ChatterBank1 min ago
The speed of light
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Light does not require massive amounts of energy to travel so why is it impossible to travel faster than light. Also the universe expanded faster than the spped of light at the begining how?
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Photons have zero mass and must travel at the speed of light in a vacuum.
Matter travelling near the speed of light will have a huge relativistic mass which tends to infinity as the speed of light is approached.
Electromagnetic radiation, such as high energy gamma rays, may have a huge amount of energy associated with its photons (E = hf)
Matter travelling near the speed of light will have a huge relativistic mass which tends to infinity as the speed of light is approached.
Electromagnetic radiation, such as high energy gamma rays, may have a huge amount of energy associated with its photons (E = hf)
As to the expansion or inflation of the early universe, Alan Guth, a theoretical physicist and cosmologist, was the first to clearly develop a model of the inflationary universe at an earlly stage around ten to the minus 34 seconds or so, the size of the universe inflated many billions of times it's intial, nearly infinitely small size.
However, if we considered the universe a crystal lattice and you were at one of the host sites or intersects, you would see everybody moving away from you at "many orders of magnitude" greater than the speed of light. But no one would feel the slightest acceleration since it wasn't mass that was expanding, it was the space that was growing so rapidly.
In this inflationary time gravity was effectively "repulsive". This kind of expansion was necessary to overcome the speed of light limitation for the calibrating of pariticles separted by large distances in order to maintain a perfect state of equilibrium while the universe achieved the minimum size to ensure continued inflation
If the unverse weren't perfectly uniform for some critical, but finite time the expansion would have failed and the universe would collapsed back on itself.
As it was, the estimation o many cosmologists is that at least 10 additional dimensions existed at that critical moment of inflation butdid fold back on themselves and only the four (width, length, height and time) formed...
However, if we considered the universe a crystal lattice and you were at one of the host sites or intersects, you would see everybody moving away from you at "many orders of magnitude" greater than the speed of light. But no one would feel the slightest acceleration since it wasn't mass that was expanding, it was the space that was growing so rapidly.
In this inflationary time gravity was effectively "repulsive". This kind of expansion was necessary to overcome the speed of light limitation for the calibrating of pariticles separted by large distances in order to maintain a perfect state of equilibrium while the universe achieved the minimum size to ensure continued inflation
If the unverse weren't perfectly uniform for some critical, but finite time the expansion would have failed and the universe would collapsed back on itself.
As it was, the estimation o many cosmologists is that at least 10 additional dimensions existed at that critical moment of inflation butdid fold back on themselves and only the four (width, length, height and time) formed...
You have to be a little careful here.
Relativity does not say you cannot travel faster than light.
It actually takes the experimental observation that light cannot be accelerated and builds on that.
It is quite possible that that observation could be incorrect in some unknown and extreme circumstances.
Secondly special relativity says that as the velocity of a body gets closer and closer to the speed of light its mass increases
At the speed of light you would be dividing by zero - which most people assume means efectively infinite in this context.
At velocities greater than the speed of light you get a negative square root.
That is not necessarily impossible.
Taking all of these together people specuated that possibly at the time of the big bang there were conditions that could allow some elementary particles to exceed the speed of light.
They called these tachyons and went looking for them. However no evidence for them was ever found.
Tachyons are a fine example of a nice theory just just turned out not to be true. However there is a slim chance that they might exist and we've just never found them.
But I wouldn't bet the farm on it
Relativity does not say you cannot travel faster than light.
It actually takes the experimental observation that light cannot be accelerated and builds on that.
It is quite possible that that observation could be incorrect in some unknown and extreme circumstances.
Secondly special relativity says that as the velocity of a body gets closer and closer to the speed of light its mass increases
At the speed of light you would be dividing by zero - which most people assume means efectively infinite in this context.
At velocities greater than the speed of light you get a negative square root.
That is not necessarily impossible.
Taking all of these together people specuated that possibly at the time of the big bang there were conditions that could allow some elementary particles to exceed the speed of light.
They called these tachyons and went looking for them. However no evidence for them was ever found.
Tachyons are a fine example of a nice theory just just turned out not to be true. However there is a slim chance that they might exist and we've just never found them.
But I wouldn't bet the farm on it
To give you some idea of how much energy to takes to get near the speed of light, consider the LHC accelerator.
At full power, the kinetic energy embodied in the circulating protons is the equivalent of a TVG train travelling at about 220km per hour. The protons carring that energy amount to the equivalent of one teaspoon of hydrogen gas at normal room temperature and pressure.
At these near light speeds every tiny increase in velocity takes an enormous and increasing amount of energy.
At full power, the kinetic energy embodied in the circulating protons is the equivalent of a TVG train travelling at about 220km per hour. The protons carring that energy amount to the equivalent of one teaspoon of hydrogen gas at normal room temperature and pressure.
At these near light speeds every tiny increase in velocity takes an enormous and increasing amount of energy.
Well be careful again about saying words like "you".
There's a huge difference between a person doing something and say sending a signal or particle that exist in that state.
For example as you accelerate a massive body closer and closer to c you require more and more energy but supposed that you reached a point where 1 quantum of energy pushed you over the light barrier. This obviously is not the sort of thing that could happen easily but in the early stages of the Universe - who knows.
Come to that of course whether special relativity holds up in those conditions is very much open to speculation.
However as I said, we actually have no reason to believe that they do exist.
There's a huge difference between a person doing something and say sending a signal or particle that exist in that state.
For example as you accelerate a massive body closer and closer to c you require more and more energy but supposed that you reached a point where 1 quantum of energy pushed you over the light barrier. This obviously is not the sort of thing that could happen easily but in the early stages of the Universe - who knows.
Come to that of course whether special relativity holds up in those conditions is very much open to speculation.
However as I said, we actually have no reason to believe that they do exist.
Faster than light speed motion is implied to this very day in the motion of the universe outside our visible horizon. This is why we see nothing of the universe that lies further than the 13.7 light years distance light has been able to travel since the big bang.
If we could somehow be transported instantly to the edge of our visible universe there is little reason to suspect we would not see a similar expansion in surrounding galaxies as we witness here.
The velocity of the motion of objects is relative to the point of observation. Super light speed expansion does/did not correspond to adjacent particles during inflation but only to particles forming beyond the light speed visible horizon.
Out of sight / Out of mind! ;o)
If we could somehow be transported instantly to the edge of our visible universe there is little reason to suspect we would not see a similar expansion in surrounding galaxies as we witness here.
The velocity of the motion of objects is relative to the point of observation. Super light speed expansion does/did not correspond to adjacent particles during inflation but only to particles forming beyond the light speed visible horizon.
Out of sight / Out of mind! ;o)
The receding of the edge of the Universe is not due to anything travelling faster than the speed of light. It is moving out of sight because the space between us and the edge is expanding so the light coming back has to travel further than the edge did to cover what would be expected to be the same distance.
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