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Is there any particle faster than light? if so, what is it? Is neutrino faster than light?
Question Date: 2014-08-17
Answer 1:

You might know that if you travel on a train at 60 MPH and walk forward briskly at 5 MPH, your overall speed would be 65 MPH. However, if Superman was running at nearly the speed of light and he turned on a flashlight pointed in front of him, he would still see the light moving as if it were moving at the speed of light. In this case, the two speeds are additive. It’s an interesting consequence of our understanding of relativity. Einstein imagined himself chasing a beam of light (when he was only 16!) and saw the logical contradictions that would lead him to conclude that the speed of light was a constant that could not be surpassed.

There are different situations where it might seem like the speed of light is exceeded. For example, if I shine a powerful laser at Betelgeuse and then, as quick as I can, point it at Rigel (both of these are stars in the Orion constellation but are 392 light years apart), it could seem like the spot of light at the tip of the laser travelled faster than the speed of light (392 light years in just a couple of seconds). However, neither the laser (in your hand) nor the light from the laser (travelling at the speed of light) move faster than the speed of light, and so the movement of the spot is delayed. There are other examples like this that might seemingly break light-speed but actually don’t.

There are also tachyons. These are hypothetical particles that move faster than the speed of light. Physicists argue whether or not it is possible for these particles to exist, although most scientists say that since our current laws of physics disallow it, it likely is not possible. Tachyons have not been observed, unless you count the small sailboat I saw in the Santa Barbara harbor (one boat was named Tachyon while its neighbor was named Tachytoo).

You might recall a few years ago when researchers in Europe observed neutrinos travelling at faster than the speed of light. The researchers didn’t report this finding without double- or even triple-checking but couldn’t find any reason the data was invalid, even though it contradicted our modern understanding of physics. They promised the scientific community that more experiments would be conducted and eventually, they noticed a fiber optic cable that had been incorrectly attached and a clock that was ticking too fast. Later, after the experimental parameters were corrected, scientists measured multiple neutrinos with velocities at or near, but not exceeding the speed of light. ​ Best,

Answer 2:

No particle we have ever seen moves faster than light - or at least faster than light in a vacuum.

The speed of light in a vacuum is a property of the universe, and no particle that we have any experience with (including neutrinos) can exceed this speed. This constant maximum speed of anything remains the same when traveling through matter, but light itself slows down when traveling through matter. Neutrinos and other things can move at speeds through matter faster than (some) frequencies of light move through that same matter, but they can never exceed the speed that light moves when in a vacuum.

Physicists have speculated about particles called tachyons, which would move faster than light, even in a vacuum. Nobody has ever observed a tachyon, so what their properties are, or if they even exist, is unknown.


Answer 3:

Good question! As far as we know, no particle faster than light actually exists in our universe. Neutrinos are SUPER light particles, so they move at almost the speed of light, but they're still slower than light.

However, there are theoretical particles ("theoretical" means you can describe it on paper, but no one actually thinks it really exists) called tachyons which travel faster than light (the name comes from the Greek word "tachys", which means "fast"). It turns out that these particles have an imaginary mass - this is imaginary in the sense of complex numbers (so if you square the mass of a tachyon, you get something negative). But the problem with tachyons is the usual problem that you get when you have things moving faster than light - you can get all sorts of weird time travel paradoxes like things causing themselves to happen, or you being able to go back in time to kill your parents before you were born, and so on. So usually when physicists see tachyons appearing in their theories, that means that something's wrong and needs to be fixed!


Answer 4:

Nothing travels faster than light.

Light speed is a physical speed limit of the universe, and not even neutrinos breach it. The results you may have seen suggesting neutrinos move faster than light was released by scientists who were confused with their result and were asking other scientists around the world to help figure out what was wrong with their experiment. The news thought this was interesting so it made headlines, but the real situation was that the people doing the experiments were asking more scientists for troubleshooting advice. It turned out that a fiber optic cable was connected badly and it ruined their time measurements. Any kind of clock or time measurement in particle physics must be incredibly accurate since the phenomena happen so quickly. Theirs just wasn't working well. New measurements showed it was under the speed of light.



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