Age of the Universe question.

[RaulDuke21]

Ok ive been looking over alot of science forums for awhile now and there is something that keeps bugging me.

 

I believe we estimate the universe at 13.7 billion years old. Hubble has taken deep field photos of galaxies that appear to be 13 billion years old. That appeared just after the dark age.

 

Here is my problem. We can supposedly see things that happened just 700 million years after the universe began, yet at that time when the light came from those galaxies we couldnt have been more than 1.4 billion lys away from them. Thats even if we were moving at the speed of light up until that point. So how could we just now be seeing that light? I would have thought that light would be long dead.

 

So please if someone could enlighten me and help me grasp what im missing here I would greatly appreciate it.

[Airbrush]

That's a good question Raul. Until Martin or someone else answers, I will take a feeble stab at it. Suppose that light we see now originated from a position 1.4 Billion LY away from us. We are only seeing it now because we never had the capability of seeing that far into space until now.

 

Correct me if I am wrong, but I think if we could go back in time a few Billion years and set up our modern telescopes that can see the object, we would see it back then also, just not as red-shifted as we see it now.

[RaulDuke21]

Thanks Airbrush for the reply, but that still doesnt fit with what I am thinking of. Ive got a couple more things I wanted to add before hitting bed that just occured to me.

 

I am under the impression that we are 13.7 billion ly from the origin of the universe. If we expanded under the speed of light, than we shouldnt be able to see that far back in time. And if we are that far from the origin than the universe is much older because of slower expansion.

 

Now if we expanded faster than light then slowed down, and we are 13.7 billion ly away than we would see that light now but the age should be much younger, so I am confused.

 

I think whats getting me on this is I hear we expanded fast but we are supposedly accelerating now, yet we are expanding under the speed of light or we wouldnt be seeing these distant objects.

 

Sorry about the post just trying to see logic in this. Thanks again for any help.

[Airbrush]

We are not 13.7 Billion LY from the origin of the universe. The furthest we can "see" is the CMB (cosmic microwave background) radiation which is now about 45 Billion LY away, or about 50% further from us that the most distant visible galaxy, quasar, or gamma ray burst (GRB), which are now about 30 Billion LY away with a red-shift of about 8 (or 8.2 for that recent GRB).

 

Sorry I don't understand the remainder of your question. Anyone else?

[Mr Skeptic]

The universe's expansion is such that each meter expands by the same amount (minus the effects of gravity). This means that for something far enough away, it will be expanding away at or faster than the speed of light (and it will essentially no longer be part of our universe, or if you prefer, we would no longer be causally connected to it). It also means that by looking the right distance away from us, we will see light that was emitted as far back in the past as we like, until the start of the universe. The farthest we can see is called the Cosmic Background Radiation.

[Severian]

yet at that time when the light came from those galaxies we couldnt have been more than 1.4 billion lys away from them.

 

That statement is the flaw in your reasoning. The universe was not created at a point, so things can have large separations right from the start.

[Sisyphus]

Indeed, it seems you are under the impression that the Big Bang and the expansion of space are like an explosion moving away from a central point. This is not the case. The universe has neither a center nor edges. Its origin is everywhere at once, and its expansion is not movement, but an increase in the amount of space itself. These are difficult and counterintuitive concepts, and it takes a while to get used to them.

 

It might help to simply ignore the "space is expanding" part at first. Just imagine that the universe, all of it, just came into existence all at once and as spread out as it is now, at the event we call the Big Bang. Suppose, again, that it is infinitely large. Looking in any direction, then, will show you the same thing, like looking back in time. The light you see from 1 billion light years away in any direction is from 1 billion years ago, etc. The farthest you can see in any direction, then, is going to be with light from the very beginning of the universe, or at least from the very beginning of when there was light to see. Because the universe is infinite in size, you will never stop seeing that early light - instead, it will just be from further and further away, and the bubble of "stuff we can see" gets larger and larger, its radius expanding at the speed of light.

 

Now, that's an oversimplification, because space is expanding, just in a different way then you're imagining. But that isn't necessary to understand to answer your initial question, I don't think.

[NowThatWeKnow]

The Ned Wright calculator gives some really neat information but may seem a little complicated at first.

http://www.astro.ucla.edu/~wright/CosmoCalc.html

If light took 13.665 billion light years to get here, the age of the universe, it was emitted when it was only 0.045541 billion light years away and is now 45.587 billion light years away. The galaxies are basically at rest in the universe and the change in distance is because of the expansion of space itself. The light coming from that same galaxy now is so far away we will never see it because space is expanding faster then the speed of light at that distance. This shows that the universe was more dense long ago but the distance we see is likely not all there is.

Edited May 6, 2009 by NowThatWeKnow

[jackson33]

The Ned Wright calculator gives some really neat information but may seem a little complicated at first.

http://www.astro.ucla.edu/~wright/CosmoCalc.html

If light took 13.665 billion light years to get here, the age of the universe, it was emitted when it was only 0.045541 billion light years away and is now 45.587 billion light years away. The galaxies are basically at rest in the universe and the change in distance is because of the expansion of space itself. The light coming from that same galaxy now is so far away we will never see it because space is expanding faster then the speed of light at that distance. This shows that the universe was more dense long ago but the distance we see is likely not all there is.

 

Please explain the expansion speed compared to distance between objects. Think we would notice our Sun's movement, or Andromeda heading away, if it's that great.....Opinion!!!

[NowThatWeKnow]

Please explain the expansion speed compared to distance between objects. Think we would notice our Sun's movement, or Andromeda heading away, if it's that great.....Opinion!!!

Local gravitational forces in a galaxy OR in a cluster of galaxies overcomes the expansion occurring in open space. I calculated the percent of expansion needed for this rate and it is actually very small. I do not recall at the moment the exact #'s but local gravitational forces overcome it. That is what the people that have a clue tell me anyway.

[RaulDuke21]

Thanks, I now see my flaw. I was under the impression that all things were created at a central point. So I can see now that as the temperature cooled down enough for gas to start coming together and lighting up, it was already larger than our visible universe. We basically have no distance to anything just a time we can put to the CMB.

 

What we are basically seeing is these stars that have just formed out of this gas from the CMB, correct? Basically any direction we point a telescope we could perhaps see these early stars and galaxies.

 

I believe I understand what is going on now. Every documentary, everything that I have read makes it seem that a singular point started it all, but that is what was confusing me as it didnt make sense with our current universe.

 

Thanks all!!

[Sisyphus]

Please explain the expansion speed compared to distance between objects. Think we would notice our Sun's movement, or Andromeda heading away, if it's that great.....Opinion!!!

 

In addition to gravity holding local structures together, remember that the rate at which things are getting farther away is proportional to their distance from us, hence the greater redshift for more distant objects. If you add an inch per second to every foot, something one foot away only moves away at 1 inch per second, something a mile away moves at 1/12th mile per second (300mph), something 12 light years away moves at the speed of light, etc.

[RaulDuke21]

Sisyphus, thanks for your posts but I am still troubles by this concept. Its the expansion that gets me the most.

 

Things farther away are expanding faster than things closer to us, correct? If this is the case how could we see distant objects at all? I guess there would have to be a limit to what we could see. Even the distant objects I would think would be moving slower to our eyes because of time dilation. Or does the speed of light just bypass expansion somehow and we cannot explain it.

 

Sorry for not quite understanding but this is really intriguing stuff.

[Airbrush]

The Ned Wright calculator gives some really neat information but may seem a little complicated at first.

http://www.astro.ucla.edu/~wright/CosmoCalc.html

If light took 13.665 billion light years to get here, the age of the universe, it was emitted when it was only 0.045541 billion light years away and is now 45.587 billion light years away. The galaxies are basically at rest in the universe and the change in distance is because of the expansion of space itself. The light coming from that same galaxy now is so far away we will never see it because space is expanding faster then the speed of light at that distance. This shows that the universe was more dense long ago but the distance we see is likely not all there is.

 

Good reference. Right, you are referring to the CMB radiation that is the furthest we can possibly detect, by any available means, because before 13.667 Billion years ago the unverse was still opaque. After that it cooled down and the dark age began that lasted until the first stars and galaxies formed about (what?) one Billion years later? I think I recall the dark age could have ended 200 Million years after the dark age began? I think it is not light at that distance but only a feeble glow near absolute zero. The first light came after the dark age when the first stars ignited. Those stars are about 30 Billion LY away now, and the cosmic background is 50% further at 45 Billion LY away.

---

Merged post follows:

Consecutive posts merged

".....how could we see distant objects at all? I guess there would have to be a limit to what we could see. Even the distant objects I would think would be moving slower to our eyes because of time dilation. Or does the speed of light just bypass expansion somehow and we cannot explain it.

 

We see such distant objects because the light, or temperature reading, left that object or area of space in time for us to see it, and that happens to be limited by the age of the universe and the age of those first stars or areas of gas and dust in space.

Edited May 6, 2009 by Airbrush
Consecutive posts merged.

[Martin]

... If you add an inch per second to every foot, something one foot away only moves away at 1 inch per second, something a mile away moves at 1/12th mile per second (300mph), something 12 light years away moves at the speed of light, etc.

 

It's a good illustration of the basic idea, but one of the numbers is off.

The 12 lightyears distance would not be growing at the rate c, but would be growing at the rate of 30 million times the speed of light.

 

This is allowed by General Relativity, since we are not talking about motion, but about changing distances (dynamic geometry). So your example is not non-physical. That kind of very rapid increase is a feature of some inflation scenarios.

 

One way to correct the post would be to say "the distance to something 12 light seconds away increases at the speed of light, etc."

 

For reference, 12 light seconds is about ten times the distance to the moon.

Edited May 6, 2009 by Martin
Consecutive posts merged.

[NowThatWeKnow]

Good reference. Right, you are referring to the CMB radiation that is the furthest we can possibly detect, by any available means, because before 13.667 Billion years ago the unverse was still opaque.

...

 

You can put in a large enough z # to take you back to the big bang but that doesn't mean there was anything to actually see then. Seems like Martin did that once just to show what the #'s would be.

 

Another thing to point out in this thread is that if you were at the edge of the observable universe, you would probably still see the universe in the same way we see it from the Milky Way in all directions. It could be really big. If it is infinite and the big bang was infinite, what size is it after expanding?

[Airbrush]

"...something 12 light years away moves at the speed of light, etc."

 

I think you mean that something over 13 Billion ly away is expanding away from us at over light speed.

---

Merged post follows:

Consecutive posts merged

"The 12 lightyears distance would not be growing at the rate c, but would be growing at the rate of 30 million times the speed of light."

 

You have got to be kidding right?

[Sisyphus]

"...something 12 light years away moves at the speed of light, etc."

 

I think you mean that something over 13 Billion ly away is expanding away from us at over light speed.

---

Merged post follows:

Consecutive posts merged

"The 12 lightyears distance would not be growing at the rate c, but would be growing at the rate of 30 million times the speed of light."

 

You have got to be kidding right?

 

Airbrush, I was using a simple example of space expanding at a rate of 1 inch per foot per second (which is obviously very very very much faster than the actual expansion), as a way of explaining why things farther away appear to be moving faster. I mispoke (miswrote?) in one example, and Martin corrected me.

[Martin]

... a simple example of space expanding at a rate of 1 inch per foot per second

 

That's a helpful kind of example because easy to picture. I don't remember ever using that kind of simplified illustration.

 

You are saying let the distances (those that are governed by the expansion law) increase by 1/12 or 8 percent, every second.

 

Currently in the real world, distances (largescale ones) increase 1/140 of a percent every million years. A tiny percentage in a mindboggling long time. So it's hard to picture.

 

What you are saying is easier to picture: 8 percent increase every second.

 

Anybody,

How are we coming with RaulDuke's questions? I have a feeling that RaulDuke is OK at this point. On the other hand, Improvision seemed to be discontented.

 

It's great to feel more like a cosmology mob than an isolate, enjoying it

[RaulDuke21]

Thanks again everyone but I understand this expansion of space, I think, say galaxyA 1mly away is moving away from us, galaxyB 2mly away is moving away,(but the galaxies arent moving just space in between is getting bigger) but also galaxy A would see both us and galaxyB moving away from it at the same rate. That is a shortened sorta version of whats in my head.

 

But what gets me is how light is being seen from far off distances from the past if we are all expanding away from each other at an accelerated rate, that light should have reached us earlier it would seem to me.

 

Thanks again, and Martin im monitoring your new thread hope to find answers there.

[Martin]

But what gets me is how light is being seen from far off distances from the past if we are all expanding away from each other at an accelerated rate, that light should have reached us earlier it would seem to me.

...

 

Raul, have you watched the wright balloon model movie yet?

 

Google "wright balloon model". It's just a simple 2 or 3 minute computer animation. It helps a lot of people to visualize what cosmologists are talking about.

 

About your question, "light should have reached us earlier", I don't understand: earlier than what?

Edited May 8, 2009 by Martin

[NowThatWeKnow]

Thanks again everyone but I understand this expansion of space, I think, say galaxyA 1mly away is moving away from us, galaxyB 2mly away is moving away,(but the galaxies arent moving just space in between is getting bigger) but also galaxy A would see both us and galaxyB moving away from it at the same rate. That is a shortened sorta version of whats in my head...

 

Watch the Wright Balloon video as Martin suggested. A picture is worth a thousand words.

 

Also, if you can visualize a balloon slowly filling up with air and the balloon has dots (dots are galaxies) all over it. No matter what dot you are on, all other dots are moving sway from you. The further away the dot is the faster it is moving away. Space is expanding between each dot. There is no center on the surface of the balloon and every location will yield the same view.

 

 

Now put an ant on the balloon (Not sure why I use ants). Say his movement represents the speed of light. He can easily get to the dots near by but if the balloon is expanding fast his speed may not be enough to get to dots far away.

 

I am tired of typing. Go watch the short video.

 

Edit - http://www.astro.ucla.edu/~wright/Balloon2.html

Edited May 9, 2009 by NowThatWeKnow

[Gag Me]

Unfortunately, this is the only thing I don`t really leave to science...

Mom says, the universe is the only thing that doesn`t have to be created...

everything else does.

 

The universe has always been here.

But this is more of a belief than a theory or facts I have found.

 

 

 

 

 

//sigh// Maybe I`ll never fit it >____>