What are we aiming to see after this?

[Matuchkin]

The farthest galaxy ever viewed by us,  GN-z11, is 13.4 billion light years away from us.

This means that if we look another 400,000,000ly behind it we will see the universe (or that exact piece of universe) when the big bang occurred. What can we gain from this? We will probably not see any more galaxies or activity behind GN-z11, but what else can we achieve by looking at that part of space?

[grawl]

Spooky...

But what am I seeing exactly ? is it some form of proto-galaxy ? Its shape is quite interesting !

 

How would one actually look past that time ? Is it like looking really well at a part of the sky, and *bam* there's the origin of the universe ?

[Steel]

2 hours ago, Matuchkin said:

The farthest galaxy ever viewed by us,  GN-z11, is 13.4 billion light years away from us.

This means that if we look another 400,000,000ly behind it we will see the universe (or that exact piece of universe) when the big bang occurred. What can we gain from this? We will probably not see any more galaxies or activity behind GN-z11, but what else can we achieve by looking at that part of space?

Just a quick note, it's actually about 32 billion light years away, but we are observing it 13.4 billion years ago.

[Wjolcz]

AFAIK JWST will be able to look farther than that. Not sure what exactly it'll be looking for though. The youngest stars and their composition?

[Matuchkin]

2 minutes ago, grawl said:

Spooky...

But what am I seeing exactly ? is it some form of proto-galaxy ? Its shape is quite interesting !

 

How would one actually look past that time ? Is it like looking really well at a part of the sky, and *bam* there's the origin of the universe ?

literally, just look at a farther distance. The light from that galaxy spent 13 billion years coming our way, so we are essentially seeing an object as it was 13 billion years ago (of course, the actual galaxy has moved over time). If we manage to look 400,000,000 light years beyond that galaxy, we would be looking at a time that was very close or at the beginning of the universe.

 

7 minutes ago, Steel said:

Just a quick note, it's actually about 32 billion light years away, but we are observing it 13.4 billion years ago.

See above. Sorry that I missed that.

[kerbiloid]

Spoiler

Or we are fishes in a glass tank, watching reflections and shadows of water bubbles on its glass wall.

 

[Streetwind]

11 hours ago, Matuchkin said:

We will probably not see any more galaxies or activity behind GN-z11, but what else can we achieve by looking at that part of space?

There are models that suggest that our universe is a self-enclosed space... like a three dimensional moebius strip, if you go far enough in one direction you will end up where you started. In such a case, we will never run out of even "older" galaxies to observe. There will always be something "behind" - because, in essence, we might already be looking at our own backs.

Should we happen to be able to see patterns that, given enough time forwarding, would look very familiar to us, this would prove that hypothesis. It would be quite a valuable insight. Of course, the reverse is more difficult... you can't really disprove the hypothesis on the grounds of not seeing repetition. The universe might just be that much larger.

[YNM]

17 hours ago, Steel said:

Just a quick note, it's actually about 32 billion light years away, but we are observing it 13.4 billion years ago.

OP is technically correct - we see the CMB's light as having traveled (or rather, expanded) for 13.8 billion ly, not ~45 bln ly.

 

Now, to OP :

What do we expect to see behind it ? There are a few thing we hope we can see directly as a single object :

- Pop. III stars - those that are very, very massive (some much above eddington limit,  and only consist of hydrogen with slight helium.

- More distant galaxies, something which can show different lifetimes.

etc.

But what's behind it ? CMB. What's behind it again ?

 

Nothing.

 

The big bang shall be the farthest we can see into it.

[Steel]

1 hour ago, YNM said:

The big bang shall be the farthest we can see into it.

In all likelihood we won't ever see that far back. The universe was opaque to light up until about 300,000 years after the big bang (I think, I might be off on that number), hence the CMB from the point it became transparent, but this means it's very difficult to observe anything further back than this.

[Matuchkin]

21 hours ago, YNM said:

But what's behind it ? CMB. What's behind it again ?

 

Nothing.

 

The big bang shall be the farthest we can see into it.

Well, we already are detecting the CMB. We won't see anything new from it, because it's just a field of radiation left over from the big bang. The only way I can imagine we can see otherwise is if the CMB is radiation from the universe before the big bang, which can explain the formation of the explosion itself. Also: why do you believe that we will not be able to see past the big bang? I mean, sure, the events prior are extremely confusing, but the mere fact that we don't know about them doesn't mean that they are guarded by some visual barrier.

P.S: I understand that the big bang is not considered to be an explosion, rather being called an "expansion". That is, however, just a subject of our educated speculations, so it's perfectly reasonable to assume otherwise.

[Steel]

19 minutes ago, Matuchkin said:

Also: why do you believe that we will not be able to see past the big bang? I mean, sure, the events prior are extremely confusing, but the mere fact that we don't know about them doesn't mean that they are guarded by some visual barrier.

Mainly because by our current best models there is no such thing as beyond or before the big bang, because the big bang is literally the beginning of time and the laws of physics.

Edited January 18, 2017 by Steel

[Matuchkin]

2 hours ago, Steel said:

Mainly because by our current best models there is no such thing as beyond or before the big bang, because the big bang is literally the beginning of time and the laws of physics.

That's our current model. And as far as that model goes, I cannot see any actual evidence that a massive explosion could have been the beginning of all physics. Please forgive me for my ignorance, but I cannot see why there couldn't have been anything else before the bang that triggered the explosion.

Edited January 18, 2017 by Matuchkin

[VaPaL]

1 hour ago, Matuchkin said:

That's our current model. And as far as that model goes, I cannot see any actual evidence that a massive explosion could have been the beginning of all physics. Please forgive me for my ignorance, but I cannot see why there couldn't have been anything else before the bang that triggered the explosion.

Well, taking olnly from what you've said, expecting to see something when our current model says there's nothing to be seen is to expect to change the current model. But change it to what? There can be some choices that are more viable than others or other proposed models than can prove to be true or even something totally new, but that's just expeculation and at this point you can say whatever you want. You can even say you'll see (forbidden topic).

Edited January 18, 2017 by VaPaL
Clarifications

[Steel]

1 hour ago, Matuchkin said:

That's our current model. And as far as that model goes, I cannot see any actual evidence that a massive explosion could have been the beginning of all physics. Please forgive me for my ignorance, but I cannot see why there couldn't have been anything else before the bang that triggered the explosion.

While it is true (I think), even if there was something that seeded our universe as a singularity which subsequently expanded out into the universe we know today, there's no way we could "see" this thing by looking back into the past of our own universe.

Edited January 18, 2017 by Steel

[Matuchkin]

4 hours ago, Steel said:

While it is true (I think), even if there was something that seeded our universe as a singularity which subsequently expanded out into the universe we know today, there's no way we could "see" this thing by looking back into the past of our own universe.

I never said we'd see the thing itself. Instead, I said we'll see particles and photons that came from that time, hence seeing an image of the universe at/ before the big bang  (like looking into Dumbledore's cauldron in the Harry Potter Series, except with actual physics involved).

Perhaps the CMB is the radiation and particles left over from a black hole as it went through Hawking Radiation, then these particles eventually turned into our known universe. Perhaps the CMB is the remnants of a universe that was near heat-death, when suddenly an explosion/ reaction (big bang) was generated and sent out another cloud of energy and matter. Perhaps it is something else.

[Steel]

1 hour ago, Matuchkin said:

I never said we'd see the thing itself. Instead, I said we'll see particles and photons that came from that time, hence seeing an image of the universe at/ before the big bang  (like looking into Dumbledore's cauldron in the Harry Potter Series, except with actual physics involved).

But we can't see particles or photons from "before the Big Bang" because those particles only began to exist after the Big Bang. 

1 hour ago, Matuchkin said:

Perhaps the CMB is the remnants of a universe that was near heat-death, when suddenly an explosion/ reaction (big bang) was generated and sent out another cloud of energy and matter. Perhaps it is something else.

This particular scenario doesn't make sense either. In this situation you have a universe which suddenly has more energy and matter put into it. This means that space and time already exists and you've just added extra stuff into it, which is not what happened at the beginning of the universe.

At the point of the big bang, there was no space - which is why people hate calling it an explosion, because an explosion implies that there is something that flys out into space that already exists. The important thing to note about big bang and the subsequent expansion of the universe is that the universe wasn't a point in space that grew outwards. The universe is space that began expanding from a singularity at the big bang. (That's not very well worded but it's a difficult concept to explain) This is why it doesn't make much sense talking about anything before the big bang because "before" then there was no space and thus no time.

Edited January 18, 2017 by Steel

[YNM]

On 1/18/2017 at 1:03 AM, Steel said:

In all likelihood we won't ever see that far back. The universe was opaque to light up until about 300,000 years after the big bang (I think, I might be off on that number), hence the CMB from the point it became transparent, but this means it's very difficult to observe anything further back than this.

Yes, free EM radiation stops at CMB (before that, think of Sun's core - very hot yet there's no way you can see anything inside it very well). But now that we have discovered gravitational signals and means to see it, I think people could come up with a way to do so - perhaps down to inflation or even down to the gravitational "decoupling" (ie. when gravity separated from the rest of the force modes).

On 1/18/2017 at 9:28 PM, Matuchkin said:

Well, we already are detecting the CMB. We won't see anything new from it, because it's just a field of radiation left over from the big bang. The only way I can imagine we can see otherwise is if the CMB is radiation from the universe before the big bang, which can explain the formation of the explosion itself. Also: why do you believe that we will not be able to see past the big bang? I mean, sure, the events prior are extremely confusing, but the mere fact that we don't know about them doesn't mean that they are guarded by some visual barrier.

P.S: I understand that the big bang is not considered to be an explosion, rather being called an "expansion". That is, however, just a subject of our educated speculations, so it's perfectly reasonable to assume otherwise.

CMB is important - you can see the imprints of what that part of the universe will be in it's anisotropies, which those fluctuations only exist in the scale of less than 10^(-5) K and we need way finer than that to see the whole picture. Last I heard there's a project to see it down to 10^(-7) K sensitivity but that has been for a long time, has it been accomplished ?

For looking beyond Big Bang - alright, this is not that easy.

Imagine a sphere (or, thanks to the two-dimensional surfaces in this three-dimensional world, a circle) with two lines in it, stretching from one end to the other, and think of it as the Universe. There are a few options :

Which ones contains parallel lines ? Parallel means "no intersection". (hint : it's the first and the second)

Similar principle applies in trying to see what's outside the Universe - even if you assume one exists, then what does it mean to us ?

Edited January 19, 2017 by YNM

[Matuchkin]

On 1/19/2017 at 5:47 PM, YNM said:

(hint : it's the first and the second)

How does the second circle contain parallel lines? Only the first does...

[Steel]

10 minutes ago, Matuchkin said:

How does the second circle contain parallel lines? Only the first does...

Because the definition of a parallel lines is two lines that never meet. On the surface of sphere, you can have two lines that never meet but are not the same distance away from each other at two different points (which is how we picture parallel lines on a plane).

[Matuchkin]

1 hour ago, Steel said:

Because the definition of a parallel lines is two lines that never meet. On the surface of sphere, you can have two lines that never meet but are not the same distance away from each other at two different points (which is how we picture parallel lines on a plane).

I was literally told my whole life that parallel lines are two lines that will never meet if you continue them infinitely.

[Steel]

6 minutes ago, Matuchkin said:

I was literally told my whole life that parallel lines are two lines that will never meet if you continue them infinitely.

That is true.

But in the picture above it's not a straight line through a circle, it's a line on the surface of a sphere, whic is why they will never meet

[DerekL1963]

1 hour ago, Matuchkin said:

I was literally told my whole life that parallel lines are two lines that will never meet if you continue them infinitely.

And does not a ring continue indefinitely?

[Matuchkin]

2 hours ago, DerekL1963 said:

And does not a ring continue indefinitely?

I was clearly not referring to the ring.

[YNM]

Ah, well, yeah, a bit of confusion there :

I didn't mess with the picture being a projection. Even if it was, the point still holds - it's more likely, thanks to Universe's accelerated expansion, we will never see beyond what we can see now - it'd just progress a few mpc but that's it. Then it will shrink.

Now, if those lines I pictured were imprinted on the very space time of the Universe, even though it looks not parallel, has the line ever crossed for us ? Probably no. And it won't.

 

Seeing something outside the universe would be like trying to find where the line cross each other while not moving anywhere, not taking a new vantage point - a mere close to impossibility, more so if that cross doesn't make any pronounced effect. If anything, they'd just make it easier to tell the geometry of the Universe we live in.

Edited January 27, 2017 by YNM