Thread: outside space?

if space is what is between two objects,than can there be "space" beyond the outermost objects in the universe? i feel like i am missing something huge.

Originally Posted by roncj5

if space is what is between two objects,than can there be "space" beyond the outermost objects in the universe? i feel like i am missing something huge.

How do you define space after the farthest object? Space is nothing well there is zero point energy but lets ignore that for now. There can be lots of "nothing" after the farthest object, if the universe is unbounded, but what would that even mean?

I think there there are a couple of concepts being brought to light.
These are what I think you are trying to make sense of:

1) expanding universe
2) how does space expand??? what does that mean for space to expand?
3) What is farther than the farthest object? OR what does space expand into?
4) is the universe infinite or not and is it bounded or not.


I will try to do my best to explain what I think are the answers to these questions:

1) expanding universe
Every point in the universe is expanding away from every other point. The farther away something is the faster it is expanding away from us. This point is also true for every other point in the universe. Going back in time it seems that the universe was expanding slower in the past than it is now and will be expanding faster in the future.


2) how does space expand??? what does that mean for space to expand?
space expands by objects moving apart from each other. The confusing thing is that there is no way to measure who is moving away from what. There is no center and there is no reference point. Co-Moving coordinates. So all we know is that it is moving away from us ( based on redshift ). Another thing is that in the past things were closer together so there was move gravity so there could be some redshift due to that .


3) What is farther than the farthest object? OR what does space expand into?
I am not even sure if space without having something observed in it is defined.


4) is the universe infinite or not and is it bounded or not.
the universe can be infinite or finite. if it is finite it could be bounded or not.

5) can gravity overcome the expansion
If it is close enough AKA gravitationally bound.

that does answer a few of the questions.thanks.

Originally Posted by roncj5

if space is what is between two objects,than can there be "space" beyond the outermost objects in the universe? i feel like i am missing something huge.

I prefer the question: If objects are what is between two spaces, than can there be 'objects" betyond the outermost spaces in the universe? I don't feel like I am missing anything. To misquote a popular philosopher: I think, therefore I think I am. To answer either question is to answer both. And the answer is: Of course there can. The catch is that there is no true evidence of a beyond so we can only speculate.

I think its a popular view that the universe could be finite but unbounded. In a sense it means it has size but no boundary or "edge" if you want to try and imagine this in your head think of living on the surface of a balloon. You can also use this simply analogy to imagine the expansion of space like what Tom has already described to you. If you take this view of the universe to be true then the definition of whats beyond the space is "nothing" this would then lead us on to the true definition of "nothing" which is another topic and open for debate.

Dmw

what is nothing would be my next question.would it be completely devoid of all matter[known and unknown]but still exisiting as a "medium" for matter to exisit in?

No, nothing is exactly what it means - completely de-void of anything. Though some would argue that to have "nothing" is to have something to define i.e "nothingness" but this is purely semantics. For all intense purposes regarding the context we are talking about, it means de-void of space, time and anything else we can imagine.

Originally Posted by David M W

No, nothing is exactly what it means - completely de-void of anything.

ok.i get that.what i mean is if the universe expanded into nothing and out side the universe is possibly nothing and the universe is possibly unbound,then that nothing must be able to "support" or act as a medium of sorts for matter to exisit in a later time.of course when "something" is introduced,the nothing ceases to be.but then if nothing is outside the universe,then doesnt that mean the universe is inside nothing therefor it becomes something.i think my brain just did a somersault!

I can see where you are trying to come from with this, its not an easy concept to imagine. In fact its impossible to imagine true nothingness because if you imagine nothing it becomes something defined. You've got try and get rid of the thought of the universe expanding into "a nothing" and think rather in the terms - the universe is everything but expanding.

This is what I was talking about when I mentioned the semantics of "nothing" true nothingness cannot be defined, even with language because as soon as you define nothing it becomes something. Can you follow what I mean?

Originally Posted by roncj5

ok.i get that.what i mean is if the universe expanded into nothing and out side the universe is possibly nothing and the universe is possibly unbound,then that nothing must be able to "support" or act as a medium of sorts for matter to exisit in a later time.of course when "something" is introduced,the nothing ceases to be.but then if nothing is outside the universe,then doesnt that mean the universe is inside nothing therefor it becomes something.i think my brain just did a somersault!

Grab a piece of paper and a pencil. Draw a balloon man. Now draw a balloon woman. Give them each an aching, rapidly pounding heart. The b-man and b-woman are totally taken by each other. But they can only see the outline that you have drawn to serve as their skin. Now give them each a brain, writhing and throbbing under the strain of contemplating whether the other feels the same. Seeing their hearts beating wildly you know that it is mutual attraction. They can only see the skin on the “outside” of each other, but not you, you can actually see “inside” them.

That is because you see in the third dimension and they are trapped in the second. Our perception is limited to three dimensions, but the universe exists in four. Although you can not make the leap perceptually, you can conceptually. There is no inside or outside to our universe. The illusion of an inside and outside is due to our dimensional restrictions and the resulting limits of perception. There is not now nor has there ever been evidence to support either an inside or an outside to the universe.

If you only wish to chew the fat over being and nothingness, I would not want to rain on your parade, but if you are genuinely interested in objective reality as it relates to the nature of our universe, you need not trouble yourself about what is outside. There is no outside. We are of the universe, but technically we are not in it. If this feels a little awkward at first, take heart, there are very few physicists alive today who can fully grasp the significance of this phenomenon.