The Naked Scientists

The Naked Scientists Forum

Author Topic: Does the universe spin?  (Read 9703 times)

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Does the universe spin?
« Reply #25 on: 11/08/2011 08:29:11 »
A meaninless question, by definition the universe is all that there is to spin it must be spinning relative to something else..........

Actually it is not a meaningless question. Rotation of a system has measurable effects from inside the system. The issue of how to define the universe may come into play of course; it may defined as a system beyond which we can never venture or, for example, a many-fold set as part of a multi-verse.

Anyway there has been some recent experimental evidence to suggest that the universe has a net angular momentum. The work involved measuring the angular momentum of a large number of surrounding galaxies. The result showed that the net momentum was non-zero to a statistically significant degree. The limitations to the experiment is that we can only see, and measure/estimate, so far and it may be that the net angular momentum in our region of space is compensated elsewhere but beyond our view. See Prof Michael Longo (University of Michigan). They looked at space up to 600 million lightyears distance. It would have a very significant impact on cosmological models.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Does the universe spin?
« Reply #26 on: 12/08/2011 21:12:23 »
Oh yes it would Graham, it would allow 'time travel' :)

And that's a totally other barrel of fish.
So I will continue to presume that it's not rotating :)
heh.
 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Does the universe spin?
« Reply #27 on: 13/08/2011 07:19:09 »
Yor_on, you lost me with the relation between a non-zero angular momentum for the universe and the concept of time travel (which I assume you mean backward time travel with all the resulting paradoxes). What/whose theory is this?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Does the universe spin?
« Reply #28 on: 13/08/2011 17:49:35 »
"In 1949, the mathematician Kurt Godel - a friend of Einstein's and a colleague at Princeton University's Institute for Advanced Study - decided to tackle a situation where the whole universe is rotating. In Godel's solutions, time travel was actually allowed by the equations ... if the universe were rotating. A rotating universe could itself function as a time machine.

Now, if the universe were rotating, there would be ways to detect it (light beams would bend, for example, if the whole universe were rotating), and so far the evidence is overwhelmingly strong that there is no sort of universal rotation. So again, time travel is ruled out by this particular set of results. But the fact is that things in the universe do rotate, and that again opens up the possibility."

"In 1949, when his good friend Kurt Gödel showed that a rotating universe allowed for time travel, he was deeply worried.

Gödel, in fact, would pester astronomers visiting Princeton and ask if there was any sign that the universe was rotating. In Einstein’s writings, he finally concluded that time travel might be inherent in his equations, but they can be dismissed "on physical grounds," i.e., they could not form using known physical mechanisms. In other words, the universe expanded, not rotated. So if the universe did rotate, then time travel might be an everyday occurrence. This argument holds even today. There are a large class of solutions of Einstein’s equations, but many can be dismissed "on physical grounds." For example, in 1937, W.J. Van Stockum showed that a spinning cylinder that was infinitely long could satisfy all of Einstein’s equations. Decades later, it was shown that the Stockum solution actually allowed for time travel. If you danced around this cosmic Maypole fast enough, you could come back before you left. But again, "on physical grounds," one can argue that cylinders can never be infinitely long, so this was just a mathematical curiosity."

Then you have Black Holes, 'stabilized' worm holes clad with 'exotic (negative) matter/energy' etc. So the math seems to allow it, but I don't think it will work in reality.

Time travel Physics.

==
I think of it like this. Assume that there is a universal 'same clock'. Let's use light as that clock. You are born and now it start ticking for you, I'm born and it starts ticking for me. But those clocks, although having the same exact durations, as we will find whn being in the same 'frame of reference' is also uniquely our own as shown by a 'time dilation'. Two synchronized clocks on a table, move one to the floor, see their durations start to differ with gravity's influence.

If you travel near light the universe might pass forward at furious pace time wise as far as you are concerned, but your rate of durations do not change, you do not become in 'slow motion' and the arrow still only have one way, for all involved. There is a symmetry in that. But there is no symmetry in assuming that your 'arrow of time' both can point forward. at the same time as it points 'backwards' to me as in backwards time travel. How would it do that?

The clocks we have is uniquely our own, although belonging to a same conceptual common 'ground state' as I see it. To assume that the rest of the universe would be the one ticking backwards becomes just as confusing, as if you share their frame surely would find only one arrow, pointing in one direction, same as always.
« Last Edit: 13/08/2011 18:07:21 by yor_on »
 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Does the universe spin?
« Reply #29 on: 13/08/2011 18:23:46 »
Shows my ignorance, Yor_on; I didn't even know Godel had worked on this stuff. I only know of his famous incompleteness theorem. Bright bloke, Godel!

It's hard to "see" why a rotating universe allows time travel; but then most solutions in GR are also fairly non-intuitive, to say the least.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Does the universe spin?
« Reply #30 on: 13/08/2011 19:50:39 »
Heh, I agree Graham, and it gives me no little headache accepting the idea. I suppose it has to do with time being a function of the room, but where to go from there to find time reversing I can't say. To me a time reversal must be a situation where the arrow still have to point into the 'future' to make it work. Maybe it becomes a question of where the 'future' points? I don't know, but I'm pretty sure that the only way 'time travel' can be consciously experienced should be when your own local arrow act 'as usual'. And that one seems always to be true when we look at 'time dilations', so to make it 'work' in reverse that arrow, and all chemical, thermodynamical,  processes should have to behave 'as usual', for me to observe it.

I mean, assume that the universe just 'backed' ah, ten minutes, From where would you have a clue? all processes in this universe should then have 'backed'. The other way is to assume that you can do so locally, relative a universe. But how would it work? Talking about 'energy expended' for example. Ten minutes of a whole universe 'expending energy' nullified? It boggles my mind that one.

==

In fact, the only way I can make sense of it is from assuming a 'static' point of view, from where we have no arrow at all. If it was that way we could assume that it takes no 'energy' at all, possibly, to reverse 'time'. That as time then can't exist. But then all our ideas about energy must be wrong, and probably most of the rest too. Because they are all a function of time as I see it.
« Last Edit: 13/08/2011 19:59:36 by yor_on »
 

Offline CPT ArkAngel

  • Hero Member
  • *****
  • Posts: 584
  • Thanked: 3 times
    • View Profile
Does the universe spin?
« Reply #31 on: 13/08/2011 19:53:58 »
If i remember well, in Godel's model, all the universe including space must be rotating to allow time reversal, which has already been disproved. In the actual observations, it is matter rotating in space...
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Does the universe spin?
« Reply #32 on: 13/08/2011 20:05:40 »
Well, then the question becomes, assume that space is 'rotating'. From the aspect of light 'propagating' space shows no resistance. From the aspect of what modulates that space into its ever changing shape, gravity, I don't think space as such will influence that. From the view point of vacuum fluctuations? I don't know. A rotating space presumes a 'motion', and is to me a mostly 'classical' definition, valid inside Planck time as I see it. From a QM perspective both time and motion seems suspect :)

It's a very weird thought, also it would once and for all stamp 'space' as a classical medium in its own right if it was correct.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Does the universe spin?
« Reply #33 on: 13/08/2011 20:21:31 »
Then again, I think of the 'space' as a function of just gravity, assuming that they are hand in glove. Without 'gravity' no measurable space, possibly. We have those other forces too of course, but somehow both space, gravity, time and matter seems to be one thing as if they come out of something united, then broken into the fragments that defines 'SpaceTime' to us. Maybe you can 'back' it, but it seems very weird to me to assume that you can back time. Assuming that you believe in lights 'propagation' you now have a scenario in where you if defined as a 'frame of reference' have your arrow still pointing into the future locally, observing all other processes reverse. It's the Wheeler-Feynman Absorber Theory all over, thinking of light there.
==

But, from a 'static perspective' it's possible though. But then you need to stop considering light as 'propagating'. In fact, in a static universe the only thing creating what we see would be the process we call 'times arrow'. It is needed for all interactions, without a arrow you can not have a interaction. And to use a chemical or thermodynamical process to define 'time' is a self-contradiction in that all such processes presumes a 'linear' causality chain, to show us this unique constant repeatability. And that 'chain' is what I call the 'arrow of time'. I think of time as a function of the room, and if that is true you can see it two ways. Either as 'time' is the room, or as if 'time' gets defined by the room. But it is weird, and I don't really know :)
« Last Edit: 13/08/2011 20:49:58 by yor_on »
 

Offline CPT ArkAngel

  • Hero Member
  • *****
  • Posts: 584
  • Thanked: 3 times
    • View Profile
Does the universe spin?
« Reply #34 on: 13/08/2011 20:48:59 »
There is no official unification theory yet and Einstein himself said that Relativity is incomplete. And you are right about propagating, it would be expansion of energy rather than propagation, by definition...  ;)

Without a unification, it is speculation...
 

The Naked Scientists Forum

Does the universe spin?
« Reply #34 on: 13/08/2011 20:48:59 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums