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FTL experiment

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Ash Small

Mon Sept 24 2012, 04:27PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
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But won't that mean that you are effectively observing the same event from two different frames of reference simultaneously?

Patrick

Mon Sept 24 2012, 05:23PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
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just out of curiosity, is garvity bound to the speed of light?

For Example, if a large gravity body suddenly changes its distrubution, if we measure gravity 5 light years out, wont it take 5 ly for the change to be revealed, at our distant position? ...

On a related note: neptune has a moon in retro grade rotational orbit, while all other known large moons are in normal orbital rotation, and ive been told by pHd's that retro grade orbits are unstable? Is this becuase gravity is a little laggy, inrelation to the larger planets gravity?

Uspring

Mon Sept 24 2012, 06:24PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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But won't that mean that you are effectively observing the same event from two different frames of reference simultaneously?

You would need two observers. One would be at rest in his frame and see the events as simultaneous. The other one would be moving with respect to the first one and observe the events as not being simultaneous.

just out of curiosity, is garvity bound to the speed of light?

That's what general relativity says. AFAIK it has never been directly verified. You need to wiggle huge masses to measure their gravitational effect and do it very fast in order to measure something as fast as light speed.

Patrick

Mon Sept 24 2012, 06:55PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Uspring wrote ...

You would need two observers. One would be at rest in his frame and see the events as simultaneous. The other one would be moving with respect to the first one and observe the events as not being simultaneous.

just out of curiosity, is garvity bound to the speed of light?

Hmmm i must think about all this then...

Ash Small

Mon Sept 24 2012, 07:17PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Uspring wrote ...

But won't that mean that you are effectively observing the same event from two different frames of reference simultaneously?

I've obviously not explained what I meant very well, sorry.

If you leave one place, and arrive at another simultaneously, or even before you leave, you are 'observing' the journey from two different frames of reference simultaneously.

One observer viewing one event from two different frames of reference at the same time. Pauli (PEP) implies that this is not possible.

BigBad

Mon Sept 24 2012, 09:55PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Uspring wrote ...

The other problem with this kind of thing is that you end up with a time machine.

Only if the transluminal drive has a single reference frame that it works with respect to, can you avoid time travel-type issues and I don't think this does.

With FTL travel you can arrive before you start if you judge this from an appropriate frame of reference. I don't believe that this alone establishes time travel or a causality violation. To create a paradox or have a time machine going backwards in time you must travel back to the origin and be there before you started off. Is that the reason why you mentioned that the FTL can only avoid time travel issues if it works only in a single frame of reference?

If you have FTL that goes relative to the current frame of reference, rather than an absolute frame the trick is to FTL somewhere, and then accelerate up to a high speed, and then FTL back.

If you do it right, you end up returning before you left.

Uspring

Tue Sept 25 2012, 10:00AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Ash Small wrote:

I've obviously not explained what I meant very well, sorry.

If you leave one place, and arrive at another simultaneously, or even before you leave, you are 'observing' the journey from two different frames of reference simultaneously.

I had the feeling, that I missed your point

I didn't mean to suggest any observers sitting _in_ the FTL device. As looked at from the outside, it is possible to see the spaceship arrive at its destination before it started, provided you are sitting in an appropriate frame of reference. For this to work you don't need instantaneous travel, just travel faster than c.

@Bigbad: Thanks for the clarification. It took me a while to realise, that the FTL drive was the one who is to be accelerated before warping back, not the observer. Getting the FTL up to speed will then make it arrive before it left in the frame of the observer. Accelerating the observer would screw up clocks in a bad way.

Ash Small

Tue Sept 25 2012, 11:17AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Well, as I understand it, the faster you go, the slower time goes, so when you reach the speed of light, time stands still. If you then accelerate through the speed of light, time starts going backwards, which results in you having 'two frames of reference' for any given time. (being in two places at one time)

I understood that 'tachyons', if they exist, 'always' travel faster than light, thus they 'always' travel backwards in time, thus avoiding the 'accelerating or decelerating' through the 'speed of light barrier' paradox.

BigBad

Tue Oct 02 2012, 11:50PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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I found some more about it, yeah, this stuff doesn't work right now. Even if they got it to work, the drive throws off enormous amounts of Hawking radiation forwards when it finally stops; so if you stopped in front of a planet, the planet would get vapourised!

I think the maths says you have to convert a good few tonnes of matter into energy (somehow) to generate the field, and it requires 'negative energy matter' which apparently has never been discovered.

Apart from that, and a good few other completely show stopping problems, it ... might work!

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