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Faster-than-light?

Posted by: spock0149 - Tue Dec 18, 2007 10:46 pm
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Faster-than-light? 
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Post Faster-than-light?   Posted on: Tue Dec 18, 2007 10:46 pm
Well I've been lurking around this forum for some time now and really enjoy reading some of the posts.

I came across an exciting paper by Obousy recently regarding the possibility of stretching space.

http://lanl.arxiv.org/abs/0712.1649

They call it a warp drive, no doubt from science fiction. The maths is pretty hairy but the idea is interesting none-the-less. It i s based on the principle of manipulating extra dimenions from string theory. Apparantly squeezing a compact dimension inflates another. They use this as their principle.

The authors don't seem to be saying that they think we can build this now...just that it is theoretically possibe.

"We have proposed that a sufficiently advanced civilization
could utilize this relation to generate a localized
expansion/contraction of spacetime creating a ‘warp bubble’
in which to travel at arbitrarily high velocities. One
vital aspect of future research would be how to locally
manipulate an extra dimension. String theory suggests
that dimensions are globally held compact by strings
wrapping around them [6], [9]. If this is indeed the case,
then it may be possible to even locally increase or decrease
the string tension, or even locally counter the effects
of some string winding modes. This would achieve
the desired effect of changing the size of the extra dimensions
which would lead to propulsion under this model."


I think that what excites me the most is that people are actually thinking about this. It seems to me quite possible that papers like this might in fact be laying the foundations for future interstellar missions perhaps next century!?

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Post    Posted on: Wed Dec 19, 2007 3:31 am
The only catch is that nobody yet knows if string theory is actually right yet.
(sigh)
But it is encouraging that people are thinking about it.

"One day we're going to go wham! straight through all the barriers."
In not sure that's an accurate quote but it's something like that from Fred Hoyles "A for Andromeda."

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Post    Posted on: Wed Dec 19, 2007 5:15 am
There are quite a lot of ("serious") FTL theories out there, I have a few books where they are mentioned in more or less detailed side notes. I'll have a look at the book titles later on.

What I see as more "important" is to use the today available physics. We are still crawling around the planets while technology already exists to boost speeds a lot.

I always have to think about something my former astronomy teacher once said: "We will never be able to go to a star, not even the closest one, Alpha Centauri."

Even with today's technology (and physics) 10% light-speed is definitely achievable, so nearby stars are under 100 (real-time) years away, something absolutely doable in my eyes.

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Post    Posted on: Wed Dec 19, 2007 9:13 am
The most remarkable property of such concepts that in particular means the fundamental difference to other concpets in my eyes is that they really don't need speeds above the speed of light but enable interstellar travels at speeds far below that of light - because they simply make the interstellar distances much shorter.

Of course the travels require much less time than at speeds below c - but this doesn't mean that the movement occurs at speeds above c. The distance temporarily is reduced instead.

But the question is open what might happen to the vehicles themselves and their paasengers. Might they be turned smaller also? Then the problem to be solved would be unchanged.

What about that?



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Post    Posted on: Sat Dec 22, 2007 8:08 am
The reality is because of time dilation you do not need to go faster than light. A major enough percentage of light speed will get the passage of time slow enough for people to arrive alive.

Warp speed is only needed for the people left behind to be alive...


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Post    Posted on: Sat Dec 22, 2007 12:12 pm
And you would need a "FTL" drive / theory to manage the energy needed as in the usual Einsteinian universe the energy needed goes infinite to reach c.

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Post    Posted on: Tue Jan 29, 2008 12:32 am
I have no doubt that 'warp drive' FTL is possible if technically challenging, after all according to inflation theory the whole UNIVERSE traveled faster than light during Big Bang. However I do not think that induvidual FTL starships aka "Star Treck" are possible. The reason for this is the little known fact that gravitons travel at the speed of light and therefore any spacial distortions would also propogate at the speed of light. This means that warp drive would be unable to exceed the speed of light. However if one was to build a "railway" made of warp generators, it be possible to set up a space distortion wave that travels faster than light, and any object surfing this wave would also travel faster than light. The bad new is that such a "railway" would be exceedingly expencive.

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Post    Posted on: Fri Nov 28, 2008 5:45 pm
I already mentioned it in quite another thread because I didn't find this one but I that time posed it under a different aspect.

According to the article "Spaceship Could Fly Faster Than Light" ( www.space.com/businesstechnology/080813 ... speed.html ) the key might be to apply dark energy.

The manipulation of the extra dimension mentioned by the initial post and the quote there might be decreased in front of the vehicle to decrease the rate of expansion of the universe.

But the crucial requirement is to be able to turn the dark energy in front to be negative - in this case the space in front would locally contract.

Problem - to move a vehicle of 1000 cubemeters volume this way the mass of Jupiter must be turned into energy...



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Post    Posted on: Fri Nov 28, 2008 8:29 pm
For a great overview of the state of the art:

The SpaceShow - Greg Meholic, June 2008

Advanced Interstellar Travel PDF

Nasa did a study of 20 completely different methods of plausible FTL with leads times of ~50 years or so. Funding was cut but a number of papers were published.

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Post    Posted on: Fri Nov 28, 2008 8:46 pm
Ekkehard Augustin wrote:
I already mentioned it in quite another thread because I didn't find this one but I that time posed it under a different aspect.

According to the article "Spaceship Could Fly Faster Than Light" ( www.space.com/businesstechnology/080813 ... speed.html ) the key might be to apply dark energy.

There is the same "problem" with this approach, than there is with the one
from the original post: we do not know enough yet!

It is not yet clear, if "dark matter" and especially "dark energy" even exist at all. There are some quite plausible theories, that can explain the increasing rate of expansion of the universe without the need for dark energy (see "Spektrum der Wissenschaft" Issue 11/08 ).

Personally I believe it is a waste of time and resources to tinker around with ideas about what might be possible IF theory "x" proves to be right after all. If all this brainpower would be used to actually find out which theory is the "right" one, then people could start to find out all the consequences next.

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