Faster than Light?

Question

Is saying we can never travel faster than the speed of light the same as saying we would never go faster than sound? Seems to me that this is a barrier that exists for the sole purpose of existing and until someone disproves Einstein it will continue to exist.

As I understood Einstien's Theory, the Light Barrier is unbreakable. Nothing that moves faster than light can slow to slower than light and nothing slower than light can mover faster than light. If we can manipulate the speed of light, have we not, in the manipulation of that speed disproved the theory?

Thank you all for your inteligent responses!

Answer 1

Let’s start with what Einstein actually said… His Special Theory of Relativity started with two postulates (or assumptions): 1) that the laws of physics are observed to be the same in any non-accelerated “reference frame” and 2) that the speed of light (c) is observed to be the same for all observers.

The first assumption basically says that as long as you’re traveling at a constant speed, all your experiments will give the same results. That seems reasonable. But the thing about the speed of light always being the same sounds a little odd: the Michelson-Morley experiment (and others) had detected no change in the speed of light when measured from a moving frame of reference, however, and a set of equations called “Maxwell’s Equations” yield a specific value for the velocity of light, which turns out to be c. (When Einstein considered Maxwell’s Equations, he realized that they don’t allow for a “standing wave” solution, which is what a light wave would look like if you were travelling at the speed of light. So he already sensed there would be a problem with travelling at very high speeds.)

Indeed, when you start with Einstein’s assumptions and re-work the addition of velocities, it comes out to be not simple addition, but a fraction that never gets larger than c. Basically, what happens is that the measurement of time and distance changes, so a physical object (e.g., a spaceship) can never achieve lightspeed.

Here’s where the infinite thing comes in. Because the laws of physics must remain the same (remember the first postulate), then the changes in length and time at high velocities also start to affect the measurements of momentum and of energy—and since E=mc^2, mass and energy are equivalent, so mass itself has to change. The rate of change has a term in the denominator that’s the square root of (1-(v/c)^2), so if the velocity (v) approaches the speed of light (c), then the denominator approaches zero; but if the denominator of a fraction approaches zero, then the total fraction approaches infinity. Thus, you start to talk about problematic things such as infinite mass and energy and size.

But remember that nothing can actually travel at the velocity of light, so although this fraction should get very big, it shouldn’t actually become infinite.

(One can also consider objects that might start out travelling faster than light, in which case they could never slow down to the speed of light. These objects would need to have imaginary mass, they’d need to lose energy as they sped up, and lots of other weird things. An interesting idea in the theoretical realm, but not so much in any kind of real terms.)

It’s important to note here that Einstein’s ideas about velcotiy and time and such are well borne out by experiment. So this isn’t simply mathematical trickery. And yes, someone will have to disprove Einstein before the speed-of-light barrier gets dropped.

Finally, you followed up with a question about manipulating the speed of light, but the “speed” being manipulated there is not the same “speed” that Einstein was talking about. Basically, in a vacuum, light (call it a photon, if you will) always travels at the same speed, namely c. This is the relavant quantity for relativity.


Ryan Wyatt
Rose Center for Earth & Space
New York, New York

Answer 2

No, unfortunately not. Unlike the "Sound Barrier", the barrier posed by the speed of light is a bit more problematic when dealing with thoughts of conventional travel. Current theory and experimentation have led us to believe that the closer to the speed of light we come, the greater the mass becomes, and the greater the energy required to drive it - and at C (the speed of light) one's mass is infinite, as of course is the energy required to push it. One interesting way around this dilema was posed by Fredrick Pohl in his "Gateway" novels - basically find a way to reduce the mass to zero. Then again, there has been ALOT of wonderful theorhetical work in dealing with "work arounds" - wormholes, subatomic particles that appear to be in two or more places at the same time... that kind of thing. Part of the question may be if you go from point 'a' to point 'b' without covering the intervening distance, did you travel faster than light? Then again physics itself is an attempt to explain the universe around us - so if something new comes along and fits all the data better than good 'ol E=m(C squared), then yep! Albert will be chucked out, and the new stuff will be ushered in. (After a span of some decades, I would imagine...)

Answer 3

No. You can never go faster than light. Not even if wormholes exist (which in theory they do not in this universe) - you would still travel slower than light through them, but they would act as a shortcut.

The issue with light is that its speed is the same for everyone, regardless of how they are moving. This has been tested experimentally. It leads to the speed of light being an upper limit.

You can see this must be correct every day - magnetism is a result of the speed of light being universal and an upper limit. If all the magnets in the world stop working, then maybe you can go faster than light. Until then...

Answer 4

Well, the idea / problem is: As your speed approaches that of light, your mass increases to infinity and you become infinitely short in the direction your travel. So obviously, you the space traveler, will be dead long before you get even close to the speed of light. Also, to accelerate an object to speed of light would require infinite time with any limited amount of acceleration, or infinite acceleration for any limited amount of time. This is for in a vacuum with a space ship.

Now as for just plain old energy- like radiation; particles can move faster than the speed of light in a material, which is less than the speed of light in a vacuum. When this happens, we get something called Cerenkov radiation. That’s is the funny blue glow you see when you look into the water pool of an atomic reactor.

As for your question- yes people are working on faster than light – experiments, perhaps not travel. Faster than light speeds are possible in principle depending on the actual structure of the space-time continuum, which contemporary physics ignores. In fact scientists have already gotten LIGHT to travel faster than the speed of light! All the future work will be on “tricky” ways of getting around conventional space-time. It’s pretty hairy to read about all the different possibilities.

Answer 5

The idea is the every object in the world contains the same amount of energy. In fact, despite what your middle school or high school science teacher says matter is energy. E=MC^2 proves this point. So where is all that enrergy if we aren't using it to move around? All the energy left after our or other matter's spatial movements (movements left, right, up or down, or on the x, y, z axises) is applied to traveling through time. Thus, as Einstein pointed out (and later proved) an object devoting a huge portion of its energy to spatial movement at high velocity will travel slower through time. Or as often stated in lay terms, time will pass slower when moving quickly. The speed of light is actually the constant representing the maximum amount of energy an object can possess. Other answers lead you astray. Light cannot travel faster than the constant C. It can travel at slower rates by being impeeded by objects, thus it has been "sped up and slowed down in labs." Additionally, Einstein did not think we wouold ever travel faster than the "constant speed of light." He did beleive in "wormholes." Rips in space time that allow an object to move through one of the other 6 or 7 dimensions, thereby bypassing the need to accelerate to or beyond the speed of light. But that gets into String Theory, Super String Theory, and M Theory. Read my cites.

Answer 6

No, because sound is a transverse wave, therefore the speed of sound is different in different mediums, we simply had to design a craft capable of moving faster than the waves before it shattered, light however, does not need a medium to travel through, and seeing as how light either has no mass or has an infinitely small mass it can gain tremendous momentum only by moving at incredibly high speed (the speed of light), we have a huge mass comparatively, and before we could achieve the speed of light our molecular structures would begin to give way and we'd become flying pudding.

Answer 7

There are any number of contrived conditions under which the speed of light seems to be exceeded. Before buying your ticket for a FTL trip to Vega, I'd recommend you take a careful look at this website ==>http://physicsweb.org/articles/world/13/9/3

Also, those here at YahooAnswers who have implied that a trip through a wormhole involves FTL are dead wrong. Travel through a wormhole would simply be following a short cut through spacetime, not moving as fast as light, let alone faster than light.

Answer 8

I agree with Kevin R,the speed of light is absolute,nothing can come even near the speed of light,even if someone would build a ship that would travel at the speed of light,the energy to make it get to that speed would be measure in solar systems and not in gallons or tons,you also would have invented the first time machine as a bi product

Answer 9

no.we cant travel faster than light for these reasons:the faster sumthing t accelerates,the more energy it takes to accelerate it farther.because the faster sumthing goes,the more mass it gains and the more energy u need to accelerate it farther,so to get to the speed of light,u would need an infinite amount of energy and thats impossibleand einsteins theory is right,its been proved million of times.and this "barrier" doesnt exist,there is no light barrier,we cant go faster than light and thats all,the end of it all,nothing more just that.

Answer 10

Actually Einstein believes we can travel faster than the speed of light thru wormholes, by making the distance between two places/objects into zero.