hi. i'm john green and this is crash coursebig history, in which we'll be looking at the history of, like, everything. i'm talking about13.8 billion years, from the big bang to now. i mean, in this series, we are literallygoing to attempt to tell you the story of what douglas adams famously called"life, the universe, and everything." mr green! mr green! that's not history. that'sscience, and science is for nerds!
crash diet eggs and grapefruit, oh, me from the past! things would be so mucheasier for you if you would just accept that you are, in fact, a nerd! and that's okay!i mean, look at this picture, dude! anyway, academics often describe history aslike, all the stuff that's happened since we started writing things down, but they only start therebecause that's where we have the best information.
and yeah, i think that the advent of writingwas a huge deal, obviously, but as a start date for history, it's totally arbitrary! it's just a line wedrew in the sand and said "okay, history begins now!" in big history, we're gonna start historywhen it really starts - at least, we think - at the creation of the universe, and we'regonna end that story where it ends - please let that be after i die! well, i guess it will definitelybe after i die, just - i want it to be a while after i die! so we're even gonna terrify traditional historiansby using physics to make some predictions about the future, and we're gonna end manytrillions and trillions of years from now, when the universe itself, spoiler alert: dies.at least, in a manner of speaking. [theme music]
hey! i'm not john. if you're thinking we looka little bit the same, that's because we're brothers. i'm hank. anyway, if you wanna learn the 13.8 billionyear history of the universe in the same amount of time that we usually cover the 238 years of americanhistory, you're not gonna get the same resolution. of course, knowing the names and dates of american history is important, but we just can't do that in big history. there are much broader historical questionsin the story of the universe that can only be explored by zooming out to the ultimatescale. as you zoom out, you see a lot more of the picture. the details get a little fuzzy,but we quickly realize that history is everything. cosmology, geology, biology, social sciences,literature, physics... everything! you might think that such a scale would befilled with way too much detail, but the amount
of detail an answer requires, depends on thenature of the question. some questions can only be explored by zooming out. that is whatbig history does. speaking of zoomed out, this is earthrise,one of the most famous photographs of all time. william anders, an apollo astronaut,took it in 1968. from the surface of another world, we see our planet as a little ballin space. no borders, no people, no buildings. just oceans and clouds and continents beingshined upon by the sun. that sheer expansion of scale gives me perspective.it lets me imagine all the complexity of life on earth, from the gasoline engine that poweredmy trip to the studio, to political instability in nepal as part of a thriving, living, teemingmass of life floating in the emptiness of space.
so what that photograph does for physicalspace, big history aims to do for everything. i mean, we wanna contextualize all of existence.we wanna outline the most powerful and important breakthroughs, the tremendous scale of existence, and how we know what we know, and why we're sure we know it. all right, let's go to the thought bubble. sothe universe is big. like, really big. and it's also old. like, 13.8 billion years old, which is enoughyears that there is no way to actually comprehend it. so let's just compress that age to 13 years,small enough that our puny brains can handle it. on that timescale, the universe would havebegun 13 years ago, in 2001. george w bush had just been sworn in as president, most americans onthe internet were connecting to it with dial-up modems. right, so the first stars and galaxies wouldhave formed 12 years ago, but seven and a
half more years would pass until the earthformed, about 4.5 years ago. move a little bit up to four years ago - that's when thefirst single celled life formed on earth. then leap forward nearly three and a halfmore years before the first multi-cellular organisms in the cambrian explosion... what i'm trying to explain is that all complexlife on earth is a fairly recent development. like, on this scale, the dinosaurs wentextinct about three weeks ago -- roughly the last time i changed my facebook status. humans and chimpanzees split from their lastshared ancestor about three days ago! the first homo sapiens emerged fifty minutes ago,roughly the last time i checked my email.
we left africa 26 minutes ago. the american-indiansreached the americas 6 minutes ago -- roughly the last time i checked my twitter. we invented agriculture 5 minutes ago. ancientegypt? 3 minutes ago! the black death? 24 seconds ago. the industrial revolution - 6seconds. world war one, 2 seconds. the cold war, th e first man on the moon, your birth, the internet,the big mac? all within the last second. but in many other ways, complex life and humanityare exceptional. thanks, thought bubble! also exceptional, by the way, the mongols![mongoltage] okay, let's begin at the beginning! the bigbang! hank, wait a second! woah, woah, woah, woah,woah. i- i don't understand how we know that
the big bang is really the beginning. like,what happened before the big bang? well. okay. uh... theoretical physicists saythat space and time are not two different things. they are two expressions of one thing- space-time. and space-time was created by the big bang, thus time didn't exist beforethe big bang, so it doesn't make much sense to ask what happened before it. there wasno "then", then! of course, this, like many ideas in cosmology,doesn't really make any sense to our puny human brains. it's largely beyond our comprehension,rather like explaining color to a blind person. we know that it's true because the math worksand it explains our observations so elegantly, but it's so far outside of how we directlyperceive the world, that i don't think it's
something even the most genius physicistsare able to imagine. but yeah, if you're gonna do a chronologicalstudy of the universe, the creation of time is probably a pretty good place to start thestory. so the big bang wasn't something that happenedinside the universe, nor did it expand into some kind of void. it was literally the momentwhen both time and space were created. the thing that was banging was the universe itself.it was expanding from an unimaginably tiny point to an unimaginably large universe, unimaginablyquickly. unimaginable is basically the subtitle tothe story of the big bang, but then again, it's also kind of the subtitle to everythingelse in big history.
i mean, i can only do this occasionally, butsometimes you look outside and you're like, "oh, my goodness! this is nuts! how did we get trees?"needless to say, we will be talking about that. anyway, the universe is a hard worker, andit got most of the heavy lifting done in those first few seconds. for comparison, it takesme about twenty minutes after i wake up for me to even get myself into a standing position.but the universe is somewhat more efficient. in the barest fraction of the first second,the universe inflated from something many, many, many times smaller than an atom to aboutthe size of a grapefruit. like, think of it this way: in much less than a blink of aneye, if it'd originally been the size of a tennis ball, it would have inflated to overninety billion light-years across.
this inflation theory has been well backed-upby mathematics for a long time now, but it has recently received some staggering newsupport from the bicep project at the south pole, which sadly has nothing to do with myguns. ten seconds after the big bang, the universehad expanded enough that the normal rules of the universe, with atomic forces and gravityand electromagnetism that we know and love today, were already in charge. all of theanti-matter created in the big bang had combined with matter and annihilated itself, leavingbehind only one billionth of the matter created in the big bang, and that billionth is everything!and i mean everything. every grain of sand, every blueberry you will ever eat, every starthat you will ever see - everything!
we've already tried to understand how big a billion is,but just pause to think about that - everything! everything! is one billionth of the mattercreated in the big bang. [explosion sound] the first law of thermodynamics is that matterand energy cannot be created or destroyed. everything we have now, we had then. the matterthat makes up your body right now has been around since those moments 13.8 billion yearsago. it's simply changed form. after just three minutes, the universe wascool enough that the nuclei of atoms started forming - just hydrogen and helium back then,the two simplest elements - keep those two in mind, however, because it turns out, ifyou take a bunch of hydrogen and you wait like, several billion years, you might justgrow yourself some humans!
let's remember: at this time, the universewas still very, very hot. i don't wanna use the word unimaginable too often, but it wasunimaginably hot! the universe remained like an uber-hot seadominated by radiation, but then luckily, it simmered down to a balmy 5,000 degreesfahrenheit about 380 thousand years after the big bang, allowing matter and radiationto separate. and remember, matter is just a more congealedform of energy. i mean, you are a somewhat firm bag of energy. in my case, not that firm. so anyway, at 5,000 degrees fahrenheit, radiationwas finally able to move freely through the universe, and we see that radiation todayas the end of the dark ages that followed
the big bang, and the beginning of a brilliantflash that we call cosmic background radiation, which is a great name for a band. physicists call it the fingerprint of theuniverse and it's one of the most important pieces of historical evidence we have forthe big bang, because cbr is everywhere. tune your radio to a frequency that doesn'thave a station - a portion of the static you hear is actually that cosmic background radiationbeing picked up by your radio. so you can literally hear the universe in its infancy! sometimes it can be tricky to know what'strue, especially when we're talking about stuff that happened so far in the distantpast. that is why we created science, that
elegant system for sorting out the facts fromthe fertilizer. so just using your limited human senses, youmight come to the same conclusion as 19th century scientists, that the universe is static,eternal and infinite... but then, using our minds, if the universe is infinite and containsinfinite stars and it has always existed, then the night sky, and the day-time sky forthat matter, would literally be filled with stars - so much that day and night would beindistinguishable! this is clearly not the case, so something must be amiss. the universe must either be not static, notinfinite or not eternal. so which is it? you know how when an ambulance drives towardsyou, the sound-waves are compressed and the
siren sounds higher pitched, and as it speedsaway, the waves are stretched out and the pitch is lower? it's the doppler effect. well, here's another name you've heard. edwinhubble. he realized that light does the same thing. galaxies and stars moving away fromus have their light stretched out, making it more red, and stars moving toward us havetheir light compressed, making it more blue. combined with the work of henrietta leavitt,which allowed us to accurately estimate how far away stars are, hubble was able to determine thatstars, on the whole, are flying away from each other. he discovered that the most remote objectsin the sky were all red-shifted and were actually other galaxies beyond the milky way, movingaway from us. from here, he built upon the
work of belgian catholic priest georges lemaitre,who hypothesized that the universe began at a single point. big bang cosmologists wantedproof though. they knew that the amount of radiation released by the big bang would bemassive, and they wanted to see it. it wasn't until the 1960s that it was foundaccidentally, by two guys working on an antenna at bell laboratories in new jersey. they weretrying to eliminate all the background noise from an extremely sensitive radio antenna, but theyfound this faint hum coming from every direction. they tried everything they could to get ridof it, including murdering the pigeons that kept pooping on the antenna - kinda sad, butthose pigeons - they gave their lives for one of the most profound discoveries in modernscience. a conversation with a local radio
astronomer lead them to show their findingsto an astronomer at princeton, who confirmed the existence of what had been predicted foryears. the final piece of that big bang puzzle isthat we can see it. light has a speed. when we look at the sun, we're seeing the lightthat left it eight minutes ago, but if we look at something that's 13.8 billion light-yearsaway, we're seeing the stuff that happened 13.8 billion years ago! that radiation has beentraveling since the very beginning of the universe. not only can we tell very clearly that therewas just nothing there before that, we can now study that radiation to learn the sequenceof events of the big bang. we can also see that the chemical composition of the earlyuniverse is what we'd expect to see - a lot
of hydrogen, a lot of helium and a tiny pinchof lithium. the rest of the periodic table had to wait for the fiery furnaces and thebellies of stars to be created. but more on that, next episode! as far as we've come in the past century incrafting a history of the universe, there are still many things cosmologists have yetto discover. for instance, the universe behaves as if there's a bunch of matter in it thatwe can't see or detect. galaxies' gravitation is affected by this matter, but it's otherwisecompletely invisible to us. physicists call it dark matter, but we have no idea what itis! but as in any historical endeavor, new discoveries will alter the story in futureyears, so expect the big histories of ten
or twenty years from now to look very differentfrom today's. but this isn't discouraging, because like,knowing everything would be boring! there's a lot left to discover, and at the currentpace of scientific inquiry, many of those amazing discoveries will await us in our lifetime!or at least in your lifetime. whether it be world war two or the life ofabe lincoln, all histories ultimately start with the big bang. yeah, it would be sillyto start your typical world war two textbook with the big bang, but it would be about ahundred trillion, trillion times more ridiculous to say the big bang - the mother of all historicalevents - was not history. and that's why big history reaches into thelives of every person on this tiny speck of
dust we call home, regardless of nation, classor creed, and forms our common story. see you next time!
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