Faster Than Light
As we already know speed of light is 299 792 458 m/s. The speed of light 'c' is an absolute physical constant. No matter where you are in the universe or how fast you are moving relative to something also the speed of light in vacuum is always the same.
Why is it finite?, what came it to move?, it always move in a straight line, no matter the frame light is in. Why is that? Is it possible to travel faster than light( FTL)? Of course ,as you have already seen FTL in many tv series( star trek) or science fiction movies. They go faster than the speed of light every show and travel into the past like it's a trip to Disneyland. It is fun to think about and enjoy in science fiction, truly going faster than light is not that possible.
Actually, there are some hypothetical ways and natural phenomenon which allows FTL. It is possible to travel faster than light, but not faster than speed of 'c'. Let me explain, there is difference between faster than light and faster than 'c'. Even light can't travel faster than this, what if you strapped a torch to the front of a moving rocket or train, wouldn't the light coming faster than the 'c'.
When light travel through material or medium, its effective speed is reduced. Where the effective speed of light is c/n and in some material other particle can travel faster than c/n. Because of this it is possible to break the light barrier in a material while still traveling less than 'c'. One example of this is our sun. In the sun light is produced in it's core through nuclear fusion. Traveling at the speed of light, it should be just a two or three second journey to the surface of sun. But the sun interior core is pack so densely with charged particles that light can't simply travel in a straight line. Imagine photon trying to leave the sun but getting bounced in a random direction every cm. It is scattered in random direction, this random walk of a photon through the Sun actually takes about 20000 to 150000 years to travel from the Sun's core to it's surface. But in case of sound wave, it can travel through Sun faster than light because sound wave propagate in different way, they are pressure waves. As a result they are not hampered by ions in the core. Sound waves can travel through Sun faster than light. This may appear to travel faster than light but this do not convey any object or mass.
Another phenomenon which actually convey mass faster than light is the rate of cosmic expansion. The way our universe is expanding as measured by red shift, the more distant a galaxy is the greater it's apparent red shift and thus the faster is appear to be moving away means that distant galaxies are traveling away from us faster than nearby galaxies. Because of this if you consider two points in space far enough apart they will be moving away from each other faster than the speed of light. A galaxy about 16 billion light years away is moving away from us faster than light, but that galaxy isn't defying relativity, relativity requires that nothing can move through space faster than speed of light 'c'.
Another hypothetical way to go faster than light is 'closing speed'. The rate at which two objects in motion in a single frame of reference get close together is called mutual or closing speed. Imagine two fast moving particles approaching each other close to speed of light, the closing speed would be the rate at which the distance between two particles is decreasing from the point of view of an observer standing at rest relative to reference frame, the rate will be slightly less than twice the speed of light. This may be seems faster than light but in special relativity, it is impossible to accelerate an object to the speed of light. However it might be possible for an particle to exist which move faster than light, the hypothetical elementary particle called tachyon. A tachyon would always move faster than light so it would not be possible to see it. Most physicist think that faster than light particle can not exist because they are not consistent with the known law of physics. Experiments have been conducted to search the evidence for the existence but there is no evidence that this particle exist.
A possibility predicted by general relativity is the famous traversable wormhole of science fiction which would create shortcut between arbitrarily distant points in space but this have disadvantage that this need negative energy and exotic matter to keep open and as with the alcubierre drive, this also need region of high negative energy, which we don't know how to create. It also have other problem such as that this might destroy everything at it destination when it slows down.
It still far beyond we could do and it is straight forward to create device which allow FTL travel but that's because relativity forbid the transfer of information or object through space at a speed of greater than that of light in vacuum and if any theory which permit's true FTL travel also has to cope with time travel, pretty much interesting, what if one were to go back in time and kill one's own grandfather before one's father conceived?
In special relativity it is impossible to accelerate an object to the speed of light or for a massive object to move at the speed of light . According to relativity 'c' is the maximum speed all matter and information in the universe can travel, because faster something travel, the more massive it get's, and the more time slows until you reach the speed of light at which time stops altogether and if time stops, well then so does speed and so nothing can travel faster than the speed of light.
As we already know speed of light is 299 792 458 m/s. The speed of light 'c' is an absolute physical constant. No matter where you are in the universe or how fast you are moving relative to something also the speed of light in vacuum is always the same.
Why is it finite?, what came it to move?, it always move in a straight line, no matter the frame light is in. Why is that? Is it possible to travel faster than light( FTL)? Of course ,as you have already seen FTL in many tv series( star trek) or science fiction movies. They go faster than the speed of light every show and travel into the past like it's a trip to Disneyland. It is fun to think about and enjoy in science fiction, truly going faster than light is not that possible.
Actually, there are some hypothetical ways and natural phenomenon which allows FTL. It is possible to travel faster than light, but not faster than speed of 'c'. Let me explain, there is difference between faster than light and faster than 'c'. Even light can't travel faster than this, what if you strapped a torch to the front of a moving rocket or train, wouldn't the light coming faster than the 'c'.
When light travel through material or medium, its effective speed is reduced. Where the effective speed of light is c/n and in some material other particle can travel faster than c/n. Because of this it is possible to break the light barrier in a material while still traveling less than 'c'. One example of this is our sun. In the sun light is produced in it's core through nuclear fusion. Traveling at the speed of light, it should be just a two or three second journey to the surface of sun. But the sun interior core is pack so densely with charged particles that light can't simply travel in a straight line. Imagine photon trying to leave the sun but getting bounced in a random direction every cm. It is scattered in random direction, this random walk of a photon through the Sun actually takes about 20000 to 150000 years to travel from the Sun's core to it's surface. But in case of sound wave, it can travel through Sun faster than light because sound wave propagate in different way, they are pressure waves. As a result they are not hampered by ions in the core. Sound waves can travel through Sun faster than light. This may appear to travel faster than light but this do not convey any object or mass.
Another phenomenon which actually convey mass faster than light is the rate of cosmic expansion. The way our universe is expanding as measured by red shift, the more distant a galaxy is the greater it's apparent red shift and thus the faster is appear to be moving away means that distant galaxies are traveling away from us faster than nearby galaxies. Because of this if you consider two points in space far enough apart they will be moving away from each other faster than the speed of light. A galaxy about 16 billion light years away is moving away from us faster than light, but that galaxy isn't defying relativity, relativity requires that nothing can move through space faster than speed of light 'c'.
Another hypothetical way to go faster than light is 'closing speed'. The rate at which two objects in motion in a single frame of reference get close together is called mutual or closing speed. Imagine two fast moving particles approaching each other close to speed of light, the closing speed would be the rate at which the distance between two particles is decreasing from the point of view of an observer standing at rest relative to reference frame, the rate will be slightly less than twice the speed of light. This may be seems faster than light but in special relativity, it is impossible to accelerate an object to the speed of light. However it might be possible for an particle to exist which move faster than light, the hypothetical elementary particle called tachyon. A tachyon would always move faster than light so it would not be possible to see it. Most physicist think that faster than light particle can not exist because they are not consistent with the known law of physics. Experiments have been conducted to search the evidence for the existence but there is no evidence that this particle exist.
A possibility predicted by general relativity is the famous traversable wormhole of science fiction which would create shortcut between arbitrarily distant points in space but this have disadvantage that this need negative energy and exotic matter to keep open and as with the alcubierre drive, this also need region of high negative energy, which we don't know how to create. It also have other problem such as that this might destroy everything at it destination when it slows down.
It still far beyond we could do and it is straight forward to create device which allow FTL travel but that's because relativity forbid the transfer of information or object through space at a speed of greater than that of light in vacuum and if any theory which permit's true FTL travel also has to cope with time travel, pretty much interesting, what if one were to go back in time and kill one's own grandfather before one's father conceived?
In special relativity it is impossible to accelerate an object to the speed of light or for a massive object to move at the speed of light . According to relativity 'c' is the maximum speed all matter and information in the universe can travel, because faster something travel, the more massive it get's, and the more time slows until you reach the speed of light at which time stops altogether and if time stops, well then so does speed and so nothing can travel faster than the speed of light.
