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FrozenGate by Avery

Is the universe infinite or finite?

Speaking of, ever notice on some sci fi films or TV shows, radio communications taking place from light years away and they are talking like neighbors on the phone??

I love how most producers forget or just toss the laws of physics out the window when making these films. (sarcasm)
 





photonaholic said:
Speaking of, ever notice on some sci fi films or TV shows, radio communications taking place from light years away and they are talking like neighbors on the phone??

I love how most producers forget or just toss the laws of physics out the window when making these films. (sarcasm)
Click to expand...

Lol yeah, that always annoys me. Good authors or writers can usually explain it, hell a large chunk of the ender series was specifically about faster than light communication. One of the characters basically WAS faster than light communication :wtf:
 
I've always liked authors that work in a lot of physics into the sci-fi. After all. it's SCI-fi not justmakesomeshitup-fi. I quite enjoyed the book "gravity dreams" by l.e. modessit mostly because the main characters had to deal with things like objective vs subjectinve time and age when dealing with space flight. Although there was of course a large amount of things not well explained, it was still a very good read. Just enough science thrown in. (most of the authors books, however are not so good. but some of his older sci-fi is quite good)

In reality, even shows like star trek with it's "warp drive" still would have to deal with the logistics of time dilation with the "impulse drives" etc. and other high sublight movement. The fact that the people on the star ships aren't seeing the people left behind on the planets die of old age always did annoy me. Enders game of course also had the effects of relativity worked in. One of the things that helped make the series good.
 
Also, back to the gravity side topic. I've always found it funny, that generaly people explain that space-time is curved by gravity. Yet nobody claims gravity is curving in a 4th spacial dimension. Yet I've never seen a realistic 3D graph of HOW 3D space can curve, without requiring an extra dimension. Everyone's seen the classic black hole graph. where space is depicted as a flat 2 dimensional plane, curving down into a bottomless funnel. But in this, space is being drawn as 2 dimensional to allow for the use of the third dimension to curve it in. *shrug* I've always felt that while the curve of space-time from gravity is well known, how to picture it in 3 dimensions is problematic. Makes you wonder if gravitational curvature of space-time really IS bent in just 3 dimensions. Just a thought.
 
Awesome, I love this thread :yh:

My perspective on the original question (infinite or finite universe) is that it can be thought as either; the universe is constantly expanding although it seems that this expansion is accelerating due to dark energy (just remembering this off the top of my head, hopefully I'm somewhat correct). So in a way it is infinite assuming this expansion will continue forever.
However, at the same time there is technically an end to the universe so it is also finite.

On the other hand, if there is some point where expansion will stop then it can only be thought of as finite (IMO).
You can't really bring in the idea of something beyond the universe IMO because it is not a part of this universe (as far as we know) and thus may not abide by the Laws of Physics as we know them.
Personally, I can't really grasp the concept of multiple dimensions, parallel universes or the multiverse. I listened to a podcast about multiple dimensions "stacked upon each other" once which explained the idea quite well. I'll have to give it another listen, my memory of it is a little fuzzy.
I guess what I don't understand about parallel universes is why are they the same as ours? What's stopping them from being different? Also, what is separating theirs from ours, what's in between? The latter I believe could be explained that simply there is a void/vacuum, maybe "void stuff/particles" lol.

Onto light lol. I read a couple of posts that said something like "nothing can travel greater than c in a vacuum, relative to anything".
Isn't it possible that, if two points, A and B, were moving apart from each other in opposite directions at c, an observer at their starting point would say they are both traveling at c. However, an observer at the now moving point A would say point B is moving at 2c. Is this true?

@StridAst: I've noticed how curvature of space-time by gravity is always represented on a 2D graph as well. Thinking of it in a 3D sense is crazy, how would you imagine it? It would be really cool to actually see it plotted on a 3D graph.
 
^I think that when two objects are moving away from each other the difference can be 2c. But we'll see.... and about the multiverse, maybe there have been multiple big bangs in the same spacial plane. Meaning maybe like a trillion to the trillionth to the trillionth power light-millenias away there is another universe that formed like ours, and could be reached by simply floating through space for a long-ass time (your ship would atomically decay by then) LOL
 
SciFi communications: There is always some construct that allows immediate communication across light years of distance in good sci-fi movies. Bad sci-fi just avoids the issue. Star Trek, as an example, utilizes sub-space communications that short cuts the distance. Fans have quite good elaboration on sub-space communication theory regarding Star Trek that has even made it into the thoughts of real physicists.

2D Representations: Space for the layperson has to be shown in 2d. Anything more than that and the science show on the science channel becomes an exercise in mathematics. The general rule of thumb is that to directly observe a dimension you need to be at least one dimension above it. Mathematically, we can demonstrate how an object appears in any dimension but there is no way to construct it so it is visible in our commonly experienced dimensions. A tesseract is a classic example. A cube in 4 dimensions cannot be envisioned but the shadow of a 4th dimensional cube can be drawn. By removing a single dimension we can see what the "shadow" looks like but not the original form. If you like math, look up tesseract. Now this is the same for the representation of a black hole in planar space. It does look like that but only when represented by that plane but we all know space can be bisected in an infinite amount of directions about a point. Each planar representation looks like the standard 2d model but realize it's that model doing that in every conceivable orientation. It starts to get complicated in representation.

Two individuals moving apart, each at the speed of light will experience relativistic effects. Once a reference frame is determined the effects result in time dilation, length contraction, or mass changes. Because the speed of light is constant, it is the other variables that change. Regardless of what is selected as the reference frame, those effects come into play to keep c constant. What we consider constants, time, distance, and mass are actually not constants at relativistic speeds. The speed of light is the only constant in the equations which is counter-intuitive based on our every day experience at non-relativistic speeds. Unfortunately, it takes some pretty advanced mathematics to see the light (pun intended) which is beyond the layperson in most cases.
 
MrGreenJeans said:
2D Representations: Space for the layperson has to be shown in 2d. Anything more than that and the science show on the science channel becomes an exercise in mathematics. The general rule of thumb is that to directly observe a dimension you need to be at least one dimension above it. Mathematically, we can demonstrate how an object appears in any dimension but there is no way to construct it so it is visible in our commonly experienced dimensions. A tesseract is a classic example. A cube in 4 dimensions cannot be envisioned but the shadow of a 4th dimensional cube can be drawn. By removing a single dimension we can see what the "shadow" looks like but not the original form. If you like math, look up tesseract. Now this is the same for the representation of a black hole in planar space. It does look like that but only when represented by that plane but we all know space can be bisected in an infinite amount of directions about a point. Each planar representation looks like the standard 2d model but realize it's that model doing that in every conceivable orientation. It starts to get complicated in representation.
Click to expand...

It's quite possible with software to model things in 3 dimensions. You can make a 3d model of an apple for instance, or a ball, a cube, whatever. then use the software to rotate your viewing angle. One can observe anything purely contained WITHIN the 3 dimensions that is our plane of reference. Now while your post deals with observing a dimension itself, rather then an item within a dimension, a gravity well is still enclosed within 3 dimensional space. (excluding time from this entirely) So your post deals little with the logistics of modeling in 3D a gravity well. It doesn't need to be a black hole, it could simply be the curvature of space-time around a planet.
Any way you spin it. I would love to see any serious attempt to model gravity curved space in. Assume space is like a cube shaped crystal structure of say table salt. Where the structure is essentially a "grid of grids" where instead of squares you have cubes. Now show how the lines bend from the gravity a sphere shape inside the cube., WITHOUT needing to show or describe mathematically more than 3 dimensions. If more then 3 dimensions are required to plot out gravity with mathematics, then gravity itself demonstrates a 4th spacial dimension.
I would love to be proved wrong. I am certain I am, however the concept that gravity is a force that bends 3 dimensional space in only 3 dimensions just doesn't feel right to me.
 
Actually, I'm not saying anything about higher dimensional sources for gravity. I'm only describing why we always see its effects represented on a plane.

Current theory, particularly the super-gravity people have mathematically determined that the theorized graviton and gravitino can only be represented by 4 to 11 spatial dimensions plus a time dimension. They all seem to be settling on the 11 dimension format but it depends on the mathematics. String theory also seems to support the 11 dimensional model. Essentially, based on the theory, gravitation in three dimensions is derived from up to 11 spatial dimensions with dimension 4 through 11 wrapped within quantum sized strings. Gravity within one of the higher dimensions could be incredibly strong which would align quite well with the field strength of the strong nuclear force, the electromagnetic force, and the weak force. It would explain why gravity is so exceedingly weak within our three dimensional space when compared to the other fundamental forces. So your gut feeling about gravitational interaction existing beyond just 3 dimensions is well aligned with current string and super-gravity theories.

As far as modeling it in software, I'll leave that to you. The mathematics exists to do the modeling but I don't have the programming prowess to make such a thing work.
 
MrGreenJeans said:
SciFi communications: There is always some construct that allows immediate communication across light years of distance in good sci-fi movies.
Click to expand...

Well, there is little way around that. Otherwise a movie exchanging only hello's between two star systems would span a couple of decades just to do only that.

I suppose that's why the genre is called science FICTION ;)
 
Another nice thought:
In quantum mechanics, a potential barrier that is too high for a particle can still be passed with a certain probability, called tunneling. So if we have a wave (the probability function of the particle) coming in from the left, and a wide barrier in the middle, the wave will decay exponentially in the barrier. Past the barrier, the wave has a much lower amplitude, but it's still there. The lower amplitude means that the particle isn't likely to be there.
The fun thing is, the exponential decay isn't periodic, the phase on the left side of the barrier is equal to the phase of the right side, it's directly connected through space without delay.
So take for example a microwave signal, and send it through a short waveguide that's too narrow. Classically, it would reflect, but it partially tunnels though this short piece, without any delay in phase from where it enters to where it exits. But it has travelled that distance!

I have this though from my professor, he said it was experimentally verified, but scientist don't really know what to think about it concerning the faster than light travel of the information through that short piece of waveguide.
 
nikokapo said:
We need a string theory thread...
Click to expand...
Hah that could be interesting...but there's so much debate even among the most educated in the field that I think any debating we would do would be mainly crazy speculation unfortunately haha. It's also changing all the time, and "classical" string theory doesn't have much merit these days anyhow...M-theory is what a lot of people are debating about these days.
 
Speaking of quantum tunneling, Michio Kaku, in his book Physics of the Impossible, discusses teleportation from science fiction as well as from a real quantum level. Because of the Schrodinger wave equation an electron from your body can realistically be anywhere in the universe, albeit the probability is infinitesimally small. Factoring in all the wave equations for all the particles in your body you get a probability of waking up on some remote planet due to "teleportation." (i.e. all of the wave functions happen to be exactly the same at the same time so all of your particles happen to be on some other world.) Of course such an occurrence would occur maybe once in several universal lifetimes. This is the basis for teleportation in Hitchhikers Guide. Build a device that can alter quantum probability and boom, you are there.
 
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