Study rejects "faster than light" particle finding | Hacker News Reader

Study rejects "faster than light" particle finding

reuters.com

10 pointsElement_16 comments

I don't really get the point of articles like these. I don't think anybody is seriously arguing that the neutrinos were FTL. The real question is why the measurements showed that they were.

Declaring that the neutrinos weren't superluminal Because Of Science misses the point.

It doesn't just miss the point, it misses the point of Science. The day you dispute a measurement on the grounds of Science is the day you have forgotten how Science works. If Science disagrees with measurements, Science is wrong or the measurement was taken wrong. Fix one, don't tell me that the measurement is wrong because Science is right.

Aka you can't disprove reality with Science.

> They argue, on the basis of recently published studies by two top U.S. physicists, that the neutrinos pumped down from CERN, near Geneva, should have lost most of their energy if they had travelled [sic] at even a tiny fraction faster than light.

So let me get it straight: it's clear that the observation is incorrect because it can't be correct based on existing theories?

Abstract: Assuming current theories are right, experiment that disproves current theories is wrong.

The fact this is a Reuters article notwithstanding, has anyone considered the neutrinos move at the speed of light, and photons don't due to gravity's effect on spacetime (ie, real speed of light vs relativity)?

The OPERA experiment wasn't a race between neutrinos and photons going from one place to the other - the neutrinos travelled the measured distance between the two detection points faster than c.

I never implied it was a race. c is effected by relativity, and the speed of a photon is generally described as c.

My question is, have neutrinos merely ran past relativity but not actually broke anything, merely bent it?

c is not affected by relativity. It is a constant.

The speed that a specific photon travels at is affected by many things - the medium it's travelling through, for one - but that has no effect on c.

His point as I gather is, what if c was incorrectly calculated, and photons move at 99.9999% of c while neutrinos move at c. This would of course mean "The Speed of Light" is a misnomer, but that could be adapted.

That would certainly be an interesting outcome that does not break the existing understanding we have of c.

That would certainly be an interesting outcome that does not break the existing understanding we have of c.

It absolutely does. A massless particle moving slower than a particle with mass is just as much a break in relativity as neutrinos moving faster than the speed of light. In fact, they're equivalent. The speed of light isn't just "the speed at which photons move," it's the speed at which photons move (minus restrictions) because they're photons.

Edit: I should say that this is all only true in the case of a vacuum.

Naturally "The Speed of Light" is the speed at which photons move, photons are light. But the stipulation being, what if there is some other constant "x", and it's really e = m * x, and c =~ x? (When I say "c =~ x" I mean in a similar way to how c(air) =~ c(vacuum)) Do we know that cannot be the case?

Alternatively, what if the speed of light in a vacuum is not actually the true full speed of light? What if something else is acting on the photons that we haven't thought about, such as gravity or charge?

c cannot be changed without changing E=mc^2, equations for time dilation, equations for adding velocities, and many others, that have been verified experimentally with great precision.

Even as small diffeence would show up in past experiment. So If the true c is greater than old c, old c still has to be there for these equations. So no - updating c is not an solution.

Remember that neutrinos have mass, while photons don't. The speed of light, while not a misnomer, is often confusing. To be more accurate, c can be considered the fastest a massless particle/wave can travel through space-time in a vacuum without the influence of mass or gravity.

So to answer your question, the thing without mass will always move as close to c as possible in a given environment. In the instance of photons vs neutrinos in the OPERA experiment, they both operate under the same environment.

#Edit (thanks @cperciva below) The thing without mass doesn't always move faster than particles with mass. See Cherenkov radiation, http://en.wikipedia.org/wiki/Cherenkov_radiation.

the thing without mass will always move as close to c as possible in a given environment

Not true. In water, photons travel at ~0.75c, but other particles can travel faster (and emit Cherenkov radiation in the process).

Very true. Thanks for the correction.

One could argue that those photons are massive, because they are partly excitations of the water, which increase its mass. Others could argue otherwise. This leads to rather wanky debates over the precise meaning of "mass".

Reply on news.ycombinator.com