How far back in time could we possibly look?

[Realitycheck]

They are talking about Hubble's successor at http://news.bbc.co.uk/1/hi/world/americas/6645179.stm , which will "enable us to look further back towards the beginning of the universe."

 

Surely, the limits to "how far back we can look" start fizzling out at a time when the universe is already quite old, though I suppose that doesn't count for parts of the universe that spread out in the opposite direction from this presumed central focal point of the Big Bang, wherever that may have occurred. Taking this into consideration, it would still be rather old stars that we would see moving into the other direction and have very little relation to the "beginning of the universe". Either way, it seems that the light from the beginning of the universe should be long gone from any perspective, since light surely travels faster than the rate at which the universe is expanding.

[geoguy]

They are talking about Hubble's successor at http://news.bbc.co.uk/1/hi/world/americas/6645179.stm , which will "enable us to look further back towards the beginning of the universe."

 

Surely, the limits to "how far back we can look" start fizzling out at a time when the universe is already quite old, though I suppose that doesn't count for parts of the universe that spread out in the opposite direction from this presumed central focal point of the Big Bang, wherever that may have occurred. Taking this into consideration, it would still be rather old stars that we would see moving into the other direction and have very little relation to the "beginning of the universe". Either way, it seems that the light from the beginning of the universe should be long gone from any perspective, since light surely travels faster than the rate at which the universe is expanding.

 

Good question. Your follow up, however, misses the very essence of the expansion of space/time. There is no 'central focal point'. You are the no less the beginning point or focal point than any other point in the universe. There is no point to look at when the universe began to expand from...it is everywhere. One uses a telescope to look back in time and not at a physical place. It's the same as if an astronaut spoke to us from Mars. The words are not a physical event happening on Mars 'now' at a particular point but an event that happened in the past.

 

 

In theory we should be able to view the universe in any direction back to the time when light energy (or detect other energy) that had the means to escape the gravitational pull as the universe expanded beyond the point where radiation was trapped by gravity. There is no consensus on the amount of time after the initial expansion...some cosmologists put the time at several hundred thousand years but this is not accepted by all.

[Realitycheck]

Ahh, now I understand.

 

I already knew that there should not be a way to focus on any central point of the Big Bang, as it scattered to the 4 winds right away. In the article it claims that with greater telescopic power, we should be able to see further back to the beginning of the universe. I have seen claims like these in other articles. This is what didn't make sense to me.

 

But scientists say the JWST will enable them to look deeper into space and even further back at the origins of the Universe.

 

"Clearly we need a much bigger telescope to go back much further in time to see the very birth of the Universe," said Edward Weiler, director of Nasa's Goddard Space Flight Centre.

 

How can light be seen from the beginning of the universe? I can see how we could possibly see light from entities existing near the beginning of the universe (if they are still even alive), but I don't believe that the light would be from that time, only much older.

[Realitycheck]

In the following article, they describe being able to observe a star that is 13.2 billion years old, nearly as old as the universe. However, they do not make the claim that it is being observed in its near-original state.

 

http://news.yahoo.com/s/space/20070511/sc_space/ancientstarnearlyasoldastheuniverse;_ylt=AlQztREu66IUvTPm3ZwYuPb637YB

[Martin]

agent,

no optical telescope can see farther back in time than what whe already see when we look at the CMB

 

as far as looking back in time, what new optical telescopes need to do is help us see BETTER and CLEARER DETAIL of the formation of the first stars and galaxies and black holes.

 

(and they will answer other questions to, in astronomy the equipment tends to be multipurpose and creatively used)

 

the reason is that the universe was OPAQUE until it was 380,000 years old.

 

the CMB light comes from the moment when the universe was 380,000 years old and became TRANSPARENT, so that light which was trapped in the opaque plasma was released and has been flying unobstructed (mostly) ever since.

 

========

to see back before age 380,000 you need a different kind of telescope that sees NEUTRINOS because the ancient universe was not opaque to neutrinos.

 

Look at the sun. The outer layer is just hydrogen gas. But it is opaque! Why? Because it is so hot it has been partly ionized into a *plasma*. Plasma has ions and free electrons running loose that scatter light so badly they make it opaque to light. But plasma is still transparent to neutrinos. So we can "see" the core of the sun with neutrinos because they come to us from there and can be detected. Solar neutrinos have different energy ("wavelength") from big bang neutrinos. So far we dont have instruments that can see bigbang neutrinos.

 

before 380,000 the universe was very hot hydrogen gas (mostly) and it was enough of a plasma to be like the glowing outer layers of the sun and be opaque

but then it COOLED and became transparent. the light that escaped was rather like sunlight, only a bit more reddish because it was released when the plasma cooled to about 3000 kelvin (sun is more like 5600 kelvin----different color mix)

=========

 

agent I suggest you go here:

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

 

and type the number 1100 into the z box.

 

then ask some more questions

==========

 

the universe has expanded by a factor of 1100 in size since the CMB light was released, so its wavelengths are 1100 times longer

 

it used to be a wavelength mix like a star a bit more reddish than the sun, now it is a wavelength mix of the kind of light we call microwaves

because the wavelengths are all stretched out 1100-fold

[Bettina]

Martin... I'm playing with those numbers now. You still amaze me.

 

Bettina

[Martin]

Martin... I'm playing with those numbers now. You still amaze me.

 

Bettina

 

it's mutual. some kind of delight with the other person's mind.

I hope college is going well for you.

Also it would be neat if you put z=1100 into Wrights calculator.

 

if you did you saw the estimated age of universe when the CMB light got loose is, in this case, 372,000. I said 380,000 which may be a little off, but the numbers are not entirely certain.

 

also notice where it says "45 Gly". that means that at this moment the crud that released the CMB light that we are now receiving is 45 billion LY away.

It is that far away because expansion of distances carried it away from us. It used to be closer. By a factor of 1100.

 

how close is that? actually he says the current distance is 45.65 Gly and if you divide that by 1100 you get about 41.5 million LY, I think.

 

so the hydrogen plasma crud whose redshifted glow we are now seeing USED to be 40-some million LY away (which is pretty close really) and the universe was 370,000 years old and celebrating the Birthday of CMB or the Liberation of Light and it suddenly became transparent.

 

But it was expanding so fast that even though the emitting crud was only 40-some million LY away the light had to struggle to get to us! it kept getting swept back!

Finally, some 13.6 billion years later, the light gets here!

by that time the crud is now 45.6 billion LY away and the light is all stretched out so it has microwave wavelengths and we call it CMB.

 

sorry about all the messy numbers but I just put z = 1100 into the calculator and that's what came out. I am not bothering to round things off or to be neat.

[ajb]

It may be possible to look further back than the CMBR by looking for other types of radiation; gravitational waves and neutrinos.

 

But I am sure there are plenty of techincal issues to address before this becomes possible.

[Martin]

But I am sure there are plenty of techincal issues to address before this becomes possible.

 

That's right, ajb!

 

the temperature of the cosmic neutrino background has already been estimated and a number of papers written---indicating that people would dearly love to observe the CNB

 

but they cannot because of the technical difficulty of detecting neutrinos of the relevant energy. I forget what the energy range for CNB is.

 

if anybody is especially interested they can look it up keyword on arxiv.

 

it will be a great day when we can see bigbang neutrinos, but it wont be very soon!

[astrocat]

Either way, it seems that the light from the beginning of the universe should be long gone from any perspective, since light surely travels faster than the rate at which the universe is expanding.

 

NASA's Cosmic Background Explorer Satellite, COBE, showed, in 1998, that the Early Cosmos started out in a way that was perfectly smooth and evenly distributed, with no sign of any Big Bang, or 'Clumps', anywhere.

 

I don't think you can look back any further than that.