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In summary, the conversation discusses the concept of the universe being infinite in size, with theories about a warped universe being deemed incorrect. It is demonstrated that, even if one could travel at the speed of light in a straight line parallel to a yard stick, they would never reach the end of the universe because it has no end. The idea of parallel universes is also dismissed, as there can only be one universe. The possibility of the universe having a non-Euclidean geometry is also mentioned, with evidence from General Relativity supporting this idea. The speaker also explains that our current understanding of the universe is limited and that there may be other, more exotic geometries that we have yet to consider.

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Space news on Phys.org

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best wishes.

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Between universes is NOT nothing, and NOT something. It is neither.

It does not exist. This is a difficult concept for some to swallow. Our universe has it's boundaries by matter and light - it is a closed system.

Other universes to not connect ours, because the moment they did we would become one universe.

But the distance one would travel between universes is a distance of not nothing and not something, it's just ______.

It's not in existence - that is to say that once you are traveling, you being matter, is extending your universe and turning it into something.

Nothing - Empty space

Something - filled space

_____ - a nonexistant coordinate that doesn't exist.

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Please stop parading theory around like it is fact.Originally posted by BiologyForums

It does not exist. This is a difficult concept for some to swallow. Our universe has it's boundaries by matter and light - it is a closed system.

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Originally posted by Glok

Please stop parading theory around like it is fact.

Theory and fact have no necessary boundaries.

A theory adheres to evidence - and so does a fact. A theory might be a fact, in fact many of them are.

Our universe has it's boundaries of matter and light. This is as accepted as (if not more than) the opposing claim.

I would be no more sure of myself if it was fact. And I would not ever present a theory in any manner differently than a fact. Because they have no necessary boundaries.

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Originally posted by wolram

best wishes.

Our universe, from recent WMAP results looks to be infinite, this is a result of it having apparently flat geometry on a global scale.

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There's plenty of evidence that space

In general, lines don't have to bend to return to their starting points. A common example (at least it was a couple decades ago) is a video game like Asteroids; when you go off of one edge of the screen you appear on the other side. Believe it or not, but the "universe" in which those video game objects live is a perfectly valid geometry. We see edges since we've embedded the geometry into our 3-dimensional universe in a non-faithful way, but there are no edges to those living in this geometry, and it's everywhere flat to boot... yet you can go in a straight line and end up back where you started.

(Incidentally, this geometry is called the flat two-dimensional torus)

Mathematics (and the laws of physics) certainly permit this type of geometry for the universe, and even much stranger ones. Currently we only consider geometries of space that look Euclidean on small scales (actually, geometries of space-time that look Minowski on small scales), but theoretical physical theories consider more exotic things.

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In mathematics there are many geometries in which parallel lines converge. In more realistic terms, mass distorts space-time, essentially changes the path that a straight line will travel. As mass distorts space, there are 3 possible geometries for the universe, depending on mass; zero curvature, positive curvature and negative curvature. In a universe with a positive geometry (imagine being confined to the surface of a sphere), two parallel lines will intersect (imagine on a basketball), and also if you set off in one direction you could keep traveling in a line and come back to the same point. One problem when people talk about the geometry of space is when they get confused about 'infinite yet finite' space. However if you are confined to the surface of a sphere, you can keep going to infinity and never reach the 'end', but the sphere has only a finite surface area.

Chris

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Only in flat geometries (like Euclidean or Minowski) does it make sense to talk about parallel directions at widely separated points; in general all you can do is say that the line is everywhere straight... geodesics

But even flat geometries are capable of permitting straight lines to return to where they started. For instance, take my Asteroids example; that is a flat geometry. If you take your yardstick and point it upwards and draw a vertical line, the line will always be parallel to the yardstick, yet it returns to its starting point.

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Originally posted by zydubion

You are mistaking unbounded with infinite. If the universe were a two dimensional space curved through a third dimension into a three dimensional shape - say a ball or a torus, then the same argument you use above would be true, yet the area would be finite.

Take a volleyball. Place an ink pen to the surface. Draw a line, without removing the pen's point from the surface as far as you want to, you will never reach the "end or beginning of the ball".

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\hold a yard stick and pick any direction including up/down and imagine traveling out into the universe along a STRAIGHT line parallel to the yard stick.

Something is serious wrong with this argument, I just did this experiment. Even leveled the yard stick. Set out walking, swimming, more walking and more swimming, more walking, always following the direction pointed by the leveled yardstick, By golly, I just got home again, there is the other end of the yardstick! But you told me it couldn't happen!

Your argument falls apart simply by looking at a globe. Toroidal geometries are not necessary, just the simple shpere we live on will do the job.

EDIT: If simple observation cannot reveal the fact that the Earth is not a plane, how can you draw any conclusions about the universe by this argument?

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Thanks to all for the interesting posts.

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I did follow a straigt line, I always checked the level of my stick. Like I said you cannot prove anything about the surface of the Earth with your argument let alone the universe.

In other words, with observations from your postition, prove to me that the Earth is anything but flat.

In other words, with observations from your postition, prove to me that the Earth is anything but flat.

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Zydubion: Integral was trying to make an analogy to demonstrate to you, without having to try and explain differential geometry, how it is geometrically permissible to for one to travel in a perfectly straight line and return to your starting point.

Between Integral and myself, we have shown you the two-dimensional analogues of two of the simplest closed three-dimensional geometies, the hypersphere S

Since you don't accept this, I see only two options at this point: we explain differential geometry to you so we can demonstrate how the universe can have a shape that permits straight lines to return where they started, or you can prove to us that straight lines cannot return where they started. Which do you want to do?

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Ok you guys, I know you are much smarter than I am, but let me take just one more shot at this. The level will always say "level" because the bubble is directed by gravity. So instead of walking, let's shoot a bullet out into space. We all know that gravity will affect it, but let's just pretend it doesn't so I can again ask for a straight line in another way. The bullet travels in a straight line (never looses speed) and if one could look back through the path of travel, one could always confirm the straight line because you could always see back into the barrel of the rifle. I would lay odds and pull the trigger myself and wait for the bullet because it will NOT hit me in the back of my head. If you still say "zydubion, you're going to die" then I give up on this one, and I think I will just stick with the geometry that I now understand. Thanks again. By the way these different geometries you mention, is this all factual/proven or is this theory? Has anyone ever looked out into space with a good telescope and were surprised when they zoomed in on their bald spot?

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Incidentally, if the universe was closed, seperable into space & time, and small enough for this to happen, if you shot the bullet forward and it hit you in the back of your head, you

Oh, and when you fire a bullet up and it comes back down, it

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The Unlimited Universe theory proposes that the universe is infinite and has no boundaries or edges. It challenges the traditional belief of a finite, bounded universe.

The theory suggests that the concept of a warped universe, where space curves and bends, is a result of our limited perception and understanding of the vastness of the universe. In an unlimited universe, there is no need for space to be warped.

There is currently no direct evidence to support the theory, as our technology and understanding of the universe is limited. However, the theory is based on logical reasoning and challenges the assumptions of a finite universe.

The Unlimited Universe theory is often linked with the concept of a multiverse, where there are multiple universes existing simultaneously. This is because an unlimited universe would allow for the existence of multiple universes within its infinite expanse.

The theory challenges our current understanding of the universe and opens up new possibilities for exploration and discovery. It also raises questions about the nature of space and time and the concept of infinity. Further research and evidence are needed to fully understand the implications of this theory.

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