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Cosmology and astronomy
Course: Cosmology and astronomy > Unit 1
Lesson 2: Time scale of the cosmosCosmological time scale 2
Cosmological Time Scale 2. Created by Sal Khan.
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- if the big bang was a small point that contained the entire universe in it, wouldn't it be so dense that it would a black hole?(5 votes)
- Is it true that if you get sucked into a black hole, you'll be ripped appart atom by atom?(1 vote)
- You would get turned into very long and thin noodle some time after hitting the event horizon by the difference in gravity, then you would rip apart once you got to a microscopic chain of atoms and you couldn't stretch any further assuming the black hole was that large. Then your atoms would be shoved onto the singularity at the center, where it would be stuck until Hawking radiation sent it out perhaps billions of years later. And of course nobody would be able to tell what the heck your particles were once it came out.(8 votes)
- If the first "modern" humans were on earth over 200,000 years ago then why did it take over 195,000 years for them to start making things like say... a wheel?(2 votes)
- "Modern humans" doesn't mean modern only in technological sense, instead here it means when humans started interacting with each other, cooking food etc. So 200,000 years ago they just started out doing the basics, but for them the wheel was something huge which could reduce their muscular force and making things easy to carry etc. you can say that it lay foundation for today's engineering.(5 votes)
- Why is light the fastest possible speed?(3 votes)
- Anything that has no rest mass will travel at the maximum possible speed. Light being massless travels at this speed.(5 votes)
- Is it possible that the "life" of light is 13.1 billion Years, i mean could the light by dessintegrated or "die"?(2 votes)
- My understanding is that light itself is not though to experience time. An individual photon is simultaneously emitted and absorbed, from it's own perspective. This implies that, unless something else stops it, a photon will not "die". There might be some stuff stopping it that we don't know about, but there doesn't seem to be any reason to believe that this is is the case.(3 votes)
- wher did the big bang even occure?(4 votes)
- Wow this page is old. You can now put a place (approximately) on where the Big Bang occurred. As mentioned above it is the Doppler shift. Every Galaxy is moving at it's own rate but all at about the same speed. Galaxy Andromeda is on a collision course with us (3 billion years before we have to worry about it) but Hubble is still witnessing Galactic convergences right now.
Jesus may have been on the Roman/Jewish census but never mentioned that he was the son of God. New DNA sequencing of parthogenetic life forms shows that if he was born of an immaculate conception, he would have to have been female!
New info shows that the Big Bang happened 13.739 Billion years ago, and that it is likely that a major Black Hole at the centre of each galaxy is crucial to it's integrity.
Scientist do not make things up (well, charlatans do) they use observable data and test it. Any experiment that cannot be reproduced is a failure of the original hypothesis. Often, that is a good thing, it promotes further investigation.
Thanks for reading.(1 vote)
- it is "possible" but considering the evidence "unlikely", which if you do a little grunt research work anywhere from Wikipedia to basic biology and anthropology textbooks, is fairly well resolved. The question is whether we descended from Australpithecus or some other similar, earlier, group of hominids. At present the evidence suggests we are descended from some Australpithecus group, either Australpithecus africanus or Australpithecus afarensis. We might not, as you suggest, be related to any Australpithecus lineage but some other earlier lineage where the Australopithicine group was just a dead-end, but, given what we know this isn't entirely probable.(3 votes)
- how many dimensions are there in the universe?? and what are they??(1 vote)
- We have no idea how many dimensions may exist.
We can perceive 3 spatial dimension and 1 temporal one.(4 votes)
- So, the dinosaurs became extinct because an asteroid hit Earth? How was the Ice Age created?(2 votes)
- The mass extinction of the dinosaurs and many other living things was caused by the impact of a large asteroid on the Earth sixty-five million years ago, called the Cretaceous–Paleogene extinction event.
The causes of ice ages are not fully understood.The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane changes in the earth's orbit around the Sun ; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on the earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth-Moon system; and the impact of relatively large meteorites, including eruptions of super volcanoes.
So I may not have an exact answer to your question friend but as per scientists it's still not clear.(2 votes)
- How far from earth is the Webb telescope?(2 votes)
- About 1.5 million kilometers (932 thousand miles)(2 votes)
Video transcript
In the last video, we tried to
relate what 13.7 billion years really means by compressing
it to 10 years, which is still a pretty long time, at
least from our perspective. And we saw that these huge
periods of time, everything that's happened since
the United States Declaration of
Independence, all gets compressed into
just five seconds. And that's not much when
you think about 10 years. I mean 10 years, you
could wait around a lot. That's a huge amount of time. So hopefully, that put things
in perspective a little bit. What I want to do in this video
is kind of do the same thing, but relate the 13.7
billion years, if that were a distance or the
length of a time line, how big each of these
periods would be. So just to start off,
at the timeline-- I'm recording this in
high definition right now. There should be
1,280 pixels wide, depending on where
you're watching it. So maybe you're watching
it on a high def TV. If the timeline was
width of my screen right over here, if the timeline was
the width of my screen here, so if that was
13.7 billion years, from there-- let's say this is
the beginning of the universe and this is our present time. If that was 13.7 billion
years, the amount of time that humans have been
on this planet-- modern humans, so people who look and think
like us-- the amount of time that we have been on this
planet will not even be a pixel. This little dot I drew
is multiple pixels. The amount of time we've been
here would not even be a pixel. In fact, a pixel--
and that dot I drew here is about four pixels. But a pixel, just one
little pixel on my screen, would represent
11 million years. Let me scroll over it. It would represent
11 million years. So if this was the
timeline, the dinosaurs would have been extinct about
six pixels from the end. So it would be right about--
so six pixels from the end is when the dinosaurs
would have gotten extinct. And the amount of time that
modern humans are on the planet wouldn't even register here. It would be 1/20 of
that pixel over there. In fact, if we just expanded
that very last pixel-- if we were to expand
that very last pixel-- I'll do it in yellow-- that very
last tiny pixel that you can't see, if we were expand
that to the entire length of this screen again-- so
if we were to just expand just that very last pixel--
so I'm saying everything on this yellow line could be
contained in that very last dot right over there, then
every pixel in this would still be 8,000 years. So the entire period
of time that humanity has been on this
planet on this scale-- so we've broken out this
little tiny pixel here all the way out here, 200,000 years,
that's on the order of about 25 of these pixels. So 25 of these pixels would
be something like that, not even that, not even that. So 25 pixels on this screen--
at least at my resolution, is about that distance. So this is the fraction
of just that pixel that is the amount of time humans
have been on the planet. If you want the
time since Jesus, it would be 1/4 of a pixel
on this yellow scale. On this yellow scale, it
would be 1/4 of a pixel. And the amount of time to the
Declaration of Independence would be even a more
minuscule amount of time. So that's one way
to think about it. But these timelines to some
degree also don't give justice. So another way to
think about it, what if we had a time line
that stretched from here, where I am, in this
San Francisco Bay Area, if it stretched 1,300
kilometers to Seattle? So if this thing
stretched 1,300 kilometers all the way to Seattle, so
this thing, the Big Bang, would be sitting in Seattle. This would be
sitting in Seattle. The universe--
well, the formation of the Earth and the
solar system, this would be about 200
kilometers away, a little over 200 kilometers. And in the direction of
Seattle, I don't know, that would get us in
probably some part of northern California
with redwoods and whatnot. But just to give an
idea of 200 kilometers, that would get me from where I
am near the coast of California to about the Nevada border. So still a pretty
good distance relative to the entire timeline. The dinosaurs, the
last land dinosaurs, when the Earth got hit by an
asteroid this-- so remember, our whole timeline now stretches
all the way to Seattle. This event now would
have only occurred about 3,000 meters away. Or maybe I should just say
three kilometers away or roughly about two miles. So that's still seems like
a pretty good distance. But remember, our timelines
stretches all the way to Seattle from the
San Francisco area. So it's a pretty big timeline. So this is already a
pretty small distance. But it gets even smaller. Australopithecus,
this right over here, when they were roaming the
Earth 3 million years ago, this gets reduced
to a little bit more than a football field, about
150 meters, not kilometers. Let me write that in a color
where there's some contrast. 150 meters is
where-- so 150 meters in the direction of
Seattle, if that's the timeline that
we're talking about. And then the first
humans, even shorter. It's only going to be 10 meters,
10 meters of this timeline that stretches all the
way to Seattle. The birth of Jesus,
2,000 years ago, would be 10 centimeters, 10
centimeters on a time line that stretches from San
Francisco to Seattle. And then finally, the
Declaration of Independence, the American Declaration
of Independence, would be 1 centimeter on a time
line that stretches to Seattle. Anyway, I don't know
if that put things in more or less perspective. But it was worth
giving it a shot.