# Where Does Space End? It Must End Somewhere!

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..., it would never have an end.
Yes! It's simply infinite. Infinite expansion fits in infinity too!
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half a quark

With regards to the Universe size:     So, just for the record; It isn't an issue of - could, not - 50%, not even 99.99%. The Universe is Infinite by 100%.

matter cannot always be divided into smaller protions. do the words "elementary particles" mean anything to you?

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When you say that the universe is expanding, do you mean the volume taken up by mass, or the actual region that mass could theoretically take up space in.

If you are saying that space itself is expanding, how fast is it expanding. If the size of space depends on mass, then i guess the rate of expansion of space can't be the speed of light. So what would happen if you travel faster than the rate of expansion till this ever expanding edge?

I imagine a cup of honey. You pour all of it onto a table. At first, you get a thick bulging circle of honey. As time progresses the radius of this circle gets larger and larger and the height if the circle/bulge gets smaller and smaller. In that case you can easily get to the edge and beyond, since it is traveling slower then you finger could easily move. Whats beyond it...the table - so the honey, while being the 'space' in the sense that it is the region that could be occupied by honey bubbles, anagolous to stars, it still exists in a larger region that can be occupied by honey univererses, just as my #4 suggests, the table, which exists in my house, which exists on earth and so forth and so forth.

Unless when you mean that space is expanding, you mean to say something else.

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If the size of space depends on mass, then i guess the rate of expansion of space can't be the speed of light.
I made the same question too. Check out post #293

Unless when you mean that space is expanding, you mean to say something else.

Universe is expanding, and universe defined as matter. It's not really like the mass is increasing and there is always more and more matter. No, everything is moving away from everything, but the mass has remained constant since the Big Bang. Conservation of matter!

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Universe is expanding, and universe defined as matter.

I was under the impression that 'universe' meant everything everywhere, which is made up of, matter floating around in space. Space, is just a container for matter. So the question is how large is this container. (atleast i think thats the question), because if the question is about the size of the volume whose boundaries are defined by actual energy/matter being there, then the question isn't whether space ends, but whether there is a limited amount of matter in the universe spread over a finite volume at any specific moment (so that volume is expanding.)

Otherwise, if space is only where energy exists, that results in the paradox of motion - can something move in such a way that the next place its at, is only available to be at, because it will be there; sort of like building a bridge while crossing it.

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Is this always what it's like when astronomers smoke too much pot?

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• 5 weeks later...

I always imagined space to be an infinitely large vacuum, and our universe is only a tiny section of it. It is possible to have an infinitely large vacuum because a vacuum does not contain matter or energy, therefore there are no problems (in my mind) to having it infinite. I also think that other universes probably exist somewhere in space, but this is pure speculation.

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I always imagined space to be an infinitely large vacuum, and our universe is only a tiny section of it. It is possible to have an infinitely large vacuum because a vacuum does not contain matter or energy, therefore there are no problems (in my mind) to having it infinite. I also think that other universes probably exist somewhere in space, but this is pure speculation.

I don't see how that picture of an infinitely large vacuum with matter only in a tiny section of it would work, dylan.

It is very different from the picture you get in conventional cosmology.

Among mainstream cosmologists that actually fit models to data, the picture everybody give you is that space can be either infinite or finite and on average the density of matter is the same everywhere.

that is, matter and radiation are distributed more or less uniformly throughout-----so if space is finite, then so is the amount of matter.

And if space is infinite then the amount of matter is also infinite.

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also in the conventional cosmology picture there is no boundary-----no boundary to space.

And of course also no boundary to where matter is, because matter is scattered more or less uniformly throughout.

these assumptions are essential to the mathematical model that cosmologists typically use----some equations derived from Einstein's GR field equations. the model of the universe that is used is based on General Relativity, which is the best theory of spacetime geometry we have, the best theory of gravity----it has been checked to high precision. It may be found to be off at the tenth decimal place some day and be replaced by some refinement, but probably the basic features of the cosmology model derived from it will not change all that much even if the theory is revised and improved some.

So I'm inclined to accept the conventional mainstream view.

Everyone is free to invent their own, you can go with the infinite vacuum with a tiny finite patch of matter if you want, but I don't think it is going to either fit the observational data or be consistent with the basic GR theory.

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Wow Martin, that's the second time you pointed out a large mistake for me today. I feel kind of stupid now. Especially because I had learned about the uniformity of space before, I had just never thought about it in depth. Anyways, I can't really see how it is possible to have space and space-time end, so I'd be willing to say that space is infinite.

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... I had learned about the uniformity of space before, I had just never thought about it in depth. Anyways, I can't really see how it is possible to have space and space-time end, so I'd be willing to say that space is infinite.

Friend! It's good to have someone else sharing that perspective.

It COULD end, could have some kind of boundary. I can't imagine what that would look like, but we really don't know. As Bee often reminds us, there can be things we can't imagine. But if the business is fitting model to data, then it is a heck of a lot simpler not to add unnecessary detail like boundaries.

I can't guarantee that the mainstream usual cosmologist's model is right but it keeps matching the data and it is certainly the simplest that provides a decent fit.

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I can't guarantee that the mainstream usual cosmologist's model is right but it keeps matching the data and it is certainly the simplest that provides a decent fit.

Isn't this what it's actually theoretically necessary:rolleyes:...

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Isn't this what it's actually theoretically necessary:rolleyes:...

Yes I think standard cosmology is so far doing great, darkshade.

But in a year or two we could see some new observations that force it to be revised. Probably nothing in empirical science is ever ultimately and completely correct.

You are right, and provisionally I am quite happy to accept the mainstream model.

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But in a year or two we could see some new observations that force it to be revised. Probably nothing in empirical science is ever ultimately and completely correct.

I absolutely agree! It is on the nature of science to progress all the time. Knowledge has no borders, neither does the desire for knowledge. Mainstream model might be the best right know, but science will sure come up with better understandings of the universe. After all, this is what science does and is valuable for.

A pleasure discussing with you Martin!

Cheers,

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• 3 months later...

Could it be possible that one of those distant galaxies that has taken millions of light years to reach our eyes is in fact our own galaxy, it's just that our galaxy has now evolved and moved to our current location?

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hey, for all we know the universe could be a round ball just like Earth, and we're the tiny microorganism living in it. We're just a small piece of dirt for all we could gues

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and how would our galaxy move faster than the speed of light? and how could our galaxy have had so many different shapes and sizes in its past? and what about the galaxies our one is devouring as we speak? is our galaxy eating its past self?

kind of a bit absurd with some temporal paradoxes thrown in.

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and how would our galaxy move faster than the speed of light? and how could our galaxy have had so many different shapes and sizes in its past? and what about the galaxies our one is devouring as we speak? is our galaxy eating its past self?

kind of a bit absurd with some temporal paradoxes thrown in.

Well there goes my theory!!! Thanks for answering insane_alien, unfortunetaly I haven't had much of an education but I have always found this topic most fascinating.

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well, everyone has to start somewhere. made a few stupid suggestions when i was starting out as well(like how to turn my remote control car into a perpetual motion device through regenerative breaking)

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I believe that the universe is 4D. For instance if you could bring a 2D person to Earth their 2D brains would not understand the concept of 3D objects and would not see the 3D universe in the first place. This is like us 3D humans, we are unable to understand the concept that the universe has a 'Fourth' dimension. dark matter could also be 4D as it cannot be see or detected by anything 3D but we know that it has a fundamental part in the creation of the universe

If the universe were 4d we could still see the 3d shape of the 4d object. Taking your example a 2d person would be able to see a 3d object along the plane on whnich it exists. As that 3d object moves through the plane the 2d vision of the object would change for the viewer until it completely evaporated. The evaporation for the 2d viewer would take place when the 3d object passes completely through the 2d plane.

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Space is infinite yet finite. I look at it much like a really big coordinate plane with an x, y, and z axis because numbers on a grid never end.

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If I were to see space, it would basically be what Dark matter said, but what space is, is an infinite amount of 4 dimensional planes...

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Id say that space has no end, as our dimension is most likely full, and with the coordinate planes, i dont think that that makes much sense. I dont know how exactaly to explain it, but it just doesnt

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Id say that space has no end, as our dimension is most likely full, and with the coordinate planes, i dont think that that makes much sense. I dont know how exactaly to explain it, but it just doesnt

If you think that it doesn't make sense, then you are sadly misinformed.

It's a well known fact that space consists of an infinite amount of 4 dimensional planes, though if we're speaking in the fourth dimension, it's spaces.

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If you think that it doesn't make sense, then you are sadly misinformed.

It's a well known fact that space consists of an infinite amount of 4 dimensional planes, though if we're speaking in the fourth dimension, it's spaces.

Would you mind citing a reputable source, where it specifically states that please.

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Id say that space has no end, as our dimension is most likely full, and with the coordinate planes, i dont think that that makes much sense. I dont know how exactaly to explain it, but it just doesnt

I can agree. I flaw in this design is it does not show the curvature of space and time. Instead, you can look at like this; you have at first a perfectly flat dining room table with a cloth over it. You draw perfectly straight lines crisscrossing like a graph. (as described in my previous post) Now, in order to show the curvature of space and time you can take the cloth off of the table and throw it randomly on the floor. This imitates space because the lines should theoretically be a perfect graph, but when you throw in forces and energy, it clumps up and there are more lines in some places and less in others.

Would you mind citing a reputable source, where it specifically states that please.

The Elegant Universe Written by Brian Greene... Good book I would (and probably antimatter) recommend it.

Edited by Dark matter
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Would you mind citing a reputable source, where it specifically states that please.

Elegant Universe, written by Brian Greene,

very well known, very reputable.

http://en.wikipedia.org/wiki/Spacetime

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