If this was discussed in an earlier thread, I apologize. Is it possible to exceed the speed of light? It seems to me that unless we devise some way to do so, space travel over any great distance is impractical. I’m thinking that maybe it’s possible to travel faster than light, it’s just that light is the fastest thing we currently know about. How do we know that some of these subatomic particles that are so small we can’t detect them with any instruments aren’t moving faster than the speed of light? Just theory?
Unfortunately it’s not merely difficult but, according to one of the cornerstones of modern physics, impossible for us to ever exceed the speed of light. As far as subatomic particles: if they have mass, they cannot exceed (or even reach) the speed of light. (Some physicists have hypothesized the existence of particles called “tachyons” which would have “negative” mass and could never go slower than the speed of light. However, as I understand it the only way tachyons could exist would be for them to be impossible, in principle, for us to ever detect. Otherwise, we could use them to transmit information FTL, which is impossible.)
Now, all of this is according to a theory, yes. But, this is one of the major theories of modern physics, not just a Wild-Ass Guess. The Special Theory of Relativity has been extensively tested by experiment and observation, and pretty much no one thinks it will ever simply be abandoned. It might be modified to account for some set of special (probably very bizarre) circumstances, like what happens inside black holes, or incorporated into some larger, more inclusive theory, but physicists are very, very unlikely to one day just throw up their hands and say “Well, and we guess Einstein was wrong…you can go as fast as you want!” (To paraphrase an old Harry Harrison story.)
Most even semi-plausible ways of achieving FTL travel or communications involve doing end runs around the STR (via “hyperspace” and so on); but even these aren’t really very plausible. (Note that according to relativity theory, FTL travel necessarily implies time travel too. If you start thinking about time travel paradoxes–the old “what if you went back in time and killed your grandfather?” chestnut–it’s easy to see why FTL would be classed as impossible.)
Several ways have been proposed for viable interstellar travel without FTL–generation ships (you don’t get there, but your great-grandchildren do); various sorts of suspended animation (cryonics, or even weirder things, like encoding yourself into some sort of computer bank and then rebuilding yourself at the other end); or nearly-as-fast-as-light travel, where you get to take advantage of some of the weirder effects of relativity to reduce your subjective travel time to a relatively short period. (The subjective time your trip will seem to last back home, however, will still be years or decades even for nearby stars, so interstellar astronauts had best not have any close ties to anyone back home.)
If you don’t mind a little Cherenkov radiation, a charged particle can travel faster than light in a medium with a high refractive index, n, where the velocity of light is c/n. Water, for example, has a refractive index of 1.3. Of course, that’s probably not what you meant.
Jeez, don’t you ever watch TV? Them Enterprise folk always are going a million times the speed of light, or something like that. 
True. But the OP and the first responder meant “faster than the speed of light in vacuum”. It’s formally incorrect but common to leave those last two words off when you think your intentions are clear without them.
I remember a recent news article (that was discussed here) that scientists have created a medium that light (or light-induced impulses) can travel faster than light in a vacuum.
[I remember a recent news article (that was discussed here) that scientists have created a medium that light (or light-induced impulses) can travel faster than light in a vacuum.
]
I think that’s called subatomic tunneling. Basically light is aimed at a high density material most photons get absorbed (or reflected at the surface) and a few photons get through. The speed they measured is 1.7c. I think is has to do with wormhole theory on the subatomic level.
No wormholes involved, Dave. Basically, what travels faster than light in those tunneling experiments is not light itself, nor any particular photon – only the PULSE of light goes faster than light. That is, with a differentially dispersing medium, we can make the packet velocity exceed the wave velocity (which is capped at c) over small distances. So even though it looks like the wave is leaving the medium before it’s even finished entering it, the departing wave is NOT the same light that entered, but rather a constructive interference effect, and cannot be used to carry information.
Hope that was clear =)
Well, the Special Theory of Relativity doesn’t actually explicitly say that FTL is impossible, per se. It does say two things: First, that it’s impossible to accelerate past c, because it would take an infinite amount of energy. Secondly, it says that even if there is some way of producing an FTL effect, via wormholes or tessering or hyperspace or whatever, then that same effect could be used for time travel, which is generally considered impossible, but not proven impossible. The more complicated General Theory of Relativity, which deals with gravity and the curvature of space-time, suggests a few ways in which effective FTL travel may be possible without actually accelerating past c, such as wormholes and warp bubbles, but all such methods require the use of matter with negative mass, and the jury’s still out on whether that’s possible.
As for other methods to reach the stars, we have the technology right now to launch a generation starship to any of several nearby stars, but it would cost a hell of a lot more money than anyone’s willing to spend.
Odd… I don’t think this topic has ever come up… [sarcasm]
When discussing the speed of light as the ultimate speed limit it’s important to add the phrase “in a vacuum”. Otherwise, the discussion takes on all sorts of ‘interesting’ tangents.
Short answer - no.
Longer answer, under certain
You’re assuming that the shortest distance between two points is a straight line. Consider a long strip of paper. If the linear distance between point A and point B is 10 inches, does that mean we have to move 10 inches to go from point A to point B? Answer - no, not if we fold the paper so that point A and point B are virtually the same. Some theories suggest that space may be folded and that we may be able to take advantage of these folds to jump non linearly to other points in space.
Ummm… I’m not sure there’s any simple way to explain this. You could read “The Meaning of Relativity” by the man himself (Albert Einstein). It’s a short paperback, less than 200 pages and will set you back only about $10. There are mathematical reasons why the speed of light is the maximum.
Here is a discussion of FTL travel:
http://math.ucr.edu/home/baez/physics/FTL.html
Including some basics on warp drives. All we really need is some dilithium or some other matter with negative energy density. If you know where we can get some, meet me in the delta quadrant.
Oops! My sentence got chopped. It was supposed to say:
Longer answer - under certain conditions and in certain environments, maybe, but it doesn’t help you solve your problem…
Thanks for clearing that wormhole issue up PaulT
But what subatomic tunneling was used to send information FTL at least for a short distance. A song was encoded into light and shot across at the 1.7c , the receiver was able to clearly ‘here’ song even though it had a lot of static. They explained about how probility theory stated that the chance that a single photon can get through is very low, but on a subatomic level if it can happen (even if the chance is very small) it will. They made it seem like the actual photon got through.
Ah, yes, the Mozart experiment, which employed dubious methodology in the first place, and has not been replicated since. The biggest problem with their method is that a piece of music has a lot of redundancy built into it, so that you can easily predict the signal a few milliseconds in advance to a high accuracy. Another big problem is that they already knew on the receiving end what the message would be. If they really wanted to demonstrate FTL information transmission, they should have used a random bitstream, and seen how the bitstream they got out compared to a copy of the one they sent in. In fact, other researchers have tried this, with completely null results.
Isn’t it strange how all the FTL claims are based on one unverified experiment? :rolleyes: