There are some issues with traveling faster than light.  First of all, it’s perfectly ok for things to go faster than light, happens all the time.   For instance, if I take a laser and point it at the moon, and then move the laser beam quickly across the surface, that red dot can move many times faster than light.  In fact, given the proper media, a light wave itself can travel faster than light.  But what can not go faster than light is any information.  waves can go faster than light, as long as no information is being transmitted.

they have measured neutrino speed before, there was a massive supernova in the 80’s or 90’s and they happened to be able to record the whole thing.  The light and neutrinos arrived within a few hours of each other.  If neutrinos were going at the speed this new experiment suggests they should have arrived about 3 or 4 years ahead of the light wave.

This supernova result is good, because Einstein’s theory of general relativity is one of the things we have tested the most and it would be terrible if it were to break in such a simple fashion.

One could suppose that neutrinos are a bit lighter than photons and that’s why they can go faster than light.  Photons have no mass, so to be lighter than photons they would need negative mass.  If you have a material with a negative mass, you can then build a perpetual motion machine, just make an elevator full of this lighter than nothing stuff, and haul rocks to the tops of buildings.  So your theory breaks the first law of thermodynamics. I’m not saying it’s impossible, this could be what is happening, just saying you are breaking the first law of thermodynamics.

We are already pretty sure that neutrinos have a little bit of mass, just enough so that they are not entirely massless (otherwise neutrinos would never oscillate), but so little that they travel at just about the speed of light.  Suppose for some reason, not negative mass, but some other reason, they do travel faster than light and they are carrying information.

There are many possibilities, here are three:

1) the neutrinos are violating causality, but Einstein’s theory is intact.  That is, they are traveling backwards in time, in order to go faster than light (tachyons).  This means it is possible to build time machines, and all the associated weird paradoxes with this problem.

2) Einstein’s theory is completely demolished, and we are back to a world without relativity, where somewhere in the universe is galactic point zero (0,0,0) and there is some cosmic clock ticking away at (0,0,0), and to explain all the general relativity behavior, we are going to have to bring back the “relativity ether” that  we got rid of with the michelson-morley experiment, stuff behaves just like regular relativity except it has all kinds of exceptions to explain away things like the neutrino experiment.

3) this is an edge case where they are using such massive energies that einstein’s laws can merely be modified and not thrown entirely away.  Problem with this possibility is that the energies are several orders of magnitude too low for this to be likely.

Relativity is such a mainstay of our understanding of the world that you can’t really dump it and create an exception for neutrinos unless you completely demolish all we know about science.  When we got rid of Newton’s theory of gravity, and laws of motion we didn’t demolish them entirely.  You still use Newton’s laws when you throw a baseball and want to describe the parabola it takes.  It was only in edge cases like arc seconds of perihelion precession of Mercury that they went and measured during a solar eclipse that was needed to verify general relativity.  Like the modifications made to Newton’s theory, when you make modifications to Einstein’s relativity, if there are exceptions to be carved out, they should be with edge cases, not with our general day to day application of general relativity and not this new neutrino experiment.  If you throw out all of general relativity we couldn’t use our cell phones any more because we use relativity every day in calculating transmission speeds to our geosynchronous communications satellites.  Without general relativity working as we know it to work, civilization would crash.

But you know, if you ask me my opinion, I honestly don’t know for sure.  Maybe there are ways to break causality and preserve Einstein’s theory, maybe, time travel is what these neutrinos are doing, maybe they are propagating faster than light.  Perhaps it’s a group velocity trick, like that laser beam that you send through a cesium gas, some experimenters in the 80’s were to get the group velocity of light to go 300 times faster than light, which is perfectly ok, since no information is being transmitted.  Or, simplest explanation, they are making some stupid measurement error.  You can make your own guess, I’m not sure what the explanation is for this experiment.

 

Theoretical physicist Steven Weinberg of the University of Texas at Austin, winner of the 1979 Nobel Prize in Physics


The report of this experiment is pretty impressive, but it bothers me that there is plenty of evidence that all sorts of other particles never travel faster than light, while observations of neutrinos are exceptionally difficult.* It is as if someone said that there are fairies in the bottom of their garden, but they can only be seen on dark, foggy nights.

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