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Hi. I'm John Green and this is Crash Course
Big History, in which we'll be looking at
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the history of, like, everything. I'm talking about
13.8 billion years, from the big bang to now.
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I mean, in this series, we are literally
going to attempt to tell you the story of
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what Douglas Adams famously called
"life, the universe, and everything."
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Mr Green! Mr Green! That's not history. That's
science, and science is for nerds!
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Oh, me from the past! Things would be so much
easier for you if you would just accept that
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you are, in fact, a nerd! And that's okay!
I mean, look at this picture, dude!
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Anyway, academics often describe history as
like, all the stuff that's happened since
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we started writing things down, but they only start there
because that's where we have the best information.
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And yeah, I think that the advent of writing
was a huge deal, obviously, but as a start
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date for history, it's totally arbitrary! It's just a line we
drew in the sand and said "okay, history begins now!"
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In Big History, we're gonna start history
when it really starts - at least, we think
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- at the creation of the universe, and we're
gonna end that story where it ends - please
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let that be after I die! Well, I guess it will definitely
be after I die, just - I want it to be a while after I die!
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So we're even gonna terrify traditional historians
by using physics to make some predictions
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about the future, and we're gonna end many
trillions and trillions of years from now,
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when the universe itself, spoiler alert: dies.
At least, in a manner of speaking.
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[Theme Music]
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Hey! I'm not John. If you're thinking we look
a little bit the same, that's because we're brothers.
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I'm Hank. Anyway, if you wanna learn the 13.8 billion
year history of the universe in the same amount
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of time that we usually cover the 238 years of American
history, you're not gonna get the same resolution.
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Of course, knowing the names and dates of American history is important, but we just can't do that in Big History.
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There are much broader historical questions
in the story of the universe that can only
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be explored by zooming out to the ultimate
scale. As you zoom out, you see a lot more
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of the picture. The details get a little fuzzy,
but we quickly realize that history is everything.
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Cosmology, geology, biology, social sciences,
literature, physics... Everything!
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You might think that such a scale would be
filled with way too much detail, but the amount
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of detail an answer requires, depends on the
nature of the question. Some questions can
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only be explored by zooming out. That is what
Big History does.
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Speaking of zoomed out, this is Earthrise,
one of the most famous photographs of all
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time. William Anders, an Apollo astronaut,
took it in 1968. From the surface of another
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world, we see our planet as a little ball
in space. No borders, no people, no buildings.
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Just oceans and clouds and continents being
shined upon by the sun.
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That sheer expansion of scale gives me perspective.
It lets me imagine all the complexity of life
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on Earth, from the gasoline engine that powered
my trip to the studio, to political instability
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in Nepal as part of a thriving, living, teeming
mass of life floating in the emptiness of space.
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So what that photograph does for physical
space, Big History aims to do for everything.
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I mean, we wanna contextualize all of existence.
We wanna outline the most powerful and important breakthroughs,
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the tremendous scale of existence, and how we
know what we know, and why we're sure we know it.
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All right, let's go to the Thought Bubble. So
the universe is big. Like, really big. And it's also old.
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Like, 13.8 billion years old, which is enough
years that there is no way to actually comprehend it.
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So let's just compress that age to 13 years,
small enough that our puny brains can handle it.
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On that timescale, the universe would have
begun 13 years ago, in 2001. George W Bush
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had just been sworn in as president, most Americans on
the internet were connecting to it with dial-up modems.
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Right, so the first stars and galaxies would
have formed 12 years ago, but seven and a
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half more years would pass until the Earth
formed, about 4.5 years ago. Move a little
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bit up to four years ago - that's when the
first single celled life formed on Earth.
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Then leap forward nearly three and a half
more years before the first multi-cellular
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organisms in the Cambrian explosion...
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What I'm trying to explain is that all complex
life on Earth is a fairly recent development.
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Like, on this scale, the dinosaurs went
extinct about three weeks ago --
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roughly the last time I changed my Facebook status.
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Humans and chimpanzees split from their last
shared ancestor about three days ago!
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The first homo sapiens emerged fifty minutes ago,
roughly the last time I checked my email.
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We left Africa 26 minutes ago. The American-Indians
reached the Americas 6 minutes ago --
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roughly the last time I checked my Twitter.
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We invented agriculture 5 minutes ago. Ancient
Egypt? 3 minutes ago! The Black Death? 24
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seconds ago. The Industrial Revolution - 6
seconds. World War One, 2 seconds. The Cold
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War, th e first man on the moon, your birth, the internet,
the Big Mac? All within the last second.
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But in many other ways, complex life and humanity
are exceptional. Thanks, Thought Bubble!
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Also exceptional, by the way, the Mongols!
[Mongoltage]
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Okay, let's begin at the beginning! The big
bang!
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Hank, wait a second! Woah, woah, woah, woah,
woah. I- I don't understand how we know that
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the big bang is really the beginning. Like,
what happened before the big bang?
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Well. Okay. Uh... Theoretical physicists say
that space and time are not two different
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things. They are two expressions of one thing
- space-time. And space-time was created by
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the big bang, thus time didn't exist before
the big bang, so it doesn't make much sense
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to ask what happened before it. There was
no "then", then!
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Of course, this, like many ideas in cosmology,
doesn't really make any sense to our puny
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human brains. It's largely beyond our comprehension,
rather like explaining color to a blind person.
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We know that it's true because the math works
and it explains our observations so elegantly,
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but it's so far outside of how we directly
perceive the world, that I don't think it's
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something even the most genius physicists
are able to imagine.
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But yeah, if you're gonna do a chronological
study of the universe, the creation of time
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is probably a pretty good place to start the
story.
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So the big bang wasn't something that happened
inside the universe, nor did it expand into
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some kind of void. It was literally the moment
when both time and space were created. The
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thing that was banging was the universe itself.
It was expanding from an unimaginably tiny
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point to an unimaginably large universe, unimaginably
quickly.
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Unimaginable is basically the subtitle to
the story of the big bang, but then again,
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it's also kind of the subtitle to everything
else in big history.
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I mean, I can only do this occasionally, but
sometimes you look outside and you're like,
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"Oh, my goodness! This is nuts! How did we get trees?"
Needless to say, we will be talking about that.
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Anyway, the universe is a hard worker, and
it got most of the heavy lifting done in those
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first few seconds. For comparison, it takes
me about twenty minutes after I wake up for
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me to even get myself into a standing position.
But the universe is somewhat more efficient.
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In the barest fraction of the first second,
the universe inflated from something many,
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many, many times smaller than an atom to about
the size of a grapefruit. Like, think of it
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this way: in much less than a blink of an
eye, if it'd originally been the size of a
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tennis ball, it would have inflated to over
ninety billion light-years across.
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This inflation theory has been well backed-up
by mathematics for a long time now, but it
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has recently received some staggering new
support from the BICEP project at the South
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Pole, which sadly has nothing to do with my
guns.
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Ten seconds after the big bang, the universe
had expanded enough that the normal rules
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of the universe, with atomic forces and gravity
and electromagnetism that we know and love
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today, were already in charge. All of the
anti-matter created in the big bang had combined
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with matter and annihilated itself, leaving
behind only one billionth of the matter created
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in the big bang, and that billionth is everything!
And I mean everything. Every grain of sand,
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every blueberry you will ever eat, every star
that you will ever see - everything!
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We've already tried to understand how big a billion is,
but just pause to think about that - everything!
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Everything! Is one billionth of the matter
created in the big bang. [Explosion sound]
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The first law of thermodynamics is that matter
and energy cannot be created or destroyed.
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Everything we have now, we had then. The matter
that makes up your body right now has been
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around since those moments 13.8 billion years
ago. It's simply changed form.
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After just three minutes, the universe was
cool enough that the nuclei of atoms started
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forming - just hydrogen and helium back then,
the two simplest elements - keep those two
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in mind, however, because it turns out, if
you take a bunch of hydrogen and you wait
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like, several billion years, you might just
grow yourself some humans!
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Let's remember: at this time, the universe
was still very, very hot. I don't wanna use
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the word unimaginable too often, but it was
unimaginably hot!
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The universe remained like an uber-hot sea
dominated by radiation, but then luckily,
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it simmered down to a balmy 5,000 degrees
Fahrenheit about 380 thousand years after
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the big bang, allowing matter and radiation
to separate.
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And remember, matter is just a more congealed
form of energy. I mean, you are a somewhat
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firm bag of energy. In my case, not that firm.
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So anyway, at 5,000 degrees Fahrenheit, radiation
was finally able to move freely through the
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universe, and we see that radiation today
as the end of the Dark Ages that followed
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the big bang, and the beginning of a brilliant
flash that we call Cosmic Background Radiation,
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which is a great name for a band.
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Physicists call it the fingerprint of the
universe and it's one of the most important
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pieces of historical evidence we have for
the big bang, because CBR is everywhere.
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Tune your radio to a frequency that doesn't
have a station - a portion of the static you
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hear is actually that cosmic background radiation
being picked up by your radio. So you can
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literally hear the universe in its infancy!
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Sometimes it can be tricky to know what's
true, especially when we're talking about
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stuff that happened so far in the distant
past. That is why we created science, that
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elegant system for sorting out the facts from
the fertilizer.
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So just using your limited human senses, you
might come to the same conclusion as 19th
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century scientists, that the universe is static,
eternal and infinite... But then, using our
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minds, if the universe is infinite and contains
infinite stars and it has always existed,
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then the night sky, and the day-time sky for
that matter, would literally be filled with
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stars - so much that day and night would be
indistinguishable! This is clearly not the
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case, so something must be amiss.
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The universe must either be not static, not
infinite or not eternal. So which is it? You
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know how when an ambulance drives towards
you, the sound-waves are compressed and the
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siren sounds higher pitched, and as it speeds
away, the waves are stretched out and the
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pitch is lower? It's the Doppler effect.
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Well, here's another name you've heard. Edwin
Hubble. He realized that light does the same
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thing. Galaxies and stars moving away from
us have their light stretched out, making
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it more red, and stars moving toward us have
their light compressed, making it more blue.
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Combined with the work of Henrietta Leavitt,
which allowed us to accurately estimate how
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far away stars are, Hubble was able to determine that
stars, on the whole, are flying away from each other.
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He discovered that the most remote objects
in the sky were all red-shifted and were actually
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other galaxies beyond the milky way, moving
away from us. From here, he built upon the
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work of Belgian Catholic priest Georges Lemaitre,
who hypothesized that the universe began at
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a single point. Big bang cosmologists wanted
proof though. They knew that the amount of
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radiation released by the big bang would be
massive, and they wanted to see it.
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It wasn't until the 1960s that it was found
accidentally, by two guys working on an antenna
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at Bell Laboratories in New Jersey. They were
trying to eliminate all the background noise
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from an extremely sensitive radio antenna, but they
found this faint hum coming from every direction.
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They tried everything they could to get rid
of it, including murdering the pigeons that
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kept pooping on the antenna - kinda sad, but
those pigeons - they gave their lives for
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one of the most profound discoveries in modern
science. A conversation with a local radio
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astronomer lead them to show their findings
to an astronomer at Princeton, who confirmed
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the existence of what had been predicted for
years.
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The final piece of that big bang puzzle is
that we can see it. Light has a speed. When
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we look at the sun, we're seeing the light
that left it eight minutes ago, but if we
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look at something that's 13.8 billion light-years
away, we're seeing the stuff that happened
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13.8 billion years ago! That radiation has been
traveling since the very beginning of the universe.
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Not only can we tell very clearly that there
was just nothing there before that, we can
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now study that radiation to learn the sequence
of events of the big bang. We can also see
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that the chemical composition of the early
universe is what we'd expect to see - a lot
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of hydrogen, a lot of helium and a tiny pinch
of lithium. The rest of the periodic table
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had to wait for the fiery furnaces and the
bellies of stars to be created.
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But more on that, next episode!
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As far as we've come in the past century in
crafting a history of the universe, there
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are still many things cosmologists have yet
to discover. For instance, the universe behaves
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as if there's a bunch of matter in it that
we can't see or detect. Galaxies' gravitation
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is affected by this matter, but it's otherwise
completely invisible to us. Physicists call
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it dark matter, but we have no idea what it
is! But as in any historical endeavor, new
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discoveries will alter the story in future
years, so expect the big histories of ten
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or twenty years from now to look very different
from today's.
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But this isn't discouraging, because like,
knowing everything would be boring!
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There's a lot left to discover, and at the current
pace of scientific inquiry, many of those
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amazing discoveries will await us in our lifetime!
Or at least in your lifetime.
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Whether it be World War Two or the life of
Abe Lincoln, all histories ultimately start
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with the big bang. Yeah, it would be silly
to start your typical World War Two textbook
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with the big bang, but it would be about a
hundred trillion, trillion times more ridiculous
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to say the big bang - the mother of all historical
events - was not history.
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And that's why big history reaches into the
lives of every person on this tiny speck of
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dust we call home, regardless of nation, class
or creed, and forms our common story.
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See you next time!
