News has been flying around about new findings out of CERN that they may have detected some neutrinos which were travelling faster than the speed of light. This is one single experiment and so, as the Bad Astronomy blog deftly points out, there's ample reason to be skeptical. However, team spokesman Antonio Ereditato said:
We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing. We now want colleagues to check them independently.
I'll leave it to the real scientists to figure out the specifics on the experiment itself, and take this as an opportunity to explain the implications of this finding, which could be nothing short of revolutionary to the world of physics.
The problem with this result is that nothing is supposed to be able to travel faster than the speed of light. This is one of the basic principles that comes out of Einstein's theory of relativity. So how could this happen?
To figure that out, let's examine for a moment exactly why the speed of light is considered a universal speed limit.
Why Is the Speed of Light a Barrier?
Einstein used two principles upon which he built his 1905 theory of special relativity (and later general relativity):
Principle of Relativity - The laws of physics are the same for all inertial reference frames (regions that are either stationary or moving at a constant speed).
Principle of Constancy of the Speed of Light - Light always propagates through a vacuum at a definite velocity, c, which is independent of the state of motion of the emitting body.
If you're paying close attention, you'll notice that neither of these principles preclude the idea that something other than light is in fact able to move at the speed of light.
However, as part of this work, Einstein developed a series of mathematical relationships that needed to be used when two objects are moving relative to each other. This was built on mathematical work that had already been initiated by Henri Poincare, Hendrik Anton Lorentz, and others ... mathematical transformations which eventually earned the name Lorentz transformations. One of those relationships (we won't get into the details of how he arrived at it) is the following equation, which represents the total kinetic energy for a moving body:
There are some logistical complexities to this equation, but for our purposes the key element is that denominator. As v (the velocity of the object) is 0, or very near 0, then you'd get a result that's basically in line with the classical kinetic energy theory. Incidentally, in the scales we're talking about, even a fighter jet is "very near 0." Pretty much anything we ever come in contact with - except light and other forms of electromagnetic energy - moves much slower than the speed of light.
But what about if v is very large? Specifically, if the value of v becomes very close to the value of c (the speed of light), the v-squared over c-squared term is very close to 1, so 1 minus it is very close to 0. And when a denominator gets very close to 0, then the whole number gets very large. In mathematical terms, it "approaches infinity."
Einstein's equations also say that the object would be getting more and more massive ... approaching infinite mass, as well.
Any way you look at it, accelerating something to v = c requires infinite energy!
That is why the speed of light is a speed limit ... because you just can't get enough energy to do it.
Breaking the Rules
Photons, however, are able to get around this, because they always move at the speed of light. They are created that way. As particles of light, this is just kind of what they do by definition. Their rest mass is zero, so the above equation doesn't apply to them. Their energy is calculated in a different way.
Neutrinos were long thought to also be massless particles, but experiments have indicated that they do have a very small amount of mass, so they should be governed by the rules of the above equation. It shouldn't be possible to accelerate them to (or beyond) the speed of light.
However, consider the reasoning behind making the speed of light a universal speed limit. It was because no object could get enough energy to accelerate to the speed of light. Which leaves me with one big question:
Is there any way for an object to move faster than the speed of light without being accelerated?
If the neutrinos in this experiment came into existence going faster than the speed of light already, this wouldn't technically violate the above equation. There's certainly no indication of a force acting on the neutrinos to give them this sort of boost, so really the expectation would be that they were moving this fast as soon as they were created, which is consistent with this idea.
While this wouldn't require an infinite amount of energy, the energy involved would still be very unusual. The above equation would then contain a negative number within the square root, which means that the total kinetic energy would be an imaginary number. As a rule, when imaginary numbers show up in the results of physics problems, they lead to all sorts of problems with the theory (or represent some sort of error in the experiment).
If confirmed, the experiment would force physicists to take a good long look at the theory of relativity and figure out how to revise it to account for this new evidence.
One Other Possibility
One possibility is that these particles are not actually neutrinos, but perhaps some other type of exotic, heretofore-unknown form of matter which has properties similar to neutrinos ... similar enough to be detected by the OPERA detector, but strange enough that we've never encountered them before in our other experiments. I don't know enough about the details of the experiment to even guess how possible this is, but it might explain why we've never observed this effect before.
Perhaps the exotic form of matter is governed by rules other than relativity, in some unknown way. It's just an idea.
It'll definitely be interesting to see what the real scientists come up with as they delve deeper into this sort of mystery. I'll keep my eyes peeled and my ear to the ground, and let you know as soon as I have more information.
Because if this pans out, this could be the biggest science story of the decade ... and we're only in 2011!
- Science - Neutrinos Travel Faster Than Light, According to One Experiment
- Discover magazine's Bad Astronomy blog - Faster-than-light travel discovered? Slow down, folks
- ArXiv.org - Measurement of the neutrino velocity with the OPERA detector in the CNGS beam (the actual research paper)
- Reuters - Particles found to break speed of light
- The Telegraph - CERN scientists 'break the speed of light'
- Oscillation Project with Emulsion -tRacking Apparatus (OPERA)
- USA Today - Particle might have traveled faster than speed of light