Time scale of the cosmos
Cosmological Time Scale 1 Cosmological Time Scale 1
⇐ Use this menu to view and help create subtitles for this video in many different languages.
You'll probably want to hide YouTube's captions if using these subtitles.
- What I've done here is that I've copied and pasted a bunch of
- pictures that, uh, uh, signify events in our history, when you think about history
- on a grander scale that most of us have some, uh, relation to
- or we have kind of have heard it,uh,uh, talked about it, a little bit,
- and the whole point of this is to try to understand, or try to begin to understand how long 13.7 billion years is.
- So just to start off, I have here, this is the best depiction
- I could find where I, it didn't have copyrights, this is from NASA,
- of the Big Bang, and I've talked about it several times,
- the Big Bang occured 13.7 billion years ago.
- And then if we go a little bit forward, actually a lot forward,
- we get to the formation of our actual Solar System and the Earth.
- This is kind of the proto-planetary disc, or a depiction
- of the proto-planetary disc forming around our young sun,
- and so this right here is 4.5 bilion years ago. Now this over here,
- once again, these aren't pictures of them,
- these are just depictions, cause no one was there
- with a camera. This is what we think the asteroid
- that killed the dinosaurs looked like when it was impacting
- the Earth. And it killed the dinosaurs 65 million years ago.
- 65 million. 65 million year ago. Years ago. so until then,
- we had land dinosaurs, and then this, as far as the current
- theories go, got rid of them. Now we'll fast forward
- a little bit more, at about 3 million years ago.
- 3 million. Let me do this in a color that you can see.
- About 3 million. So 3 million years ago. Years ago.
- Our ancestors looked like this. This is Australopithecus afarensis.
- This, she's, uh, this is, I think is a depiction, uh
- This is Lucy. uh, this is one of our, uh, probably
- many of us share, uh, I, i believe the theory is that all of us
- have some of, some DNA from her. But this was 3 million years ago.
- And you fast forward some more and you actually have the
- first modern humans appearing on the planet. People
- that looked and thought like you and me. This is 200,
- 200,000 years ago. That's right over here. Obviously
- this drawing was done much later, but this is a depiction
- of a modern human, so 200,000 years ago. And then
- you fast forward even more , and I don't want to keep
- picking on Jesus. I, I did that when him getting on the jetliner,
- and I, I genuinely don't mean any offense to anyone,
- I just keep picking Jesus because frankly our calendar
- is, uh, is, is, uh, kind of, he, he was a good person that
- most people, most people know about 2000 years ago,
- It's when we associate, you know, kind of a lot of modern history occuring
- after his birth, so i'll put this right here as, obviously
- a painting of the birth of Jesus, and this is 2000
- years ago. 2000 years. And then this might be a little
- bit, uh, a little bit, uh, uh, american centric, but
- you know, the Declaration of Independence, it was a
- major event, actually, even on a world-wide basis
- it was the first, uh, secular democracy, that, based on kind of a
- constitutional democracy that, that, showed up on the
- planet, they had gotten rid of, uh, they said we don't
- want the King of England anymore, and, uh, this was
- about 234 years ago. 234, and I always remembered cause
- I was born almost on the 200th anniversary, so you just
- have to add my age to 200. So this is 234 years ago.
- So these are all, these are all events or periods of time
- that, that we've heard about and we've talked about and
- people throw around these types of years, but what I want to do
- in this video is relate it to time scales that we can
- comprehend, so instead of the Big Bang occuring 13.7 billion
- years ago, let's pretend like it occured 10 years ago,
- cause we can, most of us, especially if you are over the
- age of 10, can kind of understand what 10 years is. It's
- a very, very long period of time, but something that's well
- within our lifetimes, well within our experience. So let's say,
- let's say that 13.7 billion, instead of saying the Big Bang
- occured 13.7 billion years ago, let's pretend like it occured
- 10 years ago. 10 years ago. And if we pretend that it occured
- 10 years ago, let's think about how many years or minutes or hours
- ago each of these events would've occured. So the Big
- Bang, which is really 13.7 billion years ago, if it really had
- occured 10 years ago, and we scaled everything down,
- if we had scaled everything down, then the Earth, the
- Earth, would have been created about 3.3 years ago. So
- this would have been 3.3 years ago. So still, nothing, you know nothing
- kind of amazing about this. This is a significant fraction of the
- age of the universe, so not that, not that
- mind-blowing just yet. But if we go all the way to
- when the dinosaurs were extinct, the last land dinosaurs.
- Now the 65 million years, this will give you an appreciation
- of the difference between million and billion, if the universe
- was only ten years old, then the dinosaurs would have been
- extinct 17 DAYS ago! Not even a month ago, the dinosaurs would
- have been extinct! So, if the universe was created when I was,
- you know,uh, you know, just graduated, well, i'm in my thirties
- now, so when I was 24, Just last month, the dinosaurs
- would have gone extinct! And it gets even crazier!
- 17 days ago, the dinosaurs would have been extinct.
- Australopithecus afarensis would have walked on Earth
- 19 hours ago! Yesterday! 19 hours ago. 19 hours ago,
- she would have been walking around on the planet. And
- modern humans, modern humans, wouldn't have showed
- up until eighty minutes ago. Eighty, eighty minutes.
- A little over an hour, there wasn't even a modern human.
- Then, you know, the universe was ten years, It didn't take until just very
- recently, last hour, for we, us to see someone that looks something
- like us. Looks and thinks something like us. Fast forward
- even more, the birth of Jesus, if the Universe
- was 10 years old instead of 13.7 and, billion, and if we scaled
- everything down, then the birth of Jesus would have been
- 46 seconds ago. 46 seconds ago. And then if we fast forward
- all the way to the Declaration of Independence, this would
- have occured, this would have occured 5 seconds ago. 5 seconds
- ago. So this isn't quite, quite as mind,as mind-blowing as the scale
- of the universe, but in my mind, this is pretty, still pretty amazing,
- I mean all that has happened since 1776, on a global basis,
- could have been encapsulated in 5 seconds if the Universe was,
- if the age of the universe was 10 years. So hopefully,
- that gives you a, a little bit of perspective. In the next video,
- i'm going to compare, instead of, instead of condensing things
- in time, i'm going to compare this scale to kind of a distance scale,
- so we can kind of say "Hey, if the age, if the universe was the,
- the number of pixels on my screen,how big will each of these things be".
Be specific, and indicate a time in the video:
At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger?
|
Have something that's not a question about this content? |
This discussion area is not meant for answering homework questions.
Discuss the site
For general discussions about Khan Academy, visit our Reddit discussion page.
Flag inappropriate posts
Here are posts to avoid making. If you do encounter them, flag them for attention from our Guardians.
abuse
- disrespectful or offensive
- an advertisement
not helpful
- low quality
- not about the video topic
- soliciting votes or seeking badges
- a homework question
- a duplicate answer
- repeatedly making the same post
wrong category
- a tip or feedback in Questions
- a question in Tips & Feedback
- an answer that should be its own question
about the site
Share a tip
Suggest a fix
Have something that's not a tip or feedback about this content?
This discussion area is not meant for answering homework questions.