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Author Topic: General Relativity Question - Expanding Universe  (Read 1869 times)

Johnnyb

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General Relativity Question - Expanding Universe
« on: 05/02/2010 09:52:22 »
Something struck me about Arthur Eddington's 1919 observation helping to confirm Einstein's theory of general relativity, with regard to gravitational lensing and the whole big bang theory. This is considered ambiguous now, but lets assume that it worked as planned.

What interests and confuses me is, what happens to something inside an area of relative space/time?

Say for example, you have (in space obviously) a sphere of empty space with a diameter of one mile. Then in the centre of the sphere you place a man with a mile long tape measure.

Now, outside the sphere, we have another man many thousands of miles away (for safety's sake!) with an extremely powerful telescope and the ability to observe and measure the size of the sphere the other gentleman is in, relative to his own space/time.

Now, somehow, we apply a gravitational force on the sphere, spherically. That is to say, an equal gravitational force pushing at the sphere's space/time from all 360 x 360 degree angles at the same time. This could either be done with some kind of mass, like the Sun, or by speeding the sphere up to approaching the speed of light (although I prefer the Sun / Mass approach as I'm not sure that the same with regard to the physics!).

Imagine then, that this squeezing of the space/time sphere went on forever.

To the man in the sphere (apart from obviously being dead - which I assume most things were after the big bang! - nothing that a couple of billion years of evolution couldn't resolve!) - how would his perspective be any different to OUR view of the Universe?

To the man inside the sphere, surely it would appear as though his bubble of space/time was expanding infinitely, when in fact what was happening was that he and everything in his sphere was shrinking at the speed of light. Yet to the man outside of the sphere (at safe distance from any gravitational interference) it would appear that the sphere appeared to be the same size and the man just got smaller and smaller until he disappeared completely?

Wouldn't this account for our sense of time and maybe why time slows down as we approach the speed of light (not to mention get smaller)? After all, moving at any speed, in any 360 x 360 degree direction inside the sphere would be moving against the collapse of the spheres space/time itself balancing oneself against the singularity's forces?

I was thinking that with a so called "Gravistar" or super massive black hole at the centre of most galaxies, maybe what we thought was a big bang in our universe may just be the centre of what one of these black holes looks like (a big shrink of space time). After all if light itself is turned back in on itself in one of these things, what's to say that space/time itself isn't turned back in on itself, creating another "Universe" where everything inside that universe has the identical physical and chemical laws and properties of our own?

There are probably many scientific flaws to this and it's just a throw away "what if question", but I'd be very interested to hear people's thoughts and comments on the subject!

Another question I have on a similar principle to this is, if you have a nuclear generator zooming around the earth at the speed of light - and a cable sending power from the generator to the earth (impossible obviously - but lets suspend belief for a moment - again!). Given that there is a time differential between something moving at the speed of light and the stationary Earth, would the nuclear generator generate the same, less or more power as it got closer to the speed of light?

graham.d

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General Relativity Question - Expanding Universe
« Reply #1 on: 05/02/2010 12:43:00 »
I read through this a few times but have lots of difficulties. One problem with your questions are that some of the assumptions are already outside of possibility (not just engineering , but physics) so thinking of the implications of subsequent events may be not at all realistic.

One issue is that gravity can't push (I don't think) so I can't imagine how you would shrink the man's sphere by external means. Perhaps you could give him a black hole to put in his pocket :-) Trying to view such a scenario from distance would then be similar to viewing a non-rotating black hole for which there are mathematical solutions. The view from inside is rather problematic though, and somewhat speculative I believe.

If you are trying to think through the effects of gravitational time dilation it may be better to start with a more plausible and simpler scenario. Is what you are getting at something like trying to see if the expanding universe is an illusion (this may not be the right word) because our local surroundings are shrinking?

The nuclear generator thing is less problematic. I think you can ignore GR to get an idea based on Special Relativity. The generator is moving with respect to the people on the ground so its clocks will run slow. This means that the nuclear reactions will be slow and the energy output thus reduced. As it gets close to lightspeed the energy output will diminish towards zero. This effect is observable anow on GPS satellites.

Johnnyb

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General Relativity Question - Expanding Universe
« Reply #2 on: 05/02/2010 20:01:29 »
Cheers for the reply Graham. Interesting about the nuclear reactor answer, many thanks. I "naturally" thought that the power output would increase exponentially as the reactor reached the speed of light and that the fuel rods would probably burn out giving the whole reactors lifespans worth of energy within a few seconds of near light speed! Or that we would get almost limitless amounts of energy from the reactor as it's time slowed down almost to a stop, but it's power output/energy remained constant! How wrong I was! Would this also be the case if the energy being sent down the "cable" was in the form of pure thermal radiation, say light? I'm guessing it would.

There goes my efficient nuclear fusion reactor technology! (Damn, I should have checked that out before I built it! - no point launching it now!).

Q2:

Yes a "pushing" as oppose to "pulling" gravity is "right out", lol. What I was thinking about was essentially the frame dragging / lensing effect of gravity and its consequences to matter. Something like what might be happening within a black hole (which fascinate me).

The fact that space and time are linked and are "stretchy / elastic" and the effect that would have on elements which pass through it or are stationary "within" it. If we see the light from stars "bent" around to the edge of the Sun during a solar eclipse, what process is that "light" going through and would the light remain fairly "unbroken" and intact.

It seems to me that light is bent back in on itself within a black hole. It seems logical to say then that "light" which travels in a straight line is not bending, but the actual space time that light is travelling through itself. I was proposing / examining therefore that if we have a bubble or sphere of space time being turned back in upon itself and assuming for a second that this process reached some kind of "stability" how would that "view" of inside a constantly shrinking bubble of space/time filled with hot gases and such differ to the view of our "own" Universe.

If our Universe was in fact a massive black hole (like the ones observed at the centre of every Galaxy) and the mass of our own Universe balanced with the external mass of say a fictional Galaxy encircling our Universe (bare with me!) was causing our bubble of space/time or "singularity" or Universe, Q: what laws in THIS galaxy could we use to prove that this scenario was not the case? Because when I think of the similarities of a black hole and the big bang and then think of the repetitive "nature" of what we observe in nature / plants, fractals etc. etc. and the Universe itself - well - the properties of the two seem almost identical to my untrained brain! Someone told me for example that red shift tells us that galaxies are moving away from us. But how would that appear any different if everything in this constantly shrinking sphere of space/time (our Universe) was shrinking in exact proportion with the space/time and everything in it.

Space/time shrinking, therefore everything in it constantly shrinking proportionally to that sphere of space/time. You, me, the Earth, the Moon, the Galaxies etc. all shrinking getting smaller at the same time within this bubble. Surely this would appear to US as though the Universe was expanding in exactly the same way as we currently observe it to be?
« Last Edit: 06/02/2010 08:31:06 by Johnnyb »

Soul Surfer

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General Relativity Question - Expanding Universe
« Reply #3 on: 05/02/2010 22:38:27 »
This topic is getting quite popular and you can see other similar ideas in the new theories area via

http://www.thenakedscientists.com/forum/index.php?topic=27463.new#new

Johnnyb

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General Relativity Question - Expanding Universe
« Reply #4 on: 06/02/2010 00:00:52 »
Thanks Soul Surfer, I'm going to read up on that. I'm glad that people may be seeing this as a possibility for a Unified Theory. Another thought struck me the other day. If we downloaded our brain to two computers, and just as both computers were "switched on", our original brain was "switched off/killed", which computer if any, would we consider to be our conciousness?

If I answered none, I am dead, then logically I must never have existed in the first place; as both computers are an identical duplicate of my brain and if my conciousness doesn't exist in either computer it stands that it must never have existed!

Then it struck me, it's not the brain which is actually alive. It's the electrical energy within the brain which is living! The energy which is in a constant state of change. Pure energy, unable to be copied, unique and individual! The brain cells are just there for the electricity to call on for stored memory and bodily movement.

I'm not a great believer in God. Not as far as atheist but I think I'm starting to believe in a "one" universal conciousness scenario. With the absence of meaning to space/time for such a being (all matter being connected etc.), it could be quite possible that we are all one being, dreaming of currently being "whoever or whatever" we are, all at the same time! That would be so cool. If you murder someone, then eventually you will experience being murdered by yourself. Any crime you commit is eventually committed by yourself against yourself! You are the guy buying a Chicken Kebab and what's in the Kebab at the same time! Eww!!!! That would certainly seem fair judgement indeed! Ultimate Karma! Seems to upset people when I present them with this possibility, but I think if you were never aware of being anything else but a bird or a slug, then being a bird or a slug would probably seem the best and most natural thing in the world!

Anyway, that's strayed from well away from the thread, but its a thought I think I'll leave you all with.
Thanks for your replies, I'll check back to read any further comments. Much appreciated. Very nice forum / domain. Cheers.
« Last Edit: 06/02/2010 08:39:19 by Johnnyb »

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General Relativity Question - Expanding Universe
« Reply #4 on: 06/02/2010 00:00:52 »