Well, this could change things (neutrinos)

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Re: Well, this could change things

Postby doogly » Sat Sep 24, 2011 2:57 am UTC

I suppose I can link these guys an extra few times, cause they have a good chat of it here:
http://blogs.discovermagazine.com/cosmi ... neutrinos/

the tl;dr:
prolly not a statistical error
super probably a systematic one
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Re: Well, this could change things

Postby Malconstant » Sat Sep 24, 2011 3:15 am UTC

@Ollie, Argon,

The thing is, relativity is correct, it really truly is. It's literally the most well-tested theory in physics, to many orders of magnitude greater than this measurement. It may be that we'll find evidence which will require a better theory in some regimes, but such a theory would have to yield the same results as relativity in the regimes we've already measured it to be correct in.

So there is no point where we will say "oops, I guess we were wrong then, better start back at square one", because this isn't a rationalist thought experiment, this is utterly verified stuff. It may be that there is a goddamn wormhole between the two sites which bends things into a fourth spatial dimension to shortcut the trip, and that would play fair with the rules of relativity. But there is no abandoning relativity.

For an example, GPS and all modern particle accelerators fundamentally rely on relativity to function. If it was "wrong" they would just explode and break. That doesn't mean this experiment isn't interesting or that these scientists were necessarily wrong, but it does mean that there is no calling into question the legitimacy of relativity. And nobody serious is actually calling relativity into question, it's just the media.
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Re: Well, this could change things

Postby Diadem » Sat Sep 24, 2011 3:39 am UTC

I have a question about SN87A. Why is it the only supernova for which we detected neutrinos? It was over 20 years ago, our ability to detect neutrinos has greatly increased since then. Why don't we detect them for more supernovae?

If neutrinos do travel FTL, then, given that we can't detect what direction they come from, and given that distances to supernovae vary greatly, we would expect neutrino bursts and observed supernovae to be pretty much completely uncorrelated. If we only ever detected one neutrino burst, then how do we know it belonged to SN87A? You can't infer correlation from a dataset of one. It may have been from any other supernova in the following few years or even decades. It would be a coincidence for our only ever detected neutrino burst to arrive at roughtly the same time as a supernova, but supernovae are not so uncommon as to make this completely unlikely. Certainly more likely than a 6 sigma result being due to chance.

But why is it the only one? That's what i can't wrap my head around. Am I missing something obvious here?
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Re: Well, this could change things

Postby Malconstant » Sat Sep 24, 2011 4:05 am UTC

Supernovae aren't super common, and they don't all give off enormous bursts of neutrinos. For instance the one that we just saw a couple weeks ago was a type 1A (SN 2011fe), which is a wonderful kind of supernova except that it doesn't give off huge percentages of its energy as neutrinos.

Also, in case there was any confusion, when neutrinos reached us before the light did in the case over 20 years ago that was because the light had to travel through the other debris of the star exploding, whereas the neutrinos just couldn't be bothered to give a fuck about anything, so the neutrinos didn't travel faster than light in a vacuum.
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Re: Well, this could change things

Postby thoughtfully » Sat Sep 24, 2011 4:34 am UTC

Supernovae occur about once every 100 years per galaxy. The last one we know about for sure in the Milky Way was Kepler's Star early in the 17th century. The one twenty years was quite close but in a satellite galaxy of the Milky Way. There's some chance a supernova could have gone unobserved since Kepler's if it was sufficiently obscured, such as being on the far side of the galactic disc. I don't know what the ratio of core-collapse (neutrino-producing) supernovae to Type Ia supernovae are.
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Re: Well, this could change things

Postby Carnildo » Sat Sep 24, 2011 5:20 am UTC

++$_ wrote:In this case we have a result that contradicts not only a very well-tested theory, but also the SN1987A "experiment," which despite being completely unplanned, actually has a much more convincing methodology.

How does it contradict SN1987A? Under general relativity, the only particles that travel at a fixed velocity are massless particles, which must travel at the speed of light (in all reference frames). If neutrinos have imaginary rest mass, they follow the rules for tachyonic particles: they don't have a fixed speed, rather, they travel faster than light in all reference frames, and adding energy to them slows them down. If SN1987A's neutrinos were higher-energy than CERN's neutrinos, it's quite possible for them to arrive only four hours before the light from the supernova.

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Re: Well, this could change things

Postby ++$_ » Sat Sep 24, 2011 5:31 am UTC

They were lower energy. I believe they were on the order of 10 MeV.

(EDIT: They ranged from 10 to 40 MeV.)

(EDIT 2: The neutrino pulse lasted 13 seconds. If the velocity of the neutrinos depended in any significant way on their energy, surely this range of energies and corresponding velocities would have been large enough to "blur" the pulse over an interval somewhat longer than that?)

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Re: Well, this could change things

Postby dainbramage » Sat Sep 24, 2011 7:23 am UTC

Diadem wrote:I have a question about SN87A. Why is it the only supernova for which we detected neutrinos? It was over 20 years ago, our ability to detect neutrinos has greatly increased since then. Why don't we detect them for more supernovae?

If neutrinos do travel FTL, then, given that we can't detect what direction they come from, and given that distances to supernovae vary greatly, we would expect neutrino bursts and observed supernovae to be pretty much completely uncorrelated. If we only ever detected one neutrino burst, then how do we know it belonged to SN87A? You can't infer correlation from a dataset of one. It may have been from any other supernova in the following few years or even decades. It would be a coincidence for our only ever detected neutrino burst to arrive at roughtly the same time as a supernova, but supernovae are not so uncommon as to make this completely unlikely. Certainly more likely than a 6 sigma result being due to chance.

But why is it the only one? That's what i can't wrap my head around. Am I missing something obvious here?


Malconstant wrote:Supernovae aren't super common, and they don't all give off enormous bursts of neutrinos. For instance the one that we just saw a couple weeks ago was a type 1A (SN 2011fe), which is a wonderful kind of supernova except that it doesn't give off huge percentages of its energy as neutrinos.

Also, in case there was any confusion, when neutrinos reached us before the light did in the case over 20 years ago that was because the light had to travel through the other debris of the star exploding, whereas the neutrinos just couldn't be bothered to give a fuck about anything, so the neutrinos didn't travel faster than light in a vacuum.


In addition to this, 1987A was close - it originated in the LMC. I think in total ~24 neutrino events occurred thanks to it over several different detectors. Compare that to SN2011fe (which malconstant brought up), which originated in the pinwheel galaxy. Even if it did release neutrinos, the neutrino flux would be ~10-6 of what was recorded from 1987A - which means we've got a bugger all chance of recording a neutrino event from it. Even if our neutrino detectors could manage to detect a reasonable amount of neutrinos from something like it, it wouldn't be discernable from the background anyway.

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Re: Well, this could change things

Postby zombie_monkey » Sat Sep 24, 2011 10:23 am UTC

Is it a possibility that the speed of photons in a vacuum is not the speed limit, but the speed of some neutrinos instead? IIRC only a certain portion of the neutrinos created arrived early? Or was that the supernova? Is interaction with virtual particles enough to slow the photons down enough for this kind of difference? Do neutrinos interact less with virtual particles?

Do we know the speed limit from other experiments other than measuring the speed of light in a vacuum? I vaguely remember it being mentioned the limit speed is probably slightly faster than the one we've arrived at through measurement, because of virtual particle interaction.

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Re: Well, this could change things

Postby Minerva » Sat Sep 24, 2011 2:09 pm UTC

zombie_monkey wrote:Is it a possibility that the speed of photons in a vacuum is not the speed limit, but the speed of some neutrinos instead?


Let's assume that something like that is true, just for the hypothetical sake of argument, and ask some questions.

Why do neutrinos, which have mass, travel faster than photons which do not?

If a massive particle travels faster than light in vacuo, what are the implications of this for special relativity and classical electrodynamics... as well as relativistic quantum field theories which all depend on SR?
What are the implications of this for causality?

Is this superluminal velocity characteristic of only muon neutrinos, or of the other neutrino generations as well?

What makes neutrinos different to other leptons?

If this behavior is different for different generations of neutrinos, why does it apply to one generation of neutrinos but not to the others?
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Re: Well, this could change things

Postby Giallo » Sat Sep 24, 2011 2:11 pm UTC

If it were possible that the neutrinos are tachions (which I don't know), wouldn't this fact be "easy" to check using the fact that their energy would be negative? (it should, right? I haven't checked, too lazy :oops: )
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Re: Well, this could change things

Postby zombie_monkey » Sat Sep 24, 2011 3:01 pm UTC

MInerva, yeah, I was just throwing stuff out there... My idea was that a possible explanation is that something might be slowing photons down that we don't know about. So the speed limit would be even higher than the speed of these neutrinos, rather than their speed itself. I'm still interested, just for the sake of it, whether we know the speed limit from other experiments other than measuring the speed of light in a vacuum.

Minerva wrote:Is this superluminal velocity characteristic of only muon neutrinos, or of the other neutrino generations as well?

What makes neutrinos different to other leptons?

If this behavior is different for different generations of neutrinos, why does it apply to one generation of neutrinos but not to the others?

Yeah, those are a huge problem.

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Re: Well, this could change things

Postby TrlstanC » Sat Sep 24, 2011 3:49 pm UTC

I'd vote for systematic error, but while we're throwing wild theories out there... Does anyone know enough string theory to know if it puts a limit on the maximum length of a neutrino? I have read about some (relatively) recent developments that allow string theory membranes or p-branes to be arbitrarily large, leading to theories like "the universe is a 3D p-brane." What's the reason (and I'm assuming there is one) that neutrinos couldn't be 60meters long? Especially since they interact so rarely, I can imagine that whatever size they actually are, it might not be able to detect their "orientation" to the detector. Or that it could be much more likely to detect a neutrino if it was traveling through the detector in one orientation as opposed to the other.

I'm assuming that this is a simple idea that's ruled out by some straightforward interpretation of string theory, but if anyone knows why, it would be interesting to hear.

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Re: Well, this could change things

Postby doogly » Sat Sep 24, 2011 3:58 pm UTC

It's ruled out by the things we already know. String theory does not change the quantum mechanics and QED we know, it changes things at lower scales.
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Re: Well, this could change things

Postby TrlstanC » Sat Sep 24, 2011 5:02 pm UTC

doogly wrote:It's ruled out by the things we already know. String theory does not change the quantum mechanics and QED we know, it changes things at lower scales.

I was assuming it was ruled out, but was wondering why. For example, if we accept that brane-world is possible in the way that was raised with M-theory then we have D3 branes of an arbitrarily large size, they would have properties described by the open strings whose endpoints are trapped, which would seem to imply that there must be open strings of arbitrarily long length. (I obviously haven't studied or worked through the math to prove those possibilities, so if I've misstated something horrendously, please correct me).

I've just never heard if neutrinos are a kind of lepton that could be defined by an open string like this. I had assumed not since I think we had string theory definitions of neutrinos before we had theories of p-branes, and I believe at the time all particles were defined by extremely small strings (much smaller then originally proposed to describe the nuclear force). But it would be interesting to hear if anyone knew of an upper limit on the size of these kinds of open strings.

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Re: Well, this could change things

Postby Nat » Sat Sep 24, 2011 9:23 pm UTC

curtis95112 wrote:
sourmìlk wrote:
curtis95112 wrote:
sourmìlk wrote:So if we can send messages back in time. What happens if I tell a computer to send a boolean value to itself three minutes ago, at which point the computer saves the value and sends the opposite one back three minutes later?


Either the universe splits in half or your computer can't run that program for some reason.

If it turns out the universe is consistent despite causality being broken, we get to solve NP problems in polynomial time.


What do you mean by "splits in half?" And as an observer just watching the computer, what value do I see when I say "cout <<futureBool ? 'true' : 'false';"


By that I meant every time you send information back to the past, you send it to a parallel universe that's not really your own. So you may receive "True", and send "False, and it's perfectly consistent. More likely (insofar as any of this is likely), you'll find that quantum uncertainty caused your computer to malfunction because the probability of it functioning was zero. Or so says Novikov, http://en.wikipedia.org/wiki/Novikov_self-consistency_principle

You can't program a computer like that, because that would create a paradox, which by definition can't happen. So for whatever reason, that particular computer program is impossible.

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Re: Well, this could change things

Postby invisifly2 » Sat Sep 24, 2011 10:31 pm UTC

How about a few thousand Nutrinoes took Lights car out for a spin, but didn't manage to get it back to Lights house before getting caught?

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Re: Well, this could change things

Postby ojno » Sat Sep 24, 2011 10:39 pm UTC

Do you like reading Internet forum discussions? Do you enjoy watching people being successfully trolled arguing with hopelessly convinced deluded conspiracy theorists?

You're in luck!

For one week only, in recognition of the recent intriguing findings at CERN, the JREF are running a special two for one deal on Relativity denial!

Don't miss out, and remember -- every scientist ever has been collaborating in an effort to deceive you for no coherent reason!

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Neutrino breaks speed of light?

Postby BrettIsEpic » Sun Sep 25, 2011 12:07 am UTC

I'm sorry if there is already a topic about this, however I have a question about the neutrino.

As I explained my question to a friend of mine who isn't great with physics. (Copied and pasted due to laziness. :P )

If you went at 3c/4 (c=speed of light, btw)
And I went at -3c/4
(minus, assuming exact opposite direction)
We would have a relative speed of 3c/2
Or 50% faster than the speed of light
However, if one body was to
increase in speed towards the speed of light...
It would gain weight
And it would become infinitely massive by the time it reaches "c"
The speed of the earth and sun, etc though the universe is unknown
I assume that instruments are not sensitive enough to notice the difference in weigh changes from objects moving quickly in opposite directions
Most of the weight increase happens near the speed of light
It's insanely weighted towards "c"
So what if the neutrinos were headed "against" the Earth's direction?
However, I would find it hard to believe that scientists could make such a crucial mistake.


Thoughts?

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Re: Well, this could change things

Postby scarecrovv » Sun Sep 25, 2011 12:15 am UTC

I had no idea that Relativity Deniers existed! I thought I'd seen it all when I learned about Vaccine Denialism. This is great entertainment. My favorite chunk of conversation in the shorter thread:
Anders Lindman wrote:Ok, let's try again : Could there exist scientific knowledge kept hidden from the public for military purposes?

DrDave wrote:Of course. For example the Manhatten project. But I think that most foreign governments still knew more than the US wanted. So completely secret is unlikely.

Anders Lindman wrote:Is it possible that the Manhattan project was a hoax?

:lol: HAHAHAHAHA!

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Re: Well, this could change things

Postby capefeather » Sun Sep 25, 2011 1:34 am UTC

The Nazis denied relativity.

That guy kind of reminds me of this guy I know. Maybe it's not entirely fair to criticize him because he has pretty severe short-term memory problems, but he's obsessed with airplane crashes and conspiracy theories, and he goes around saying that planes are death traps and that everyone who's flown in a plane is lucky to be alive (inb4 define-"lucky" joke).

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Re: Well, this could change things

Postby Meem1029 » Sun Sep 25, 2011 1:55 am UTC

My oh my some of those posts are absurd. It's quite humorous actually.
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Re: Well, this could change things

Postby Diadem » Sun Sep 25, 2011 3:09 am UTC

Wow, I had a good chuckle out of that. Thanks for the links!

I don't believe this guy is serious though. He must be trolling. Noone can be that crazy.
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Re: Well, this could change things

Postby thoughtfully » Sun Sep 25, 2011 3:13 am UTC

Diadem wrote:Noone can be that crazy.

Famous last words, anyone? :)
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Re: Well, this could change things

Postby Mr_Rose » Sun Sep 25, 2011 3:30 am UTC

thoughtfully wrote:
Diadem wrote:Noone can be that crazy.

Famous last words, anyone? :)

Ah, yes, the poe.
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Re: Well, this could change things

Postby Carnildo » Sun Sep 25, 2011 5:39 am UTC

Giallo wrote:If it were possible that the neutrinos are tachions (which I don't know), wouldn't this fact be "easy" to check using the fact that their energy would be negative? (it should, right? I haven't checked, too lazy :oops: )

If neutrinos were tachyons, the square of their rest mass would be negative. Some experiments have indicated that this might be the case, but measuring the rest mass of a neutrino is a very tricky operation.

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Re: Neutrino breaks speed of light?

Postby gmalivuk » Sun Sep 25, 2011 6:53 am UTC

BrettIsEpic wrote:If you went at 3c/4 (c=speed of light, btw)
And I went at -3c/4
(minus, assuming exact opposite direction)
We would have a relative speed of 3c/2
Or 50% faster than the speed of light
Nope. With relativity, it's not so simple.
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Re: Neutrino breaks speed of light?

Postby Tass » Sun Sep 25, 2011 8:32 am UTC

gmalivuk wrote:
BrettIsEpic wrote:If you went at 3c/4 (c=speed of light, btw)
And I went at -3c/4
(minus, assuming exact opposite direction)
We would have a relative speed of 3c/2
Or 50% faster than the speed of light
Nope. With relativity, it's not so simple.


And we already have a sticky thread for it because this question comes all the time. I propose we move all the generic time travel, FTL and relativity stuff there, and keep this thread about the experiment.

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Re: Well, this could change things

Postby Giallo » Sun Sep 25, 2011 12:56 pm UTC

Carnildo wrote:
Giallo wrote:If it were possible that the neutrinos are tachions (which I don't know), wouldn't this fact be "easy" to check using the fact that their energy would be negative? (it should, right? I haven't checked, too lazy :oops: )

If neutrinos were tachyons, the square of their rest mass would be negative. Some experiments have indicated that this might be the case, but measuring the rest mass of a neutrino is a very tricky operation.


Ok, so if we have [imath]m = im'[/imath] with [imath]m'[/imath] real moving with a speed [imath]v > c[/imath] we get [imath]\gamma = \frac{1}{\sqrt{1 - \frac{v^2}{c^2}}} = -i\gamma'[/imath] with [imath]\gamma'>0[/imath]. The energy will be [imath]E_v = \gamma E_0 = -i\gamma' mc^2 = \gamma' m' c^2[/imath], right?
Now my question is: [imath]m'[/imath] should be positive or negative? If it's negative would it be possible to check if a neutrino is a tachion shooting them against matter and mesuring the variation of energy?
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Re: Well, this could change things (neutrinos)

Postby yurell » Sun Sep 25, 2011 1:25 pm UTC

Shooting neutrinos against matter is the hard part.
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Re: Well, this could change things (neutrinos)

Postby Giallo » Sun Sep 25, 2011 1:37 pm UTC

Yeah, I thought so... after all they shoot neutrinos through the earth for 730km in the experiment :wink:
But would it be theoretically possible, if we were able to produce enough neutrinos to have a significant number of events in this sense?
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Re: Well, this could change things (neutrinos)

Postby BlackSails » Sun Sep 25, 2011 2:04 pm UTC

http://blogs.discovermagazine.com/cosmi ... ent-182263

I thought that was a pretty interesting idea.

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Re: Well, this could change things

Postby Malle » Mon Sep 26, 2011 11:44 pm UTC

Minerva wrote:http://webcast.web.cern.ch/webcast/

Webcast. Now. Watch.
Any possibility of a recorded version of this, since I couldn't catch it live?

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Re: Well, this could change things

Postby WarDaft » Tue Sep 27, 2011 1:30 am UTC

Minerva wrote:
zombie_monkey wrote:Is it a possibility that the speed of photons in a vacuum is not the speed limit, but the speed of some neutrinos instead?


Let's assume that something like that is true, just for the hypothetical sake of argument, and ask some questions.

Why do neutrinos, which have mass, travel faster than photons which do not?


This could (but not necessarily should) be explained by the fact that neutrino interact with practically nothing. After all, how many forms of EM radiation could be easily beamed through 730 KM of the Earth's crust? If we find that neutrinos have little-to-no interaction with the quantum vaccuum, but photons and other particles do and to a similar extent, that could be a sign that the 'speed of light' is actually just a little bit faster than we thought, and not actually the speed photons assume assume in the not-perfectly-empty quantum vacuum. Of course, if the curve of relativistic mass vs. velocity does not agree with the possibility for a slightly higher c, then that's out. I have no idea if it has been measured finely enough to make such a ruling.

It also supports more energetic neutrinos travelling slightly faster than less energetic neutrinos, as opposed to neutrinos with imaginary mass, which would have the reverse effect.
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Re: Well, this could change things

Postby Malconstant » Tue Sep 27, 2011 2:07 am UTC

WarDaft wrote: Of course, if the curve of relativistic mass vs. velocity does not agree with the possibility for a slightly higher c, then that's out. I have no idea if it has been measured finely enough to make such a ruling.

Afraid so. the universal speed limit of c has been verified for particle accelerator physics to orders of magnitude better than this difference. Maybe some neutrinos can move faster than c, but this faster speed is not "the new speed limit" for everything else. That's still c.
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Re: Well, this could change things (neutrinos)

Postby Game_boy » Tue Sep 27, 2011 3:42 pm UTC

Tracking this thread.
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Re: Well, this could change things

Postby Giallo » Tue Sep 27, 2011 5:30 pm UTC

Malle wrote:
Minerva wrote:http://webcast.web.cern.ch/webcast/

Webcast. Now. Watch.
Any possibility of a recorded version of this, since I couldn't catch it live?


http://cdsweb.cern.ch/record/1384486

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Re: Well, this could change things

Postby Technical Ben » Tue Sep 27, 2011 5:49 pm UTC

Malconstant wrote:
WarDaft wrote: Of course, if the curve of relativistic mass vs. velocity does not agree with the possibility for a slightly higher c, then that's out. I have no idea if it has been measured finely enough to make such a ruling.

Afraid so. the universal speed limit of c has been verified for particle accelerator physics to orders of magnitude better than this difference. Maybe some neutrinos can move faster than c, but this faster speed is not "the new speed limit" for everything else. That's still c.


Just to make sure the clarification is made, you do mean the "universal speed limit" has been verified to c? As suppose to the speed of the photons being verified to c? We can measure the effects of relativity directly, without the speed limit of photons, right?

One possible thing I saw posted was that neutrinos avoid any interactions that might interrupt or slow down a photon. This still leaves the problem that the speed of c is still fixed by the other equations.
It's all physics and stamp collecting.
It's not a particle or a wave. It's just an exchange.

Malle
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Re: Well, this could change things

Postby Malle » Tue Sep 27, 2011 6:03 pm UTC

Giallo wrote:
Malle wrote:
Minerva wrote:http://webcast.web.cern.ch/webcast/

Webcast. Now. Watch.
Any possibility of a recorded version of this, since I couldn't catch it live?


http://cdsweb.cern.ch/record/1384486

:wink:
Splendid; thanks :D Watching it now.

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Malconstant
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Re: Well, this could change things

Postby Malconstant » Tue Sep 27, 2011 6:44 pm UTC

Technical Ben wrote:Just to make sure the clarification is made, you do mean the "universal speed limit" has been verified to c? As suppose to the speed of the photons being verified to c? We can measure the effects of relativity directly, without the speed limit of photons, right?

One possible thing I saw posted was that neutrinos avoid any interactions that might interrupt or slow down a photon. This still leaves the problem that the speed of c is still fixed by the other equations.

Yeah, we have tremendously good evidence that the speed of light in a vacuum, c, is the universal speed limit for everything we've ever seen, except for maybe goddamn neutrinos. This is verified through relativistic effects, rather than by racing particles against photons. These relativistic effects depend on a parameter for a universal speed limit, and our precision of measurements in accelerators has given us our most accurate experimental verification/measurement of the universal speed limit = the speed of light. And this precision beats out the difference between the photon and neutrino by orders of magnitude. So light's standing as the universal speed limit isn't going anywhere, it has tremendous observational evidence and experimental consequence.

Maybe this one flavor of neutrino is a tachyon. Maybe there's a wormhole between CERN and Italy. Maybe it was systematic error (which will take about a year to be conclusively tested at other sites). But regardless of the answer, Einstein's relativity isn't going anywhere. It never will go anywhere. The furthest it will ever leave us will be as a regime-approximation to an even weirder more general theory. No matter what. This is because what's gone on for the past hundred years hasn't been a rationalist thought experiment.
Technical Ben wrote:PS, doogly, way to miss the point.


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