I'd like to pick your brains. Are there any *plausible* theories re: FTL propulsion?

[Occulus]

Any? At all?

I'm asking this question because it's something we should always have in the backs of our minds. Undoubtedly, such would require vast amounts of energy and probably (as of today's technology) impossibly powerful accelerators/magnets/whatever. Making this happen would undoubtedly usher in a new era of exploration, and mark the pinnacle of mankind's achievements thus far.

Are there any clues at all? Any avenues of theoretical exploration that do not sink to the level of "crackpot"? Are there any plausible theories out there?

Bueller?

(If you deign to respond, please link to anything of interest. Anything testable is a definite plus.)

[truedelphi]

1. Not to be snarky - but what is FTL?

Acronyms never stay in my head very long.

[virgogal]

2. Ditto !

[Occulus]

5. Faster Than Light

In this context, though, I mean 'faster' to be anything that can get an object from point A to point B at any arbitrarily faster speed than light travels through normal space. The method doesn't need to (and, in future reality, probably will not) involve 'normal' spacetime as we experience it.

[virgogal]

7. Thanks !

[arcane1]

4. FTL = Faster Than Light

Yes, I'm a geek, and no, I am not aware of anything new in this realm, but I'm bookmarking this thread :)

[doc03]

17. Fruit of the loom n/t

[truedelphi]

22. It would be funny I fthe guys from Fruit of theLoom

Got us through the "Time Warp" before the other "more scientific" crowd did. (Fruit of the Loom does have a better handle on warp and weft, right?)

[Ratty]

3. Nope

Sorry, but no. Short answer. Sad but true.

http://en.wikipedia.org/wiki/Category:Faster-than-light_travel

[Occulus]

6. Is that just that it's not being researched, or that it's "impossible" so it's not BEING researched?

[Ratty]

12. In serious science and engineering it is considered impossible

But even physicists like to daydream. Einstein's relativity doesn't expressly forbid wormholes or warped spacetime but relativity is widely considered to be incomplete. A true theory of quantum gravity is expected to tidy things up in that regard and show expressly such things are impossible.

[Ildem09]

8. Faster Than Light (FTL)

outside of a matter anti-matter reaction on the order of several pounds I know of no way of generating the force you would need to create a warped bubble of space that would allow you to skirt the speed-limit.

As something accelerates towards C it increases in mass, thus requiring more power to propel it eventually needing an infinite amount of power as you approach 99% C.

There are a few ways around this. create a bubble outside space time, which would require enormous amounts of power punch a hole basically through reality and somehow keep the vessel tethered to our universe (This is how Star Trek does it)

You could warp regular space time, either by increasing mass or decreasing it, the Higgs Boson might come into play here, Imagine a rug on a floor laying flat (normal space) now imagine that rug scrunched up so the points are closer (This is how Futureama Does it)

You could bore a wormhole through local regions of space time, to another region in the universe, this would require two black holes one stationary and one rotating. (this has temproal issues weee time travel) ( think of the Movie Event Horizon, sans the horrible acting)

The only way i've heard of possibly being able to violate C is by using Negative Energy or figure out how to create an anti-higgs boson particle, or figure out a way to Harness Tachyons. Insanely expensive and impracticable

I'd say were another 50 years before viable LEO Commercial flights. and at least another century from anything traveling at anything remotely a percentage of C.

[Ildem09]

9. until recently

NASA has an exotic propulsion lab out of JPL. i think it got the axe during the budget crunch though

[Ozymanithrax]

10. There are several theories...

Warp Drive Engine Would Travel Faster Than Light

[zipplewrath]

11. Time travel

In essence, anything that would qualify is going to probably involve some sort of "time travel". Worm holes are one way, and about the only way you'll find right now. But any other concept that is created is going to look alot like "traveling back in time" even if it is really just arriving early than you should.

[GreenStormCloud]

13. Very doubtful.

If inter-stellar space travel were possible, it is unrealistic to think that Earth would be the first in our galaxy to discover it. Somebody else would have found it first. Once having found it they would then begin to colonize planets that didn't yet have intelligent life. Earth would then have been colonized tens, maybe hundreds, of millions of years ago. That we are here strongly suggests that star to star travel doesn't exist.

[TheWraith]

18. Nonsense.

To say that someone would have found us by now is to underestimate the scope of the universe. Earth is one planet out of roughtly 300 billion stars in just this one galaxy. That's enough room that you could have ten thousand spacefaring races, each of which controlled ten thousand star systems, and you still would only have used up one third of one percent of the space in this galaxy alone. We're sitting on the spiral arm, in the outer reaches of our galaxy, where stars are sparse and far apart. To say that there must be no interstellar travel because we haven't seen it is like standing in the Canadian Rockies, and because you can't see any people, deciding that there's no travel-capable civilization on this planet, otherwise someone would be living here.

[GreenStormCloud]

23. Sense

Assume that a space faring civilization is capable of taking a planet from freshly discovered to fully industrialized in 1,000 years. That would be a gross overestimate of the time needed, but it makes a convenient one. So from one home planet they would have two industrial planets in one millennium. Then that colony would establish a new colony as would the home planet also establish another one. Repeat each millennium. The number of industrialized planets doubles each millenium.

For a starting point, assume that the other planet has got there first by a mere one million years. In astronomical terms, that is nearly simultaneous. So the other planet has only 1,000 doublings. They would have colonized 2^1,000 planets. Yes, two raised to the 1,000th power.

By the 64th doubling, in a mere 64,000 years they will have colonized 9.2 quintillion (9,223,372,036,xxx,xxx,xxx)star systems.

When one considers the 300 billion stars in our galaxy, it is reasonable to conclude that if star travel were possible, somebody else would have already discovered it. And in somewhat less 40,000 years, they would be here.

If we allow a space faring civilization to colonize several planets at the same time, and to bring them up to independent civilization status in only a few centuries, then they get here rather quickly, as they fill the entire galaxy rather quickly.

[qazplm]

28. just a whole lot of assumptions there

1. a space faring civilization is a stable civilization. Disease, internal conflict, accidents, even conflicts with other space-faring civilizations could result in your consistent pattern of doubling not taking hold.

2. Every colony will produce another colony/the home-world will continually send out new colonists. All sorts of reasons why that wouldn't be true. Religious or other dogmatic reasons might cause some colonies not to ever spawn another colony. It might also cause the original home-world to cease sending out more colonies. Heck a home-world could send out it's first colony, and then be taken out by a Gamma Ray Burst, or Super Volcano, or Asteroid/Comet impact, or huge CME, etc.

3. We aren't the first/most advanced intelligent life-form in the galaxy, or one of the first. No evidence one way or the other, we have no idea how long it takes. Certainly odds are it requires a second-generation star or later to get the heavier elements necessary, we think, for complex life to take hold and certainly for technology to reach the level of interplanetary flight.

4. When we were "discovered," we were habitable/appealing. You only have to go back to early human times to see a glacial, cold period where we almost went extinct because of the world climate. There have been plenty of times in our planet's history where it's not been appealing to live here. A civilization could have come by at the wrong time, said, eh, not worth it, and left.

5. That if they did colonize a planet, they would ignore the indigenous life. Let's assume you are right, and a civilization would have already come here, why does it then follow that they'd have colonized? Perhaps they saw intelligent, but non-advanced life, and somewhat like the Prime Directive, simply went somewhere else so as not to get involved. Perhaps that's too naive but I suspect that even we would at least have that conversation if we were to come across another less advanced civilization sometime in the future.

Just a ton of assumptions in your somewhat glibly confident statement. There are a lot of reasons why "they" may not currently be here, and none of them require that "they" not exist.

[Occulus]

31. GreenStormCloud has never played Spore.

Prime directive?

Planet buster.

:D

[Occulus]

25. You're presuming such technology exists concurrent with our civilization.

For all we know, it's been invented a dozen times in our galaxy alone, but the timespan between its multiple rediscoveries is so huge that species die out somehow even if they can expand using FTL travel, and there's never any sign that anyone's home.

We're delving into a science fiction aspect of the question, though, and that's something I'd like to avoid for the purposes of my OP. Whether or not it's ever been invented before isn't relevant, even taking into account the "but they would have been here before if it were possible" speculation.

I want to know if anyone's seriously thinking about doing it, period, now, for us. As I tried to make clear, I seriously doubt it's impossible.

What I'm looking for are plausible methods, or theories that might actually pan out. The Alcubierre bubble is one that's certainly intriguing, but might only be half to solution, or merely a good 'what-if' that gets us on the right track. I don't know. I do sincerely believe that FTL travel must be possible, somehow, and we only need to figure out how it might be done.

I'm looking for serious ways to maybe, somehow, do that.

[qazplm]

29. I'm assuming you are doing this for a book?

If not, if this is just a thought exercise, remember, you don't need to go FTL to in a shorter period of time than you might think colonize an entire galaxy.

You can very quickly, relatively speaking, colonize a galaxy just with sub-FTL. Now that requires all of those assumptions I waylaid in another post in this thread, and so IMO it's only theoretically quick, but I fully expect that as we accomplish sometime five hundred years from now travel at .5 C or greater, that we will come across life, probably will come across intelligent life and just may come across advanced life up to or even surpassing us.

[Occulus]

30. No, not for a book

Although the concept appears (as I know you know) in a great many science fiction novels. I personally liked Stephen Baxter's proposition in one of his "Manifold" novels: that every so often there's a gamma ray burster that drives all life in the galaxy back to the level of pond scum, and that's why FTL travel hasn't ever been invented... no species can survive long enough to get that far.

He had another thought, too: as a civilization expands through space, the pressure from the core of the civilization for resources and real estate becomes so great that the wavefront of colonization must at some point approach c, making further meaningful colonization impossible, which then leads to extinction.

What I was suggesting was that even if such colonization/FTL travel had taken place throughout our galaxy, it doesn't necessarily exist concurrently with our own species. It could have happened, and been over with, a million+ years ago. Of course, we're not talking about other pressures on a species, such as disease, war, 'bad' genetic engineering, cosmic disasters, etc. All those factors would play a role in species survival as well.

I guess I just don't buy the "if they were there, we would see them" argument. There are just too many reasons for that to not necessarily be true.

[leveymg]

14. There's a relativistic effect that might appear to "slow down" time for those traveling at close to

the speed of light.

The formula for computing the "time saved" for travelers on a starship accelerating and then decelerating at 1G has been calculated to slow down apparent time for a voyage traveling 27 light years from 100 years (earth elapsed time) to only 6.58 perceived years (proper time). This calculation is based upon a technologically feasible fusion pulse reactor drive.

We're still a long way from a pulse fusion reactor for space travel, although it may actually be a better application than electrical generation here on earth, as one could theoretically just hang a reactor way, way back behind lots of shielding with a rear-directed outlet (magnetic nozzle), to get a pulse reaction drive. Starships with such a propulsion system have been termed "torchships."

Theoretically, they are capable of sustained 1 g acceleration for many, many years. Long enough to get to a near-light speed velocity with a practical possibility of human flight to nearby star systems and return within one lifetime. Because time "slows down" according to the relativistic constant the closer one gets to the speed of light, one could travel enormous distances in a perceived period of only a few years, as illustrated by the following equation. 6.58 years (crew perceived time) to get to Vega (27 light years away):

From The Relativistic Rocket in the Usenet Physics FAQ
In the following equations, note that a*T/c = (Ve / c) * ln(R)
Time elapsed (in Terra's frame of reference)

t = (c/a) * Sinh (given acceleration and proper time)

t = (c/a) * Sinh<(Ve / c) * ln(R)> (to expend all propellant, given exhaust velocity and mass ratio)

t = sqrt<(d/c)2 + (2*d/a)> (given acceleration and distance)
Distanced traveled (in Terra's frame of reference)

d = (c2/a) * (Cosh - 1) (given acceleration and proper time)

d = (c2/a) * (Cosh<(Ve / c) * ln(R)> - 1) (when all propellant is expended, given exhaust velocity and mass ratio)

d = (c2/a) (Sqrt<1 + (a*t/c)2> - 1) (given acceleration and Terra time)
Final Velocity (in Terra's frame of reference)

v = c * Tanh (given acceleration and proper time)

Δv = c * Tanh<(Ve / c) * ln(R)> (given exhaust velocity and mass ratio)

v = (a*t) / Sqrt<1 + (a*t/c)2> (given acceleration and Terra time)
Time elapsed (in starship's frame of reference, "Proper time")

T = (c/a) * ArcSinh (given acceleration and Terra time)

T = (c/a) * ArcCosh (given acceleration and distance)
Gamma factor

γ = Cosh (given acceleration and proper time)

γ = Cosh<(Ve / c) * ln(R)> (given exhaust velocity and mass ratio)

γ = Sqrt<1 + (a*t/c)2> (given acceleration and Terra time)

γ = a*d/(c2) + 1 (given acceleration and distance)
where
a = acceleration (m/s2) remember that 1 g = 9.81 m/s2
T = Proper Time, the slowed down time experienced by the crew of the rocket (s)
t = time experienced non-accelerating frame of reference in which they started (e.g., Terra) (s)
d = distance covered as measured in Terra's frame of reference (m)
v = final speed as measured in Terra's frame of reference (m/s)
c = speed of light in a vacuum = 3e8 m/s
Δv = rocket's total deltaV (m/s)
Ve = propulsion system's exhaust velocity (m/s)
R = rocket's mass ratio (dimensionless number)
γ = gamma, the time dilation factor (dimensionless number)
Sqrt = square root of x
ln = natural logarithm of x
Sinh = hyperbolic Sine of x
Cosh = hyperbolic Cosine of x
Tanh = hyperbolic Tangent of x
The hyperbolic trigonometric functions should be present on a scientific calculator and available as functions in a spreadsheet.

In many cases it will be more convenient to have T and t in years, distance in light-years, c = 1 lyr/yr, and 1 g = 1.03 lyr/yr2.

Here are some typical results with a starship accelerating at one gravity.
T Proper time elapsed t Terra time elapsed d Distance v Final velocity γ Gamma
1 year 1.19 years 0.56 lyrs 0.77c 1.58
2 3.75 2.90 0.97 3.99
5 83.7 82.7 0.99993 86.2
8 1,840 1,839 0.9999998 1,895
12 113,243 113,242 0.99999999996 116,641

Of course, as a general rule starships want to slow down and stop at their destinations, not zip past them at 0.9999 of the speed of light. You need a standard torchship brachistochrone flight plan: accelerate to halfway, skew flip, then decelerate to the destination (which makes sense, since such starships will have to be torchships). To use the above equations, instead of using the full distance for d, divide the distance in half and use that instead. Run that through the equations, then take the resulting T or t and double it.

Example: The good scout starship Peek-A-Boo is doing a 1 g brachistochrone for Vega, which is 27 light-years away. Half of that is 13.5 light-years. How long will the journey be from the crew's standpoint (the proper time) ?
T = (c/a) * ArcCosh
T = (1/1.03) * ArcCosh<1.03 * 13.5 / (12) + 1>
T = 0.971 * ArcCosh<13.9 / 1 + 1>
T = 0.971 * ArcCosh<13.9 + 1>
T = 0.971 * ArcCosh<14.9>
T = 0.971 * 3.39
T = 3.29 years
That's the crew time to the skew flip. The total time is twice this
T = 3.29 * 2
T = 6.58 years

[hunter]

15. Not that I've seen.

I don't believe "STL" or time travel is possible either.

In my universe EVERYTHING is zipping along at the speed of light. What we perceive as time and distance and mass and all that stuff is simply an interference pattern on the light everything is made of.

[TheWraith]

16. Sort of, yes, under loose definitions of FTL.

None of these technically allow you to exceed the speed of light within normal relativistic space/time. However, they're all potential methods for getting around faster than would otherwise be possible.

The Alcubierre drive would bend space in order to allow a ship to move at what would be, to an outside observer, FTL speeds. Within the gravity bubble, of course, it's still sublight, and therefore relativity isn't violated.

http://en.wikipedia.org/wiki/Alcubierre_drive

There's some ideas batted around that I don't know the details of, but the basic idea would be to use quantum effects to increase the speed of light within a given area, effectively raising the speed limit for sub-light craft. Again, you wouldn't be going really faster than light, but you'd be going faster than light normally goes.

Another possibility would be some new ideas that are going around which combine quantum tunneling and quantum entanglement teleportation, under which an object would simply spontaneously stop existing in one place and start existing in another place. Technically it didn't move faster than light, because it didn't "move," but it still got there faster than it would have by traveling. Supposedly they've had good initial experiments teleporting information in the form of music or laser light emissions.

[qazplm]

20. that's a good point because

a. we don't know that C hasn't changed or can't change over time

b. we don't know that we can't find a way to temporarily change C locally

There are just too many ways a future advanced society could approach the problem that we can't even comprehend to say never.

[qazplm]

19. the answer is ask again later but probably not that we know of

in other words, using current or foreseeable technology, no you can't do it without gathering prohibitive amounts of energy/matter, or prohibitive amounts of exotic matter/energies (like negative energy).

Now does that mean a civilization 1 billion years more advanced than ours could not in fact marshal that much energy into one place or create the negative energy need to keep a wormhole open? I dont see how anyone can definitively or even speculatively say the answer is no.

My personal belief is that if there are ways which do not violate the laws of the universe, eventually, somewhere in the universe it will be done, even if the odds are really low. But we can get a good percentage away from our planet in the space of the life of a human if we can figure out how to get significantly close to the speed of light (and I see no reason why we couldn't in say 500 years ignoring global catastrophe and a reasonable rate of technological evolution).

So meeting ET or finding a new place to call home are both realistic options in the coming millennium.

[Duer 157099]

21. I thought quantum entanglement proves that FTL is possible

No?

[pokerfan]

24. It doesn't

Certain phenomena in quantum mechanics, such as quantum entanglement, appear to transmit information faster than light. According to the No-communication theorem these phenomena do not allow true communication; they only let two observers in different locations see the same event simultaneously, without any way of controlling what either sees. Wavefunction collapse can be viewed as an epiphenomenon of quantum decoherence, which in turn is nothing more than an effect of the underlying local time evolution of the wavefunction of a system and all of its environment. Since the underlying behaviour doesn't violate local causality or allow FTL it follows that neither does the additional effect of wavefunction collapse, whether real or apparent.

http://en.wikipedia.org/wiki/Faster-than-light#Quantum_mechanics

[TheWraith]

26. I strongly disagree with this interpretation.

1. The simple fact that an event is occurring is, in itself, information.

2. There are general relativity problems with the idea of simultaneity in two points potentially separated by a substantial distance at C.

[Ratty]

27. Problem with that

Is that the two observers can't agree an event has actually happened without a slower than light channel. It's really complicated and I sort of understood it when i read about it in The Tao of Physics (an OUTSTANDING book, BTW) but the details are now fuzzy. But basically when physicists do experiments with entangled particles they have to use two channels. One is the instantaneous entangled channel, and the other is a standard channel such as a laser or the internet. The entangled channel is indistinguishable from random noise by itself and it must be combined with the standard channel to get any non-random information out. Even something as simple as "an event has occurred" can't be gleaned from the entangled channel alone. This makes entanglement useful for things like quantum computers and 100% secure communication but useless for FTL. Like everything it has to do with Heisenberg (that BASTARD!). The universe is sneaky at protecting her secrets.

[mochajava666]

32. The book "Physics of the Impossible" by Michio Kaku

covers this subject looking at all of the current theories of faster than light travel, as well as sub-light speed propulsion systems. He also covers transporters like in Star Trek, force fields, invisibility cloaks, mind reading, and other stuff like that.