Suppose the Light Speed was just 330 [m/sec];-)

General physics and astronomy discussions not directly related to Celestia
julesstoop
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Post #21by julesstoop » 27.06.2003, 01:31

Probably I'm continuously making the mistake of trying to describe this low-c universe from within our own. Thus concluding wrongly.

The idea of a low-c universe with a normal G would lead to nothing, the big-bang would re-collapse in a few milliseconds. So I assumed that somewhere (outside our physical definitions) c would have to be dependant of G. Of course it may not be, but there are certain absolute boundaries. If c is as low as proposed and G stays the same: there wouldn't be any universe.

You are right with your first remark, but please note that I'm trying to describe this low-c universe from the point of view of an outside (normal universe) observer. I allready fully admitted that from within this universe one probably wouldn't notice any difference. The slowdown of information contained within any photon however, would be equal to the red-shift of the photons once they have crossed the boundary between our fictive and our real universe.

I think the debate should probably be: "Within which G/c-ratio range could any universe exist, ceteris paribus?"
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Post #22by granthutchison no log-on » 27.06.2003, 10:32

julesstoop wrote:The idea of a low-c universe with a normal G would lead to nothing, the big-bang would re-collapse in a few milliseconds
Cosmic inflation might perhaps rescue it from that fate - it causes the very early Universe to expand many times faster than light. That would leave us with a large Universe that could not then collapse except over many, many billions of years because of the lightspeed constraint. (But if we were somehow to visit such a place, at an age equivalent to our own Universe, we would find that our view of it was quite constrained - light would still be crawling in from just the equivalent of our own galaxy, and everything beyond would be invisible.)
I haven't a clue whether the lightspeed constraint could potentially influence the nature of inflation, however - that's why in my first post I suggested that the Big Bang aspect of the scenario was very much Fridger's territory.

Grant

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Post #23by MKruer » 27.06.2003, 18:16

Actually they found out just recently that the speed of gravity if you can call it that is equal to the speed of light. To give you an example of what this would mean, if you could suddenly insert a massive object into the universe, then you would feel its effects at the same time you could see it. So this really would mean that if light speed was lowered, the universe should scale down as well. This is just how gravity affects the object. Now if the MASS of the universe would stay the same, things become very interesting. To place it into our physics think of it this way. First you would need to take the inverse the difference in c i.e. 300m/s take the inverse of that and multiply it onto our universe that would mean that out universe as a whole would be 100,000 times more massive. If the sizes (area) of the universe stayed the same, then that means on average our system would be 100,000 times denser. That would also mean that our sun would become a super massive black hole.

In the end, what julesstoop said is true. The universe in order to be stable would have to scale it self appropriately. i.e. the universe would work on a much smaller level or larger level.

The final catch. All of the above is based upon applying the same physical model for all levels of the universe. However, this is not the case. Thing is the larger world do not act the same as thing in the smaller world If the physic would not scale proportional to c then two things would happen. There would never be a sufficient energy to cause the universe, or there would be so much energy released and not enough velocity for matter the escape and the universe would have imploded the instant it was created.

The only real way for use to know how the universe would react at any give levels, would be to figure out quantum theory and apply it to a smaller universe.

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Post #24by t00fri » 27.06.2003, 18:35

Christophe wrote:...
And wouldn't the Sun be a black hole? And all the planets too?


It's really odd...

0) Despite my considerable background in these matters, I feel somehow like an amateur, since 'in my trade' we always work with units c = h-bar (Planck's constant/4Pi) = 1;-)

So mostly the crucial dependences on c are hidden....

1) Schwarzschild radius (Black hole limit):
===========================

Well, when a body's radius decreases below the so-called Schwarzschild radius:

R_S = 2 gamma M/c^2,

with gamma being the gravitational constant and M the body's mass, a singularity of space-time will occur and light cannot even escape anymore from that body...

You can easily see that 1/c^2 scaling, I guess!

Since we talk about a scaling factor realistic/slow light speed ~ 300 000 000/ 300 ~ 10^7 (!), we have to rescale the usual Black hole radius by a factor 10^14!!!

So large parts of our galaxy would be eating up everything;-)...

NB: one has to be careful not to use blindly formulae that were derived for a /non-relativistic/ environment.
In most cases of interest , our discussion is highly relativistic.

I have just decided to become crazy over this 'slow light speed' issue;-)

Bye Fridger

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Post #25by granthutchison » 27.06.2003, 19:58

MKruer wrote:Actually they found out just recently that the speed of gravity if you can call it that is equal to the speed of light.
If you're referring to Kopeikin and Fomalont's observations of the deflection of light by Jupiter, it seems like the dust hasn't settled on that one - a lot of physicists disagree with their interpretation of their results. (Though many of them would probably agree that gravity propagates at light-speed - they just don't think that K&F have demonstrated that.) But no matter - the velocity of propagation of gravity has no bearing on its strength. Whether the pull arrives early or late, it could still be the same pull. So I still don't see any particular reason why the Universe should alter its gravitational behaviour (other than, perhaps, the speed of propagation) just because the speed of light is different.

Grant

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Post #26by Guest » 05.07.2003, 03:16

Sorry for posting a little late on this topic but I couldn't resist. I'm new to this forum and I find this topic fasinating. I wrote a paper where I considered similar points.

Degrees of Freedom

Don't worry, I'm not a crank; at least I don't think I am.. ;)
I'm not trying to pass this off as some kind of ground-breaking work. It's mostly speculation but the math is consistant with special relativity.
I extrapolated from the equation for the spacetime interval (I?=X?+Y?+Z?-C?T?) that we move through time at the speed of C. To figure out the spacetime distance between two events, the time component has to be converted to 'equivalent' units in the equation. This is done by multipying the time in seconds by C?. This gives you the equivalent amount of meters in one second in spacetime. We move through time at the rate of 1 second/ second or 299,792,458 m/s.

I'm not sure if this has any direct bearing on why the speed of light is measured to be this value; I find that it is a interesting coincidence. This is what I speculate about in the document. Just condidering the equation E=MC? raises a lot of interesting questions.

I welcome any comments, criticisms that anyone wants to share.

I think that changes in the speed of light would have many ramifications. I believe that the measured speed of light is a critical factor in the gravitational constant.


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