Aterna's question---the unexpected cosmic horizon

[Martin]

And that's kinda where I was trying to get to with my original question. It was meant to sound something like: if I could right now leave the earth and go in a straight like (this is not a matter of reaching other galaxies) at a speed faster than anything else and eventually reach the "edge" what would I find?

 

Dragons, of course!

and maybe sea monsters.

 

Andrei Linde makes up fantastic imaginings of what you might find if you came to an "edge". And the Stanford physics department pays him for it. There is a small industry fantasizing about an "edge" of the universe and what could lie beyond.

 

But no one has shown that an edge is logically necessary. So the most usual approach to take is not to assume there is an edge. This is called Occam's Razor----the first commandment: don't make unnecessary assumptions. Make the picture only as complicated as you need to accomodate the known details. Beyond that, keep it simple. Linde doesn't obey that rule, but he has something called tenure which means they can't fire him.

 

I know that the universe is shaped in such a way that you'd be back where you started,

 

You know, but I don't know! I think it COULD be shaped that way. Analogous to a ring, where there is only the ring and no inside or outside. All existence is on that ring and there is nowhere else you can imagine being. That would be one way to picture it.

 

But space might also be analogous to an infinite straight line. Where you travel forever and never get back home. And where there is no boundary to stop you continuing on forever.

 

Those are the two basic possibilities and there are ways to measure to see which we are in. I think in the next 10 years, with some new spacecraft observatories scheduled to go up in April 2009, after they have collected data, we may have a better idea which it is: the infinite space or the case where you get back home after making full circuit.

 

the important thing for now is to have clear focused ideas of the two main possibilities, and don't mix them up, and to be patient because we dont know which is right.

 

A. space is like an infinite line, with all existence in that line (no existence to the right or left or up or down from it, only in that line itself) Then it is impossible to be anywhere else so you don't picture yourself being anywhere off that line.

 

Or equally well use the analogy of an infinite flat plane. All existence is on that plane, nothing exists above or below. Don't imagine being above or below the plane.

 

the idea of the universe is that it is every thing and every where. so you have to concentrate if you want to imagine a lower-dimension analog like a line or plane. keep it pure. nothing external.

 

B. space is like a ring, with all existence concentrated on that ring. It is impossible to be anywhere except there. So you of course don't picture yourself inside or outside the ring. That would be mixing the picture up with the plane picture of case A. Everywhere it is possible to be is a point of that ring itself.

 

Or equally well, space is like a sphere surface. All existence is concentrated on that surface. there is nowhere inside or outside. The only locations are on that 2D surface, given by some latitude and longitude.

 

These are the two cases. A and B are the infinite and finite space---the two main possibilities. We don't know which is right, so for the time being we have to keep both possibilities open. More data will help decide. Basically because in case B the sum of the angles of a triangle is not exactly 180 degrees. We have a chance to detect some tiny discrepancies that will tell us which is right.

 

I always think of a circle (which is neverending and you always end up where you started). So I picture myself in the middle of the circle,..

 

Heh heh. Don't do that Aeterna! That is mixing the two cases. The ring is case B, but if you hop off the ring and walk inwards or outwards then you are on the plane, which is case A. Mental exercise: concentrate and keep the idea pure. In case B all existence, every thing and every where, is on the ring. Impossible to depart from it and stroll into the middle.

 

Don't confuse the two cases, otherwise it defeats the purpose of imagining them in the first place.

Edited October 18, 2008 by Martin

[Aterna]

OHHHHHHHH!

 

Hahahahaha, what have I been thinking all this time? Glad I met you. You actually took the time to explain all that to a dummy like me. If I could bow 1000 times to you, I'd do it. Thank you. I understand it now. I really don't know what else to say. My question has been pretty much cleared up.

[Martin]

Aterna,

I'm delighted to know you got something from the previous posts. I thought you raised one or more good questions. Thanks for the comment.