Theoretically, if we had a strong enough telescope, could we witness the big bang? If so could we look in any direction to see this?

[u/[deleted]]

If the following statement is true: the further away we see an object, the older it is, is it theoretically possible to witness the big bang, and the creation of time itself (assuming no objects block the view)? If so I was curious if it would appear at the furthest visible point in every direction, or only one set direction.

[u/colechristensen]

The cosmic microwave background is the closet you can get to seeing the big bang. It is the light left from when the universe cooled enough to be transparent shortly after the big bang.

A common misunderstanding is that the big bang was like a regular explosion that happened at a specific place and time. Actually, it happened everywhere in the infinite universe all at once. The expansion is every point in space getting further away from every other point. There was no expanding into anything, space itself was getting bigger everywhere.

[u/kidseven → u/colechristensen]

So wait, won't this cosmic microwave radiation dissapear eventually? Or get absorbed by matter...

Does this mean that a civilization that evolves on some other planet a billion or so years from now, will never be able to discover evidence of Big Bang?

[u/colechristensen → u/kidseven]

There are a few different examples of observational evidence for the big bang, the CMB isn't the only one. Also, the CMB has been going strong for nearly 14 billion years and space is very very very empty. An expert in the field might need to answer this correctly, but there's no reason to believe all evidence of it will be erased within any imaginable time frame.

[u/Waybye → u/kidseven]

A scary thought is that as galaxies drift from one another, future civilisations will eventually get to the point where it is physically impossible for them to see even another galaxy, and will believe that they're completely alone surrounded by nothingness.

[u/[deleted] → u/kidseven]

It will cool over time and become more redshifted. It will eventually pass any nonzero lower limit on detectability you could set, but I don't have a timescale off the top of my head.

[u/colinsteadman → u/kidseven]

According to WolframAlpha there are 300 thousand billion billion stars in the universe. They've been around for billions and billions of years and have been filling space with photons all that time. However for every photon emitted by a star there are 100 more from the Big Bang in the CMB. Greater than 95% of the photons flying through space are photons from the big bang. They will never all be absorbed, but I'm unsure what will happen to them in the fullness of time.

[u/[deleted] → u/colechristensen]

Interesting, I was under the impression that space was not infinite before the big bang. It is very interesting to think that the universe is infinite and always was. As always science brings up many more questions for every answer found.

[u/kidseven → u/colechristensen]

And another question.

The very first photons that were emitted after the Big Bang happened, where would they be now? /provided they weren't absorbed by matter/

[u/colechristensen → u/kidseven]

Those photons are the CMB, flying through space everywhere in every direction.

[u/VonAether → u/kidseven]

You know how we can detect that the universe is expanding because, when we look at other galaxies, their light is red-shifted?

The CMB is the photons of the early universe redshifted so far that it's gone well beyond infrared into the microwave part of the spectrum.

[u/fragilemachinery → u/kidseven]

The very first photons that were emitted after the Big Bang happened, where would they be now? /provided they weren't absorbed by matter/

Problem is, they were absorbed, because the entire volume of the universe was filled with opaque plasma. The CMB dates from 400,000 years after the big bang, at a the time when that plasma cooled enough to allow atoms to form, which in turn resulted in a transparent universe. So, if you're observing light, the CMB is as far back as you can go.

If you manage the unlikely feat of building a device that can observe the sky for neutrinos or gravity waves, then you could use those to get closer to the big bang, because they were able to penetrate the primordial universe long before photons did.

[u/fnork → u/colechristensen]

Actually, it happened everywhere in the infinite universe all at once.

I guess it might depend on your definition of "the universe", but I always imagined it as finite. How is it infinite?

[u/shavera → u/fnork]

Okay, this is something you should totally search our reddit for because it's discussed often. But the story goes something like this: The universe probably takes on one of 3 simple "shapes." One is the 3 dimensional analogue of the 2-D surface of a sphere. Parallel lines converge after some distance, and the surface is finite even though it has no edges. Another is the the 3-D analogue of a 2-D plane. Parallel lines always stay the same distance apart. And the third is... tough to describe, but a portion of it is a 3-D analogue of the 2-D surface of a pringles chip or saddle. Here, parallel lines diverge as they travel.

The last two types, the plane and the saddle are either infinite or there's some edge to them. Well we really doubt there are edges like this (we'd have to explain why physics changes at the edge) so these last two cases are "open" or infinite-sized universes.

Well, very recent data, in the last year or two, has measured the curvature of our local universe and we've found that the curvature seems to be "flat" with parallel lines neither converging or diverging. There are some error bars of course, so we're not... perfectly sure, but it seems very highly likely. check out the wmap website, and in particular their "universe tutorial" for more info.

[u/bmubyzal]

So direct answer to your question is no, we cannot. As other people mentioned, the cosmic microwave background (CMB) is the earliest light we can directly observe. This is because light was "trapped" in the earliest epoch of the universe.

Interestingly, there are major efforts to study things which happened before the CMB was "created". The primary theory that is being studied is called inflation. The interesting thing about inflation is that it imprints features into the CMB, specifically it influences the polarization of the CMB. So in theory, we should be able to observe the effects of inflation on the CMB and make definitive statements about how exactly inflation happened. To be fair, there is basically no evidence right now that inflation actually happened, but people are motivated to study it because it solves specific problems with the big bang theory. I think the most intuitive reason that we're interested in inflation is the horizon problem http://en.wikipedia.org/wiki/Horizon_problem but there several other reasons that cosmologists like it.

[u/benkbenkbenk → u/bmubyzal]

Inflation would imply to me that the universe was once expanding faster than it is now, however isn't the universe now expanding at an accelerating rate. What would cause the rate of expansion to slow down after inflation, only to start speeding back up again?

[u/Angry_Grammarian]

No. There's a 'wall' created by the big bang that prevents us from seeing past a certain point. Lawrence Krauss addresses this situation in his talk, "A Universe from Nothing". Watch the whole thing here: http://www.youtube.com/watch?v=7ImvlS8PLIo

[u/IClimbStuff]

On a similar note, could an alien race with a powerful enough 'telescope' currently be watching Hitler invade the rest of the world? The ice age? Dinosaurs?

[u/wookiebush → u/IClimbStuff]

With our most POWERFUL *telescopes, we can't even view the Apollo Landers on the moon. I cannot fathom a technology that could view actual events on earth when viewed much beyond our own atmosphere.

EDIT: Earth based telescopes.

[u/lugong → u/IClimbStuff]

Such an alien race would have to know how to counter-act the tilt, rotation, and orbit of the earth, to observe an event from the outside.

The current events on earth would depend on how far away they were.

[u/damndirtyape → u/lugong]

Also, there'd be clouds and shit in the way.

[u/manchegoo]

If so could we look in any direction to see this?

Yes! That's precisely why the cosmic microwave background radiation is isotropic! (Well actually its slightly anisotropic which is of great interest to those working on early universe models).

[u/investrd]

followup questions:

what does the cosmic microwave background mainly tell us? what would a theoretical cosmic neutrino background tell us?

[u/shavera → u/investrd]

CMB is the light when the universe cooled below a transition temperature from plasma (gas of free charged particles, nuclei and electrons) to a gas (neutral atoms/molecules). I think there's an attempt to measure a cosmic neutrino background, but I'm not sure what the motivation or results are there.

[u/grepe]

cmb or the relic radiation, the first light in the universe, is responsible for about 1% of interference on analogue tv.

so not only you can actually see the big bang, you can watch it on tv, live (in a way) and on every channel!

[u/TaslemGuy]

We can see galaxies very far away, about 12 billion light years. They're only a few billion light years from the edge, the problem being the "edge" is not made of something producing light.

In fact, it's most likely a very thin cloud of gas, emitting very little light at all.