Comment by foob | Hacker News Reader

Comment by foob | Hacker News Reader

If this result is valid then it would mean that neutrinos are capable of traveling .0025% faster than light. There was a supernova that we observed in 1987 (SN 1987) that occurred 168,000 light years away from us. A neutrino burst was observed in 3 different labs about 3 hours before the light was observed. If neutrinos are capable of traveling .0025% faster than the speed of light then why would we observe these neutrinos at a time that is consistent with them traveling at almost exactly the speed of light (slightly less due to their finite mass)? A difference of .0025% would correspond to the neutrinos arriving 4 years earlier! This is the first experimental contradiction to this result that pops into my head but there are probably many more.

Plain and simple, this is most likely due to a systematic error in their experiment that isn't being properly taken into account. The result would tear apart well established theories that have been tested time and time again in thousands of different ways. Of course that doesn't mean that they're absolutely right but it does mean that any contradictory result has to be initially taken with a grain of salt (kudos to the article writer for doing this). It's easy to mess up a calibration in such a complicated system and 60 nanosecond errors could potentially pop up. It will be interesting to see the results from other labs but I would advise against getting your hopes up for any new physics.

Um... is there any trace of neutrino bursts before that? Im not sure anyone bothered checking, since such a correlation would have been very hard to justify. A neutrino burst 4 years before a supernova... so what?

Could a physicist clarify whether neutrinos could travel at different speeds in vacuum like any 'normal' particle, or are 'fixed speed' like photons. We could well have had several waves with the bulk arriving at c-epsilon and no one bothering to check outside the expected time frame.

Well, the point is that there was a neutrino burst coincident with SN87a. So if there was one 4yr earlier, too, then you'd have to explain how the same event produced two bursts of neutrinos with different speeds, while within the burst they apparently had exactly the same speed.

If neutrinos have mass, they can travel at any speed <c depending on their energy, like any other massive particle. Of course, the upper mass limit is quite low, so even with very little energy they will go very fast.

(Edit: In fact, the arrival interval of those neutrinos puts an upper limit on the neutrino mass, because the larger the mass, the more different the speed and the more dispersed the arrival of them at Earth.)

I'm no physicist, so I am just guessing.

It could be some phenomenon similar to what we see in emission spectrums, where a pure source can emit photons at multiple precise energy levels. except that in the case of particles with mass(apparently neutrinos have a mass) this would result in a difference in speed. Not a big enough difference to be noticed on 700 km , but enough to make a 4 yr difference on 170kly.

Of course this is still wild speculation without much background.

Neutrinos released in type II supernova explosions are thermal, so they should have a broad spectrum unless pretty much everything we think we know about SNe is wrong.

Maybe the neutrinos that appeared 3 hours before the event are from another event altogether (one that occurred even further away, whose light particles haven't even reached us yet)?

Given that the flux goes as 1/r^2, and the sum total of the neutrinos detected in association with 87a was something like 17, a SN in any external galaxy would be undetectable.

I don't think the claimed potential result is that neutrinos always travel exactly 0.0025% faster than c, but that they can - perhaps under very specific and special circumstances. I agree with your skepticism and think we should approach this slowly, but your I don't think that your particular example disproves or contradicts the claim.

The result would tear apart well established theories that have been tested time and time again in thousands of different ways.

That's what makes this so exciting!

No, I'll wait until it's replicated in another lab before I get excited.

Failing that, I'll at least wait three years for the "Ohhh yeah, so we checked again and it turns out that [simple explanation X]".

On the offchance that this is a startlingly new breakthrough in physics, I don't lose much by waiting three more years before I believe it.

If you're not looking for something, it's hard to find it.

If you assume nothing travels faster than light and you have a burst of neutrinos a couple of years before an event, you'll look for other explanations or maybe simply ignore the readings. Generally they expect the neutrinos burst a couple of hours before the photons arrive.

Now it's suspected that a flavor of neutrinos can travel faster than light, maybe there's going to be some data digging to find correlations...

The universe if full of mysteries and it's highly likely Einstein's theory although verified and correct in many cases is incomplete not to say totally incorrect in other cases, as Newton's theory was.

Let's not assume anything.

You forget one crucial thing in the experiment. A neutrino reacts with almost nothing. A photon on the other hand, react with almost any damn thing you place around its path - metal? Yes. Mirror? Yes. Wood? Yes. Air? Yes!

I very much doubt they completely vacuumed the path of the neutrino to the same degree as it is in outer space. It is possible that neutrinos travel at the same speed as light in vacuum, but travel much faster when there's other material present in the way.

The speed they got in this experiment was faster than light would travel in a vacuum, according to the abstract.

If the nutrinos were from the same supernova, doesn't the fact that they arrived BEFORE the light still mean they traveled faster than light? Whether it should've been 4 years instead of 3 hours seems besides the point as far as the significance of the recent observation is concerned. Unless I'm missing something here.

The faster-than-light neutrinos got slowed down on their way to us by other faster-than-light neutrinos they encountered on the way?

those neutrino's could be from anywhere in the universe. we measured them 3 hours before the light of the supernova because we were looking for them at that time

Right, because those scientists were psychic? Neutrino observatories look for neutrinos continuously. They do not throw away data, if there are neutrinos detected they will be logged. Never in the long history of neutrino observation has there been a spike in detections similar to what was observed with SN 1987a. Moreover, that observation heavily confirms our pre-existing models of neutrino generation and behavior in Type II supernovae.

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