SoylentNews is people
SoylentNews
Phys.org reports that in a new paper accepted by the journal Astroparticle Physics, Robert Ehrlich, a recently retired physicist from George Mason University, claims that the electron neutrino is very likely a tachyon or faster-than-light particle. Ehrlich's new claim of faster-than-light neutrinos is based on a much more sensitive method than measuring their speed, namely by finding their mass. The result relies on tachyons having an imaginary mass, or a negative mass squared. Imaginary mass particles have the weird property that they speed up as they lose energy – the value of their imaginary mass being defined by the rate at which this occurs. According to Ehrlich, the magnitude of the neutrino's imaginary mass is 0.33 electronvolts, or 2/3 of a millionth that of an electron. He deduces this value by showing that six different observations from cosmic rays, cosmology, and particle physics all yield this same value (PDF) within their margin of error. One check on Ehrlich's claim could come from the experiment known as KATRIN, which should start taking data in 2015. In this experiment the mass of the neutrino could be revealed by looking at the shape of the spectrum in the beta decay of tritium, the heaviest isotope of hydrogen.p
But be careful. There have been many such claims, the last being in 2011 when the "OPERA" experiment measured the speed of neutrinos and claimed they travelled a tiny amount faster than light. When their speed was measured again the original result was found to be in error – the result of a loose cable no less. "Before you try designing a "tachyon telephone" to send messages back in time to your earlier self it might be prudent to see if Ehrlich's claim is corroborated by others."
(Score: 2, Informative) by moondrake on Saturday December 27 2014, @09:38PM
Its been too many years since I had this on university. But I am guessing you are not looking for a detailed math explanation anyway (wiki pages probably address most of that).
I also find it difficult to point to only 1 key factor for assuming light speed is constant. Einstein was actually not the first to do so. But he did it so rigorously, and worked out all the consequences for mechanics, than things just fell in place for many people.
In Einstein's time, some things in physics did not really match up. Several of these had to do with light. The electrodynamics pioneered by Maxwell and modified by Lorentz was best able to describe many experimental findings (I also tend to believe that it mattered that the theory was aesthetically appealing, believe it or not). But believing it meant that light moved with equal velocity, in all directions, independent of the source velocity. The problem may not seem very obvious, as this theory considers light not to be actual particles, but as as soon as you think about light as particles, you have to wonder why the velocity of a light source does not add to the velocity of the light itself.
If light is a wave, and not a particle, you may feel that you need something to carry this wave (like air carries sound waves). A so-called "luminiferous ether" was proposed to do this. Apart from having ridiculous properties (a solid mass-less material that is surrounding everything and everywhere, without interacting with us) to be able to explain several experimentally verified properties of light , it also means that you should imagine some universal reference framework in which the light moves (i.e. the velocity of this ether). People looked hard for this ether, but no one could experimentally show it was there...
Is it, to you, more self evident to have a defined light speed (related to the energy it needs to increase velocity) or an ultimate framework in which you can define speed=0? Absolute space and time seemed a silly concept to several scientist around Einstein's time, especially in the absence of some object (ether) to define such absolute. But an amount of energy necessary to accelerate to infinite speed (i.e. light speed) can be easily defined [if you would define speed in units corresponding to the amount of energy necessary for acceleration light speed is infinite. The fact that it is some silly number in other scales is just an effect of the unity used to described it].
Einstein postulated this and derived a logical framework that could describe many problematic experimental data of that time (relativistic doppler effects for example). Without requiring the ever-growing and more ridiculously list of properties of the light ether. So it became the accepted view (until the day that something better comes along)
Note that nothing is special about light. "light-speed" is just a way of speaking. It would be better to say that particles with no rest mass have a constant speed in vacuum. This happens to be true for light, or any other particles with no rest mass. If there is something such as negative or complex mass, it will be interesting as according to _current_ theory, it could travel faster than light (as well have a lot of other weird properties). But I do not think the people working with this kind of physics have really considered non-positive mass to a great extend... (since the real question is whether such thing can exist at all).