"THEY"
I want to start a discussion about whether or not the universe is bound or unbound. Also, how either relates to the speed of light.

What should we see happen in a bound universe?

What should we see in an unbound universe?

Does light push out the envelope of the "edge" of the universe?

Or if it is bound, does the light eventually wrap back around? What should we see then? Or could we ever "see" a photon that has been to the edge and back of a bound universe?
kjw
QUOTE
"THEY" Posted on Today at 1:00 PM I want to start a discussion about whether or not the universe is bound or unbound. Also, how either relates to the speed of light.

What should we see happen in a bound universe?

What should we see in an unbound universe?

Does light push out the envelope of the "edge" of the universe?

Or if it is bound, does the light eventually wrap back around? What should we see then? Or could we ever "see" a photon that has been to the edge and back of a bound universe?

i often think about these questions, as the large scale interests me greatly.

if the universe is bound (now where is Oldwoman1904 when there is a joke to be made) that would mean you could travel in a straight line and end up where you start, right ? unbound would mean you could travel in a straight line without ending up where you started, right ?

i think light, and anything for that matter, would push the boundary of the universe if the universe were unbound. as long as something can get there, it is a part of the universe if the universe were bound, could you escape the boundary by punching through another dimension (that is if there was an extra dimension to punch through of course)

from an estimation of the size of the universe, if it were bounded, the universe is so big that by the time a photon made the round trip, the universe would of already collapsed back in on itself. if i find a link i will post it.

one thing i do not understand is when physics describes closed loops of not only space but time ie when you travel in a straight line you can end up not only back to where you started but when you started (weird). from memory (haha i made a funny) this only works if the entire universe is rotating or something like that.

kjw
i may have messed up
QUOTE
kjw Posted on Today at 1:56 PM from an estimation of the size of the universe, if it were bounded, the universe is so big that by the time a photon made the round trip, the universe would of already collapsed back in on itself. if i find a link i will post it.
it appears the other way around ie that the universe may epxand faster than the photon can travel
QUOTE (->
 QUOTE kjw Posted on Today at 1:56 PM from an estimation of the size of the universe, if it were bounded, the universe is so big that by the time a photon made the round trip, the universe would of already collapsed back in on itself. if i find a link i will post it.
it appears the other way around ie that the universe may epxand faster than the photon can travel
Even if the universe is closed, you can never see all the way round it, because by the time a photon travels all the way round the universe, the universe will have recollapsed in the Big Crunch.
This is another result which depends on the two questionable assumptions discussed in the previous item.
dennis_kane
I believe that the universe cannot have boundaries, because this would mean there there are points in space that are not totally surrounded by other points. This doesn't make any sense to me. I can't imagine ever running into some kind of wall at the edge of the universe.

However, this is not the same as asking whether the universe is finite. It is a tired analogy, but to the residents of a 2D universe that exists on the surface of a sphere, the third dimension is the thing that allows the universe to be unbounded, yet finite.

So, if there were a fourth spatial dimension, then it would allow our universe to curve back into itself in exactly the same way. If this were the case, then it would be theoretically possible to see ourselves, but only after many ages have passed.

However, the universe may also be unbounded and flat. This case is that we normally call the infinite case.

I rather prefer to say that the universe is indeterminably large, and leave it at that. In other words, if the universe is truly finite, I believe that the "observable universe" is but a molecule of water in the universal ocean.

And I truly do believe that the universe is ultimately an ocean that is everywhere teeming with "extra-atomic" bits of matter. I don't believe that the space of the universe is empty on any level. It might be less dense at parts, but this is far from being empty.

And when there are ripples through this ocean, this is what we call "light". However, these ripples are energy waves just like any other, and all energy waves dissipate. That is, as they lose intensity over time (because of wavefront surface expansion and losing energy to the bits in the universal ocean) they propagate slower and slower until they eventually stop.

Over large enough distances, the speed of light is always zero! (When t=infinity, v=d/t=0)
kjw
QUOTE
dennis_kane Posted on Today at 5:08 PM I believe that the "observable universe" is but a molecule of water in the universal ocean.

that is a point worth expanding (wait i smell a pun). if we need the density of the universe to determine if the universe is bound or unbound, how confident can be be in saying the observable universe is representative of the entire universe ?

QUOTE (->
 QUOTE dennis_kane Posted on Today at 5:08 PM I believe that the "observable universe" is but a molecule of water in the universal ocean.

that is a point worth expanding (wait i smell a pun). if we need the density of the universe to determine if the universe is bound or unbound, how confident can be be in saying the observable universe is representative of the entire universe ?

Over large enough distances, the speed of light is always zero! (When t=infinity, v=d/t=0)

in such a case would not d also be infinite ?
dennis_kane
Those who ask about whether the universe is "open" or "closed" are not the same as those who ask whether it is "bound" or "unbound". To me, "open" and "closed" are unfortunate terms that really mean to ask whether the universe's expansion will or will not infinitely continue.

However, I just find that the entire concept of universal expansion is the result of an unnecessarily mystical interpretation of the nature of light-energy propagation. Ever since Maxwell, the scientific community has upheld that light has to do with some kind of never-ending dance between the two things called electric fields and magnetic fields. It is said that this dance can occur through a perfectly vacuous space. That is, there is precisely nothing substantial about light-energy propagation. The common concepts of dissipation and slowing that apply to substantial energy waves, therefore, should not apply, and light should always have the same frequency no matter how far it travels.

However, to speak of an "insubstantial field" raises difficult philosophical questions. In this view, a field is simply "a space that holds values". We normally think that values must be associated with some kind of real phenomenon in order to have any meaning.

All that we know about light waves is that something is oscillating. However, post-Maxwellian interpretations of light propagation have changed this to mean: All that we know about light waves is that nothing is oscillating. They have just managed to get around this embarrassing claim by replacing the word, "nothing" with the word, "field".

Once someone comes along to call their bluff, the "fieldists" reply by saying: In other words, you are claiming the existence of a universal aether... you silly-billy, don't you know that the aether was disproved in the nineteenth century?

This is when we start rehashing all of the "aether disproving" types of experiments that have been conducted ever since the Michelson-Morley days.

Anyone with a bit of logical sense, however, knows that all has been "disproved" is that, as far as we can tell, the surface of the earth does not move relative to the light propagation medium. And why should it? If there were undetectable bits of matter that everywhere pervaded the universe, why wouldn't they move along with the surface of the earth just like the earth's atmosphere does? Why would they just stand still, impervious to all of the commotion happening around them?

QUOTE (kjw+)
in such a case would not d also be infinite ?

The point here is that, if an EM wave is never detected, the time of detection is infinity, and any value of d will yield a velocity of zero. That is, any number divided by infinity always equals zero.
iseason
QUOTE (kjw+Apr 22 2008, 04:56 PM)
i often think about these questions, as the large scale interests me greatly.

if the universe is bound (now where is Oldwoman1904 when there is a joke to be made) that would mean you could travel in a straight line and end up where you start, right ? unbound would mean you could travel in a straight line without ending up where you started, right ?

i think light, and anything for that matter, would push the boundary of the universe if the universe were unbound. as long as something can get there, it is a part of the universe if the universe were bound, could you escape the boundary by punching through another dimension (that is if there was an extra dimension to punch through of course)

from an estimation of the size of the universe, if it were bounded, the universe is so big that by the time a photon made the round trip, the universe would of already collapsed back in on itself. if i find a link i will post it.

one thing i do not understand is when physics describes closed loops of not only space but time ie when you travel in a straight line you can end up not only back to where you started but when you started (weird). from memory (haha i made a funny) this only works if the entire universe is rotating or something like that.

Hey ! wouldn't structure work well (conservatively) if light was traveling across a rotating universe at exactly the correct speed to meet it's starting point. (kinda like jumping up and staying up till the earth rotated a day).

Then Light governs reality by virtue of itself verses the rotation of the universe. It means that both must draw on each other/keep in sinc. a faster rotation speed = faster light speed , but only relative to itself/universe. We wouldn't know the difference, but variance in time is possible because of the universal scale of light turnover.

just some fun.

Cheers
Iseason
"THEY"
QUOTE (kjw+Apr 21 2008, 08:56 PM)
one thing i do not understand is when physics describes closed loops of not only space but time ie when you travel in a straight line you can end up not only back to where you started but when you started (weird). from memory (haha i made a funny) this only works if the entire universe is rotating or something like that.

I have heard this before also, but i have a hard time accepting it.... I can't quite grasp how it would work with OUR reality. But it is a nice concept to roll around the mind.....

I have a problem with there being an edge of the universe, but then I also have a problem with it expanding into nothingness. Unless there is a multiverse! It is so hard to visualize either concept without running into HUGE problems!
kjw
QUOTE
"THEY" Posted: Today at 5:58 AM I have a problem with there being an edge of the universe,
i let go of the idea that the universe must have an edge. what specific problems does that then cause for you ?

QUOTE (->
 QUOTE "THEY" Posted: Today at 5:58 AM I have a problem with there being an edge of the universe,
i let go of the idea that the universe must have an edge. what specific problems does that then cause for you ?

but then I also have a problem with it expanding into nothingness. Unless there is a multiverse!
if there is no edge to the universe then how can the idea that the universe is expanding into nothingness work ? i let go of that idea also.

QUOTE
It is so hard to visualize either concept without running into HUGE problems!
me too that is where math comes in handy, not that i can use math much. you do not need math to visualise the area bounded by a line in when rotated around its centre in 2d ie circle, nor is math required to visualise the area bounded by the same line when rotated around its centre in 3d ie sphere. but how can you visualise this system to 4,5,6,n dimensions? just keep integrating !

"THEY"
QUOTE (kjw+Apr 24 2008, 02:27 PM)
me too that is where math comes in handy, not that i can use math much. you do not need math to visualise the area bounded by a line in when rotated around its centre in 2d ie circle, nor is math required to visualise the area bounded by the same line when rotated around its centre in 3d ie sphere. but how can you visualise this system to 4,5,6,n dimensions? just keep integrating !

Thats why I created this thread. I love hearing how other people think through it. We only understand 3% of the universe, but there are a few things that I WANT THE ANSWERS TO NOW!

dawn
THEY, (great one), all,

Have a meeting (last moment) will reply IMHO, when possible.

dawn