Photons are emitted by electrons losing an energy rating/level, but don't they actually also energize any electrons they hit, thus effectively potentially reproducing themselves, Mr. Khan?
@garyliu6589
5 жыл бұрын
How do we get the radius of 46b ly?
@jonjonjon1370
14 жыл бұрын
Yeah, I was confused
@chissstardestroyer
4 жыл бұрын
Referencing your correction, Mr. Khan: we're not even sure when the first stars formed, are we? So in the end, it mightn't make that much of a difference, with the exception of the science of the issue regarding the science of math.
@rimbaud1020
11 жыл бұрын
Light years is a measure of distance, not time. Years is a measure of time, not distance. It is an easy mistake. And "Space" can expand faster than light can travel. That is what he is explaining. It's counter intuitive to our brains, I know. But it is reality. The terms are also easy to confuse.
@moneyeye24
3 жыл бұрын
@00:33 should be 1 million years away
@zalida100
14 жыл бұрын
haha funny, I noticed that when you were dealing with billions and hundreds of thousands etc. but I think it would be fairly obvious to most people that it was just a small error. (It was still 3 orders of magnitude out, but hey. No big deal) Enjoying these vids very much - I'm looking forward to when you explain olbers' paradox - That'll be fun. Just kiddin.
@quaz3
11 жыл бұрын
I didn't confuse those terms. In what theory is the (visible) universe several million light years across 300,000 years after the Big Bang? None that I know of. Besides that was not the point he was making. He does fantastic work, but errors happen...
@DMSJagXK
2 жыл бұрын
The Universe is 13.8 billion years old and the edge of the Observable Universe is 46.5 billion light years away, how do you explain that. We know we are not seeing what it was like 46.5 billion years ago, since time and it didn’t exist then! Imagine you had 25 people standing in 5 lines of 5 to represent the singularity, then free space grew by 1 metre between each of them so they would now all be a metre apart. The middle did not move faster than the edges because none of the people actually moved in free space. There was relative velocity between the people but no real velocity since none of them had actually moved through free space. If originally the 25 people were standing on black crosses, they would still be standing on the same black crosses after the expansion. Each person had a zero displacement, therefore zero velocity. Whichever person was the observer, they would see all the other people going away from them, the people furthest from them would have had the biggest relative velocity to them. Imagine you were a person at the end of one of these lines of 5 people. The nearest person to you would have moved an extra 1 metre from you while the person at the other end of the line would have moved 4 metres from you. If you now imagined there were millions of people and they all moved an extra metre apart due to the expansion of free space between each of them how the furthest person could have had a RELATIVE velocity exceeding the speed of light. This also explains why the edge of our Observable Universe is about 46.5 billion light years away even though the Universe is only 13.8 billion years old. The most distant galaxies didn’t have to move faster than the speed of light in a vacuum, it was free space expanding the space-time away from us faster than the speed of light that enabled them to be that far away.
@quaz3
11 жыл бұрын
Plus 300,000 years after the Big Bang a distance of several million light years between two objects wouldn't have been possible.
@timjohnson3913
2 жыл бұрын
Wouldn’t have been possible in our observable* universe agreed, but it’s definitely possible as we don’t know the extent of the universe which includes the unobservable portion.
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