I’m sure this is a hopelessly uninformed question but that won’t stop me from asking.
I believe the age of the universe is in part derived from determining the most distant stars, and how long it took for the light to get here.
How do we know there aren’t other stars, farther away, for which the light just hasn’t reached us yet?
The Big Bang happened some 13.5 billion years ago. However, the observable universe is much larger than it would be if the expansion happened at the speed of light. A big part of that is due to what is called the inflationary period not long after the Big Bang itself, but also because space itself is expanding as well… And getting faster.
So, the radius of the observable universe is not 13.5 billion LYs as you might assume, but rather about 46 billion light years away. We’re pretty sure there are galaxies beyond that point, but we’ll never be able to observe them.
Also note, if we see a galaxy 12b LY away … we see it in it’s position 12b years ago … it’s further away now
This sounds confusing.
When we look out into the universe, we’re looking back in time. If you look out really far, we see the galaxies in more primitive states, and eventually get to the point where it was just a hot, dense, pretty even distribution of atoms. That’s what is 14 billion light-years away. If you’re asking what is NOW at that distance, not what it was 14 billion years ago, we don’t have access to that.
Well the light is only about 14 billion years old, but it can be up to 46 billion LYs away, due to the expansion of the universe/space. Anything emitting light beyond that point is impossible to observe, though it may exist.
When you look into a night sky
You see the stars far away
You’re seeing them because of the light
Which travels from them to you
Now it takes time for light to travel here
So what you’re doing is seeing the stars as they were in the past
The amount of time it has taken for the light to reach us
And the further and further away those stars are
The further back in time you are looking
Now you are seeing a star that is say six thousand years ago
Imagine somebody on that star looking at us
They would be seeing us as we were six thousand years ago
Which of those two is now?
So space and time are linked together
As we are looking across space, we are looking back in time
Alan Parsons Project - Temporalia, ©1999
Your starting assumption is wrong. The age of the universe is derived from determining the redshift of light from the most distant galaxies and using that apparent speed to determine how fast the universe is expanding.
We assume there’s no end to the stars, but we’re fairly close to seeing as far as is possible, the further away we see the further back we see, and the most distant/ancient regions don’t yet have galaxies, single stars are too faint to make out, and beyond that any emitted light will never reach us because the total space in between is expanding faster than it approaches.
Everywhere we look, looks pretty much the same, so it’s reasonable to assume if you could magically travel to the edge of what we can see from Earth, the surrounding universe would still look the same. If something really weird were going on just outside the observable universe, we’d probably see its effects on the edges of what we can see.
But, if the universe is infinite or near-infinite, then if you could travel muuuuch further than the observable universe, things get mysterious. The big bang and expansion didn’t necessarily occur there. Who knows what could be there, or what could be going on there.
Really weird restaurants.
I’m not sure what that would mean, if the light we’re seeing has been traveling 14 billion years, then it’s traveled 14 billion light-years. 14 gly is the distance. Are you saying that it’s farther away NOW? What does “now” mean?
Try the large fat meaty quadruped of the bovine type!
Now is relative, of course. So in this case it’s particularly meaningless. IANACosmologist, but isn’t this where red-shifting comes into play; since it’s the space between galaxies that is expanding (and in some reference frames compared to another, faster than c)?
“That’s cool… we’ll meet the meat!”
Imagine a rubber band one meter long. An ant starts walking from one end to the other. As he’s doing this, the rubber band is gradually being stretched, so that when he reaches the other end, it’s now 10 meters long. So his starting point is 10 meters from his ending point, but he hasn’t walked a total of 10 meters, because some of the stretching was applied to the part of the band that he had already traversed.
–Mark
Good analogy.
Keeping in mind that astronomers have a LONG history of being WRONG…
Why must the universe have a"beginning"? Because we as humans are born? (Our beginning) And therefore everything else must be the same?
No, there was no “beginning” to the universe. It has just always been here. Period! (And always will be here.)
How do you reconcile that view with the Hubble expansion?
See Observational evidence for the Big Bang for a whole list of observed phenomena that are explained by the Big Bang but are inconsistent with a Steady State universe.
–Mark
But people who haven’t examined the evidence have an even richer history of being wrong.
Look at it this way: the Universe is much like a big runaway train rolling down a hill, once it is set in a certain course of motion it is just going to keep on going. If we look back to the top of the hill using physics we see that the track has a definite beginning and we conclude the Universe had a definite beginning (obviously this is a metaphor here).
Now it could be that appearances are deceptive the train doesn’t behave quite as we thought, maybe for example it travelled around the hill and then rolled onto the track, but this goes very much against what we know about runaway trains and is also rather outlandish. We also concede we don’t know that much about the very top of the hill where the train started and there could well be a less visible and very different track which we don’t know about from which the train came onto the track we can see (i.e. there is some very early Universe physics that means the Universe doesn’t have a beginning as such), but we know the phase of the Universe where it started rolling down the visible track definitely had a beginning and anything else is pretty much conjecture.
We don’t think that the Universe had a beginning just because we do. Indeed, we knew that we have beginnings long before we knew anything about the history of the Universe, and yet the first scientific models of the Universe assumed that it did not have a beginning. We only changed our mind about that based on observed evidence.
I can kind of grasp the universe expanding (or at least appearing to) at an increasing rate or even varying rates depending on the distance you measure over.
Picture two boards side by side. Shove another board between them. now you’re three boards wide. Shove a board between each of those three. now you’re 5 boards wide.
Why do you seem so certain on this? This isn’t what the science or evidence points to.
“Hey, look! All the evidence and research supports the Big Bang model.”
“Yeh, but astronomers have been wrong before.”
“Ahh, yes, you’re right. I guess we’re wrong now as well.”
dumps 100 years worth of study, research and evidence in the trash
I think it’s a bad sign that I seem to find a use for this Asimov quote more often than ever:
“When people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.”
No, that’s how ancient philosophers and theologians thought. One of the most famous Church fathers said that there are four and only four Gospels because there are four winds. Science follows the evidence, not some stupid analogy to an unrelated phenomenon.
Great, let’s see your proof.