mating season — by looking at the levels
of carbon and oxygen isotopes in their tusks. They’re high in the summer and lower in
the winter, and Benny and George looked like they’d just passed the winter low point. And they also had the thin growth rings in
their tusks that were consistent with mature males when they’re in musth. During their battle, one of the two bulls
must have slipped, dragging the other to the ground. Exhausted and locked together, they starved. Their heavy bodies started to sink into the
wet, muddy earth. And then they were covered with sediment,
maybe from a flood, preserving them for thousands of years, to become one of the most unique
mammoths ever discovered. And, like Benny and George, most of the mammoths
recovered by paleontologists again are male. Even a 2017 genetic study of Siberian mammoth
bones, teeth, tusks, and hair revealed that over two-thirds of their 98 mammoth fossils
were male. So why is the mammoth fossil record so male-dominated? It may be because female mammoths knew how
to stay out of trouble a bit better. Just like modern elephants, young female mammoths
probably stayed close to their female relatives. Elephants live in matriarchal family groups,
led by wise, old females. The matriarch uses her decades of experience
to keep her younger sisters, nieces, and grandchildren fed, hydrated, and safe. Mammoths likely had a similar family structure,
and we can infer this from their remains. When we find the bones of a single mammoth,
they’re usually from a male. And only in rare cases are huge groups of
young and female mammoths found together, having met their end in a sudden catastrophe,
like we see at Waco Mammoth National Monument in Texas. It all points to a female-centric family group. Female mammoths likely stayed close and learned
from their family members, while the males, on the other hand, went off on their own early
and unprepared. After leaving their family group and in their
quest for mates, these young male mammoths made deadly mistakes that females rarely made. But like, that’s how’d I would explain it to you. TierZoo can explain it to you another way: In order to complete the mating questline,
the male Mammoth build generally was forced to engage in much riskier gameplay and more
PvP than a female mammoth was. Just like the elephants of today’s anthropocene
meta, a successful playthrough on a male mammoth involved leaving the safety of their party
once they’d leveled up enough to reach sexual maturity. With no teammates to defend them if things
got ugly, far more low level male mammoth players died from things like environmental
hazards and ambushes than female ones did, and on top of that, the mating questline forced
them into potentially deadly duels with other bulls. Female players on the other hand would have
far more protection from ambushes, had more opportunities to learn to avoid common environmental
hazards, and never were forced to battle each other to reproduce. Thanks TierZoo! This is very cool to be doing. The natural traps of the Pleistocene were
great at preserving the remains of males who made mistakes in wonderful detail. Which means that we have better fossils from
them than we do from mammoths who lived long, boring lives. So it’s not that there were more male mammoths;
it’s that they tended more often to die in ways that would better preserve their remains. And also their mistakes for us to examine in the future And now museums around the world are stocked
with male mammoths. But what does this mean for people who study
mammoths? Isn’t it a problem that most of our information
about them comes from males? Well yes and no. With mostly male remains, we miss out on a
lot of important parts of mammoth life because we don’t have a good comparison point for
the males. Although mammoths show some sexual dimorphism
– like differences in pelvis size – we can’t get a good sense of the degree of that dimorphism. Like did male mammoths have bigger feet? Did female mammoths have smaller ears on average? It’s hard to say without a good set of remains
from both sexes. But the hole in the fossil record in the first
place also tells us something, because it’s there. It tells us that male mammoth life was somehow
very different from female mammoth life, because young male mammoths were much more likely
to die in accidents. So as TierZoo might put it: For low
level male mammoth builds, not knowing about the traps in the Ice Age meta often led to
an early game over. And for human players, the lack of female
mammoth loot clued them into the mysterious early game of the most famous build of the
Quaternary Expansion. But for us here at Eons, our takeaway is:
Sometimes the information you don’t have is just as important as the information you
do have – for which is good news for anyone working with a limited fossil record. And if you haven’t checked out TierZoo, Why not!? What a wonderful lens through which to view the biology of our planet Check it out at youtube.com/tierzoo. Also Thanks for watching Eons, produced by
Complexly. We produce over a dozen shows, including Ours
Poetica, which is a co-production between Complexly, The Poetry Foundation, and poet
Paige Lewis. Ours Poetica brings you a new poem three times
a week, read by poets, writers, artists, and sometimes unexpected, yet familiar, voices. Check out John Green reading Poetry by Marianne
Moore below! And a big thanks to this month’s Eontologists:
Patrick Seifert, Jake Hart, Jon Davison Ng, and Steve! Go level up and become an Eonite by supporting
us at patreon.com/eons! Thanks for joining me in the Konstantin
Haase Studio. Be sure to subscribe at youtube.com/eons for
more adventures in time.

35 Facts About Mr. Fred Rogers – mental_floss on YouTube (Ep.2)


Hi, I’m John Green, welcome to my
neighborhood. This is mental_floss and today we’re going to talk about Mr.
Rogers, with whom I have a lot in common. By the way, thanks to copyright laws,
that’s the only picture of Mr. Rogers we can afford so you’ll be seeing a lot
of it today. But yes, Fred Rogers and I have many similarities. We both
considered becoming ministers, he actually did, both happily married to women named
sara(h), and we both make stuff for young people. …Although I don’t think that his
work has been banned from several dozen high schools in Tennessee. Mr. Rogers was an Ivy League dropout. He
completed his freshman year at Dartmouth and then transferred to Rollins College
so he could get a degree in music. And he was an excellent piano player, not
only did he graduate from Rollins “Magna cum laude,” but he wrote all of the songs on the show, as well as more than 200 other songs and several kids operas including one called
“All in the Laundry.” Mr. Rogers decided to get into TV because
when he sought for the first time he, “hated it so.” When he turned on a
set all he saw was angry people throwing pies in each other’s faces and he vowed to use the medium to make
the world a better place. Over the years, he talked to kids about their feelings,
covering topics as varied as why kids shouldn’t be afraid of haircut, or the
bathroom drain (because you won’t fit) to bigger issues like divorce and war. In
the opening sequence of Mr. Rogers’ Neighborhood, the stoplight is always on yellow. That’s a reminder to kids and parents to slow down a little. Also,
Mr. Rogers wasn’t afraid of dead air time, unlike me: Once he invited a marine
biologist and explorer onto his program to put a microphone into his fish tank,
because he wanted to show the kids at home that fish make sounds when they eat. However, while taping the segment, the
fish weren’t hungry so the marine biologist started trying
to egg the fish on, saying “C’mon,” “It’s Chowtime,” “Dinnerbell.” But Mr. Rogers just waited quietly.
The crew thought he’d want to retape it, but Mr. Rogers just kept it…to show kids the importance of being patient. Fred Rogers was a perfectionist and so he disliked ad libbing. He felt that he owed it to children to make sure that every word on his show was thought out. But here at mental_floss we love ad libbing because it’s much less work. In a Yale
psychology study, when Sesame Street and Mr. Rogers’ Neighborhood went “head to
head,” kids who watched Mr. Rogers not only remembered more of the story lines
but their, “Tolerance of delay,” a fancy term for their ability to wait for
promised treats or adult attention, was considerably higher. Mr. Rogers was also
beloved by Koko the Gorilla, you know Koko the Stanford educated Gorilla who
can speak about 1000 of American Sign Language, she watched The Neighborhood, and when Mr. Rogers made a trip to meet her she not only embraced him but she did what she’d
always see him do on screen: She proceeded to take his shoes off. Those
shoes were store bought, by the way, but every one of the cardigans Mr. Rogers wore on his show was knit by his mother. Today one of them
resides in the Smithsonian–a red one. Mr. Rogers chose to donate that sweater because the cameras at his studio didn’t pick up the color very
well. Mr. Rogers could start to feel anxious and overwhelmed, and when he did,
he liked to play the chords to the show’s theme song on the piano on set in order
to calm himself. The other way you could tell he was exasperated? If he said the
word, “mercy.” Mostly, he said it when he got to his desk in the morning, and the mountains of fanmail were a little bit
too tall. But, “mercy” was about the strongest word in his vocabulary. And yes,
Mr. Rogers responded to every single piece of fan mail. He had the same
routine every morning: wake up at 5:00AM. Pray for a few hours for all of his
friends and family, study, write, make calls, reach out to every single fan
who took the time to write him, go for a morning swim, get on a scale, then start the day. My morning routine is
a bit less ambitious than that, Mr. Rogers, I thought you were supposed to make me
feel good about myself! You just made me feel terrible! But speaking of that daily weigh-in, Mr. Rogers watched his weight very closely. And he’d like to weigh exactly 143 lbs (65 kg). By the way, he didn’t drink smoke or eat the flesh of any animal. NATCH. Why did mister rogers like the number 1-4-3 so much? Because it takes 1 letter to say “I”.
4 letters to say, “love.” And 3 letters to say, “you” (Jean Luc Picard). Now it starts to get a little weird. So, journalists had a tough time covering Mr. Rogers because he’d often befriend them, ask them tons of questions, take pictures
of them, compile an album for them at the end of their time together, and then call them afterwards to check in on them and hear about their families. He genuinely loved hearing the life
stories of other people. And it wasn’t just reporters. Once, on a fancy trip
up to a PBS executives house, he heard the
limo driver was gonna have to wait outside for two hours, so Mr. Rogers
insisted that the driver come in and join them. Then on the way back,
Rogers sat up front, and when he learned that they were passing the drivers house on the way, he asked if they could stop in to meet the
family. And according to the driver, it was one of the best nights of his life.
The house lit up when Rogers arrived. He played jazz piano and bantered with them late into the night. Okay so thieves, Smithsonian curators, reporters, limo
drivers, kids, all these people loved Mr. Rogers, but someone has to hate him, right? Well, LSU professor Don Chance certainly
doesn’t love his legacy: He believed that Mr. Rogers created a, “culture of
excessive doting” which resulted in generations of lazy, entitled, college students… …and that makes sense, because generally
the deterioration of culture can be traced back to a single public television
program… Other curious theories about Mr. Rogers that are all over the
Internet: That he served in the army and was a
sniper in Vietnam; that he served in the army and was a sniper in Korea; that he
only wore sweaters to cover up the tattoos on his arms. These are all untrue. He was never in the army, he never shot
anyone, (and) he had no tattoos. One other rumor we’d like to quash? That he used to chase kids off his porch on Halloween. That’s crazy! In fact, his house
was known for being one of those generous homes that give out full-size candy bars… because of
course it was! In fact, for all the myths that people want to create about him, Mr. Rogers seems to have been almost exactly the same person “offscreen,” as he was, “onscreen.” As an ordained presbyterian minister and man of tremendous faith, Mr. Rogers preached tolerance first. He never engaged in the culture wars,
all he would ever say is, “God loves you just the way you are.” He was also kind of
a superhero, like when the government wanted to cut public television funds in
1969, the then relatively unknown Mr. Rogers went to Washington
and almost like straight out of a Capra film, his testimony on how TV had the
potential to give kids hope and create more productive citizens was so passionate and convincing, that
even the most gruff politicians were charmed…and instead of cutting the
budget, funding for public TV jumped from $9M to $22M. Years later, Mr. Rogers also swayed the Supreme Court
to allow VCRs to record TV shows from home. It was a cantankerous
debate at the time, but his argument was that recording a program like his allowed
working parents to sit down with their children and watch shows as a family. Plus it allowed them to watch Captain Stubing on The Love Boat anytime they wanted, without having to stay up till 8:30PM. He was also heavily parodied, but most of the people who made fun of him, loved him. Johnny Carson hoped his send up of
The Neighborhood would make Mr. Rogers more famous, and the first time Eddie Murphy met
Mr. Rogers, he couldn’t stop himself from giving the guy a big hug. Alright, we’re
running out of time so lets speed this up. Mr. Rogers was color blind. I mean that
figuratively, his parents took in African American foster children, and he
loved people of all backgrounds equally, but also literally. Michael Keaton got his start on the show:
He was a puppeteer and worked trolley. Mr. Rogers once made a guest appearance on Dr. Quinn Medicine Woman as a pastor’s mentor, and many of the characters on his show
took their names from his family. Like, Mr. McFeely was his grandfather’s name,
Queen Sara is named for his wife. And lastly we return to the Salon so I can
tell you probably my favorite story about Mr. Rogers: that he could make a
whole NYC subway car full of strangers sing. He was rushing to a
meeting and there were no cabs available so Mr. Rogers jumped on the subway.
The car was full of people, Rogers assumed that he wouldn’t be noticed, but
he quickly was of course, and then people burst into song, chanting
“It’s a beautiful day in the neighborhood” Thanks for watching mental_floss, which is made with the help of all of these lovely people and
remember that you make every day special just by being you. If you have a
fascinating question, you’ve always wanted the answer to, submit in comments and we’ll
try to start answering them here at the end of the video April. In the meantime, DFTBA!

Eclipses: Crash Course Astronomy #5

November 15, 2019 | Articles, Blog | 100 Comments

Eclipses: Crash Course Astronomy #5


We humans of planet Earth benefit from a great
coincidence. It’s a coincidence of time, and of space. And of math. The coincidence is this: the Sun is about
400 times wider than the Moon, and it’s also on average about 400 times farther away
than the Moon. The apparent size of an object in the sky
depends on how big it is and how far away it is… so these numbers being equal means
the Sun and the Moon appear to be about the same size in the sky. And that’s where another interesting thing
comes in: Sometimes, the Moon passes directly between the Earth and the Sun. It doesn’t happen all
that often, but when it does, you get magic. Or even better: You get SCIENCE. You get an eclipse. An eclipse is a generic term in astronomy
for when one object passes into the shadow of another object, darkening or blocking it. A solar eclipse is when the Moon blocks the
Sun, casting a shadow on the Earth, and a lunar eclipse is when the Earth blocks the
Sun, casting a shadow on the Moon. But how do they work? Well, the Moon orbits the Earth once per month,
and the Earth orbits the Sun once per year. If the Moon’s orbit were perfectly aligned
with the Earth’s, essentially sharing the same plane, we’d get a solar eclipse every
new Moon and a lunar eclipse every full Moon! But we don’t. That’s because the Moon’s
orbit is tilted with respect to Earth’s, by about 5°. What that means is that, at new Moon, the
Moon can be as much as 5° away from the Sun, passing “above” or “below” the Sun
in the sky, thereby missing it, from our perspective. But sometimes the Moon is in the right place
at the right time, and at new Moon, it lies perfectly in line between the Sun and the
Earth. And when that happens, we get a solar eclipse. This geometry happens at least twice per
year, and sometimes as much as five times per year. What’s happening physically in space is
that the Moon is casting a long shadow. Usually that shadow misses the Earth, but during an eclipse
the Moon’s shadow falls on the Earth’s surface. In fact, there are two shadows from the Moon,
one inside the other. One is a narrow cone, tapering to a point away from the Moon. If
you’re anywhere physically inside this cone, the Moon appears big enough to completely
block the Sun. That means this shadow is very dark, and we call it the umbra (which is Latin
for – you guessed it – “shadow”). Outside of this deep umbral shadow is a wider
conical region where, if you’re in it, the Sun is only partially blocked; you can still
see some of the Sun past the Moon. You’re getting less light, and so you’re technically
shadowed, but it’s not quite as dark as the umbra. This region is called the “penumbra”; “pen”
in this case for Latin meaning “almost,” or “nearly.” When the umbra touches the Earth, we get a total solar
eclipse. But what does that look like from the ground? You don’t get a total eclipse right away.
First, the edge of the Moon slips in front of the Sun, and we see a little dip in the
Sun’s limb, its edge as seen from Earth (that’s the start of the penumbra sweeping
over you). As the Moon slowly moves, that dip grows,
becoming a bite. The Sun becomes a thick crescent, then a thin one. As the Sun becomes an ever-thinner crescent,
the sky begins to darken. Then, finally, the Moon’s black disk completely covers the
Sun — the umbra sweeps over your location. And at that moment, totality begins. You might think that this just means the sky
gets dark, and it’s like night outside for a while. But a total eclipse is far more than
that. And that’s because of the Sun’s corona. As I’ll cover in more detail in a future
episode, the corona is the sun’s atmosphere, an ethereally thin envelope of gas that stretches from
the Sun’s surface into space for millions of kilometers. It’s really faint, and therefore usually
completely overwhelmed by the intensely bright light from the Sun. But when the Moon blocks the Sun’s face,
the corona becomes visible. It surrounds the Sun, filaments and tendrils extending into
the sky, an incredibly beautiful sight. I know many people who have said it’s the
most spectacular thing they have ever seen. And there’s more. The Moon’s edge isn’t
smooth — there are craters and other depressions. Craters right at the Moon’s edge allow sunlight
to stream past. We see these as bright patches around the eclipsed Sun, which are called
Baily’s Beads – because they were first described by English astronomer Francis Baily
in 1836! Because the Moon and Sun are very nearly the
same apparent size, totality is brief. The longest it can last is only about seven
or eight minutes. That’s how long it takes the umbra to move over one spot on the Earth.
When totality ends, and the Moon starts to move off of the Sun’s face, for a moment
just a single spot of the Sun is unblocked, glowing fiercely on one side of the Moon.
Sometimes you can get a circle of light around the Moon’s surface, and together with the
bright spot it looks like a celestial wedding ring. In fact, this is called the Diamond
Ring effect. Then, inexorably, the Moon pulls away from
the Sun, and the order of events is reversed. The umbra is gone, but you’re still in the
penumbral shadow. The Sun shows a thin crescent, then a thick one, then a dip in its side…
and then it’s all over. The umbral shadow of the Moon is pretty small
where it hits the Earth, so a total eclipse is a local event. If you’re too far north
and south, you don’t get a total eclipse, you only get a partial one. Which is still
cool, but lacks the mystique of a total eclipse. Remember too that the Moon’s orbit around
the Earth is an ellipse. That means sometimes it’s closer to the Earth, and sometimes
farther. If a solar eclipse happens when the Moon is
at the far end of its orbit, it can actually be smaller than the Sun in the sky. It doesn’t
block the entire face of the Sun, and it leaves a ring of light around the black circle of
the Moon. This technical name for this shape is annulus,
so this event is called an annular eclipse. A lot of people think if you look at a total
solar eclipse you can go permanently and completely blind. That’s really not true. But, some parts of
eclipse-watching are more dangerous than others. I mean, obviously it’s not a good idea to
stand there and stare at the sun. Looking at even the uneclipsed Sun for more than a
moment is painful, and that pain is the result of the damage that solar radiation is doing
to your retinas. So I don’t recommend it — Duh. But when viewing an eclipse, the real concern
is right after totality ends. During totality it’s dark, so your pupils have dilated to
let more light in. But then there’s the flash of sunlight when the Moon moves off, and
that’s intense enough to damage your retinas. That’s why astronomers recommend extreme
caution when viewing an eclipse; because that flash can catch you by surprise. When viewing the Sun, don’t just stand there
and stare at it; you should always have eye protection. And make sure you have safety-approved
filters; don’t try the the home-made tricks you might have heard of — like looking through
an old CD or DVD, or using old-style camera film as a filter. These can let through too much infrared and
ultraviolet light, and again can dilate your pupils, actually making things worse. Lots of companies make inexpensive filters
that are great for Sun-spotting; we have links in dooblydoo for more information on eye safety. Now, you don’t have to worry about hurting
your eyes at all when viewing a lunar eclipse. Because, in that case, it’s the Earth that
blocks the Sun, and the Earth’s shadow falls on the Moon. So go nuts. But one big difference between the two kinds
of eclipses is who can see them. A solar eclipse is localized to one spot on
the Earth, or really a swath along the ground as the Moon’s umbral shadow sweeps across
the Earth’s surface. But a lunar eclipse is when the Moon moves
into Earth’s shadow, so anyone on Earth facing the Moon can see a lunar eclipse. This
is why I’ve seen dozens of lunar eclipses but never a total solar one. I’ve never
been at the right place at the right time. Not that I’m bitter. The Earth has umbral and penumbral shadows,
too. When the Moon first enters the Earth’s penumbra, the dimming is so slight you hardly
notice it. But as the Moon moves deeper into the penumbra, it starts to darken. Sometimes
it changes color, turning a deep orange or blood red. That’s because the Earth is starting to
block the sunlight heading toward the moon, and the only light that gets through is coming
through the thickest part of our atmosphere. This blocks blue and green light, leaving
only red to come through. That’s why the Moon and Sun look red to
us when they’re on the horizon, rising and setting, too. When you look upon the red eclipsed
Moon, you’re seeing the light from all the sunrises and sunsets in the world hitting
the Moon and reflecting back to us. Finally, the Moon starts to enter the Earth’s
umbra, and the real eclipse begins. At first it looks like a bite is taken out of it — that
curving arc is the shadow of the edge of the Earth! The Moon moves deeper and deeper into
the shadow until it’s completely darkened. The Earth is bigger than the Moon, so the
Earth’s umbra is much wider; while a solar eclipse is over in minutes, a total lunar
eclipse can last nearly two hours. I once saw a lunar eclipse so deep that it took me
a minute to find the Moon in the sky! There’s not a lot of new science you can
do with a lunar eclipse. But if you know a little geometry, you can use the size and
shape of the Earth’s shadow on the Moon to get the relative sizes of the Earth and
Moon. Ancient Greeks did just this, and got a number
that wasn’t too far off. They also knew how big the Earth was using other methods,
and so they had a decent estimate for the size of the Moon…nearly 2000 years before
the invention of the telescope! They also knew the shape of the Earth’s
shadow was always a circle, which only makes sense if the Earth were a sphere. If the Earth
were flat, it would sometimes cast a thin shadow, but it never does. Pretty clever,
those ancient Greeks. One final note. Because of tides from the
Earth — which we’ll learn more about in detail in a later episode — the Moon is
slowly moving away from the Earth, by about 4 centimeters a year. As it recedes, it’s slowly getting smaller
in the sky. This means that, eventually, it will be too far away to completely cover the
Sun, and we won’t get any more total eclipses. Doing the rough math, that will be in about a billion
years. Better watch eclipses while you can. Today you learned that a solar eclipse is
when the Moon blocks the Sun so its shadow falls on the Earth, and a lunar eclipse is
when the Earth’s shadow falls on the Moon. We don’t get them every two weeks because
the Moon’s orbit is tilted. And if you’re clever, you can use lunar eclipses to figure
out how big the Earth and Moon are. This episode is brought to you by Squarespace. The latest version of their platform, Squarespace Seven, has a completely redesigned interface, integrations with Getty Images and Google Apps, new templates, and a new feature called Cover Pages. Try Squarespace at Squarespace.com, and enter the code Crash Course at checkout for a special offer. Squarespace. Start Here. Go Anywhere. Crash Course Astronomy is produced in association
with PBS Digital Studios. Head on over to their channel and discover more awesome videos. This episode was written by me, Phil Plait. The script was edited by Blake de Pastino, and our consultant is Dr. Michelle Thaller. It was co-directed by Nicholas Jenkins and Michael Aranda, edited by Nicole Sweeney, and the graphics team is Thought Café.

How a Bill Becomes a Law: Crash Course Government and Politics #9


This episode of Crash Course is brought to
you by Squarespace. Hi, I’m Craig, and this is Crash Course: Government
and Politics, and today, I’ve got my work cut out for me because I’m going to try to
do something that every single social studies teacher in the U.S. has tried to do, even
though there is a perfectly good cartoon you could just show. It’s from the ’70s. It’s
catchy. It’s fun. That’s right, today we’re going to learn how
a bill becomes a law. But we’re not going to be able to license the Schoolhouse Rock song. I’m just a bill, yes, I’m only a – you know
what has a bill? An eagle. [Theme Music] Okay, I think the only way we’re going to possibly
be able to compete with Schoolhouse Rock is to jump right into the Thought Bubble with our own
cartoon. And to stop talking about Schoolhouse Rock. So let’s start at the very beginning, which
in this case is a Congressman or a Senator introducing a bill. The real beginning is
when he or she has an idea for a law. And even this might come from an interest group,
the executive branch, or even the constituents. But the formal process begins with the
legislator introducing the bill. After it’s introduction, bill is referred to a committee. Although most bills can start in either house,
except for revenue bills, which must start in THE House, let’s imagine that our bill
starts in the Senate, because it’s easier. Congress has the power to make rules concerning
the Armed Forces, so let’s say this is a bill about naming helicopters. Anywho, this bill
would be referred to the Senate Armed Services Committee, which would then write up the bill
in formal, legal language, or markup, and vote on it. If the markup wins a majority in the committee,
it moves to the floor of the full Senate for consideration. The Senate decides the rules for debate – how
long the debate will go on and whether or not there will be amendments. An open rule
allows for amendments and a closed rule does not. Open rules make it much less likely for
bills to pass because proponents of the bill can add clauses that will make it hard for
the bill’s proponents to vote for. If opponents of our helicopter name bill were
to add a clause repealing the Affordable Care Act or something, some supporters of the bill
probably wouldn’t vote for it. If a bill wins the majority of the votes in the Senate, it
moves onto the House. Thanks Thought Bubble. We’re going to have to go the rest of the
way without fancy animation. But I could sing it. Laaaa- I’m not going to sing it. I’m not
going to use a funny voice. The Senate version of the bill is sent to
the House. The House has an extra step, in that all bills before they go out to the floor
of the House must go to the Rules Committee, which reports it out to the House. If a bill
receives the majority of votes in the House, 238 or more to be exact, it passes. YAY! Now, this is important. The exact same bill
has to pass both houses before it can go to the president. This almost never happens though.
Usually the second house to get the bill will want to make some changes to it, and if this
happens, it will go to a conference committee, which is made up of members of both houses.
The conference committee attempts to reconcile both versions of the bill and come up with a new
version, sometimes called a compromise bill. Okay, so if the Conference Committee reaches
a compromise, it then sends the bill back to both houses for a new vote. If it passes,
then it’s sent to the President. And then the President signs the bill, boom, done.
That’s the only option. Oh, no, there’s two other options, actually. Option 2 is for him to veto the bill and we’ve
gone through all of this for nothing. The 3rd option is only available at the end
of a congressional term. If the President neither signs nor vetoes the bill, and then
in the next 10 days, Congress goes out of session, the bill does not become a law.
This is called a pocket veto, and is only used when the President doesn’t want a law to pass,
but for political reasons, doesn’t want to veto it either. Congress can avoid this all together by passing
bills and giving them to the President before that 10 day period. If the President neither
signs nor vetoes a law and Congress remains in session for more then 10 days, the bill
becomes a law without the President’s signature. So that’s the basic process, but there is one wrinkle,
or if you want to be all Madisonian about it, check, on the president’s power. If Congress really wanted a bill and the President
has vetoed it, they can override the veto if it gets a 2/3rd majority in both houses on
a second vote. Then the bill becomes a law over the President’s signature. Aw snap! This is really rare, but it does happen once
in a great while. The Taft-Hartley Act of 1953 passed over Truman’s veto. I like to
call it the Tartley Act. Shorten it. It’s a portmanteau. It doesn’t happen that often because if the
President knows that two thirds of the Congressmen supported the bill, he won’t veto it. And
if Congress knows that they don’t have two thirds support, they won’t try to override
the veto. Nobody wants to try something and fail in public, right? Except for me obviously,
if you look at my other YouTube channel, WheezyWaiter. Eh. So there you have it, how a bill becomes a
law. I’ll admit, the process is a little cumbersome, but it’s designed that way so that we don’t
get a lot of stupid or dangerous laws. Still this doesn’t quite explain why so few laws
get passed. Bills have a very high mortality rate, and it’s way more common for a bill
not to become a law than to become one. The main reason is that there are so many places
where a bill can die. The first place that a bill can die is at
the murderous hands of the speaker or majority leader, who refuses to refer it to committee.
Then the committee can kill the bill by not voting for it at all. And if they do vote
and it doesn’t get a majority then the bill doesn’t go to the floor, and it’s dead. In the Senate the murderous leadership can
kill a bill by refusing to schedule a vote on it. And any senator can filibuster the
bill which is when he or she threatens to keep debating until the bill is tabled. It’s
a bit more complex than that, but the filibuster rules have changed recently, so hopefully we won’t
have as many filibuster threats in the future. The House doesn’t have a filibuster but it
does have a Rules Committee that can kill a bill by not creating a rule for debate.
The entire House can also vote to recommit the bill to committee, which is a signal to
drop the bill or change it significantly. And of course if either house fails to give
a bill a majority of votes, then it dies. This applies to compromise bills coming out
of conference committees too. Even if a bill gets a majority in both houses then there’s that whole
veto thing that the President can do. Remember? So, there are many more ways for a bill to
be killed than to become a law. These hurdles are sometimes called veto gates. They can’t call ’em Bill Gates because that’s
a person. Veto gates make it very difficult for Congress
to act unless there’s broad agreement or the issue is uncontroversial like naming a post
office or thanking specific groups of veterans for their service, which are two things that
Congress actually does pretty efficiently. Think of all the post offices that aren’t
named. You can’t think of one, can you? Name it. You can’t. It’s not named. Veto gates are purely procedural, which means
they don’t draw a lot of attention from the media. The easiest way for Congress to kill
bills is to simply not vote on them or even schedule votes for them. This way they don’t
have to go on record as being for or against a bill, just whether they support having a vote. And
constituents rarely check up on this sort of thing. So I hope I managed to do a good job of both
explaining how a bill becomes a law and why it’s difficult for most bills to pass. And
I hope I looked good doing it, as well. This might be frustrating but it’s strangely
comforting to consider that Congress and the government as a whole were designed to make it
difficult to get things done. A single super-powerful executive like a king can be very efficient, but also
tyrannical. We don’t like tyrannical around here. The founders set up these structural hurdles
of the bicameral Congress and the presidential role in legislation to reduce the likelihood
that authoritarian laws would pass. Congress added procedural hurdles like committees and
filibusters for the same reason. You can argue that Congress has become dysfunctional, but
looking at the process of lawmaking, it’s hard to argue that this isn’t by design. So next time someone accuses you of being difficult,
you just say, “I was behaving in a senatorial manner.” Thanks for watching. I’ll see you next episode Crash Course: Government and Politics is produced
in association with PBC Digital Studios. Support for Crash Course US Government comes from Voqal.
Voqal supports nonprofits that use technology and media to advance social equity. Learn more
about their mission and initiatives at voqal.org. Crash Course was made with all of these nice
people. Thanks for watching.

Jupiter: Crash Course Astronomy #16

November 13, 2019 | Articles, Blog | 100 Comments

Jupiter: Crash Course Astronomy #16


As we take our grand tour of the solar system
here on Crash Course Astronomy, we’re going to skip over the asteroids for now—we’ll
get to ‘em, I promise—and instead pay a visit to the King of the Planets, the big
guy, the top dog, the big cheese, the head honcho, the one and only: Jupiter. Jupiter is the largest planet in the solar
system. It’s not even close: All the other planets could fit inside it with room to spare.
It’s a gas giant, which means it’s gassy, and… giant. And I do mean giant. It’s 11 times wider
than Earth—more than a thousand Earths could fit inside it, and it has a mass over 300
times that of our planet. Despite its bulk, it rotates extremely rapidly: One day on Jupiter
is a mere 10 hours long! That’s the fastest spin of any of the planets in the solar system. Not surprisingly, a planet that big can reflect
a lot of sunlight, and even though it orbits the Sun on average at a distance of about
800 million kilometers, it’s one of the brightest objects in the night sky. With binoculars or a small telescope, Jupiter
is a wonder. You can easily see it as a disk, and its four biggest moons are readily visible—if
they weren’t hidden by the planet’s glare, they’d be naked eye objects. Galileo himself
discovered those moons. They’re worlds in their own
right, and so we’ll dive into them—literally—in the next episode. When we look at Jupiter we’re not seeing
its surface. We’re seeing the tops of its clouds, and they’re a strange mix of permanence
and change. The atmosphere of Jupiter is banded, with multiple stripes running parallel to
its equator. The lighter-colored stripes are called zones, and the darker ones belts. They’re
fairly stable, though their shape and coloring change over time. Belts and zones circulate around the planet
in opposite directions. They form due to convection in Jupiter’s atmosphere. Upwelling air cools
and forms white ammonia clouds; that creates the light colored zones. That air flows to
the sides and sinks, and sunlight changes the chemistry in the clouds forming molecules
that color the air yellow, red, and brown. This is what causes the darker belts. In May of 2010, one of Jupiter’s biggest
belts sank so deeply it disappeared from view completely, covered by other clouds! Then,
a few months later, it popped back up and reappeared, none the worse for wear. This
has happened several times in the past, too. I saw one of these events once through a telescope,
and Jupiter looked really weird. Lopsided. Turbulence in the regions between zones and
belts can create storms, gigantic vortices raging in the clouds. Dozens of them dot the
face of Jupiter all the time, but there is one to rule them all: the Great Red Spot,
a fittingly huge storm for a giant planet. It’s actually a colossal hurricane, several
times larger than our entire planet Earth, with sustained wind speeds of 500 kph. And
it’s old; it was first seen in the late 17th century—imagine a storm on Earth lasting
for more than three centuries! And it may be far older; the 1600s is just when we first…
spotted it. So, why is it so stable? It turns out that
a vortex, a local spinning region in a fluid, can persist if the fluid in which it’s embedded
is itself rotating. Jupiter’s rapid spin is what keeps the Red Spot circulating! And
the redness is probably due to cyanide-like molecules that absorb blue light, letting
redder light pass through. Weirdly, the Red Spot appears to be shrinking!
It was substantially bigger and more elongated just a few decades ago. It changes color over
time, too, having gone from deep red to salmon and then back again. No one knows why its
shape, size, and color change, but given how long the Spot’s been around, I doubt it’s
going to evaporate any time soon. Remember, we’re only seeing the tops of
the clouds on Jupiter. Its atmosphere is thick, several hundred kilometers deep! Like the
composition of the Sun, the air on Jupiter is mostly hydrogen and helium, but it’s
also laced with ammonia, methane, and other poisonous gases. As you dive into Jupiter’s atmosphere, the
pressure increases with depth. But you’ll never reach the surface; the planet doesn’t
really have a proper surface. The gas gets thicker and hotter, and eventually just sort
of smoothly changes into a liquid over a several hundred km range below the clouds. Below that is where things get really weird.
Instead of a mantle, like terrestrial planets, Jupiter has a huge region made up of liquid
metallic hydrogen. We think of hydrogen as being a gas, or, if it gets really cold, a
liquid. But under the ridiculous pressures generated deep inside Jupiter, hydrogen undergoes
this strange transformation. Individual atoms don’t hold on to their electrons, but instead
share them. This means the hydrogen can conduct electricity, and has other properties more
like a metal. This substance is hot, too: about 10,000° C, hotter than the surface
of the Sun! If we could see it, it would glow tremendously bright. Finally, at its center is most likely a dense
core of material, probably composed of rock and metal. We really don’t know, because
it’s incredibly difficult to understand the physics and chemistry of material locked
in at those pressures and temperatures. What’s weirder is that we’re not even sure if Jupiter
has a core! If it did, it’s possible it was eroded away by currents of hot metallic
hydrogen early on in Jupiter’s formation process. It’s also possible it never had a core in
the first place. The solar system formed from a flat disk of
gas and dust. The center of this disk is where the Sun was born, and it’s thought that
the planets formed as smaller particles of material stuck together during random collisions
farther out in the disk. As they got bigger—much bigger—these protoplanets eventually started
to grow even faster by drawing in material around them due to their gravity. Jupiter formed where the disk was thick, rich
with material. It’s possible that several large protoplanets were forming, collided,
and stuck together to really kickstart Jupiter’s growth. If that were the case, it started
out with a rocky metallic core, and once it got big enough it drew in that gas that made
it the giant we see today. Another idea is that Jupiter didn’t grow
from the bottom up, but from the top down: The disk itself collapsed in several places
to form huge, distended clumps. These then would have collided, stuck, and created the
planet. If that’s the case, then Jupiter might not have a core at all. These two different mechanisms make different
predictions about Jupiter’s structure, and that means that, hopefully, we can eventually
figure out which is correct by studying Jupiter more carefully. But at the moment we still
don’t know. Either way, Jupiter grew immense, and it’s
mostly liquid under all that atmosphere. Couple that with its rapid rotation, and you can
see it’s noticeably flattened! It’s wider at the equator than through the poles by about
6% due to centrifugal force. So, Jupiter is a big bruiser of a planet.
But how close was it to becoming a star? Sometimes, people ask me if Jupiter is a “failed
star”; in other words, as it formed it almost got massive enough that nuclear fusion could
start in its center, turning it into a star. I see this a lot on TV shows and in articles,
and it really burns me up. When a star forms, hydrogen fusion starts
when the star gathers so much mass that its gravity can compress atoms together in its
core hard enough to get them to fuse. This happens when a star has roughly 1/12th of
the Sun’s mass. In fact, the smallest stars we see do have about that mass. What about Jupiter? The mass of Jupiter is
about 1/1000th the mass of the Sun, far too little to undergo fusion in its core. If you
want to turn Jupiter into a star, you’d have a lot of work ahead of you: You’d have
to take Jupiter… and then add about 80 more Jupiters to it! Saying Jupiter is a failed star is really
unfair. It’s not a failed star. It’s a really successful planet. Even though Jupiter isn’t a star, it does
have another funny property: It emits more heat than it receives from the Sun. The Earth and other terrestrial, rocky planets
are in a heat balance with the Sun; we emit pretty much the same amount of heat that we
receive. But Jupiter is different. After it formed, it started to cool by radiating away
heat from its upper atmosphere. A large fraction of the planet is gas, remember, and when you
cool a gas in contracts. So the atmosphere cools and contracts, but this increases the
pressure inside the planet, so it heats up! That heat works its way out of Jupiter, and
gets radiated away as infrared light. In the end, the amount of heat Jupiter gives off
is more than it receives from the Sun. It’s still actively cooling, 4.5 billion years
after it formed! Oh and hey, remember the belts and zones, the stripes we see in Jupiter’s
atmosphere, and all the storms that pop up? Those are driven in large part by Jupiter’s
internal heat. On Earth our weather is powered by heat from the Sun, but on Jupiter they
get their energy from the planet itself! Jupiter has a very strong magnetic field,
no doubt due to all of that metallic hydrogen inside it coupled with its rapid rotation.
Like Earth it has aurorae at its poles as the solar wind is funneled down to the cloud
tops. As we’ll see next week, Jupiter’s moons affect the magnetic field and aurorae
on Jupiter as well. Jupiter also has a ring, though it’s not
nearly as grand as Saturn’s. It wasn’t even discovered until we sent space probes
to the planet. The ring is made of dust, probably thrown into orbit around the planet due to
meteorite impacts on its smaller moons. Speaking of impacts, we know that Earth gets
hit by interplanetary debris all the time: Go outside for an hour and you’re bound
to see a few meteors. Jupiter, being larger and with more gravity, gets hit a lot more.
A lot. A lot more. And sometimes it gets hellaciously whacked. In 1994, the comet Shoemaker-Levy
9 impacted Jupiter. Multiple times: Jupiter’s fierce gravitational tides had ripped the
comet into dozens of pieces, and each slammed into the planet one after the other with the
force of millions of nuclear weapons. The scars left in the upper atmosphere from the plumes
of material that exploded outward lasted for months. Several smaller impacts have been seen in
Jupiter’s atmosphere since then, and it may suffer an impact large enough to see from
Earth every year or so. And while that sounds scary, it might actually
be our savior. There’s an idea that Jupiter’s gravity tends to take comets that fall toward
the inner solar system and fling them away into interstellar space. Over the eons, this
has cleaned out a lot of otherwise dangerous objects that could have eventually hit Earth.
On the other hand, Jupiter has a tendency to warp the orbits of some other comets so
that they do swing by the Earth. It’s hard to say if Jupiter’s influence is a net benefit
or not. But either way, it’s clearly the 2 septillion
ton gorilla in the solar system. Today you learned that Jupiter is really,
really big. It’s the biggest planet in our solar system, a gas giant. It has a dynamic
atmosphere, including belts and zones, and a gigantic red spot that’s actually a persistent
hurricane. Jupiter is still warm from its formation, and has an interior that’s mostly
metallic hydrogen, and it may not even have a core. It has the fastest spin of any planet,
and it’s not a failed star. Crash Course Astronomy is produced in association
with PBS Digital Studios. Head on over to their channel to discover more awesome videos.
This episode was written by me, Phil Plait. The script was edited by Blake de Pastino,
and our consultant is Dr. Michelle Thaller. It was co-directed by Nicholas Jenkins and
Michael Aranda, edited by Nicole Sweeney, and the graphics team is Thought Café.

Separation of Powers and Checks and Balances: Crash Course Government and Politics #3


Hi, I’m Craig, and this is Crash Course Government
and Politics. Today, I’m going to try to explain two fundamental concepts of American government
that students and citizens often confuse. Team Jacob and Team Edward. No. Separation
of powers and checks and balances. Team Jacob! [Theme Music] So separation of powers is really simple.
The national government is divided into three separate branches: the legislative branch,
the executive branch, and the judicial branch. I put them in this order because that’s the
way the Constitution has them. And I’m not going to argue with the Constitution, except
for that stupid 3/5ths of a person thing. So the legislative branch comes first, because
it’s supposed to be the most important branch, and Article I is the longest and most detailed
of the 7 Articles in the Constitution. The main job of the legislature is to make laws.
The secondary job is to say, “No, it’s your fault.” “No, it’s your fault!” “No, it’s your
fault! I’m going home, I have to campaign.” Then we have the executive branch, and here
the Constitution is a little less helpful. Article II Section I states “The executive
power shall be vested in a President of the United States of America.” The executive branch
is obviously more than one guy or girl. The executive branch is in charge of executing
the law, which basically means carrying them out. The President is like the CEO of the
US, making sure that the government governs. Interestingly, the President’s power as executive
is found in the Oath of Office. “I do solemnly swear (or affirm) that I will faithfully execute
the office of the President of the United States, and will to the best of my ability,
preserve, protect and defend the Constitution of the United States.” Ruh ruh ruh! Wait, Stan, I just gave the Presidential Oath
of Office, so I’m President now, right? Totally. Oh, elections, yeah, we didn’t have those. Last and, in the eyes of many, least, is the
judicial branch. The job of the judiciary, also sometimes called “the Courts,” which
I’m going to also call “the Courts,” because judiciary is really hard to say, is to interpret
the law, to explain what it means. Article III, which describes the judicia- the courts
is even shorter than Article II. It only has 3 sections instead of 4, and the courts today
don’t really look like this description. Here is the first sentence of Article III
Section I: “The judicial power of the United States, shall be vested in one Supreme Court,
and in such inferior courts as the Congress may from time to time ordain and establish.”
At least the Framers realized that the entire United States would probably need more than
one court. But notice right there in the sentence, that Congress has the power to create all
other courts. And this lead us nicely into the second important
concept of American government – checks and balances. Yeah, that was a segue right into
it. It was a nice job, by me. I’m going to need a little help explaining checks and balances,
so let’s do that part in the Clone Zone. Checks and balances is a confusing term because
it implies two things. But really, it would be better to think of them as checks that
balance, although that might be confusing to people who actually try to balance their
checkbooks. Anyways, the point here is that each of the branches has the power to limit,
or check, the other two and this creates a balance between the three separate powers.
In the same way that the Constitution lays out the legislature in the greatest detail,
it also gives the legislature the greatest number of checks on the other branches. Legislative
clone… Legislative Clone: So the Framers of the Constitution
were really concerned about the President becoming a tyrannical figure a la King George
III. That guy was a jerk. So the Constitution gives the legislature a lot of power over
the Executive. The House of Representatives can impeach the President, then the Senate
can remove the President from office, but only if two thirds of the Senators vote for
impeachment. The Senate can also check the President’s appointment of judges and officials
by rejecting them. This is known as advice and consent. Either branch of Congress can investigate
executive activities and officers. If the President vetoes a law, Congress, with a two
thirds vote in both houses, can override the veto. Congress can also refuse to pass laws
that the executive wants, and probably most important, they can refuse to appropriate
funds for executive programs. You might think that since the judiciary is the third and
presumably least important branch, Congress would have fewer checks on it. But that would
be wrong! Here are the ways that the legislative branch
can limit the judicial branch: Congress can impeach and remove judges as it can do with
the President. Congress can be a bunch of jerks sometimes. Huh, that’s me. Heheheh.
Senates can reject judicial nominees, which is a check on judges before they even get
there. Congress can change the federal court system by adding or taking away courts like
it says in Article III. And it can change the jurisdiction of federal courts. Congress
can pass new laws that override the Supreme Court decisions, as long as the decisions
aren’t based on the Constitution. Don’t want to do that, no. And as a very last, super
drastic resort, Congress can propose Amendments to the Constitution, as it did with the 13th, 14th, and
15th Amendments, overruling the Dred Scott decision. Craig: Wow, legislative clone. Looks like
the Framers were so scared of an all-powerful super president that they gave Congress most
of the power. Executive Clone, you know, I’ll be Executive Clone because I’m basically president
of the clones. The executive branch can check the power of
the legislature in the following ways: the president can veto Congress’ laws so that
they don’t go into effect. The president can call Congress into a special session, but
he can’t make them pass new laws. The executive branch carries out the laws, and may do so
in ways that are contrary to what Congress wanted. Although this rarely happens, the
vice president is given power to break ties in the Senate, which is one of his only real
powers other than embarrassing the president. The president nominates Supreme Court justices,
and this can change the way the courts work. He also nominates federal court judges, and
this shapes the entire court system. The president can pardon people convicted by the courts,
which cancels out their judgments. The president can also, in his capacity to carry out the
laws, refuse to carry out court decisions. So you can see, even with a number of checks that it
has, the executive branch is weaker than the legislature. Judiciary Clone: But not as judiciary branch.
Many political scientists consider the judiciary the weakest branch because without
legislative and executive action, it doesn’t have a whole lot to do. Being the weakest
branch, the judiciary also has the fewest checks on the other two branches. Here’s what it can do: The judiciary checks
the legislature by declaring its laws unconstitutional. The Chief Justice presides over impeachment
trials, and sometimes he gets to wear a special robe when this happens. Perk of the job, it’s
a perk of the job. It’s really nice. And the judiciary checks the executive branch
by declaring executive actions unconstitutional. A really good example of this was Youngstown
Sheet and Tube Company vs. Sawyer, a super important case. Look it up, look it up! The court also issues warrants in federal
crime cases, and again presides over impeachment trials in the Senate. But the big check that
the courts have is invalidating laws and executive actions. We’ll talk about how courts actually do
this and where they got this power in a later episode. Craig: No, I’ll talk about it in a later episode,
okay? Let’s go back to the regular desk. Judiciary Clone: You’re out of order! Craig: Thanks clones. Now some of you are
probably saying, Craig, this is very helpful information but why do we have checks and
balances in the first place? To you I say, “Stop talking to your computers, that’s weird!”
I also say, “Let’s go to the Thought Bubble.” So the Framers of the Constitution were terrified
of a tyrannical central government that would destroy people’s rights like they felt the
British had. The powers of the national government are separated, and each branch are able to
check others because this makes it more difficult for the government to act in ways that harm
the acts and interests of the citizens. One of the best explanations of this comes
from, you guessed it, the Federalists Papers. In this case, Federalist 51, which was written
by James Madison, who also wrote a lot of the Constitution and became president, so
he kind of knows what he’s talking about. And really, it’s kind of a shame that he’s
not on our money because Americans would pay him more attention, and they would also pay
him, literally. In Federalists 51, the title which also contains
the phrase, “checks and balances,” Madison wrote, “But the great security against a gradual
concentration of the several powers in same department, consists in giving to those who
administer each department the necessary constitutional means and personal motives to resist encroachments
of the others. It may be a reflection on human nature, that such devices should be necessary
to control the abuses of government. But what is government itself, but the greatest of
all reflections on human nature.” That’s right, he wrote with an accent. Don’t know
how that’s possible. Thanks, Thought Bubble. Madison was talking about checks and
balances; I’ll leave it up to you to decide if human nature requires that we build safeguards
into our government to protect us from our leaders. But Madison thought so, and I think so
too. But this isn’t about me; this is about government. And it’s helpful to remember that when people
tell you that the Framers of the Constitution were infallible, James Madison actually that
they were outfallible, or just fallible. Anyways, see you next time. I’m so fallible. Crash Course Government and Politics is produced
in associate with PBS Digital Studios. Support for Crash Course US Government comes from
Voqual. Voqual support non-profits that use technology and media that advance social equity.
Learn more about their mission and initiatives at Voqual.org. Crash Course is made by all
these nice people, they’re very nice. I know them. Thanks for watching.

Introduction: Crash Course U.S. Government and Politics


Hi, I’m Craig. I’m not John Green, but
I do have patches on my elbows, so I seem smart. And this is Crash Course Government
and Politics, a new show, hurray! Why are fireworks legal or illegal? We
might find out. Will we find out Stan? Anyway, I have a question for you. Have you
ever wondered where your tax dollars go or why people complain about it so much? Or who
pays for the highway that runs past your house? Or why you use the textbooks you use in science
class? Or why you need a license to drive, or to hunt or to fish or to become a barber?
I’ve always wanted to cut my own hair, back when I had it.
Have you ever wondered why you have to be 21 years old to drink alcohol but only 18
to vote? Or gamble. Sometimes voting is a gamble – actually always. Do you get confused
when you hear people talk about news about Wall Street regulations, or Obamacare, or
the national debt? Do you wonder why there are so few cell phone carriers and cable companies?
How about why it’s ok for student groups to lead prayers in schools but not for the
principal to do so? Have you ever wondered if there are any limits on when, where, and
how the police can search your home, or your car, or your locker, or you, or your friend,
or your grandma, or your grandma’s friend? And do you know why you can stand outside
a government office with a sign and a bullhorn complaining about military action that you
think is unfair and the police can’t stop you, but you can be fired from your job for
doing the exact same thing? Have you ever been sued? Or fined? Ever wonder
what the difference is between being sued and being fined?
Have you ever wondered why the government does the things it does and why it doesn’t
do other things? Have you ever wondered what it would be like if we had no government at
all? That would be anarchy. Can we play the Sex Pistols, Stan? That’s probably illegal.
Why is it illegal? And probably the most important, have you
ever thought about how you can change the things that seem unjust or unfair or that
you just don’t like? Ok so that was more than one question, and
obviously there isn’t a single answer to all of those questions, except in a way, there
is. The study of government and politics. And that’s what we’re going to talk about
today, and this whole series: Crash Course Government and Politics – aptly titled. [Theme Music] So let’s start by doing what human beings
do when confronted with complicated questions they can’t answer. We’ll answer a simpler
one. In this case, what are government and politics and why do I need to learn about
them. Government is a set of rules and institutions
people set up so they can function together as a unified society. Sometimes we call this
a state, or a nation, or a country, or Guam. And I’ll use these terms somewhat interchangeably
– except for Guam, that might be a little confusing. So, we study government in order
to become better citizens. Studying government enables us to participate
in an informed way. Anyone can participate, but doing so intelligently that takes a little
effort, and that’s why we need to learn about how our government works.
Politics is a little different. Politics is a term we used to describe how power is distributed
in a government. And in the U.S it basically describes the decisions about who holds office
and how individuals and groups make those decisions.
Following politics is a lot like following sports in that there is a winner and a loser
and people spend a lot of time predicting who will win and analyzing why the winner
won and the loser lost. The outcome of an election might affect your
life more than the outcome of a sports game though. Unless you’re gambling – which might
be illegal. Government is really important. Everyone born
in America is automatically a citizen, and many people choose to become citizens every
year so that they can have a say in the government. The USA is a republic, which means that we
elect representatives to govern us, and a democracy, which means that citizens are allowed
to participate. This ability to participate is something we take for granted, but we shouldn’t.
History tells us that that citizen participation is the exception rather than the rule. But
we’re not going to look at history. Who has time? That’s what history courses are
for with that other guy. So one way people can participate in government
is through voting. And many people will tell you that that’s pretty much the only way
we can participate in government and politics, but THEY’RE WRONG. And I love pointing out
when people are wrong. Let’s go to the Thought Bubble. Sure, when you mark a ballot, you are participating
in the political process, but there are so many other things you can do to be an active citizen.
You can contact your representatives and tell them what you think about a political issue.
People used to do this by writing letters or sending telegrams, but now they tend to
call or send email, although there’s nothing like a good old-fashioned angry letter.
People can work for campaigns or raise money or give money. They can display yard signs
or bumper stickers. They can canvass likely voters, try to convince them to vote or even
drive them to the polls on election day. You participate in politics when you answer
a public opinion poll. Or when you write a letter to the editor or comment on an online
article. You participate in politics when you blog, or tumbl, or make a YouTube video,
or tweet. I guess even YouTube comment counts. First!
Ever been to a march or a rally or held a sign or worn a t-shirt with a slogan on it,
or discussed an upcoming election at the dinner table and tried to convince your parents who
to vote for? You’ve participated in the political process.
And if you’ve actually run for office you’ve participated, even if you didn’t win, and
if you did win, congratulations, now get back to work. You should already know this.
But probably the most important thing you can do to participate in government and politics
is both the easiest and the most challenging. Become more educated! Anyone can be a citizen,
but to be a good citizen requires an understanding of how government works, and how we can participate.
It requires knowledge and effort and we have to do it because otherwise we end up being
led rather than being leaders. We learn about politics because knowledge is our best defense
against unscrupulous people who will use our ignorance to get us to do things that they
want rather than what we think should be done. Thanks, Thought Bubble. That was my first
Thought Bubble narration! Hurray! You guys are fun. This is fun.
So that’s where we comes in. Over the course of this series we will be looking in depth
at American government and politics. We’ll be talking about stuff like the structure
and function of the branches of government, the division of power between the national
government and the state governments, what political parties are, what they do, and how
they are different from interest groups. We’ll examine the role the media plays in
government and politics, how the legal system and the courts work and how they protect civil
rights and civil liberties. We’ll look at political ideologies: what
it means when you say you are a liberal or a conservative or a libertarian or a socialist
or an anarchist – okay we probably won’t talk about anarchy because that’s sort of
the rejection of government. Again, Sex Pistols, Stan? Can’t… copyright issue. I’ll take care of it. ANARCHY – WOOO! I’ve
been known to do that from time to time. We’ll try to understand the forces that
are shaping American government and politics today. And we’ll work towards becoming more
involved and developing our knowledge so that we make our government more responsive and
our politics more inclusive. By the end of this series – and actually
before the end – you will understand how our government works and how you can make
it work better for you and your community. Not only will you be able to answer most of
the questions I started this episode with, but you will become, if you pay attention
and think for yourself, a more engaged and active citizen. And you might have a beard
– if you don’t shave. Next week we’ll talk about Congress, how
it works, and what it does, when it does anything. Thanks for watching, I’ll see you next week.
And that’s my first Crash Course episode! Are we out of poppers Stan? I’ll just throw
‘em… wooohoo! Bang! Wooo! Bang! Crash Course Government and Politics is produced
in association with PBS Digital Studios. Support for Crash Course U.S. Government comes from
Voqal. Voqal supports non-profits that use technology and media to advance social equity.
Learn more about their mission and initiatives at Voqal.org.
Crash Course was made by all of these nice people. Thanks for watching. Can we call Craig
Course, Stan? No? Crash Course Craig? …Can’t.

Federalism: Crash Course Government and Politics #4


Hi, I’m Craig and this is Crash Course Government
and Politics. And today we’re going to talk about a fundamental concept to American government:
federalism. Sorry. I’m not sorry. You’re not even endangered
anymore. Federalism is a little confusing because
it includes the word, “federal,” as in federal government, which is what we use to describe
the government of the United States as a whole. Which is kind of the opposite of what we mean
when we say federalism. Confused? Google it. This video will probably come up. And then just
watch this video. Or, just continue watching this video. [Theme Music] So what is federalism? Most simply, it’s the
idea that in the US, governmental power is divided between the government of the United
States and the government of the individual states. The government of the US, the national
government, is sometimes called the federal government, while the state governments are
just called the state governments. This is because technically the US can be considered
a federation of states. But this means different things to different people. For instance,
federation of states means ham sandwich to me. I’ll have one federation of states, please,
with a side of tater tots. Thank you. I’m kind of dumb. In the federal system, the national government
takes care of some things, like for example, war with other countries and delivering the
mail, while the state government takes care of other things like driver’s license, hunter’s
licenses, barber’s licences, dentist’s licenses, license to kill – nah, that’s James Bond.
And that’s in England. And I hope states don’t do that. Pretty simple right? Maybe not. For one thing,
there are some aspects of government that are handled by both the state and national
government. Taxes, American’s favorite government activity, are an example. There are federal
taxes and state taxes. But it gets even more complicated because there are different types
of federalism depending on what period in American history you’re talking about. UGH!
Stan! Why is history so confusing!? UGH! Stan, are you going to tell me? Can you talk Stan? Basically though, there are two main types
of federalism -dual federalism, which has nothing to do Aaron Burr, usually refers to
the period of American history that stretches from the founding of our great nation until
the New Deal, and cooperative federalism, which has been the rule since the 1930s. Let’s
start with an easy one and start with dual federalism in the Thought Bubble. From 1788 until 1937, the US basically lived
under a regime of dual federalism, which meant government power was strictly divided
between the state and national governments. Notice that I didn’t say separated, because
I don’t want you to confuse federalism with the separation of powers. DON’T DO IT! With
dual federalism, there are some things that only the federal government does and some
things that only the state governments do. This is sometimes called jurisdiction. The national government had jurisdiction over
internal improvements like interstate roads and canals, subsidies to the states, and tariffs,
which are taxes on imports and thus falls under the general heading of foreign policy.
The national government also owns public lands and regulates patents which need to be national
for them to offer protection for inventors in all the states. And because you want a
silver dollar in Delaware to be worth the same as a silver dollar in Georgia, the national
government also controls currency. The state government had control over property
laws, inheritance laws, commercial laws, banking laws, corporate laws, insurance, family law,
which means marriage and divorce, morality — stuff like public nudeness and drinking
– which keeps me in check — public health, education, criminal laws including determining
what is a crime and how crimes are prosecuted, land use, which includes water and mineral
rights, elections, local government, and licensing of professions and occupations, basically
what is required to drive a car, or open a bar or become a barber or become James Bond. So, under dual federalism, the state government
has jurisdiction over a lot more than the national government. These powers over health,
safety and morality are sometimes called police power and usually belong to the states. Because
of the strict division between the two types of government, dual federalism is sometimes
called layer cake federalism. Delicious. And it’s consistent with the tradition of limited
government that many Americans hold dear. Thanks Thought Bubble. Now, some of you might be wondering, Craig,
where does the national government get the power to do anything that has do to with states?
Yeah, well off the top of my head, the US Constitution in Article I, Section 8 Clause
3 gives Congress the power “to regulate commerce with foreign nations, and among the several
states, and with the Indian tribes.” This is what is known as the Commerce Clause, and
the way that it’s been interpreted is the basis of dual federalism and cooperative federalism. For most of the 19th century, the Supreme
Court has decided that almost any attempt by any government, federal or state, to regulate
state economic activity would violate the Commerce Clause. This basically meant that
there was very little regulation of business at all. FREEDOOOOOOMM! And this is how things stood, with the US following
a system of dual federalism, with very little government regulation and the national government
not doing much other than going to war or buying and conquering enormous amounts of
territories and delivering the mail. Then the Great Depression happened, and Franklin
Roosevelt and Congress enacted the New Deal, which changed the role of the federal government
in a big way. The New Deal brought us cooperative federalism, where the national government
encourages states and localities to pursue nationally-defined goals. The main way that
the federal government does this is through dollar-dollar bills, y’all. Money is what
I’m saying. Stan, can I make it rain? Yeah? All right, I’m doing it. I happen to have cash in my
hand now. Oh yeah, take my federal money, states. Regulating ya. Regulator. This money that the federal government gives
to the states is called a grant-in-aid. Grants-in-aid can work like a carrot encouraging a state
to adopt a certain policy or work like a stick when the federal government withholds funds
if a state doesn’t do what the national government wants. Grants-in-aid are usually called categorical,
because they’re given to states for a particular purpose like transportation or education or
alleviating poverty. There are 2 types of categorical grants-in-aid:
formula grants and project grants. Under a formula grant, a state gets aid in a certain
amount of money based on a mathematical formula; the best example of this is the old way welfare
was given in the US under the program called Aid to Families with Dependent Children. AFDC.
States got a certain amount of money for every person who was classified as “poor.” The more
poor people a state had, the more money it got. Project grants require states to submit
proposals in order to receive aid. The states compete for a limited pool of resources. Nowadays,
project grants are more common than formula grants, but neither is as popular as block
grants, which the government gives out Lego Blocks and then you build stuff with Legos.
It’s a good time. No no, the national government gives a state
a huge chunk of money for something big, like infrastructure, which is made with concrete
and steel, and not Legos, and the state is allowed to decide how to spend the money.
The basic type of cooperative federalism is the carrot stick type which is sometimes called
marble cake federalism because it mixes up the state and federal governments in ways
that makes it impossible to separate the two. Federalism, it’s such a culinary delight. The key to it is, you guessed it — dollar
dollar bills y’all. Money. But there’s another aspect of cooperative federalism that’s really
not so cooperative, and that’s regulated federalism. Under regulated federalism, the national governments
sets up regulations and rules that the states must follow. Some examples of these rules,
also called mandates, are EPA regulations, civil rights standards, and the rules set
up by the Americans with Disabilities Act. Sometimes the government gives the states
money to implement the rules, but sometimes it doesn’t and they must comply anyways. That’s
called an unfunded mandate. Or as I like to call it, an un-fun mandate. Because no money,
no fun. A good example of example of this is OSHA regulations that employers have to
follow. States don’t like these, and Congress tried
to do something about them with the Unfunded Mandates Reform Act or UMRA, but it hasn’t
really worked. In the early 21st century, Americans are basically living under a system
of cooperative federalism with some areas of activity that are heavily regulated. This
is a stretch from the original idea that federalism will keep the national government small and
have most government functions belong to the states. If you follow American politics, and I know
you do, this small government ideal should sound familiar because it’s the bedrock principle
of many conservatives and libertarians in the US. As conservatives made many political
inroads during the 1970s, a new concept of federalism, which was kind of an old concept
of federalism, became popular. It was called, SURPRISE, New Federalism, and it was popularized
by Presidents Nixon and Reagan. Just to be clear, it’s called New Federalism
not Surprise New Federalism. New Federalism basically means giving more power to the states,
and this has been done in three ways. First, block grants allow states discretion to decide
what to do with federal money, and what’s a better way to express your power than spending
money? Or not spending money as the case may be. Another form of New Federalism is devolution,
which is the process of giving state and local governments the power to enforce regulations,
devolving power from the national to the state level. Finally, some courts have picked up
the cause of New Federalism through cases based on the 10th Amendment, which states
“The powers not delegated to the United States by the Constitution, nor prohibited by it
to the States, are reserved to the States respectively, or to the people.” The idea that some
powers, like those police powers I talked about before, are reserved by the states, have been used
to put something of a brake on the Commerce Clause. So as you can see, where we are with federalism
today is kind of complicated. Presidents Reagan, George H.W. Bush, and Clinton seem to favor
New Federalism and block grants. But George W. Bush seemed to push back towards regulated
federalism with laws like No Child Left Behind and the creation of the Department of Homeland
Security. It’s pretty safe to say that we’re going to continue to live under a regime of
cooperative federalism, with a healthy dose of regulation thrown in. But many Americans
feel that the national government is too big and expensive and not what the framers wanted. If history is any guide, a system of dual
federalism with most of the government in the hands of the states is probably not going
to happen. For some reason, it’s really difficult to convince institutions to give up powers
once they’ve got them. I’m never giving up this power. Thanks for watching, I’ll see
you next week. Crash Course Government and Politics is produced
in association with PBS Digital Studios. Support for Crash Course US Government comes from
Voqal. Voqal supports non-profits that use technology and media to advance social equity.
Learn more about their mission and initiatives at Voqal.org. Crash Course is made with the
help of these nice people. Thanks for watching. You didn’t help make this video at all, did
you? No. But you did get people to keep watching until the end because you’re an adorable dog.

Let’s make an AI that destroys video games: Crash Course AI #13


Jabril: John Green Bot are you serious?! I made this game and you beat my high score? John-Green-bot: Pizza! Jabril: So John Green Bot is pretty good at Pizza Jump, but what about this new game we made, TrashBlaster? John-Green-bot: Hey, that’s me! Jabril:Yeah, let’s see watch you’ve got. John-Green-bot: That’s not fair, Jabril!! Jabril: It’s okay John Green Bot we’ve got you covered. Today we’re gonna design and build an AI
program to help you play this game like a pro. INTRO Hey, I’m Jabril and welcome to Crash Course
AI! Last time, we talked about some of the ways
that AI systems learn to play games. I’ve been playing video games for as long
as I can remember. They’re fun, challenging, and tell interesting
stories where the player gets to jump on goombas or build cities or cross the road or flap
a bird. But games are also a great way to test AI
techniques because they usually involve simpler worlds than the one we live in. Plus, games involve things that humans are
often pretty good at like strategy, planning, coordination, deception, reflexes, and intuition. Recently, AIs have become good at some tough
games, like Go or Starcraft II. So our goal today is to build an AI to play
a video game that our writing team and friends at Thought Cafe designed called TrashBlaster! The player’s goal in TrashBlaster is to
swim through the ocean as a little virtual John-Green-bot, and destroy pieces of trash. But we have to be careful, because if John-Green-bot
touches a piece of trash, then he loses and the game restarts. Like in previous labs, we’ll be writing
all of our code using a language called Python in a tool called Google Colaboratory. And as you watch this video, you can follow
along with the code in your browser from the link we put in the description. In these Colaboratory files, there’s some
regular text explaining what we’re trying to do, and pieces of code that you can run
by pushing the play button. These pieces of code build on each other,
so keep in mind that we have to run them in order from top to bottom, otherwise we might
get an error. To actually run the code and experiment with
changing it, you’ll have to either click “open in playground” at the top of the
page or open the File menu and click “Save a Copy to Drive”. And just an fyi: you’ll need a Google account
for this. So to create this game-playing AI system,
first, we need to build the game and set up everything like the rules and graphics. Second, we’ll need to think about how to
create a TrashBlaster AI model that can play the game and learn to get better. And third, we’ll need to train the model
and evaluate how well it works. Without a game, we can’t do anything. So we’ve got to start by generating all
the pieces of one. To start, we’re going to need to fill up
our toolbox by importing some helpful libraries, such as PyGame. The first step in 1.1 and 1.2 loads the libraries,
and step 1.3 saves the game so we can watch it later. This might take a second to download. The basic building blocks of any game are
different objects that interact with each other. There’s usually something or someone the
player controls and enemies that you battle — All these objects and their interactions
with one another need to be defined in the code. So to make TrashBlaster, we need to define
three objects and what they do: a blaster, a hero, and trash to destroy. The blaster is what actually destroys the
trash, so we’re going to load an image that looks like a laser-ball and set
some properties. How far does it go, what direction does it
fly, and what happens to the blast when it hits a piece of trash? Our hero is John-Green-bot, so now we’ve
got to load his image, and define properties like how fast he can swim and how a blast appears when he uses his blaster. And we need to load an image for the trash pieces, and then code how they move and what happens if they get hit by a
blast, like, for example, total destruction or splitting into 2 smaller pieces. Finally, all these objects are floating in
the ocean, so we need a piece of code to generate the background. The shape of this game’s ocean is toroidal,
which means it wraps around, and if any object flies off the screen to the right, then it
will immediately appear on the far left side. Every game needs some way to track how the player’s doing, so we’ll show the score too. Now that we have all the pieces in place,
we can actually build the game and decide how everything interacts. The key to how everything fits together is
the run function. It’s a loop of checking whether the game
is over; moving all the objects; updating the game; checking whether our hero is okay;
and making new trash. As long as our hero hasn’t bumped into any
trash, the game continues. That’s pretty much it for the game mechanics. We’ve created a hero, a blaster, trash,
and a scoreboard, and code that controls their interactions. Step 2 is modeling the AI’s brain so John-Green-bot
can play! And for that, we can turn back to our old
friend the neural network. When I play games, I try to watch for the
biggest threat because I don’t want to lose. So let’s program John-Green-bot to use a
similar strategy. For his neural network’s input layer, let’s
consider the 5 pieces of trash that are closest to his avatar. (And remember, the closest trash might actually
be on the other side of the screen!) Really, we want John-Green-bot to pay attention
to where the trash is and where it’s going. So we want the X and Y positions relative
to the hero, the X and Y velocities relative to the hero, and the size of each piece of
trash. That’s 5 inputs for 5 pieces of trash, so
our input layer is going to have 25 nodes. For the hidden layers, let’s start small
and create 2 layers with 15 nodes each. This is just a guess, so we can change it
later if we want. Because the output of this neural network
is gameplay, we want the output nodes to be connected to the movement of the hero and
shooting blasts. So there will be 5 nodes total: an X and Y
for movement, an X and Y direction for aiming the blaster, and whether or not to fire the
blaster. To start, the weights of the neural network
are initialized to 0, so the first time John-Green-bot plays he basically sits there and does nothing. To train his brain with regular supervised
learning, we’d normally say what the best action is at each timestep. But because losing TrashBlaster depends on
lots of collective actions and mistakes, not just one key moment, supervised learning might
not be the right approach for us. Instead, we’ll use reinforcement learning
strategies to train John-Green-bot based on all the moves he makes from the beginning
to the end of a game, and we’ll evolve a better AI using a genetic algorithm which
is commonly referred to as GA. To start, we’ll create some number of John-Green-bots
with empty brains (let’s say 200), and we’ll have them play
TrashBlaster. They’re all pretty terrible, but because
of luck, some will probably be a little bit less terrible. In biological evolution, parents pass on most
of their characteristics to their offspring when they reproduce. But the new generation may have some small
differences, or mutations. To replicate this, we’ll use code to take
the 100 highest-scoring John-Green-bots and clone each of them as our reproduction step. Then, we’ll slightly and randomly change
the weights in those 100 cloned neural networks, which is our mutation step. Right now, we’ll program a 5% chance that
any given weight will be mutated, and randomly choose how much that weight mutates (so it
could be barely any change or a huge one). And you could experiment with this if you
like. Mutation affects how much the AI changes overall,
so it’s a little bit like the learning rate that we talked about in previous episodes. We have to try and balance steadily improving
each generation with making big changes that might be really helpful (or harmful). After we’ve created these 100 mutant John-Green-bots,
we’ll combine them with the 100 unmutated original models (just in case the mutations
were harmful) and have them all play the game. Then we evaluate, clone, and mutate them over
and over again. Over time, the genetic algorithm usually makes
AI that are gradually better at whatever they’re being asked to do, like play TrashBlaster. This is because models with better mutations
will be more likely to score high and reproduce in the future. ALL of this stuff, from building John-Green-bot’s
neural network to defining mutation for our genetic algorithm, are in this section of
code. After setting up all that, we have to write
code to carefully define what doing “better” at the game means. Destroying a bunch of trash? Staying alive for a long time? Avoiding off-target blaster shots? Together, these decisions about what “better”
means define an AI model’s fitness. Programming this function is pretty much the
most important part of this lab, because how we define fitness will affect how John-Green-bot’s
AI will evolve. If we don’t carefully balance our fitness
function, his AI could end up doing some pretty weird things. For example, we could just define fitness
as how long the player stays alive, but then John-Green-bot’s AI might play TrashAvoider
and dodge trash instead of TrashBlaster and destroy trash. But if we define the fitness to only be related
to how many trash pieces are destroyed, we might get a wild hero that’s constantly
blasting. So, for now, I’m going to try a fitness
function that keeps the player alive and blasts trash. We’ll define the fitness as +1 for every
second that John-Green-bot stays alive, and +10 for every piece of trash that is zapped. But it’s not as fun if the AI just blasts
everywhere, so let’s also add a penalty of -2 for every blast he fires. The fitness for each John-Green-bot AI will
be updated continuously as he plays the game, and it’ll be shown on the scoreboard we
created earlier. You can take some time to play around with
this fitness function and watch how John-Green-bot’s AI can learn and evolve differently. Finally, we can move onto Step 3 and actually train John-Green-bot’s AI to blast some trash! So first, we need to start up our game. And to kick off the genetic algorithm, we
have to define how many randomly-wired John-Green-bot models we want in our starting population. Let’s stick with 200 for now. If we waited for each John-Green-bot model
to start, play, and lose the game… this training process could take DAYS. But because our computer can multitask, we
can use a multiprocessing package to make all 200 AI models play separate games at the
same time, which will be MUCH faster. And this is all part of the training. This is where we’ll code in the details
of the genetic algorithm, like sorting John-Green-bots by their fitness and choosing which ones will
reproduce. Now that we have the 100 John-Green-bots that
we want to reproduce, this code will clone and mutate them so we have that combined group
of 100 old and 100 mutant AI models. Then, we can run 200 more games for these
200 John-Green-bots. It just takes a few seconds to go through
them all thanks to that last chunk of code. And we can see how well they do! The average score of the AI models that we
picked to reproduce is almost twice as high as the overall average. Which is good! It means that the John-Green-bot is learning
something. We can even watch a replay of the best AI. Uh… even the best isn’t very exciting
right now. We can see the fitness function changing as
time passes, but the hero’s just sitting there not getting hit and shooting forward
– we want John-Green-bot to actually play, not just sit still and get lucky. We can also see visual representation of this
specific neural network, where higher weights are represented by the redness of the connections. It’s tough to interpret what exactly this
diagram means, but we can keep it in mind as we keep training John-Green-bot. Genetic algorithms take time to evolve a good
model. So let’s change the number of iterations
in the loop in STEP 3.3, and run the training step 10 times to repeatedly copy, mutate, and test the fitness of these AI models. Okay, now I’ve trained 10 more iterations. And if I view a replay of the last game, we
can see that John-Green-bot is doing a little better. He’s moving around a little and actually
sort of aiming. If we keep training, one model might get lucky,
destroy a bunch of trash, has a high fitness, and gets copied and mutated to make future
generations even better. But John-Green-bot needs lots of iterations
to get really good at TrashBlaster. You might consider changing the number of
iterations to 50 or 100 times per click… which might take a while. Now here’s an example of a game after 15,600
training iterations just look at John-Green-bot swimming and blasting trash like a pro. And all this was done using a genetic algorithm, raw luck, and a carefully crafted fitness function. Genetic algorithms tend to work pretty well
on small problems like getting good at TrashBlaster. When the problems get bigger, the random mutations
of genetic algorithms are sometimes… well, too random to create consistently good results. So part of the reason this works so well is
because John-Green-bot’s neural network is pretty tiny compared to many AIs created
for industrial-sized problems. But still, it’s fun to experiment with AI
and games like TrashBlaster. For example, you can try to change the values
of the fitness function and see how John-Green-bot’s AI evolves differently. Or you could change how the neural network
gets mutated, like by messing with the structure instead of the weights. Or you could change how much the run function
loops per second, from 5 times a second to 10 or 20, and give John-Green-bot superhuman
reflexes. You can download the clip of your AI playing
TrashBlaster by looking for game_animation.gif in the file browser on the left-hand side
of the Colaboratory file. You can also download source code from Github
to run on your own computer if you want to experiment (we’ll leave a link in the description). And next time, we’ll start shifting away
from games and learn about other ways that humans and AI can work together in teams. See ya then. Crash Course AI is produced in association
with PBS Digital Studios. If you want to help keep Crash Course free
for everyone, forever, you can join our community on Patreon. And if you want to learn more about genetics
and evolution check out Crash Course Biology.


Hello world, I’m Carrie Anne, and welcome
to CrashCourse Computer Science! Over the course of this series, we’re going
to go from bits, bytes, transistors and logic gates, all the way to Operating Systems, Virtual
Reality and Robots! We’re going to cover a lot, but just to
clear things up – we ARE NOT going to teach you how to program. Instead, we’re going to explore a range
of computing topics as a discipline and a technology. Computers are the lifeblood of today’s world. If they were to suddenly turn off, all at
once, the power grid would shut down, cars would crash, planes would fall, water treatment
plants would stop, stock markets would freeze, trucks with food wouldn’t know where to
deliver, and employees wouldn’t get paid. Even many non-computer objects – like DFTBA
shirts and the chair I’m sitting on – are made in factories run by computers. Computing really has transformed nearly every
aspect of our lives. And this isn’t the first time we’ve seen
this sort of technology-driven global change. Advances in manufacturing during the Industrial
Revolution brought a new scale to human civilization – in agriculture, industry and domestic life. Mechanization meant superior harvests and
more food, mass produced goods, cheaper and faster travel and communication, and usually
a better quality of life. And computing technology is doing the same
right now – from automated farming and medical equipment, to global telecommunications and
educational opportunities, and new frontiers like Virtual Reality and Self Driving Cars. We are living in a time likely to be remembered
as the Electronic Age. With billions of transistors in just your
smartphones, computers can seem pretty complicated, but really, they’re just simple machines
that perform complex actions through many layers of abstraction. So in this series, we’re going break down
those layers, and build up from simple 1’s and 0’s, to logic units, CPUs, operating
systems, the entire internet and beyond. And don’t worry, in the same way someone
buying t-shirts on a webpage doesn’t need to know how that webpage was programmed, or
the web designer doesn’t need to know how all the packets are routed, or router engineers
don’t need to know about transistor logic, this series will build on previous episodes
but not be dependent on them. By the end of this series, I hope that you
can better contextualize computing’s role both in your own life and society, and how
humanity’s (arguably) greatest invention is just in its infancy, with its biggest impacts
yet to come. But before we get into all that, we should
start at computing’s origins, because although electronic computers are relatively new, the
need for computation is not. INTRO The earliest recognized device for computing was the abacus, invented in Mesopotamia around
2500 BCE. It’s essentially a hand operated calculator,
that helps add and subtract many numbers. It also stores the current state of the computation,
much like your hard drive does today. The abacus was created because, the scale
of society had become greater than what a single person could keep and manipulate in
their mind. There might be thousands of people in a village
or tens of thousands of cattle. There are many variants of the abacus, but
let’s look at a really basic version with each row representing a different power of
ten. So each bead on the bottom row represents
a single unit, in the next row they represent 10, the row above 100, and so on. Let’s say we have 3 heads of cattle represented
by 3 beads on the bottom row on the right side. If we were to buy 4 more cattle we would just
slide 4 more beads to the right for a total of 7. But if we were to add 5 more after the first
3 we would run out of beads, so we would slide everything back to the left, slide one bead
on the second row to the right, representing ten, and then add the final 2 beads on the
bottom row for a total of 12. This is particularly useful with large numbers. So if we were to add 1,251 we would just add
1 to the bottom row, 5 to the second row, 2 to the third row, and 1 to the fourth row
– we don’t have to add in our head and the abacus stores the total for us. Over the next 4000 years, humans developed
all sorts of clever computing devices, like the astrolabe, which enabled ships to calculate
their latitude at sea. Or the slide rule, for assisting with multiplication
and division. And there are literally hundred of types of
clocks created that could be used to calculate sunrise, tides, positions of celestial bodies,
and even just the time. Each one of these devices made something that
was previously laborious to calculate much faster, easier, and often more accurate –– it
lowered the barrier to entry, and at the same time, amplified our mental abilities –– take
note, this is a theme we’re going to touch on a lot in this series. As early computer pioneer Charles Babbage
said: “At each increase of knowledge, as well as on the contrivance of every new tool,
human labour becomes abridged.” However, none of these devices were called
“computers”. The earliest documented use of the word “computer”
is from 1613, in a book by Richard Braithwait. And it wasn’t a machine at all – it was
a job title. Braithwait said,
“I have read the truest computer of times, and the best arithmetician that ever breathed,
and he reduceth thy dayes into a short number”. In those days, computer was a person who did
calculations, sometimes with the help of machines, but often not. This job title persisted until the late 1800s,
when the meaning of computer started shifting to refer to devices. Notable among these devices was the Step Reckoner,
built by German polymath Gottfried Leibniz in 1694. Leibniz said “… it is beneath the dignity
of excellent men to waste their time in calculation when any peasant could do the work just as
accurately with the aid of a machine.” It worked kind of like the odometer in your
car, which is really just a machine for adding up the number of miles your car has driven. The device had a series of gears that turned;
each gear had ten teeth, to represent the digits from 0 to 9. Whenever a gear bypassed nine, it rotated
back to 0 and advanced the adjacent gear by one tooth. Kind of like when hitting 10 on
that basic abacus. This worked in reverse when doing subtraction,
too. With some clever mechanical tricks, the Step
Reckoner was also able to multiply and divide numbers. Multiplications and divisions are really just
many additions and subtractions. For example, if we want to divide 17 by 5,
we just subtract 5, then 5, then 5 again, and then we can’t subtract any more 5’s…
so we know 5 goes into 17 three times, with 2 left over. The Step Reckoner was able to do this in an
automated way, and was the first machine that could do all four of these operations. And this design was so successful it was used
for the next three centuries of calculator design. Unfortunately, even with mechanical calculators,
most real world problems required many steps of computation before an answer was determined. It could take hours or days to generate a
single result. Also, these hand-crafted machines were expensive,
and not accessible to most of the population. So, before 20th century, most people experienced
computing through pre-computed tables assembled by those amazing “human computers” we
talked about. So if you needed to know the square root of
8 million 6 hundred and 75 thousand 3 hundred and 9, instead of spending all day hand-cranking
your step reckoner, you could look it up in a huge book full of square root tables in
a minute or so. Speed and accuracy is particularly important
on the battlefield, and so militaries were among the first to apply computing to complex
problems. A particularly difficult problem is accurately
firing artillery shells, which by the 1800s could travel well over a kilometer (or a bit
more than half a mile). Add to this varying wind conditions, temperature,
and atmospheric pressure, and even hitting something as large as a ship was difficult. Range Tables were created that allowed gunners
to look up environmental conditions and the distance they wanted to fire, and the table
would tell them the angle to set the canon. These Range Tables worked so well, they were
used well into World War Two. The problem was, if you changed the design
of the cannon or of the shell, a whole new table had to be computed, which was massively
time consuming and inevitably led to errors. Charles Babbage acknowledged this problem
in 1822 in a paper to the Royal Astronomical Society entitled: “Note on the application
of machinery to the computation of astronomical and mathematical tables”. Let’s go to the thought bubble. Charles Babbage proposed a new mechanical
device called the Difference Engine, a much more complex machine that could approximate
polynomials. Polynomials describe the relationship between
several variables – like range and air pressure, or amount of pizza Carrie Anne eats and happiness. Polynomials could also be used to approximate
logarithmic and trigonometric functions, which are a real hassle to calculate by hand. Babbage started construction in 1823, and
over the next two decades, tried to fabricate and assemble the 25,000 components, collectively
weighing around 15 tons. Unfortunately, the project was ultimately abandoned. But, in 1991, historians finished constructing
a Difference Engine based on Babbage’s drawings and writings – and it worked! But more importantly, during construction
of the Difference Engine, Babbage imagined an even more complex machine – the Analytical
Engine. Unlike the Difference Engine, Step Reckoner
and all other computational devices before it – the Analytical Engine was a “general
purpose computer”. It could be used for many things, not just
one particular computation; it could be given data and run operations in sequence; it had
memory and even a primitive printer. Like the Difference Engine, it was ahead of
its time, and was never fully constructed. However, the idea of an “automatic computer”
– one that could guide itself through a series of operations automatically, was a
huge deal, and would foreshadow computer programs. English mathematician Ada Lovelace wrote hypothetical
programs for the Analytical Engine, saying, “A new, a vast, and a powerful language
is developed for the future use of analysis.” For her work, Ada is often considered the
world’s first programmer. The Analytical Engine would inspire, arguably,
the first generation of computer scientists, who incorporated many of Babbage’s ideas
in their machines. This is why Babbage is often considered the
“father of computing”. Thanks Thought Bubble! So by the end of the 19th century, computing
devices were used for special purpose tasks in the sciences and engineering, but rarely
seen in business, government or domestic life. However, the US government faced a serious
problem for its 1890 census that demanded the kind of efficiency that only computers
could provide. The US Constitution requires that a census
be conducted every ten years, for the purposes of distributing federal funds, representation
in congress, and good stuff like that. And by 1880, the US population was booming,
mostly due to immigration. That census took seven years to manually compile
and by the time it was completed, it was already out of date – and it was predicted that
the 1890 census would take 13 years to compute. That’s a little problematic when it’s
required every decade! The Census bureau turned to Herman Hollerith,
who had built a tabulating machine. His machine was “electro-mechanical” – it
used traditional mechanical systems for keeping count, like Leibniz’s Step Reckoner –– but
coupled them with electrically-powered components. Hollerith’s machine used punch cards which
were paper cards with a grid of locations that can be punched out to represent data. For example, there was a series of holes for
marital status. If you were married, you would punch out the
married spot, then when the card was inserted into Hollerith’s machine, little metal pins
would come down over the card – if a spot was punched out, the pin would pass through
the hole in the paper and into a little vial of mercury, which completed the circuit. This now completed circuit powered an electric
motor, which turned a gear to add one, in this case, to the “married” total. Hollerith’s machine was roughly 10x faster
than manual tabulations, and the Census was completed in just two and a half years – saving
the census office millions of dollars. Businesses began recognizing the value of
computing, and saw its potential to boost profits by improving labor- and data-intensive
tasks, like accounting, insurance appraisals, and inventory management. To meet this demand, Hollerith founded The
Tabulating Machine Company, which later merged with other machine makers in 1924 to become
The International Business Machines Corporation or IBM – which you’ve probably heard of. These electro-mechanical “business machines”
were a huge success, transforming commerce and government, and by the mid-1900s, the
explosion in world population and the rise of globalized trade demanded even faster and
more flexible tools for processing data, setting the stage for digital computers, which we’ll
talk about next week.