Can you disprove my theory that if you travel straight up into space you'd eventually end in the same place?

Question

In much the same way that people once thought the world was flat, can we be certain that travelling through space far enough won't eventually bring us back to where we started?

Is there evidence to

Answer 1

The problem is that the universe is expanding faster than light, and we certainly cannot move faster than light. Even with an infinite time-scale, we wouldn't make it back.

If it were theoretically possible to travel faster than the universe is expanding, your theory may be possible -- but this is simply not the case.

Answer 2

If three-dimensional space is "positively curved" (like Earth's surface in two dimensions) then if you travel long enough in a straight line, you must end up in the same place (although, after such a long trip that you would probably not recognize the place).

If 3-D space is negatively curved, then no (or, to say it differently, it would take "longer than an infinite time").

If 3-D space is flat (Euclidean), then no (or: it would take "exactly" an infinite time).

Latest data from WMAP (a probe sent to examine the microwave background) favours a flat 3-D universe. So, if it is really curved, then the "radius" of curvature must be very, very large.

----


space-time [(3+1)-Dimensions] is really curved. However, for your concept to work, we need the "physical" 3 dimensions to be curved (i.e., the universe being a hyper-sphere with a finite radius -- whatever 'radius' means when the universe is all there is).

The idea is not new, but it is still worth thinking about as we continue to gather information to determine if the universe is finite or infinite in extent (and the WMAP data has eliminated most finite models -- but not all of them... yet).

Answer 3

The universe expands radially from it's point of origin.
It is a finite entity so it must have a maximum size.
As you approach the cosmic interface that defines it's maximum size space reaches it's minimum density and goes out of existence.
Proving or disproving a theory about the universe can't be done otherwise it would not be a theory any longer.

Answer 4

Well, conveniently for all of us, there is no need to loose any sleep over this question. In fourteen of the sixteen Astronomy texts I checked a few minutes ago, the Universe was agreed to be 40 Billion Light Years deep (straight out) in every direction from us. That was the stated limitation of the most sophisticated optical and radio telescope equipment that we have at this time. Beyond that distance we are unable to get any useable information from our equipment. That does not, however, mean that space ends there. We just cannot make out anything beyond that, and if we cannot see it, we cannot study or investigate it.

Now, i don't know how fast you are traveling straight up, or where on the planet you are standing at the beginning of your imaginary trip. Straight up might be straight down, or out to the side compared to where I am standing. I also don't know what you are traveling in, or what supply of consumeables you have on board. But, your trip will be greatly in excess of 40 Billion Light Years heading out, and if you plan to come back, the return trip will be another 40 Billion Light Years. Were you to try and send an EMail home to MaMa, the transmission would take Billions of Years to reach her, and she probably would never get it.

So, I plan to have a good nights sleep and not worry about where you will be tomorrow, or the next day.

The concept that you will come rocketing back to us via the GREAT CIRCLE (LOOP) ROUTE is just a bit stretched at this point, because I won't plan to see you for way in excess of 80 Billion Years if you could travel at the speed of light. And, I know that I (we) (the Astronomers) can see out in a straight line for at least that (40 BLY) distance.

To get this concept settled in your mind, try to write down the actual number of miles in the distance = 40 Billion light years. I think you will be hugely surprised, and scratch your head for a moment or two. Go ahead. Try to do that. Get a big hunk of paper.

Answer 5

In our current best model of cosmology, that won't happen. Many lines of evidence indicate that our universe is "just open" and also "inflating". In such a Universe, if you moved away from the Earth in a straight line as fast as possible (the speed of light, or a little less), you would wind up in intergalactic space all alone, with all of the galaxies having receeded beyond your event horizon. You'd be in an empty Universe by yourself, likely forever.

Answer 6

This is the answer I got from an astrophysics doctoral candidate from the University of Virginia:

In order for this to happen, the geometry of the universe must be spherical, a 3D analog of the 2D surface of a sphere. However, observations of the cosmic microwave background rules this out. The geometry of the universe is instead "open", meaning that given enough time, moving in one direction would only lead you further away from where you started.

Answer 7

If by straight up you mean that you would travel for ever without changing deirection with respect to your starting point you will have some problems with the Big Bang theory and the expanding universe. What if you were initially propelled sraight away from the center of gravity with no means of changing directions?

Answer 8

Actually, it has been postulated before that since we know light curves in gravitational fields, it is possible one of the distant galaxies we see might be our own Milky Way! Maybe more than one of the galaxies since it light would curve back to here no matter which direction we looked. Maybe the universe looks so big because of a funhouse mirror effect that makes us see the same scene of the same cluster of galaxies no matter where we look!

Answer 9

I can't prove you wrong, because what you gave me wasn't a theory, but just an assumption. Theory is an opinion based on certain data that you offer to be reexamined by other people. That's what makes science - science.

Can you disprove my theory that if people started growing wings (yes, wings, I didn't write it by mistake), they would be able to dive to the deepest bottoms of the ocean?

Answer 10

You will always be traveling away from your start point... so if your going in a straight line.... NO YOU WILL NEVER END UP BACK THERE. You ask for evidence but I say what you need is common sense!

Oh... and if you was to "curve with the universe and end up back at the same place" as some seem to think then you did not go in a straight line did you!!!!!!!!!!