Direction of the big bang

Factual Questions
1

If we can look back to the start of the universe,
using the standard candle red shift theory and see the starting point of the big bang… How do
we know that in the opposite direction it does not expand the same or even more? Also, the earth is round
so how do we know what direction to look in to find out what direction the big bang was created?

If the wake is going in all directions and the universe is saucer-shaped, then have the shockwaves going in opposite directions met each other and over-lapped

2

The big bang happened everywhere, not in a single point. If you look in any direction you will see evidence of the background radiation. There is no direction towards the big bang.

3

No matter in what direction we look, we always look towards the big bang, because, since light travels at a finite speed, the ‘farther out’ we look, the more to the past we look, and the big bang is the one event to the past of everything in the universe.

Think about the balloon analogy for the universe’s expansion. Galaxies are little dots painted on the surface of an expanding balloon; that surface represents a two dimensional version of our three dimensional universe – one dimension is left out for clarity. If you take this universe at any given point in its existence, you thus have a sphere of a certain size; if you then reverse time, that sphere will shrink, until it contracts down to a point – the big bang singularity. Now it’s important to notice that this singularity is not anywhere in space, rather, it is all of space – there’s no point on the balloon to which you could point and say: ‘there, that’s where the big bang happened’. In a manner of speaking, it happened everywhere.

Now, pick one of those galaxies on the surface of the balloon as ours. If you look from that galaxy to a nearby one, you will not see it as it is ‘right now’, but rather, as it was at the time it emitted the light you now see – so if, say, it is a million light years away, you’ll see it as it was a million years ago. Consequently, everything you see a million light years away will appear as it was a million years ago. But a million years ago, the universe was slightly smaller than it is now – so in whatever direction you look, if you look at the parts of the universe a million light years away, you’ll look at a slightly smaller universe.

You can extend this game to things ever farther away – something a billion light years away will appear to you as it was a billion years ago, and the universe a billion years ago was smaller than it is today. It’s clear where this goes – no matter in what direction you look, if you look far enough, you will see the universe as it was a long time ago, so theoretically, if you could look far enough, you would see the universe as it was at the big bang in every direction.

However, there’s a catch to this – the early universe was not, in fact, transparent; it was opaque until about 380,000 years after the big bang, so this is the furthest back you can look using ordinary light (neutrinos or gravity waves could be used to look back yet further than that). It’s from this time that the cosmic microwave background hails.

4

Everything that has said has been true, but I’m going to adda pointless nitpick that probably only serves to muddy the water:p

There is anistropy (directional bias) observed in the evidence for the big bang (i.e. the CMB - cosmic microwave background) and that’s larger (well I’m fairly certain it should be larger) and seperate from the anistropy thought to be caused by random fluactuations in the early universe. This is caused by the Earth’s movement relative to the CMB-frame (it’s also variable, depending on for example the time of year).

5

Usually people who ask where the big bang took place have a fundamental misunderstanding of the universe. They think of the big bang as everything in the universe starting at a single point and expanding out into an already existing space.

There was no already existing space. Space itself started as a single point, and expanded outward. It is still expanding. If you were to magically pick a point in space (let’s call it X) and another point in space a thousand miles away from it (let’s call that Y) and you could magically put markers on those points that never, ever moved, they would still move away from each other, not because they are moving (they aren’t) but because the space between them is expanding. The more you move forward through time, the more the space in between those points will expand, moving those points farther and farther apart from each other.

If you rewind that and go back in time, those points get closer and closer together. All points in the universe get closer and closer together, and not just the little bits of matter in the universe, but all of those magical little unmoving points in space get closer and closer together as well. This is when you realize that every point in the universe was once right next to each other. It all started from a single tiny point, aka the big bang.

It doesn’t matter what point you pick in the universe. The big bang started at that point. From that point perspective, the entire universe expanded away from it. Pick another point, and it looks like exactly the same thing, the rest of the universe expanded away from it as well. Every point expanded away from every other point. Space itself got bigger.

That is what the balloon analogy that Half Man Half Wit mentioned is trying to convey. Unfortunately, it sometimes causes confusion because people see a balloon expanding into three dimensional space, and that is not what that analogy is trying to say. Picture the balloon as a two dimensional universe. Instead of being flat and fixed like a piece of paper, it’s like an expanding balloon. The surface of the balloon keeps getting bigger and bigger. Our universe is the same way, except that unlike the surface of a balloon, we have three dimensions instead of two.

ETA: By the way, the guy that figured out that the universe itself was expanding was this really smart guy named Edwin Hubble. You may have heard of him. This revelation was so significant that they named a space telescope after him.

6

Thanks for the replies so far. So this all mean that parts of the universe expanding in opposite directions cannot merge head on, correct?

Is the middle point gradually getting more sparse of objects?

7

There is no middle point. You are still thinking about it in terms of a universe expanding into an already existing space. This is not the case.

Pick any point. The universe expanded away from that point. Pick any other point. Same thing. Every single point in the universe is the middle point. They were all one point initially.

8

Just like the surface of the baloon in the examples given above. Remember: nothing else exists except the balloon’s (3D) surface.

Make two marks on the surface, and blow up the baloon. The marks appear to move apart, but it’s the underlying balloon (space) material that’s “expanding”. They are not leaving the surface of the balloon, and from their own perspectives, everthing on the balloons surface is receding from them.

9

Yes, but this is only true because nothing is expanding towards anything else.

That you phrase the question this way shows you still have a misunderstanding (which is okay! this stuff is hard to internalize). There is no middle point. There is no end point, or side point, or top point, or bottom point. There is nothing you can call an exterior, or an interior, or anything that would even let you infer the existence of an exterior or interior.

However.

What we do know is that everywhere aside from small, localized regions where high densities already exist (like galaxies and clusters of galaxies), the density of objects is decreasing. Density, roughly, is a mass-to-space ratio. The expansion of the Universe, which is accelerating, means there is more space and the same amount of mass. Overall, that means less density.

10

Ok, is it conceivable then, to hypothesize that somewhere there is a single particle that’s farther away from some certain other singular particle than any other two particles in the universe?

Do you know what I mean? As in, “There ain’t nuthin’ further apart in the entire universe than this here neutrino named Jeff and that proton named Gary way over there.”

11

There is a region of space that’s relatively empty Boötes Void - Wikipedia. There you might find particles that are farther away from other particles by substantially more than the average distance between particles in “normal” intergalactic space.

12

I don’t think Rysdad was asking about nearest neighbors, but about any pair of particles. The question is complicated, though, by whether we’re referring to the entire Universe, or the observable Universe. Nobody knows of any limit to the size of the entire Universe, and the most popular guess is it’s infinite: In that case, there would be no upper bound on how far apart particles are. For any given distance, there would be pairs of particles at greater than that distance. Now, the observable Universe is finite, but then we get the additional complication that every observer has a different observable universe: Do you mean the observable universe of one of the particles, or that of a third-party observer? In any event, if you specify a particular observable universe, then within that region at any given moment, there will be some pair of particles for which the distance between them is a maximum, though of course you’d never be able to identify exactly which two particles those are.

13

I fart in the general direction of the big bang!

14

I always have two questions whenever this topic comes up.

  1. What is the difference between two points moving further apart and the space between them increasing. Seems semantic to me.
  2. I just don’t get the balloon analogy. Dots on the surface of a balloon move further apart because it is a 2-sphere and exists in a third dimension. One implication of this is that a straight line of the balloon’s surface will eventually meet up with itself from behind. (I know there is a tidy topological way to say this but it escapes me for now.)
    As i understand it, no one is claiming that the universe is a 3-sphere bent into a fourth dimension. And I am not aware of anyone saying that a ray of light will meet up with itself. (notwithstanding that the rate of expansion is believed to be close to c.)

Care to clarify me?

15

It’s not a perfect analogy. People aren’t saying the universe is actually a balloon; they’re just trying to find an everyday example which illustrates the concept that every point is moving away from every other because it helps some people wrap their head around an unintuitive concept.

While the difference between two points moving further apart and space expanding may seem like semantics, that’s only because we don’t have the language to describe it in non-mathematical terms. That doesn’t mean that it’s not happening, or that the difference isn’t important and doesn’t have profound and fundamental effects on our environment* and the laws which make it work; just that when we try to talk about it in normal everyday English, we end up using language which isn’t designed to accomodate the concept.

Essentially, to really understand what it means, we have to understand the math. Which is too difficult for me; so I take the analogies with a certain level of trust.
*As in our universe, not as in global warming!

16

Instead of a balloon, imagine the scaling feature on AutoCAD or a similar program. (Try Paint or Photoshop or GIMP if you aren’t familiar with AutoCAD, though the effect is lessened without vector graphics because the dots get bigger too.)

Make a square, draw some randomly spaced dots inside of it, “select all” and “scale 500%”. The dots all got farther apart, and the “space” they inhabited got bigger. You can do the same thing with a cube or any other shape (at least mentally, not sure about 3D objects in AutoCAD).

The next step is to imagine yourself inside of that cube and ignore the boundaries. What would it be like during the scaling? Everything moving away from everything else and space getting bigger.

17

I"ll tell ya, the cosmologists need to hire YOU to explain this to the general public, that balloon analogy and those stupid raisins in the loaf of bread, aaaauuuugggghhh, never could get the concept clear, two points in the universe getting farther apart without moving, this actually worked for me. does this indicate more of a Big Whump (via brane theory) than a Big Bang though?(thats part of the change in thought I had to make to this work in my mind)

18

Maybe the analogy should be a small glob of shaving cream in a vacuum. Stir in some pepper to represent matter, pump out the air–instant universe.

19

ya that would work. Seems like part of the point and problem is that there is no specific central point where the big bang happened unless we can somehow provide evidence of a space outside the universe for it to expand into, which is part of where the balloon analogy breaks down. Seems like the cosmologists forget to mention this. Big Bang as a descriptive is to inaccurate and misleading, as it seems to indicate a central point. Big Whump, there was nothing and then WHUMP the universe sprang into existence and expanded. Whether or not the “outside” of the universe is expanding or not is at this time unknowable, but the “inside” of the universe is expanding

20

Chronos wrote:
Nobody knows of any limit to the size of the entire Universe, and the most popular guess is it’s infinite.

My question: Is Space infinite now, or will it be infinite?