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ЩΉӨ BЦIᄂƬ ƬΉΣ PYЯΛMIDƧ

November 20, 2019 | Articles, Blog | 100 Comments

ЩΉӨ BЦIᄂƬ ƬΉΣ PYЯΛMIDƧ


[PBS Intro] This episode is supported by 23 and Me A long time ago a guy built a tomb out of
rocks so he could live in it after he died and not be dead. His son was like “Hey that’s cool” so
he built one too.. Then his son was like “Me too” so he
made a third and they were all buried there. And that’s how we got this. The pyramids of Giza. How did people who hadn’t even invented
the wheel build these things, and… why? They’re so big! They’re so precise! They’re so directionally oriented! They’re so mysterrrrrrious. At first glance they really do look out-of-this
world. Thing is, the pyramids are much older than
you probably think. They were already ancient history to people
IN ancient history, which led to some pretty wild theories about how they came to be. But pyramid technology didn’t just show
up out of nowhere. It was the end product of centuries of scientific
and cultural evolution, of people… figuring it out. And it definitely wasn’t aliens. [OPEN] Early on, Egyptians buried their dead like
we do. The desert naturally mummified some corpses,
which influenced their religious beliefs: You need to preserve the body to reach the
afterlife, and when you get there you’ll need all your stuff. Rich people’s graves had nicer stuff, and
they needed to protect their afterlife investment. First with simple mounds, and later with mud
brick “eternal houses”. Then a king named Djoser was like “Why have
one little mud mastaba when I can have six stone mastabas in a stack?” so he stacked
six stone mastabas like a mastaba boss and the age of the pyramids had begun. This was literally the first time humans had
piled stone this high. Egyptians knew totally vertical walls got
less stable as they got taller, so Djoser’s architect stacked bricks at an incline and
let gravity do the work. Step pyramid achieved! Why pyramids and not other shapes? If you want to make a big pile of blocks,
a pyramid gets you the most stability for the least material. A third of the way up, you’ve already laid
two-thirds of your stone. Halfway, you’ve placed more than 80%. Next comes Sneferu, Mr. Pyramid. He built his own step pyramid, but then decided
he wanted a smooth one instead, so they started on a second. No one had ever built one of those before,
so they made some mistakes. For starters, they built it on sand, which
is soft, they laid blocks carelessly, and it was too steep, so halfway through they
changed the slope and ended up with this. Sneferu was like “you’re not burying me
in that”, so he ordered a third pyramid! Only this time they built a solid foundation,
laid the stones in horizontal rows, and precision cut the edges. Sneferu’s motto? If at first you don’t succeed, try again,
and then try again one more time. Sneferu had experimented his way to a blueprint
for building awesome pyramids The Great Pyramid at Giza, built by his son
Khufu, took that blueprint to the next level. Khufu’s pyramid remained the tallest structure
on Earth for almost 4000 years, until some church tower in the year 1311, which fell
down, so it was tallest again until this radio antenna was finished in 1889. Khufu’s son Khafre built his pyramid right
next to dad’s, and he didn’t stop innovating. Instead of leveling the entire 46,000 square
meter footprint, he built his pyramid over a natural stone mound and only leveled the
outer edge, which was less work, duh! It’s 3 meters shorter than his dad’s,
but this higher ground creates the illusion that Khafre’s pyramid is taller. Kids, amirite? But even these seemingly perfect pyramids
weren’t without mistakes. Khafre’s had a slight twist near the top
in order to make the edges line up evenly. What’s remarkable is Egypt’s biggest stone
pyramids were the product of just three human generations, but those were generations full
of trial and error. Pyramid building continued for nearly 700
years, and like any product, efficiency started to win out over quality. Precision-cut cores were replaced by rough-cut
blocks. Kings still wrapped their pyramids in fine
white limestone, but over the next thousand years that was removed by stone stealers and
rock robbers, leaving the cheaply-produced cores to collapse into rubble, which is probably
why you’ve never heard of them. Ironically, the kings were probably disappointed
by the whole afterlife thing, but the pyramids themselves have proven to be surprisingly
resilient. Ancient is not a synonym for stupid. The world’s first skyscrapers were tombs,
and just like our own buildings, they didn’t spring up out of nowhere, they were the product
of centuries of engineering trial and error. Go back 500 years and show someone a smartphone
and they’d probably think you were a wizard. But when we look back from the present at
the ideas and failures along the way, we see that it’s not magic at all! It’s science. And if you still think aliens did it, you’re
in de-Nile. You know, the river. Stay curious.

Why I’m Scared of Spiders

November 10, 2019 | Articles | No Comments


[MUSIC] [MUSIC] I’m scared of spiders. Not afraid to admit
it. I like pictures of them, but not a fan of the 3-D version. When I was 17, I got bitten
by one of these, and since then my policy is strictly arachNOPE. Keep at least three
feet between me and any spider, and if I walk through a web I’ll be like [SCREAMING] Yet out of 50,000 or so known spider species,
only a couple dozen have venom that could hurt me. I’m a rational guy, but I’ve
got a case of irrational fear. I’m not alone. According to the American
Psychiatric Association, 40% of phobias have to do with things like insects, snakes, and
mice, and … spiders. Some of us don’t care for those eight-legged
terrors thanks to a phenomenon called conditioning. Not the kind that has to do with soft, silky
hair, but because of a past traumatic experience that… ugh. Studies show that many people don’t even
have to have encountered a spider before being afraid of them, and that arachnid aversion
is heritable, so there might be genetics at play. And even if they don’t fear them,
children are able to pick out images of spiders and snakes faster than images of non-threatening
animals, like bunnies. We must have evolved some sort of built-in
creepy-crawly detection system for strange slithery movements or a few too many legs,
a spidey sense for spideys. That’s just the kind of thing that might
have kept our ancestors safe from possibly deadly encounters. Or just kept them from
walking through spider webs and looking like idiots. And then, there’s roaches. Slimy, stinky,
speedy little drawer demons. I like to consider myself a tough guy, but some of these things
have wings, man! That’s just not fair! [SCREAMING] The jittery way they sprint across the wall
is the same kind of non-standard movement that triggers our creepiness alarm. And their
slimy, stinky nature triggers our disgust response. That’s the instinct that drives
us away from things like spoiled food, vomit, or feces, and other disease-ridden stuff. But again, some of our roach fear might be
due to conditioning, seeing our parents jump at the sight of them at a young age, when
our brains are soaking up cues from other people on how to interpret the world. [SCARY MUSIC] [SCREAMING] But spiders and roaches aren’t going anywhere,
and we know they are here to stay, so we’d better get used to them. Luckily, scientists
say there might be a way to reduce our fear by exposing our brains to it over and over. Happy Halloween! Where is it? Get it off!

Fact vs. Theory vs. Hypothesis vs. Law… EXPLAINED!


[MUSIC] We need to get something straight. Evolution by natural selection is a theory.
So is climate change. But people keep saying that like it’s a bad thing… [MUSIC] I get it, I understand your frustration. We’re
all searching for ultimate hashtag #truth, and complex, challenging ideas don’t always
fit nice and neatly in our brains. But what is truth? Are there different levels
of truth? Are some truths truthier than others? I don’t know. But I do know this: Science
is the absolute best tool we have for understanding how the universe works, and theory is not
a 4-letter word. If we’re going to trust science together,
the least we can do is speak the same language. Words like “fact” “theory” “hypothesis”
and “law” mean something totally different to a scientist than the way they’re used in
everyday speech, so let’s get them straight. Facts are really just observations about the
world around us. And we observe things every day, like that
it’s bright outside when I look out the window, and we often develop explanations
for those observations , like “okay, the sun is probably up”
Congrats! We just developed a hypothesis! But a hypothesis isn’t something you prove,
it is something you test. So… let’s walk outside! It’s bright, the sun is up, hypothesis confirmed! Way to go! We did a science! [MUSIC] We often come up with multiple hypotheses
to explain an observation, we just eliminate the ones that are wrong. What’s left over
is not a theory or a law or an “Ultimate Truth”, it’s just a possible explanation for something,
one that can lead us to new hypotheses, which may agree or disagree with the original one.
It’s a never-ending story… only without the big fluffy dragons. “That’s so good!” When enough hypotheses have gotten the ol’
scientific check mark, we can pile these all up and turn them into something greater: a
theory. A theory is the way we know something works,
based on the evidence we’ve collected and all the hypotheses that we’ve successfully
put to the test. The best thing about a theory is that we can use it to make predictions,
and not just about the way things are, but how they will be. You may have heard someone say something like,
“I have a theory about why cats purr, I think it’s because they’re actually tiny
robots, and those are their gears” Well that’s not a theory. That’s actually
a hypothesis, it’s something that could be tested. This cycle, taking facts and observations,
thinking up possible explanations, testing those explanations, and then making predictions
based upon them… that’s what this whole science thing is about! Being a theory isn’t a bad thing, it means
that idea got the gold star, the blue ribbon, a big shiny trophy that says “Countless
experiments have shown that I’m sufficient to explain all the observations that I encompass” To see if you’ve got this down, let’s
look at some examples. FACT: People get sick. I think we can all
accept that. HYPOTHESIS: People get sick because something
gets in their body and starts doing bad things. Test each hypothesis, throw out the bad ones,
and we’re left with a framework that lets us understand why we get sick and make predictions,
the Germ Theory of Disease. Let’s try another! “Evolution” is a fact. We know that it happens,
no doubt. But how does it happen? “Evolution by natural selection” is a theory.
We’ve come up with thousands and thousands of hypotheses about it, tested them, thrown
out the bad ones, and we’ve developed a pretty darn good framework for predicting
how living things change over time. So yeah it’s a theory. Stop saying it like
a bad thing. Calling it a theory means it’s passed the toughest tests that we can throw
at it, and evolution has been tested maybe more than any other theory we know of. We should really call it the Theory of (The
Fact of) Evolution What about something as fundamental as gravity?
Is that a theory? Or is it… a law? In science, a law is a detailed description,
usually using math, of how something happens, like the movement of gas molecules related
to temperature, or how mass and energy are always conserved. But a law doesn’t tell us
why it happens. Gravity, it turns out, is a law and a theory. Newton’s Law of Universal Gravitation describes
precisely how two objects will attract each other based on their masses and the distance
between them, and gives us a nice formula we can use to figure it out. Textbook “law”.
But Newton’s equation doesn’t describe what is happening, or why. To do that, we need
a theory of Gravity. FACT: If I drop this, it’ll fall. LAW: I can mathematically describe how fast
that apple and Earth will accelerate toward one another based on their masses and distance. But why is it happening? HYPOTHESIS: There is a force pulling on the
apple, or maybe there’s something about the way the universe is structured that makes
massive things fall toward one another, or maybe the apple is, like, magnetically attracted
to Earth or something? Eliminate the bad ones, and we’re left with
a theory. Thanks to Einstein, we’ve got a Theory of
Gravity… called General Relativity. But once scientists stumbled upon quantum
mechanics, they began to realize that Einstein’s Relativity didn’t account for what was happening
on the very smallest gravitational scales of the universe. General Relativity is still great at describing
the universe at the scale that we interact with it, but even the Theory of Gravity is
incomplete. Does that mean we throw it out because it can’t explain everything? No! If you get a flat tire on your car, do
you get a new car? If you change the tire, is your car a different
car all of a sudden? All of these fit together to make the scientific
machine. We’re constantly adding and taking away parts, but it keeps on running just fine.
It just means we’ve got more work to do to make Einstein’s theory even more right. Science is never done. It is always changing,
and this bothers some people. How can we trust it, how can something be strong and robust
if it could be different tomorrow? The goal of science is to devise frameworks
that describe how things work, to truly understand why things are the way they are right now,
so we can know how things will be in the future. And if we can all learn to trust science,
in all its fuzziness and incompleteness, I predict that future is going to be very bright.
I like that theory. Stay curious.

Why Did We Blow On Nintendo Games?

October 3, 2019 | Articles, Blog | 100 Comments

Why Did We Blow On Nintendo Games?


Dang it. If you played old-school Nintendo, then this
has happened to you. Your game went all crazy, so you blew on the cartridge, and bingo. Beating a game like Mario Bros. is all about
knowing the patterns. Luckily we’re good at that
Our brains are nature’s most powerful pattern-recognition devices. They let us pick out meaning from
the chaos: in order to sense danger, so we can see consequences for our actions. For
our ancestors that could mean the difference between life and death. You eat the red berries, and you get sick.
Eat the blue ones, and you’re fine. Plant your crops in late summer, you go hungry.
Plant your crops in spring, and you eat like a king. Since those early days, our brains have kept
evolving, but maybe not as fast as the world in which we live. And while we keep upgrading
the OS, we’re operating with pretty much the same hardware that we had 10,000 years ago. And that can get us into trouble, because
our brains are SO good at picking out patterns, sometimes they see ’em when they’re not there
. . . We can see faces where there’s only shadows
Or movement in still images Or even a cause for autism in vaccines So why are we so good at being wrong? It might be a flaw in our wiring. Our pattern-obsessed
brains don’t like uncertainty. We badly want to be right about how we see the world, and
to do that we look at it through various filters. If you start with the conclusion that the
moon landing is a hoax or that man-made climate change isn’t real… maybe you can can find
some evidence that says you’re right, but you’ll have to ignore a whole lot MORE evidence
that says you’re wrong. When we filter evidence to support that conclusion
and ignore that what disagrees, we’re victims of confirmation bias When we assume that thing A caused thing B because
thing B happened after thing A, we’re victims of the post hoc fallacy. When we insist that random events have meaning,
you’ve fallen victim to the Texas sharpshooter fallacy. It’s easy to hit a bullseye if you
paint it on afterwards. Which brings us to this. I never asked myself why I was blowing on
my video games. It just worked. Except that I was wrong. So were you. It didn’t do a thing.
Our brains were playing tricks on us. The strangest part about the Nintendo thing
is that everyone did it. In a pre-digital world, it spread like a thought virus. There
was no how-to video on YouTube, it was just . . . common knowledge. In South Korea, many people still believe
that sleeping in a closed room with an electric fan on can kill you. They aren’t dumb. We
are more likely to believe something if we see that other people believe it. That’s the
common belief fallacy. Which is why when I saw my friends blow on
Nintendo games, then I blew on my Nintendo games. We thought we were clearing the dust
from the cartridge, increasing the conductivity of the metal connections . . . All it really did was give us an excuse to
take it out and try again. We saw a reason where there was only randomness. And that’s why science was invented. A way
to fight the human tendency of assuming that what we see is what’s true. Instead of starting with a conclusion, and
filtering out all the data that doesn’t agree with it, science starts with an explanation
and does everything possible to prove it wrong. Unfortunately, it’s a pretty recent invention.
Only a few hundred years ago lots of very smart people thought lambs grew on bushes,
and mice were spawned from dirty laundry. We’re fighting some very old habits. The world is complicated, and it doesn’t always
make sense. Patterns make it easier to find our way through the maze of randomness. But
if we’re not careful they can get us lost. Science, above all else, requires a desire
to disprove ourselves. It’s a sharp tool we use to poke holes in our ideas, so we’re sure
that they’ll float. And unless we do that on a regular basis, our princess will forever
be in another castle. Stay curious. Special thanks to David McRaney, without whom
I couldn’t have done this episode. To learn more about how your brain is out to trick
you, check out David’s books, You Are Not So Smart and You Are Now Less Dumb, links
down in the description.

Visiting the Largest Bat Colony on Earth!

October 3, 2019 | Articles, Blog | 99 Comments

Visiting the Largest Bat Colony on Earth!


[MUSIC] [OMINOUS SOUNDS] [MUSIC] If you collected every species of mammal on
Earth, a whopping one in four would be a bat. There’s more than 1300 species around the
world, one is as small as my fingernail, and another is as wide as my arms. There’s a
lot of bats out there. There’s also a lot of bats in there. This
is a very special place. Beneath our feet is the largest gathering of mammals anywhere
on Earth. 20 million or so Mexican free-tailed bats!
For the past 10,000 summers or so, these bats have come up here for the summer in what’s
known as a maternity colony. And they get hungry. Every night around sunset, they head out to
eat, and it’s an unforgettable sight. Different species eat pretty much every kind
of food there is, but the bats that live here are insectivores. A single Mexican free-tailed
bat only weighs about as much as two quarters, but all in all, this population will eat more
than a hundred tons of insects in a single night.
By doing so, they save farmers billions of dollars every year in lost crops and pesticides
that they don’t have to use. TV weathermen around here used to see evening
storms popping up on their Doppler radar, but then people on the ground would call in
saying there wasn’t a rain cloud in the sky. That’s because the radar was seeing
this. Every night invading hordes of moths ride
high altitude winds toward croplands in the midwest. Mexican free-tailed bats bats fly
as high as 10,000 feet to intercept them in epic aerial battle. Bats are the only mammals capable of powered
flight without using airplanes, a skill they evolved separately from birds and insects.
A bat’s wing is actually a highly-evolved hand, and the flexibility of their webbed
wing means that they can generate more lift and maneuver even better than birds. As adapted as they are, those flexible wings
can’t generate enough lift to carry the bats straight up out of the cave. So they
fly in this sort of cyclone shape to create an updraft. It’s like a bat-nado! I hope
you’re listening SyFy channel? It’s a tornado, made of bats. You know the old saying “blind as a bat”?
Well, bats are anything but blind. As they pour out of that cave by the millions, they
depend on their eyesight to keep from crashing into each other. But once the hunt begins,
in the dark of night, another sense takes over. Do you hear that? Nah, me neither. Bat echolocation
frequencies are above the range of human hearing, which is a really good thing. They’re so loud
it’s like holding a smoke detector six inches away from your ear. In fact, bats have to
inactivate their own hearing system when emitting their calls so they don’t drive themselves
deaf. Their ears are actually angled to let them
hear in stereo so they can triangulate the location of their prey. Scientists found that
one moth is even able to jam bat sonar by producing clicks of its own. Hungry bats make a lot of poop. In fact, there’s
more than 19 meters of guano at the bottom of this cave, in fact scientists ran out of
drilling equipment before they found the bottom. As the guano decomposes, it creates enough
heat to keep all the little baby bats warm. Aww. In addition to eating insects, some bats are
important pollinators, or they disperse seeds from the fruit they eat. Even though bat populations like this one
have been here since probably before humans have, they are in danger. Urbanization is taking away habitats and food
sources. And imported diseases like White Nose Syndrome are wiping out whole caves in
the eastern Unites States, and spreading. This fungus irritates the skin of hibernating
bats, forcing them to wake up and fly out when there’s no food to eat. They basically
starve and die of thirst thanks to an itch. Despite their importance and how amazing they
are, these incredible species are still feared and misunderstood. If you want to know more
about what you can do to help bats around the world, and just to learn more about these
awesome animals, check out a link down in the description to Bat Conservation International.
They’re the awesome people who brought us out here today, and they own all of this land
to protect this natural treasure. If you want some more awesome bat science,
check out these videos from our friends at Smarter Every Day and MinuteEarth. Stay curious.

Are Space and Time An Illusion? | Space Time | PBS Digital Studios


[INTRO MUSIC] Today’s episode is
about space, time, and the nature of reality. My name is Gabe, and this time,
it really is “Space Time.” [THEME MUSIC] If you pay attention,
this episode is going to blow your mind, so
we’re going to take it slow. What is spacetime, exactly? Before I can answer that, I
need you to do something for me. Give up your intuitions about
how time and space work. At first, your brain
might resist and hold onto those intuitions
for dear life. Don’t worry. That’s normal. This is challenging for
everyone, even Einstein. Ready? OK. Spacetime refers to whichever
external reality underlies our collective experiences
of the space between things and the time between events. Why can’t space and
time just be a reality? Why add spacetime
as an extra concept? Here’s why. Suppose two observers are moving
relative to each other, and particles count as observers. Fact– those observers don’t
agree about how much time passes between events. Fact– they don’t fully
agree on how much space there is between things
at any given moment. Fact– they don’t even agree
on the chronological order of all events. And yet, each observer
measures things properly and is entirely consistent,
which means neither of them is wrong. Now that sounds
absurd, but it’s true. Plenty of other
resources, some of which we link to in the description,
discuss these discrepancies and the experimental
evidence for them. For today, we’ll just
take them at face value and focus on what they imply
about the nature of reality. Because if you think about
it, some of the implications are staggering. Take this disagreement
about sequence of events, for instance. It is severe. If two observers can’t agree
on the sequence of events, it means that at
present, someone’s past is in someone else’s future. Now for nearby
events, the effect is microscopic, but so what? Any disagreement means that
there is no universal division of events into past,
present, and future, which opens major philosophical
cans of worms for things like free will and our belief
that we can change the future. So is everyone’s experience
of the universe entirely subjective? Or phrased another way, if
time and space as we usually conceive of them aren’t
part of objective reality, then what is? Causality. Let me explain. A good starting point
for objective reality is universal agreement. And as luck would
have it, all observers do agree about this thing. It’s called the spacetime
interval, or spacetime separation between two events. Even though two observers
in relative motion will measure different distances
and different elapsed times between the same two
events, they always agree about the spacetime
interval between those events. Now if everyone agrees
about spacetime intervals, they must signify something. But what? We’ll notice that since
it involves subtraction, a spacetime interval can be
positive, zero, or negative. When it’s positive, nothing
can get from one event to the other, and
there are always observers who disagree about
which one happens first. When it’s zero or
negative, signals or things can get from one
event to the other and everyone agrees
on their sequence. So it appears that the spacetime
interval between events A and B tells you whether A can
influence B. In other words, even though we can’t agree about
past, present, future, time, or distance, we all appear
to agree about causality. Now that may seem
counterintuitive. Normally we think that time
is responsible for causality. But actually it’s
the other way around. To the extent that we agree
about temporal anything, it’s only because of causality. Causality is what’s real. So what does causality
have to do with spacetime? As it turns out, everything. See, shortly after
relativity first came out, a former math professor
of Einstein’s named Hermann Minkowski noticed
that the spacetime interval resembles a weird version of
a distance formula in what’s called a non-Euclidean space. So he proposed the
following radical idea– maybe reality is not
a three dimensional space that evolves in time. Instead, it’s a four dimensional
non-Euclidean mathematical space that’s just there. No evolution. No time. That 4D mathematical
space is spacetime. Its points correspond to events. All events, everywhere, ever. And in this view,
only things that correspond to geometric
relations in that 4D space are objectively real, like for
instance, causal relations. They correspond to
spacetime intervals, which are geometric relations,
a non-Euclidean version of the distances between points. In contrast, our experiences and
measurements of time and space don’t correspond to
anything, per se. They’re more like the XY
grid we use in math class, useful for talking about
the board, but arbitrary and inherently meaningless. The board, its points
and geometric facts, are simply there whether we
put axis on that board or not. So are you objectively real? Well, kind of. If you are the sequence
of all the events of which you were
present, then you are a geometric object in
spacetime, a line segment joining the points
representing the events of your birth and your death. Do you move along
that line segment? No, no. You are the line segment. There’s no motion
through spacetime. It’s not this kind of space. It’s tense-less. And your future isn’t
merely predetermined. It already exists. There’s some zen in trying
to express what spacetime is without misleading you,
but I think the following gets the flavor right. Imagine we’re are all reading a
flip book made of graph paper. We agree on the
events of the story, but we don’t agree
where they happen on the page, on how
many pages there are between events, or
even on the order of some of those events. And yet, we’re all
reading the same book, only there’s no graph on the
paper, there are no pages, and there is no book. All of that is
just an imposition our brains make in order to
perceive whatever “it” is. So why do we perceive reality
in such a vividly spatial and temporal way? Good question. No one really knows. So have I told you all there
is to know about spacetime? No, far from it. All of this has just been a
loose introduction to what’s called a flat spacetime. Once general relativity
entered the mix, we’ll find that there are
many possible spacetimes with different geometries,
making it hard to ascertain which one this is. But we got to crawl
before we walk. We will get to that fun
stuff eventually though, so subscribe. And as always, the comments
are for your questions. I’ll do my best to answer them
at the next causally-connected point of spacetime. Last week, we asked
whether NASA could start a zombie apocalypse. You guys, as usual,
had a lot to say. Daniel Jenkins commented that
a space-based zombie outbreak assumes that a more virulent
organism would actually spread better. First of all, that
assumption is unnecessary. It’s enough for the bug
to just be more harmful and harder fight off with your
space-depressed immune system. But second, as Nicholas
Garrison pointed out, germs do spread more
easily space capsules for a variety of
reasons, including the fact that the gunk
in sneezes and coughs just hangs there
instead of falling. Pretty nasty. Joe G.P. and Dikasad2
both asked what it is about space exactly
that enhances virulence? Is it the low gravity
or the radiation? What is it? Well, the authors
of salmonella study theorised that the signal
to bacteria in microgravity might be lower shear forces
on their cell membranes from the surfaces and
fluids that surround it. But based on the
journal articles I read, that’s only one of
several suggestions and the jury is still out. We just don’t know. Joey Broda and
McKnowledge1000 both asked why human gene expression
isn’t altered in orbit if bacterial gene expression is. That’s a great question, but
I’m not a microbiologist. Maybe human cells do change. I don’t know. It’s a great question,
but I have no idea. DHGameStudios said
that it’s a shame we put a zombie tag on this video. What do you mean? Is it a shame that
“Sesame Street” teaches reading and arithmetic
with a vampire and a canary with acromegaly? Have some fun, man. Lighten up. Zombies are the best. Finally, At-Bristol
Science Centre really wants to see the
Curiosity rover battling martian zombies in a movie. Yeah, you do. You know who else does? Bjs301’s kids and their
friends, because I’m pretty sure they understand
that even though zombies aren’t real, they’re
still super awesome. Finally, quick announcement. The PBS Digital
Studios Network has been nominated for a Webby award
in the science and education category. We’d appreciate your support and
your vote at webbyawards.com. You can check out the
link in the description. [THEME MUSIC PLAYING]


This episode is supported by Skillshare. Hey smart people, so a few weeks ago we made
a video about the pyramids, and how, while they are pretty heckin’ impressive, we can
trace the evolution of their construction and see the ancient Egyptians using trial
and error, and even making a few mistakes, which basically tells us they didn’t need
aliens to build them, they just needed science. You guys really liked that video, but a few
of you were… a little bothered that, despite the fact it was called “WHO built the pyramids?”
that I didn’t talk about HOW the pyramids were made. Soooo, let’s talk about it! [OPEN] The hundred-plus pyramids scattered around
Egypt were all built a bit differently, but we’re gonna focus on THE BIG ONE. Let’s review the stats! The Great Pyramid originally rose more than
146 meters tall and contained about 2.3 million stone blocks. But the start of any construction project
truly begins with the foundation, which is impressive in its own right. Its base is level to less than 2 cm, it’s
square to within 11 (cm), and its edges are aligned to the compass within 3/60ths of a
degree. This precision is pretty incredible since
compasses didn’t actually exist yet, and since forty-five hundred years ago the North
Star was in a completely different place. But finding North is actually pretty easy,
just watch where any star rises and sets during the night, and cut the angle in half. After that, squaring the sides just requires
measuring a right angle. Pythagoras and his equation came way later,
but ancient cultures like the Egyptians knew a 3-4-5 triangle made a 90˚ corner. They could even make a right angle with two
circles: the line connecting the intersection of the arcs is perpendicular to a line through
their centers. To level the base, some theories say the Egyptians
used water filled channels as natural levels, but this isn’t likely when you consider
how much water they’d have to carry in to keep it from evaporating. But if you can make a right angle, you can
make a level. Put that on some legs, and you can level over
long distances. When you think about it, a pyramid is just
a bunch of stacked squares, so if you can master this measurement, you’re most of
the way there. Now we just need some stones. The Great Pyramid’s core is made of more
than 2 million blocks of rough yellow limestone. This was quarried right next to the pyramids,
which is a big reason why they chose sites like Giza, where prehistoric oceans had deposited
this building material right under their feet. They would dig channels and pry these blocks
right from the Earth, and the size of the blocks was actually determined by the natural
thickness of these limestone layers. You can see evidence of these layers in The
Sphinx, which was actually dug out of the Earth, not built on top of it. The pyramids were originally covered in smooth
white limestone from quarries up the Nile, which was stolen to use in other buildings
thousands of years ago. We’ve found many chisels, drills, and saws
used at these quarries, and the only metal Egyptians had access to was copper. That’s a pretty soft metal, but when a slurry
of sand and powdered rock is poured in as an abrasive, even copper tools can cut limestone. To build the Great Pyramid in 23 years, an
Olympic swimming pool’s worth of stone had to be quarried every eight days. That’s a lot, but modern pyramid building
experiments using technology available to Ancient Egyptians calculated this amount of
stone could be cut and moved by a quarry team of 1200 to 1500 workers, which is totally
doable. Heavier stones, like the granite used in the
pyramid’s inner chambers, are much harder than limestone. They were literally chipped out by hand using
heavy dolerite hammer stones, which we’ve also found… a LOT of. It would have taken a full day’s pounding
to chip away a few centimeters, but then again they didn’t have Twitter to distract them. We’ve found Egyptian boats large enough
to have floated these stones down the Nile, but how were 2 million blocks actually moved
into place? It might be hard to believe, but wheels for
transportation are a surprisingly recent invention. Not because rolling a round thing is hard
to figure out but because inventing a workable axle is. The oldest known rolling wheels on Earth date
to before the Great Pyramid, but not in Egypt. Paintings tell us Egyptians used wooden sleds
to move large objects, but they still had to deal with friction. Burying wood rails horizontally will allow
a sled to slide more freely, but researchers at the University of Amsterdam showed in 2014
that sand has an interesting property, wetting it with the right amount of water makes it
remarkably slick. A team of ten workers can easily pull a one-ton
sled, but people always seem to forget that Egyptians had animals like donkeys and cattle
around to help too. Constructing ramps to deliver stone must have
been nearly as monumental as the pyramid itself. This is one place where there’s no records
of what they looked like, but researchers have examined lots of possibilities. An engineer named Craig Smith has done probably
the most detailed ramp analysis, calculating how many stones could be delivered with each
design, and he believes the Egyptians extended a big, wide ramp near the bottom where a pyramid
requires most of its stones, and spiral ramps near the top where fewer blocks are needed. Wooden levers, and round dolerite “ball
bearings” were used to guide stones into place, where they were carved to an exact
fit. Joints between some of the few remaining smooth
outer stones are so precise you can’t even slip a credit card between them, but digs
have shown they weren’t as careful with interior stones. It’s a popular idea that the pyramids were
built by slaves, but you shouldn’t believe everything you see in the movies. Egyptologists like Mark Lehner have uncovered
enormous cities built to feed, house, and equip thousands of skilled workers, with breweries,
bakeries, tool shops… signs that whole families lived nearby. Egyptian society at all levels dedicated themselves
to what they viewed as the kingdom’s proudest work. It’s actually pretty incredible that we
have as much evidence as we DO about how the pyramids were built, but that doesn’t mean
building them was easy. In fact it’s the opposite. But difficult doesn’t mean impossible. Stay curious.

Does My Dog Know What I’m Thinking?

September 19, 2019 | Articles, Blog | 100 Comments

Does My Dog Know What I’m Thinking?


[MUSIC] [MUSIC] Hey guys! I just learned about a dog named
Chaser. Chaser is a border collie who has a vocabulary of more than 1,000 words, that’s
like the same as a 4-year-old child. What makes Chaser even more special is that he
can even separate nouns from verbs. “take lips. Do it girl!”
“Good girl, good girl.” “Paw lamb, paw lamb, Chaser”
“Good girl, good girl” “Nose ABC, nose ABC.”
“Good girl, good girl!” This is Oliver. Oliver, you think you’re smarter
than Chaser? What do you say? Yeah, let’s go find out. Come on! Get your ball. Where’s your ball? Get your bone. Where’s your bone? Nope, that’s your ball.
Where’s your bone? Bone. Bone. Nope. Find your bone? Where’s your bone?
Okay, so maybe Oliver’s not that good at this particular test, but the fact that we even
try to communicate with dogs, and that they communicate back with us, means that the human-dog
relationship is truly something special. “Who’s the best boy? (baby talk)” I… have been known to talk to dogs a little. (baby talk)
(baby talk) Or a lot. (baby talk) It’s hard to know if they’re responding
to the words, or just the emotion in my voice. Or the fact that I sound ridiculous. One recent
study suggests it’s both. Or all three. Researchers at the University of Sussex played
sounds out of speakers on both sides of a dog. When dogs heard commands stripped of
their emotional context, they turned their head to the right, suggesting they process
verbal meaning in their left hemisphere. And when they heard the emotional sounds in the
voice, but the words were jumbled, they turned to the left, suggesting they process emotional
sounds on the right. These experiments show that dogs can definitely
separate the meaning of words from the emotion attached. But how much information do they
take from each? When I ask my dogs “Do you want to go for
a walk?” they aren’t processing the real meaning of that sentence the way we do, like
“Hmm, lemme see, do I want to go for a walk right now? Get some exercise? Maybe I’m
just not feeling it today? I mean, I’m a dog, what does it even mean to WANT something?” As good as dogs are with words, in many of
our interactions there’s probably a good amount of Clever Hans at play. In the early
1900’s a horse named Hans was said to be able to solve simple math problems by tapping
his hoof to represent numbers. 2 + 3? Smart horse! It was later found, though, that
Hans couldn’t do math at all. He was just responding to tiny cues from his handlers,
maybe their facial expressions would tense as he got close to the right answer, or they
would exhale when he tapped the right number. Clever Hans demonstrates that while we might
think of language as something we experience mainly through our ears, we communicate meaning
using more than just sound frequencies. In his book “The Expression of the Emotions
in Man and Animals”, Charles Darwin argued that the way that we outwardly express and
interpret emotions evolved from animals, and that our ability to recognize fear, happiness,
sadness, even across species, is universal, and innate. It’s something that we’re
born with. Today, scientists are still debating whether
Darwin was right, but recent research suggests that we do share one special bit of emotional
intuition with our canine companions. Dogs are the only non-primate animals that
seek out eye contact with humans. Their wolf ancestors, even tame ones, although they’re
close enough genetically to interbreed with dogs, won’t look us in the eye… which
is why you can never, ever trust a wolf. “How am I doing?” When reading emotions in other people we tend
to look disproportionately and unconsciously to the right side of their face.
Dogs share this so-called left-gaze bias, but only when looking at human faces, not
when they look at other dogs. It seems like they genuinely want to understand what we’re
telling them and what it means. We seem to understand them too, or at least
we think we do. Researchers in Hungary tested people’s ability to interpret the meaning
of recorded dog barks, and found that many people really can speak dog. What do you think this bark means?
[barking] [barking]
Okay, that dog’s angry. That’s pretty easy. What about this one?
[barking] [barking]
Okay, that dog wants to go for a walk. One more.
[strange noises] I have no idea what that means. If you think about it, this dog-human language
connection makes a lot of sense. We’ve co-evolved with these creatures for the past 10,000 years
or so. We’ve molded them from wolves into puppies with our hands and our brains, and
our voices. Even if we don’t always understand each other,
well, they’re always there to listen, and that’s the real meaning of a best friend.
Isn’t it buddy? [phone ringing] Wait a second. Sorry. Hello? Um, yeah, sure. It’s for you. “Hello? This is Oliver.”
“Hello. This is dog.” “Oh, hey Luna!”
“Have you seen Vanessa? She’s been out for hours! I miss her.”
“Ruh roh!” Um, thanks Luna! If you want to find out more
about dog behavior head on over to BrainCraft and find out if they really miss us when we’re
gone. Stay curious. Good boy. Oh, and special thanks to Oliver. [MUSIC]

The Science of Marathon Running

September 17, 2019 | Articles, Blog | 100 Comments

The Science of Marathon Running


[MUSIC] In 490 BC a Greek messenger named Pheidippides
ran from the Greek town of Marathon to the capital Athens to deliver a message that the
Greek army had just beaten back the Persians, and the distance
between those two towns is 26.2 miles, and that’s the origin of the modern sporting
event that we call the marathon. You might know that story, but what they don’t always
tell you is that when he got to Athens after those 26.2 miles, Pheidippides died. So why on Earth would anyone want to run one
of those for fun? How are our bodies even able to? I decided to find out, so I ran one.
In the process, I discovered a lot about what I’m made of,
in more ways than one. You guys ready to run the marathon? My training started millions
of years before I ever got to the starting line. The first step to becoming a runner is, well,
standing up, and bipedalism is only seen in a handful of animals, except for a few species
of birds walking on two legs is only uses a temporary form of transportation. Our ancestors
first stood up over three million years ago, and well we were running probably not long
after that, were made for it. You could say that humans are built for
long distance running but the truth is, long distance running build us the most four on
the floor quadrupeds could easily beat me in a sprint, but humans are medal contenders
in nature’s distance running events. Even the cheetah, the most perfectly crafted running
machine on Earth could only run for maybe a mile and a half before it overheats. Today’s
fastest Olympic marathoners, they would only be beaten by a handful of Earth’s animals
in that long distance. One theory of human evolution says
that our adaptations for distance running work feast or hunting success like we talked
about in my episode “Why Do We Cook?”, bigger, richer meals mean that we could evolve,
well, bigger, richer brains. There’s a whole list of ways that we are made to run. In large
tubes in our skulls help us balance while we’re running, reflexes in our eyes keep
our heads steady as we move up and down. It’s short arms and thin ankles that take us less
effort to swing. Wide shoulders, a thin waist, and a pretty narrow pelvis help us counter
the rotation of our moving legs. We have sweat glands, and less body hair, and tall thin
bodies that let us disperse more heat. Better blood flow away from the brain to keep it
cool, your big gluteus maximus muscles to stabilize our upper body, high surface area
knee, ankle, and hip joints for shock absorption, and most importantly, our lower legs are built
like rubber bands. This is by far our coolest running adaptation.
Every time my body hits the ground, it delivers up to 8 times the force of my body weight.
That’s over 1400 pounds! In order to keep that up for 26.2 miles, my foot expands and
spreads like a shock absorber. This is the most important part of a running human: the
Achilles tendon. Though my foot hits the ground, my calf muscles flexed, but even then the
muscles and tendons are still a little bit elastic, and then my ankle joint acts as a
lever, which transfers as much as 50 percent of that energy into the next step. By using
stored kinetic energy, instead of chemical energy, we’re able to go farther with less
work. You can’t run a marathon with just rubber
bands though. You need power that humans are run on gasoline your car ATP. This is an image
of a striated muscle, the same type we have in our arms, in our legs, and basically everywhere
that we move. Each row of stripes contains a string of proteins called actin, next to
another string of proteins called myosin. And the head of that myosin protein, well,
it acts like a ratchet, pulling along the string of actin, shortening our contracting
the muscle. That myosin machine is powered by ATP. The thing is, our bodies only have
a couple seconds worth of ATP stored up at any moment, so instead, we’re constantly
replenishing it, thanks to our mitochondria and their little ATP factories. Just picture
me as a giant ship with trillions of mitochondria at the oars. My body cycled through something
like 75 kilograms of ATP during the marathon. That’s almost my entire body weight! It
just shows you how good our bodies are at recycling energy. Now that’s 75 kilograms
of ATP broken down release the same amount of free energy as a kilogram of TNT. My body
gets ATP in a couple of different ways. If I was running full speed the entire time,
my cells would be forced to use an inefficient process called glycolysis, but by running
slightly slower for the whole race, I let my mitochondria use a much more efficient
method called the Krebs cycle and the electron transport chain. I can burn lots of fuel and
make that ATP, like fat or protein, but my muscles prefer glucose, which is stored in
long chains like glycogen for quick access, but even they don’t keep that much just
lying around. So instead, I topped off my glycogen tank before the race by doing
something called carb loading. Look at all these waffles I have to eat. But
even eating all that before the race, my body can’t hold all the glycogen it needs to
get through a marathon, so I had to eat and drink more during the race, or else I would
hit the dreaded wall. Hitting the wall is just a big scary name
for fatigue. And there’s lots of reasons why it can happen. If you run out of glycogen,
then your muscles can run out of ATP, and that protein ratchet will get stuck in the
lock position. It’s actually why something, well, gets kinda stiff when it dies. If your
cells don’t have enough salt, then your nerves and muscles won’t have the sodium,
potassium, and calcium that they need to pass electrical signals. The main reason that people
hit the wall is because of this. See, your brain is competing with your muscles for blood
sugar, and if those levels dip too low, well, you’ll feel dizzy and loopy. “I think I’m gonna die. I’m gonna die.
” “You’ll be okay.” Your brain is actually preventing your muscles
from firing goad for some emergency power save mode. I’ve never run a marathon before
and I discovered it’s not like any other sporting event I’ve ever taken part in.
You’re not battling an opponent; you’re only battling yourself. All those feelings
of joy, and fatigue, and pain, they only exist in your mind. That mind is connected to the
physical muscles and chemical power plants and proteins doing work. I’ve never understood
more about my body, or my biology, and when I push them to the limit, and in the process,
I discovered that it wasn’t a limit after all. That was the most fun I’d never want
to have again. Like halfway through, it was like the hardest thing
I’ve ever done, and the entire second half was just pure willpower, like a competition
against yourself, and I-I won. I beat- I beat my own mind. That was awesome. Thank you,
everybody. We’re not the only social animals that sit
down to eat together, but we are the only ones who cook. Cultural anthropologist Claude
Levi-Strauss is above all cooking establishes the difference between animals and people,
although I’d think he’d agree that pants make a big difference, too.