Ok, if the universe started with a Big Bang it all began from a single point. If light travels at the universal speed limit of 186,000 miles per second how can we look back in time by looking at things like quasars? Wouldn’t all of that light already be by us? I don’t get it.
If you want to see something that happened 100 years ago, you travel to a point in space a little over 100 light years away from it, then look at it with a really powerful telescope. That’s to get the fine details. The less powerful your telescope is, the less detail you get, untiil you’re down to the point of looking at it with your naked eye, at which point you say, “white, twinkly star.”
Think of it this way; we’ll us the Andromeda galaxy (2 Million light years away) as an object.
2 million years ago a star went nova in Andromeda, you get to see that star tonight. It took 2 million years for the light to reach your eyes. You just see an event that took place when our ancestors we’re picking fleas out of each others hair.
If you mean travel real fast and look back at the earth to observe the 19th century, you can’t do that. It will take you over 100 years to travel 100 light-years. You can’t overtake light which has already left the earth.
No - I understand that. What I’m talking about is the idea that we can see almost to the beginning of the universe. Almost to the Big Bang. I may be confused, but haven’t we located objects in space that go back to almost the Big Bang? How can we still see those emissions if they travelled at the speed of light AS SOON AS the Big Bang happened? Since we all started at the one point it would seem that those emissions that we use to ‘look almost back to the Big Bang’ would have passed us by soon after the Big Bang itself. Yet, it seems that they haven’t. I don’t understand why. I talking about objects we look and can say we are looking 14 billions years in the past — those sort of objects. Sorry.
I’ve been confused about that too - is it because we’re seeing stuff on ‘the other side’ of the big bang? That is, stuff that headed the opposite direction?
Can’t be since the relative speed of light is the absolute speed limit. That is, stuff would appear different to us and relative time would change but the speed of light would not. Unless I just don’t understand.
Wait ---- does the relative time thing have somerthing to do with it?
Well, here’s a question for you: who says that the expansion of space has to be sub-luminal?
Let me try again; (hope this is right.)
Initially you have the big bang and space-time comes into existence. It’s a soup of particles and energy. No photons escape because the soup is dense enough to absorb them. So we have a period of space-time expansion with no light. As things cool down, the soup thins and we wind up with mainly hydrogen, some helium and traces of other elements none of which are emitting light and space continues to expand. Things cool down some more and now we get hydrogen forming stars and light starts to flood space.
But space is still expanding, stretching. The light travels into regions that had expanded while the universe was young. As it moves it these regions, it gets “stretched out” gives us a red shift. And since the universe is/was expanding everywhere at once we get to view the previous fireworks as their light reaches us.
As it moves in to these regions
sigh.
Thanks Grey -
Sorry I was so dense that I could not get my lightbulb to turn on :). That makes perfect sense. Thanks again.
The Big Bang was not a localized explosion that flung matter into existing space. The Big Bang was the creation of space-time and all matter/energy. It happened everywhere. It is the expansion of space itself.
If the universe is infinite, and the recession velocity is proportional to the distance, there must be regions of space receeding from us at greater than the speed of light.
Never underestimate the power of hand waving arguments. I’m just happy it was reasonably coherent.
This thread may be of help with this question.
It was a really big bang, wasn’t it?
-
There is no “other side” of the Big Bang. There is no center point, everything is symmetrical everywhere.
-
There is no space into which the universe is expanding. The universe is space. The universe has no edge.
-
The photons in the early, dark universe couldn’t escape the universe for reason 2. There is no place to escape to. What happened in the early, dark universe was that the photons were absorbed before travelling very far.
-
DrMatrix hits the nail right on the head about expansion speeds. If we appear to be moving away from a quasar at 99.99% of the speed of light, it will take a long time for that light to reach it, even if it was only a few hundred million lightyears away originally. And during the time it takes to reach us, we have appeared to move a long way from the source. (Things are a bit more complicated than that, so pardon my simplification.)
Well, you can look at the sun in theory Tigers2B1 (don’t do it in practice) & see back in the future about 8 minutes…which is about the time it takes light to reach us from the sun.