I have a question.

[hackenslash]

A couple of points:

1. There are two very distinct definitions of the word 'universe'. The first is roughly 'that which arose from the big bang', while the other is 'that which is'. cosmologists often employ the former, but that's largely because they tend to write for people who understand what they're talking about, and of course they're not accustomed to having their words equivocated by propagandists for doctrine in the same way that, for example, evolutionary biologists are. If your question is 'what lies outside that which arose from the big bang (hereinafter referred to as 'the cosmos' for brevity)?' the answer is that we don't know, but we have some good ideas. If the question is actually, 'what is our the cosmos expanding into?' the answer is 'not precisely nothing'. It's as close to 'nothing' as can be actually achieved, but it still isn't precisely nothing, because that's not possible.

2. Our cosmos is thought to be about 96 billion lightyears across (although some sources put this figure considerably higher. I got this figure from Andromeda's Wake, and he generally knows this stuff, so I'll run with it). This figure is arrived at by employing the parameters of the inflationary model, and extrapolating, which does have some problems, not least that the inflationary model suffers from some 'fine-tuning' issues. Note that this 'fine-tuning' is not the same as the idea of fine-tuning employed by cretinists, although they cite the same sources. Again, when a physicist talks about fine-tuning, he's actually talking about the requirement for the values of some parameters or other to fall within a very narrow band if the model is correct. In other words, it's the model that is fine-tuned, not the universe. In this case, certain parameters, such as the rate of inflation, have to fall within a very narrow band of values to overcome the horizon problem, among other things. At this point, it isn't clear that the inflationary model is correct, and it isn't the only game in town. Apart from anything else, it assumes a physical singularity, and it isn't even clear that such an entity is even possible.

3. The observable universe is subject to a light horizon, which means in reality that what we can observe cannot be more than 13.7 billion lightyears away, meaning that the observable universe is actually 27.4 lightyears across. Beyond this horizon is simply more of the same.

4. And this is the really important one. I must have said this at least 3,000 times in the last few years on various rationalist fora, and it can't be said enough, not least because there is an assertion that has been accepted for a long time:

It is far from having been established that time began at the big bang. This assertion again arises from the picture of a physical singularity. The pronouncement came from the work of Hawking and Penrose, when they established that the equations of General Relativity showed that the big bang arose from a singularity (of the physical variety). Given that time slows in the presence of a relativistic mass, then given a large enough mass, time would stand still. There are two major problems with taking this to mean that there was no time before the big bang. The first is that, even if the cosmos arose from a genuine physical singularity, and even if time stopped at the singularity, this in no way validates the claim that there was no time before the singularity, only that the singularity didn't experience it. Given that we have entities within our cosmos that don't experience time, and yet time clearly exists, the fallacy of this line of thought is clear. Secondly, Hawking himself no longer supports that conclusion, and hasn't done since shortly afterwards, since he realised that this conclusion didn't take quantum effects into account.

5. And finally, it needs to be established what a singularity actually is. In physics generally, a singularity is simply an event which our physical theories fail to describe, for one reason or another. In the case of black hole and BB singularities, it is a place that requires both Quantum Mechanics and General Relativity to describe it. Every time that GR and QM have been brought together, the output is infinity, which is a ridiculous answer.

So, to sum up, the big bang was probably not the beginning of time. It was also probably not the beginning of our spatial dimensions, but was more likely an unfolding of them from the dimensional manifold. Until we understand the topography of the dimensional manifold much better than we do, we must be careful of categorical statements, especially categorical statements that stem from science that is thirty years or more out of date. Thirty years is an aeon in theoretical physics.

[tymygy]

The universe is what about 13.7 billion lightyears across?

Universe Measured: We're 156 Billion Light-years Wide!

If you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth...

Interesting stuff, things are often not what they appear to be!

Thanks I think I mixed the age with the size. Lol.

It happens.

And thanks tank, I had heard it was 78 billion light-years. Half way right.  

[PoopShoot]

(I know there isn't an "edge" persay just like there isn't a "before" the big bang. However it's alot easier then "the amorpheous limit to space and time as we know them".)

If you're pedantic.

Shouldn't that be "unless your pedantic"? Lol. It was preemptive self-correcting I was getting flash backs to discussions about the big bang and people correcting me when I say "before" when they know perfectly well what I meant and that I wasn't being literal. So I thought I'd kill the fire before the smoke.

No.  IF you're pedantic.  People who say there is no before the big bang are pointing out that time is function of space.  While this is true and there can be no time without space, the argument "there can be no before..." ignores the possibility of previous iterations of the universe as well as other means by which events may be separated.  When you're right on a technicality at the expense of the point, you're being pedantic.

[DropLogic]

I don't think we can make any conclusions at all.  If we go simply by what we can observe, then one can conclude that our universe is a bubble expanding into....something.  The big bang was probably a white hole, or the exhaust of a massive black hole.  Makes me wonder if the super-massive black holes at the center of almost every galaxy are creating universes in other dimensions.  All that matter had to come from somewhere ...

[hackenslash]

People who say there is no before the big bang are pointing out that time is function of space.  While this is true and there can be no time without space,

Actually, this isn't true, and they'd be wrong. This is precisely what Einstein taught us. Time is not a function of space, it's an additional dimension, and space and time are facets of the same entity, spacetime.

the argument "there can be no before..." ignores the possibility of previous iterations of the universe as well as other means by which events may be separated.

This is most definitely true.

When you're right on a technicality at the expense of the point, you're being pedantic.

Indeed, but when the point is wrong due to a misunderstanding of the technicality, pedantry is necessary.

[DropLogic]

Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

[tymygy]

Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

I found this interesting.

http://everyjoe.com/technology/how-can- ... s-old-191/

[DropLogic]

Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

I found this interesting.

http://everyjoe.com/technology/how-can- ... s-old-191/

K I still don't understand how they can come to these conclusions.  If every galaxy is moving away from every other galaxy, why do we observe frequent galactic collisions?  Wouldn't all the energy released by pulsars, and quasars have an effect on the surrounding space?  How can we come up with a constant rate of expansion without possibly knowing the external effects that are taking place around the objects we are measuring?  The gravity of another large body changes the speed and rotation of the original body.

[hackenslash]

Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

The universe is expanding at greater than c. More importantly, during the very early inflationary period, it expanded at considerably greater than c.

[hackenslash]

K I still don't understand how they can come to these conclusions.  If every galaxy is moving away from every other galaxy, why do we observe frequent galactic collisions?  Wouldn't all the energy released by pulsars, and quasars have an effect on the surrounding space?  How can we come up with a constant rate of expansion without possibly knowing the external effects that are taking place around the objects we are measuring?  The gravity of another large body changes the speed and rotation of the original body.

A couple of things again:

1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

[DropLogic]

1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

[Tank]

1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

If 99 Galexies are moving away from each other and 2 are moving towards each other, on average galaxies are moving away from each other. This can be seen in rivers. A rivers average flow is one way but there can be local eddies where water can flow back the other way. Galactic movement is not homogeneous as gravity interactions can sling Galaxies around each other and into each other. Our Galaxy will merge with the Andromada galaxy way into the future. Local behaviour can go against the general trend.

[DropLogic]

1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

If 99 Galexies are moving away from each other and 2 are moving towards each other, on average galaxies are moving away from each other. This can be seen in rivers. A rivers average flow is one way but there can be local eddies where water can flow back the other way. Galactic movement is not homogeneous as gravity interactions can sling Galaxies around each other and into each other. Our Galaxy will merge with the Andromada galaxy way into the future. Local behaviour can go against the general trend.

I got 99 problems but a galaxy-crashing-into-my-galaxy-in-my-lifetime ain't one.

[tymygy]

I got 99 problems but a galaxy-crashing-into-my-galaxy-in-my-lifetime ain't one.

BEST. POST. EVER.

[hackenslash]

1. Clarify please.  To me, both of those mean the same thing.

OK, let me explain. On average means 'in general, but not without exception'. This means that, in general, but not without exception, galaxies are receding from each other. Locally, some galaxies are approaching each other. It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving. For example, the galaxies that are receding from us aren't moving in relation to us, but Andromeda is actually moving in relation to us, which is why it's headed straight for us. If it were just the expansion of the cosmos involved in the latter, it wouldn't be on a collision course.

2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

We're capable of understanding a good deal more than you might think, and the size of the universe is pretty well understood to within certain error bars.