Peering back to the beginning of the universe

[dogjones]

I have a question. Forgive me here lads and lassies because I am no physicist (and I am a bit of a woolly thinker) so I am sure I’m muddling plenty of concepts etc. But, here goes:

The further back in time we are able to look depends on the distance we physically are from the light source. But as the universe supposedly expanded rapidly outwards from a singularity and continues to expand, there surely must be a limit to how far back in time we are able to look, because the further we wind the clock backward (in the real sense), the closer the Earth gets to said light source. What is this limit?

Thanks!

[PatKelley]

This is why the furthest radiation is so attenuated; it's in the microwave range. As the universe expands, the radiation from each of these receding sources drops into the infrared, then the microwave, then presumably lower and lower radio. At some point the observed speed of recession will exceed that of light (if the expansion is acellerating), and we will be left with a fading after-image.

The actual limit is the surface of last scattering, or the point at which density of matter and light reached a point at which light could travel; the point at which the universe in its expansion became transparent.

[dogjones]

At some point the observed speed of recession will exceed that of light (if the expansion is acellerating), and we will be left with a fading after-image.

Hmm, that's interesting. Does this mean that us and the source can "out-run" light if we are moving away from each other sufficiently fast, or have I misunderstood?

The actual limit is the surface of last scattering, or the point at which density of matter and light reached a point at which light could travel; the point at which the universe in its expansion became transparent.

I didn't know light's ability to travel depended on the density of matter and light - how does that work? Did matter and light reach a certain density and then light just sort of shot off at c, or did light travel slower before this happened? I thought light had no density anyway? What do you mean by "transparent"?

Do we have any idea how long after the big bang did this "surface of last scattering" took place? Will we be able to observe this? Why is my brain hurting? Anyone fancy a pint?

[PatKelley]

Hmm, that's interesting. Does this mean that us and the source can "out-run" light if we are moving away from each other sufficiently fast, or have I misunderstood?

Nope, you've got it. Neither individuall will be moving at or above the speed of light; but their relative motion will appear to as space in-between expands faster than the speed of light. That is if expansion is accelerating.

I didn't know light's ability to travel depended on the density of matter and light - how does that work? Did matter and light reach a certain density and then light just sort of shot off at c, or did light travel slower before this happened? I thought light had no density anyway? What do you mean by "transparent"?

The universe had to cool to the point where it was no longer a high temperature plasma. High temperature high density plasmas are opaque to many wavelengths of radiation, as they are a soup of charged particles. When electrons began combining with protons in the cooling universe, the plasma had cooled to the temperature and lowered in density enough that it was no longer opaque. This is the surface of last scattering.


Do we have any idea how long after the big bang did this "surface of last scattering" took place? Will we be able to observe this? Why is my brain hurting? Anyone fancy a pint?
Approximately 300,000 years after the Big Bang. [LINK (http://relativity.livingreviews.org/Articles/lrr-2001-2/fig_8.html)]This is essentially the microwave background radiation, but we have not resolved details from this era as there really would be no details to resolve. Probably dehydration; it can cause headaches. Make sure you take some water with that pint.

[Bronze Dog]

Why is my brain hurting?
Because it's probably bleeding (http://www.bobandgeorge.com/Archive/Jun04.php?date=19) like mine.

[St_Hereticus]

As I undrstand it, massive objects can't travel through space at greater than lightspeed, but space itself can expand faster that the velocity of light, as it did in the very earliest (inflationary) period of the universe.

[Ohmer]

But as the universe supposedly expanded rapidly outwards from a singularity and continues to expand,

This isn't quite right. An episode of Scientific American Frontiers delt with this. Here are couple quotes I found helpful.

http://www.pbs.org/saf/1405/features/back.htm
The Big Bang - At the moment of the Big Bang, the Universe was infinitely dense and unimaginably hot. In an instant an explosion occurred simultaneously everywhere, filling all space with energy. Unlike an explosion with a distinct center, the Big Bang stretched space between every object everywhere so that everything moved further away from everything else. Cosmologists believe that all forms of matter and energy, as well as space and time itself, were formed in this instant.
http://www.pbs.org/saf/1405/segments/1405-1.htm
Most people think of the Big Bang as a monumental explosion that happened in one place and radiated out from the center. But cosmologist Max Tegmark tells Alan the universe never had a center, and the Big Bang didn't either. Instead, space was and is elastic, constantly stretching so that everything moves farther away from everything else. Or, as Alan puts it, the Big Bang was more like the Infinite Taffy Pull.

My brain also hurts and I would love a pint.

[dogjones]

As I undrstand it, massive objects can't travel through space at greater than lightspeed, but space itself can expand faster that the velocity of light, as it did in the very earliest (inflationary) period of the universe.

Can we ascribe "velocity" to space itself though? I would have thought that velocity presupposes space - ie, in order to expand at a certain velocity you need space to expand in. Oh jeez, I think I'd better make it two pints.

[dogjones]

"Most people think of the Big Bang as a monumental explosion that happened in one place and radiated out from the center. But cosmologist Max Tegmark tells Alan the universe never had a center, and the Big Bang didn't either. Instead, space was and is elastic, constantly stretching so that everything moves farther away from everything else."

So how does the current expansion of the universe work if it has no centre? If we're going from a multitude of arbitrary points then doesn't that mean contraction in some areas and expansion in others? And anyway, if the universe is finite, which apparently it is, then doesn't that automatically mean it must have a centre?

[dogjones]

Actually thinking about it I understand the elastic stretching analogy. So disregard the "multitude of arbitrary points" idea. But I still maintain it surely must have a centre.

[Ryan O'Dine]

Actually thinking about it I understand the elastic stretching analogy. So disregard the "multitude of arbitrary points" idea. But I still maintain it surely must have a centre.

Think of the universe as the surface of a balloon with dots painted on it. As you blow up the balloon, the surface expands, and all dots move away from each other without there being a center.

From the purely observational standpoint, there is something called the microwave background radiation (http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation). If there was a center to the universe, this background radiation would not look the same in every direction, which is to say be isotropic. But, in fact, it is.

[Iamme]

I have made and scrapped 5 lengthy posts, because I actually started to confuse even me, with this.

Here it is, short and sweet:

The universe we currently see already *IS* the universe out of the past. The light that we see from all the stars is showing us how they looked back the number of light years they are away from us. [i.e., the closest star from us is about 4.7 light years away. We are seeing it's light, with the naked eye, the way it appeared 4.7 years ago. And if we look at it through the most powerful telescope?; all that will do is make it clearer. It won't let us see how the light looked 2 years ago! (If I'm wrong on this, be sure to let me lknow)]

National Geographic did a map out to 13.5 billion (or so) light years, showing the positions of the various galaxies, etc. with various named galaxies and stars. But as I said, that is ALREADY out of the past, because if the light has already entered the naked eye or the telescope, that means the light has already gotten here. It has to be already here for it to enter the lens of a telescope.

Therefore, you aren't going to be able to see back any further. All you will do is see what appeared small, as being larger and more clear!

Scientists are out to lunch on this one.

All they are going to see and discover, that which has already been shining on the earth, but too faint to be seen by the naked eye.

If I am wrong, then one day that means that if they make a super collosus telescope that can REALLY peer back into time, that when they point their telescope in all directions, they will see a flash of light. They will see the singular. But it ain't goona happen for the reason I started. What WILL hapen though is that they will keep seeing a more immense and defined universe. And that's it. Period.

[AnotherSillyAlias]

Scientists are out to lunch on this one.



I think it's reasonably clear who is out to lunch.

I sincerely hope you are not now, or ever intend to become, a school teacher.

What exactly is it that you don't understand about telescopes, distant galaxies and time? If you see a distant galaxy, with or without telescope, you are seeing it as it was X million years ago. You are effectively looking back in time. What is so hard to understand about that?

Why am I bothering?

[sparks]

I'd like to remind Iamme that the larger the scope, the more light it collects (makes visible to the eye), therefore, objects previously invisible due to thier distance from us become visible. We see further into the past. Specifically, never before seen objects as they were further in the past.

[Iamme]

I think it's reasonably clear who is out to lunch.

I sincerely hope you are not now, or ever intend to become, a school teacher.

What exactly is it that you don't understand about telescopes, distant galaxies and time? If you see a distant galaxy, with or without telescope, you are seeing it as it was X million years ago. You are effectively looking back in time. What is so hard to understand about that?

Why am I bothering?

Nothing! (A response to your second to your last sentence) Can't you understand my post? I already acknowledged that. That you are seeing back in time! We already see time distant with the naked eye! Didn't you follow what I said about the closest star to us? Why should a telescope cause us to peer back into time any farther than the light that has already got here? Think real deep about this. It will go over ones head unless you can follow this.

Okay, I will explain agian, just for you:

You have this pin prick of light out there billions of light years away. That light has already struck the earth. You can't use a telescope as some aid, to suddenly fidsn light, that hasn't already been shining on the earth. Otherwise, how could it get into the lens of the telscope. Light travels TO an object. The telescope doesn't have majic to propel it's sight out to the star!

I am already acknowledging to you that that the light that has gotten here is billions of years old. Follow? When you look in the telescope, the light has to be there for it to enter the lens of the telescope. Therefore, that old light is already here as the old light! By using the telescope will in no way make you peer back further. It will just allow you to see the light that has been sooooo dimly hitting the earth, to be clearer and bigger. You aren't going to say, "ohhhh..the faint light that is hitting the earth today is 5 billion years old. But now that I can see that star that I couldn't see before means that I am seeing farther back into time. Why can't you say that? For the reason i kep harping on: Even though you cojuldn't see that star doesn't mean the light wasn't already striking the earth. It had to be. That' the only way you are able to recieve it in the telescope! (And that is what is confounding people, I think.)

If I draw a dot on a wall, and stand back in the house 40 feet and ask you if you can se tthe 'star" I made on the wall, you wil say no. Then I will offer you a telescope, to take a second look. Then you will say, "There it issssss!". In each case, that dot "star" was being received by your eye. By using the telescope you are not peering back to when I drew it on the wall. Not even by one fraction of a second! All it is doing is magnifying that which your eye was already receiving but not acknowledging, because it was so small.

[Iamme]

I'd like to remind Iamme that the larger the scope, the more light it collects (makes visible to the eye), therefore, objects previously invisible due to thier distance from us become visible. We see further into the past. Specifically, never before seen objects as they were further in the past.

Read my subsequent post. Your err in logic comes at the point of line 2 1/2....where you say, "We see further into the past." Yes, we do...in away. We see more clearly the light that was already coming into our eyes. But that's it.

Just because we now discover that which we didn't see before doesn't mean we are peering back to the beginning. All we are doing is learning that something is out there that indeed is old, siomply because we can see it better now by aid of an instrument.

So, one guy says to another guy, "Hey, The universe is only 5 billion years old. I looked. That's all the farther I can see. The last star I see is 5 billion light years out." But this second guy says, "Uh uh. It's really 13.5 billion light years out away from us right now. The universe is really 13.5 billion years old. And I'll prove it to you. Take a look through this. So he hands the guy a real powerful telescope. "Sure enough", exclaims the guy. Your'e right! I can now see 13.5 billion years into the past. I am seeing back into time 8 more billion years ago. I am seeing closer to the beginning of creation."

Not so. He is only seeing that indeed the STAR is out there 13.5 billion light year away and is 13.5 billion years old. But this has no relevance as to seeing the star in any contesxt of being closer to the Big Bang. They are two separate issues. All you are doing with the telescope is discovering more immensity. You are not able to use that star to get back closer to singulartity.

Not unless you are willing to believe that singularity is shining upon the earth right now, but our eyes are too weak to detect it, unless we have a telescope to help assist us. (Ponder this paragraph)

Unless the earth came into being at the first flash of the Big Bang, and we are traveling in space in tandem with light, then there is no way we can see back to the Big Bang, or even closer to the Big Bang than the time differential between the Big Bang and the creation of the earth. No matter how powerful the telescope we can't gain back time by looking through a telescope.

[sparks]

So, any (info) light that was generated by the BB has been red-shifted to DC and is therefore not knowable on Earth unless the Earth had been created at (or very nearly) the same moment as the BB, which is clearly absurd???? And the limit is 13.5 billion years???

Do I understand you correctly now?

[sparks]

So, any (info) light that was generated by the BB has been red-shifted to DC and is therefore not knowable on Earth unless the Earth had been created at (or very nearly) the same moment as the BB, which is clearly absurd???? And the limit is 13.5 billion years???

Do I understand you correctly now?


BTW: Sorry about the double post. Damned technology anyway!

[PatKelley]

Nope. It's just that the idea that the image could be from five billion years ago, or any other number, is escaping him at this point. The light that is hitting us did originate five billion years ago. The light that was hitting last year was also from five billion years ago, but was the light the object emitted the previous year. It's a time delay film not a static snapshot, and this is where I think there is a brain breakage.

Imagine a tape-delayed sports game. When you see it five hours after it was televised, it doesn't arrive in a single blip of one second: you see it play out as it would have, just five hours later. If you catch it partway through, that doesn't mean it didn't start transmitting before now, and it doesn't mean it will stop as soon as you start watching.

[AnotherSillyAlias]

Nope. It's just that the idea that the image could be from five billion years ago, or any other number, is escaping him at this point. The light that is hitting us did originate five billion years ago. The light that was hitting last year was also from five billion years ago, but was the light the object emitted the previous year. It's a time delay film not a static snapshot, and this is where I think there is a brain breakage.

Imagine a tape-delayed sports game. When you see it five hours after it was televised, it doesn't arrive in a single blip of one second: you see it play out as it would have, just five hours later. If you catch it partway through, that doesn't mean it didn't start transmitting before now, and it doesn't mean it will stop as soon as you start watching.

I read a really interesting short story a long while ago. It was called something like Slow Glass (I think), and it worked on the time delay principle.

These large sheets of "slow glass" were set up on hills in the country and suchlike nice places. Light went into the glass but didn't come out the other side for varying length of time, years for instance. People would buy this glass just as the light started seeping out the other side and they would install it as "windows" in their city apartments and they would have a few years of nice country scenery.

Don't know why I just thought of that!

[dogjones]

Nope. It's just that the idea that the image could be from five billion years ago, or any other number, is escaping him at this point. The light that is hitting us did originate five billion years ago. The light that was hitting last year was also from five billion years ago, but was the light the object emitted the previous year. It's a time delay film not a static snapshot, and this is where I think there is a brain breakage.

Imagine a tape-delayed sports game. When you see it five hours after it was televised, it doesn't arrive in a single blip of one second: you see it play out as it would have, just five hours later. If you catch it partway through, that doesn't mean it didn't start transmitting before now, and it doesn't mean it will stop as soon as you start watching.

OK, so if the cosmic microwave background is a "video" of the surface of last scattering, then will it eventually fade? I guess that would depend on the size of the universe?

[PatKelley]

OK, so if the cosmic microwave background is a "video" of the surface of last scattering, then will it eventually fade? I guess that would depend on the size of the universe?

It just gets older, and what we're seeing is analogous what was here 13.7 billion years ago. That's it.

The only thing special about the surface we see is that it represents the furthest light could have traveled in the time given. If the universe were five years old, you could only see objects five light-years distant; that's as far as any photons could get in five years. The radiation we see is what was emitted 13.7 billion years ago; there is nothing to see "beyond" it; our horizon (it's artificial and based on lightspeed not on us being the center) expands at the speed of light; so our horizon is 13.7 billion light-years.

There is plenty more universe beyond this, same age as us. The game was tape-delayed; doesn't mean the athletes stuck around for our benefit until we were able to watch it.

[dogjones]

Ah yes, I see.

[sparks]

I'm still waiting for proof of (and method of same) for what happened before the BB.......

Well, turkey and stuffing will do that to ya.......