# I still don't understand why there isn't a center of the universe?

1. Jul 31, 2010

### zeromodz

1) The universe increases volume by time (There is no such thing as an infinite growing infinitely fast)
2) The universe had a beginning, therefore a finite amount of volume
3) There is a finite amount of time this point in time since the beginning
4) Therefore, the universe is finite in size.
5) The universe in theory can be mapped out and a center can be determined.

Whats wrong?

2. Jul 31, 2010

### Calimero

Where is the center of surface of earth?

3. Jul 31, 2010

### zeromodz

But the universe is open! The WMAP showed us that its just flat space, not curved into a sphere.

4. Jul 31, 2010

### Calimero

Then it is infinite!

5. Jul 31, 2010

### petergreat

On cosmological scales, general relativity rather than special relativity is at work. Different parts of the universe may be receding away from each other at superluminal velocities which may approach infinity. It is entirely possible that the universe is infinitely large, but emerged from a single point. Even if the universe is not infinitely large, it could be like the surface of the Earth (though 3D rather than 2D) - the total surface area is finite, but every point is equivalent to other points, so there's no center. Of course, the Earth has a center, but in the above analogy, the curvature of the universe is considered to be "intrinsic", i.e. the curved surface is not embedded in a higher-dimensional space. There's no way you leave the surface find a center (e.g. deep in Earth) because the surface itself is everything that makes up the universe, and there's nothing outside it.

Everything said above is theoretical reasoning alone. No one knows whether the Universe is finite or infinite for sure. But either of the two cases is theoretically compatible with the non-existence of the center of the universe.

6. Jul 31, 2010

### petergreat

We know the Universe is extremely flat, but not necessarily exactly flat.

7. Jul 31, 2010

### zeromodz

No, if you really think about expanding infinitely fast, you will come to realize that its not possible. There is a quantity for everything. It could of expanded a googleplex fast but its still finite. Once again, the universe is not closed (Results from WMAP confirms its flat), so its not like the surface area of the earth analogy. You guys keep evading my argument by using invalid information.

8. Jul 31, 2010

### Calimero

Once infinite - always infinite.

9. Jul 31, 2010

WMAP confirms only that observable universe is very nearly flat. We have no idea what is the topology of the whole universe (and we cannot know how much bigger it is, than the observable part).

10. Jul 31, 2010

### Hurkyl

Staff Emeritus
Really? Even if, relative to some coordinate chart, the volume of space increased at a rate of
1 m3 / (1 yr - t)2
where t is the time parameter? Then what would the volume be after one coordinate year?

The universe is also a universe, not the surface of a planet, so they aren't analogous either!

Seriously, why do you think the difference between an open universe and a planet surface makes a difference?
(And I'm ignoring the problems with your hypothesis that the universe is open but finite)

11. Jul 31, 2010

### Hurkyl

Staff Emeritus
That does not follow.

Only if it's expanding slowly, or even contracting.

12. Jul 31, 2010

### Hurkyl

Staff Emeritus
Oh, here are some fun and easy exercises:

Exercise 1
Draw an interval on a Euclidean line.
Mark the point at the midpoint of the interval.
Find a coordinate chart for the line for which the coordinates of the point is not the average of the coordinates of the endpoints.

Exercise 2
Draw a rectangle on the Euclidean plane.
Choose one orthonormal coordinate chart, with coordinates (x,y).
For each value of y, plot the point at the center of the cross-section.
Choose another orthonormal coordinate chart, with coordinates (s,t).
For each value of t, plot the point at the center of the cross-section.
Compare the two plots

13. Jul 31, 2010

### heusdens

Point 2.

The universe does not have a begin in time, as time itself cannot be said to have begun (in what, or because of what, would time have begun then? the beginning of any something, as 'begin' denotes an event in time, already assumes time exist; outside of time, there are no events, and thus no beginning) and the Big Bang theory does not make any statement whatsoever on that (false, but widely popular, misrepresentation of the big bang theory).

14. Jul 31, 2010

### heusdens

It really does (since time and space have been happily married with each other, and are now called space-time and are eternally inseperable), but that's not the point, the point is that the premise is wrong. Time did not begin.

15. Jul 31, 2010

### Jocko Homo

You don't know that time did not have a beginning. I'm told that there have been successful (that is, consistent) theories of inflation that model a universe where time began...

16. Jul 31, 2010

### quZz

1, 2, 4, 5
where is the center of a plane?

17. Jul 31, 2010

### Hurkyl

Staff Emeritus
What relevance does your parenthetical have to anything?

That's a rather brazen thing to assert, don't you think?

18. Jul 31, 2010

### heusdens

The relevance is that - unlike the Newtonian perspective of space and time - in the modern viewpoint (married by the theory of General relativity) space and time do not have seperate existence, but are closely tied together. Space nor time have a seperate existence.

Yes, but correct. It makes no sense to speak about "begin of time", since 'begin' already assumes the existence of time. So, if before the "begin of time" time had to be already in existence (since outside of time, the event of the beginning does not make sense), this then means there was no beginning of time at all.

It's nonsensical to think about such a concept since there's a clear contradiction in the definition. You can not speak about the beginning of time, same as you can not speak about a corner of a circle.