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Old 07-17-2017, 08:39 PM
Peanuthead Peanuthead is offline
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What is the 2nd fastest thing?

We all know that light is the fastest thing in the universe. (And please don't start an argument about that. Take it as a given.) So, what is the 2nd fastest thing? I'm thinking electricity. Has the speed of electricity been measured? How fast is it? Must be at least close to light, don't you think? Any way to give it a boost so that it equals (or exceeds) light? That would be cool.
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Old 07-17-2017, 08:54 PM
boffking boffking is offline
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All electromagnetic radiation travels at the same speed, not just visible light.
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Old 07-17-2017, 08:55 PM
Bill Door Bill Door is online now
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The speed of gravity is the same as the speed of light, so tied for first, or tied for second, take your pick. The wave propagation speed of electricity varies with the medium, but can get up to 0.99c, so a close second. If you're talking about the speed of an actual electron in a wire, that's a lot slower.
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Old 07-17-2017, 08:59 PM
Palooka Palooka is offline
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Electrons in a wire are going to be way slower than random things flying around in outer space.

My WAG is some space radiation is the fastest non-light thing and it's basically moving just short of the speed of light.
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Old 07-17-2017, 09:01 PM
Peanuthead Peanuthead is offline
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Originally Posted by boffking View Post
All electromagnetic radiation travels at the same speed, not just visible light.
Does that mean radio waves and television transmissions?
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Old 07-17-2017, 09:02 PM
snfaulkner snfaulkner is online now
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Does that mean radio waves and television transmissions?
yep
  #7  
Old 07-17-2017, 09:06 PM
yellowjacketcoder yellowjacketcoder is offline
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I'm going to put in for Neutrinos, which are so fast they are sometimes erroneously measured to go faster than light.
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Old 07-17-2017, 09:10 PM
Peanuthead Peanuthead is offline
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I'm pretty sure this thread is going to go way beyond my comprehension but I'll try to hang in there. I've already learned something. Yay! Let's hear it for fighting ignorance!
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Old 07-17-2017, 09:13 PM
Channing Idaho Banks Channing Idaho Banks is offline
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A comet has some good speed as it passes its sun.
  #10  
Old 07-17-2017, 09:16 PM
Dr. Strangelove Dr. Strangelove is offline
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The Oh-My-God particle, at 99.999999999999999999999510% of the speed of light.
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Old 07-17-2017, 09:28 PM
LSLGuy LSLGuy is offline
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Originally Posted by Channing Idaho Banks View Post
A comet has some good speed as it passes its sun.
Not even remotely in the same league.

The speed of time/gravity/light/EMR in vacuum is 3E8 meters/sec or 10,000 kilometers per second.

The famous Halley's comet is going about 55 kilometers per second. About 1/200th the speed of time/gravity/etc.

Comets with longer orbits and longer periods can go much faster. So instead of 1/200th the speed of time/gravity/etc they're going 1/50 or 1/30th the speed.

Still nowhere close.


Back to the OP: The magic about the speed of time/gravty/etc is that it is a fixed number. There's nothing else in the universe like that. Any other physical motion or speed of propagation happens at a speed that depends to circumstances. So it isn't sensible to talk about the "second-fastest thing".

It might be possible to talk about the "second fastest combination of thing & circumstances". But even then we get into questions about measurement accuracy, etc.

E.g. the speed of light propagation through fiberoptic glass is measurably obviously significantly slower than the speed of light propagation through a true idealized vacuum. But what if we built slightly better glass that halved the difference? And improved it again to halve the difference again? How fast is "as fast as light in vacuum (the "official c"), less some teeny tiny amount we can barely detect?

Last edited by LSLGuy; 07-17-2017 at 09:29 PM.
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Old 07-17-2017, 09:30 PM
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All those other things are physically constrained. The speed of light (in a vacuum) is not. That's a really fundamental difference. The speed of light isn't some arbitrary "speed", it's the rate at which causality propagates in spacetime, and as such is one of the constants of the universe. Lots of things travel slower than light, but those are limited by physical properties and not universal constants. For example, the propagation speed of light in various media other than a vacuum, or the speeds to which subatomic particles can be accelerated in particle colliders. But those aren't particularly interesting limits. They depend on arbitrary material properties or available energies.

Last edited by wolfpup; 07-17-2017 at 09:33 PM.
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Old 07-17-2017, 09:49 PM
Darren Garrison Darren Garrison is offline
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Originally Posted by LSLGuy View Post
Not even remotely in the same league.

The speed of time/gravity/light/EMR in vacuum is 3E8 meters/sec or 10,000 kilometers per second.
I'll give you a moment while you facepalm.

Meanwhile, I also immediately thought "neutrinos" when I saw the thread title. Yes, you get oh my god particles under very extreme circumstances, but your garden variety neutrinos travel at just a whisker below the speed of light.
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Old 07-17-2017, 10:00 PM
LSLGuy LSLGuy is offline
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Nice catch. Thanks.

3E8 meters/sec = 3E5 km/sec = 30,000 kilometers/sec. So the rest of my numbers are mis-stated by a factor of 3.

Last edited by LSLGuy; 07-17-2017 at 10:03 PM.
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Old 07-17-2017, 10:06 PM
LSLGuy LSLGuy is offline
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One more time: Edit upon edit upon timed out edit:


Nice catch. Thanks.

3E8 meters/sec = 3E5 km/sec = 300,000 kilometers/sec. So the rest of my numbers are mis-stated by a factor of 30.

I had some alarm bells in my head as I was typing. That 1/200 number felt too big. But like an idiot I just ignored the alarm bells & hit [submit].

Halley's apehelion isn't 1/200th of c. It's 1/6000th.

Must be time for my sabbatical from the 'Dope. That's 4 dumb mistakes in utterly unrelated posts in the last 4 days.
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Old 07-17-2017, 11:18 PM
Francis Vaughan Francis Vaughan is offline
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I would vote for neutrinos as well. Indeed they would seem to fit the OP's question as perfectly as we know.

OTOH there has been some suggestion that due to the nature of the vacuum, there is an intrinsic very slight roughness to the path that photons take through space, so even though they travel at c, they do so on a very slightly longer path, and if measured at macroscopic scales the apparent speed is very slightly less than c. I'm not sure that this could not however be more akin to suggesting that the vacuum has a refractive index ever so slightly larger than one.
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Old 07-18-2017, 08:10 AM
Chronos Chronos is offline
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We can't actually compare the speed of neutrinos to the speed of the Oh-my-god particle. In both cases, what we actually measure directly is the energy. If you know the mass of the particle and its energy, then it's straightforward to calculate its speed. We're pretty sure that OMG was a proton, so we can use the mass of a proton (which we know very well) to calculate its speed. But we don't actually know the mass of the neutrino. We have an upper bound for the mass, so we can calculate a lower bound for the speed, but they might be much, much lighter, and so must be going even faster to reach that energy.

One can in principle turn that around, by taking neutrinos that have traveled a very long distance, and use the difference in their arrival time, combined with their energies, to determine their mass. This has been done with the neutrinos from supernova 1987a. But the error bars in the measurements were too large, and so you can get better results from other experiments, and we haven't been able to reproduce the measurement, since we haven't had any sufficiently distant sources of neutrinos since 1987.
  #18  
Old 07-18-2017, 09:43 AM
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Quote:
Originally Posted by Peanuthead View Post
We all know that light is the fastest thing in the universe.
How about the expansion of the universe itself?
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Old 07-18-2017, 09:44 AM
Darren Garrison Darren Garrison is offline
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But whatever the speed of a neutrino is, it is fast, and it is innate. To get an "oh my god" particle you have to take a common slow particle and stick it in a gigantic natural accelerator. So can you say that anything other than a neutrino travels at closer to the speed of light without outside help?
  #20  
Old 07-18-2017, 09:53 AM
Pleonast Pleonast is offline
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Originally Posted by wolfpup View Post
All those other things are physically constrained. The speed of light (in a vacuum) is not. That's a really fundamental difference. The speed of light isn't some arbitrary "speed", it's the rate at which causality propagates in spacetime, and as such is one of the constants of the universe.
The speed of light in a vacuum is physically constrained. It may not vary from the constant c.
  #21  
Old 07-18-2017, 09:56 AM
Leo Bloom Leo Bloom is offline
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Light is always in Hammertime.
  #22  
Old 07-18-2017, 10:51 AM
enalzi enalzi is offline
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Halley's apehelion isn't 1/200th of c. It's 1/6000th.
Just for a point of comparison, that's roughly equivalent to a giant tortoise vs. the Concorde.
  #23  
Old 07-18-2017, 11:12 AM
Chronos Chronos is offline
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Quote:
Quoth Darren Garrison:

But whatever the speed of a neutrino is, it is fast, and it is innate.
No speed other than c is ever innate to anything. There's no reason you couldn't have a neutrino sitting at rest relative to the Earth. If it's got a lot of energy, it's because some process gave it that energy.

I suppose you could say that it's "innate" in the sense that, in the typical processes we know of by which neutrinos are produced, the neutrino ends up with a large amount of energy relative to the zero-momentum frame of the process that creates it. But it's tough to compare that to the Oh-my-god particle: What's the typical process by which a proton is produced? The vast majority of protons in the Universe date back to a time when our knowledge of the Universe is sketchy at best, and the production process of those protons was surely highly energetic. If anything, we could say that we observe slow protons only because external processes have acted to slow them down.
  #24  
Old 07-18-2017, 11:41 AM
ZonexandScout ZonexandScout is offline
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The speed of gravity is the same as the speed of light, so tied for first, or tied for second, take your pick. The wave propagation speed of electricity varies with the medium, but can get up to 0.99c, so a close second. If you're talking about the speed of an actual electron in a wire, that's a lot slower.
Knowing the velocity of propagation (VoP) for an electrical pulse in a cable or conductor is essential to using a time domain reflectometer (TDR). We normally test a cable to ascertain the VoP before working on it or performing measurements.

The major contributing factor for the VoP is the construction of the cable. The distance between the conductors and the insulating material used can make a huge difference. For standard electrical cables (i.e., cables that were not specially constructed to be used in scientific experiments or to achieve much faster current flow), the VoP ranges from about 72% to 88% of the speed of light. I've never worked on one that exceeded 90%, but I'm sure they exist.
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Old 07-18-2017, 12:41 PM
wolfpup wolfpup is offline
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The speed of light in a vacuum is physically constrained. It may not vary from the constant c.
Not to nitpick, but I would argue with that wordsmithing. This is just saying that the speed of light is subject to the laws of physics. But this is not the same as saying that it is arbitrarily constrained by material properties, like the energy level of a particle or the wave-propagation properties of a material. I was just trying to get across the idea that the speed of light in a vacuum is innate, fundamental to the nature of spacetime. You can't tweak space or add energy to make light go faster -- in effect, its speed is already infinite, since photons experience zero time and move with the speed of causality.
  #26  
Old 07-18-2017, 12:45 PM
Whack-a-Mole Whack-a-Mole is offline
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My vote is for the Oh-My-God particle:

Quote:
On the night of October 15, 1991, the Fly's Eye detected a proton with an energy of 3.20.91020 electron volts.[1,2] By comparison, the recently-canceled Superconducting Super Collider (SSC) would have accelerated protons to an energy of 20 TeV, or 21013 electron volts—ten million times less. The energy of the Oh My God particle seen by the Fly's Eye is equivalent to 51 joules—enough to light a 40 watt light bulb for more than a second—equivalent, in the words of Utah physicist Pierre Sokolsky, to “a brick falling on your toe.” The particle's energy is equivalent to an American baseball travelling fifty-five miles an hour.

<snip>

How fast was it going? Pretty fast.

So taking 3108 metres per second as the speed of light, we find that the particle was traveling 2.9999999999999999999999853108 metres per second, thus 1.46710−15 metres per second slower than light—one and a half femtometres per second slower than light. If God's radar gun is slightly out of calibration, this puppy's gonna be doin' hard time for speeding. After traveling one light year, the particle would be only 0.15 femtoseconds—46 nanometres—behind a photon that left at the same time.

SOURCE: https://www.fourmilab.ch/documents/OhMyGodParticle/

Last edited by Whack-a-Mole; 07-18-2017 at 12:46 PM.
  #27  
Old 07-18-2017, 01:07 PM
Stranger On A Train Stranger On A Train is offline
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Originally Posted by Palooka View Post
Electrons in a wire are going to be way slower than random things flying around in outer space.
The drift velocity of electrons in a conductor is on the order of millimeters per hour. The phase velocity of electrical current depends upon the construction of the cable and insulation, but it is on the order of 80% of c, which is fast enough to not matter for normal purposes but does result in enough latency for submarine communications cables that fiber optic cables are necessary for high data rate applications. (Using optical signals also provides substantially more bandwidth per cable than electrical signals.)

As a class of particles, neutrinos are probably a reasonable guess as the "next fastest particle", but particles accelerated by the Penrose or Blandford–Znajek process can increase in momentum to any arbitrary fraction of c, and this is hypothesized to be a mechanism by which quasars continually produce supernova levels of radiation. On the other hand, the speed of neutrinos is limited to the energy of the beta particle it decays from and mass of the neutrino. You could, of course, accelerate a beta particle to any speed before it decays, but "second fastest thing" is going to be an arbitary selection of some object with mass being accelerated to c minus some infinitesimal amount. While the so-called "Oh My God particle" was moving very fast, statistically it is unlikely to a point of certainty that the Earth has encountered anything near the fastest particle in the universe.

Note that while we refer to c colloqually as "the speed of light", it is actually the speed of propagation of interactions in Minkowski spacetime. All gauge bosons (the photon, the gluon, and the hypothetical graviton) and any other massless particles that may exist beyond the Standard Model of particle physics have to move exactly at c by fundamental nature.

Stranger

Last edited by Stranger On A Train; 07-18-2017 at 01:12 PM.
  #28  
Old 07-18-2017, 01:20 PM
Chronos Chronos is offline
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Hm... I did some more digging, and apparently there's been a neutrino event detected with an energy of 2e15 eV. Given a maximum neutrino mass of ~1 eV (though I think there are tighter bounds than that, even, now), that means a gamma factor of 2e15, much greater than OMG's 3e11. If you really want, you can work out to what that means as a speed, but at that point you're writing so many nines that it's much more sensible to just compare gammas.
  #29  
Old 07-18-2017, 02:10 PM
Whack-a-Mole Whack-a-Mole is offline
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Originally Posted by Chronos View Post
Hm... I did some more digging, and apparently there's been a neutrino event detected with an energy of 2e15 eV. Given a maximum neutrino mass of ~1 eV (though I think there are tighter bounds than that, even, now), that means a gamma factor of 2e15, much greater than OMG's 3e11.
The OMG particle had an energy of 3.20.91020 eV.

Last edited by Whack-a-Mole; 07-18-2017 at 02:10 PM.
  #30  
Old 07-18-2017, 02:39 PM
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The OMG particle had an energy of 3.20.91020 eV.
That proton could not only smash your window, it could also knock your grandmother's framed family portrait off the mantelpiece and smash it to bits!
  #31  
Old 07-18-2017, 02:50 PM
Lemur866 Lemur866 is offline
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But the thing about measure the speed of various objects and particles in the universe is that we're always measuring their speed relative to some other reference frame. So some proton hits a detector going 99.999999999% of c. So that's the fastest thing? No, because we can always say that the the whole goddam Earth was traveling at 99.9999999% of c, and it was the particle that was stationary.

So any measured speed of anything in the universe could always be higher or lower if we just change the reference frame. Unless that thing is traveling at c, in which case it doesn't matter what crazy reference frame we use, we always measure it at c.

A neutrino emitted from the Sun is traveling really really fast relative to the Sun. But if we measure it relative to another neutrino emitted in the opposite direction, it's traveling even faster. It doesn't matter what we measure, there's always going to be something faster.
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Old 07-18-2017, 02:58 PM
Pleonast Pleonast is offline
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Originally Posted by wolfpup View Post
Not to nitpick, but I would argue with that wordsmithing. This is just saying that the speed of light is subject to the laws of physics. But this is not the same as saying that it is arbitrarily constrained by material properties, like the energy level of a particle or the wave-propagation properties of a material. I was just trying to get across the idea that the speed of light in a vacuum is innate, fundamental to the nature of spacetime. You can't tweak space or add energy to make light go faster -- in effect, its speed is already infinite, since photons experience zero time and move with the speed of causality.
I think the trouble is you're conflating "physical" and "material". There is no material constraint on the speed of light in a vacuum (since there is no matter involved). But, as you explain, there is a physical constraint on the speed of light in a vacuum--the physics of the universe permit no other speed.
  #33  
Old 07-18-2017, 05:07 PM
Chronos Chronos is offline
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Quote:
Quoth Whack-a-Mole:

The OMG particle had an energy of 3.20.91020 eV.
And a rest mass (assuming it was a proton) of approximately 1e9 eV. The energy divided by the rest mass gives you the gamma.

In other words, the OMG particle had more energy than the highest-energy neutrino, but only because protons are much more massive than neutrinos.
  #34  
Old 07-18-2017, 06:35 PM
Chopsticks Chopsticks is offline
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For practical definitions of fast, I'd agree with OMG, because we can calculate how fast it was going. For more oddball situations...

AFAIK, Kamiokande demonstrated that neutrinos have mass and therefore can't travel at c, but couldn't calculate what the mass was. I don't know if any more recent experiments got us any closer to a value, so it's not really possible to say how close to c it can go. But, watch supernovae for long enough and you might find a super-OMG neutrino.

Cherenkov radiation. It may not be anywhere near 3e8 m/s, but being able to say "this particle traveled through air faster than the speed of light in air" is fast and cool.

With quantum effects, speed is probably closer to NaN than 'very fast', but quantum tunneling, and general effects like electron jumping between atomic orbitals, are traveling a non-zero distance in a very very very small time. Hawking radiation from the "photon travels faster than c to escape the black hole" point of view.

Under sort-of-illusionary speed, you have expansion of space and galaxy-sized pairs of scissors, where two objects move faster than c relative to a third observer, but each object itself is slower than c.

For slowest speed, I nominate 'how long is it until lunch'.
  #35  
Old 07-18-2017, 07:18 PM
Chronos Chronos is offline
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Even if we can't say precisely how fast that super-neutrino was moving, we can still say that its gamma factor was at least four orders of magnitude greater than OMG's. Given that, I think that it's probably safe to say that the fastest neutrino in the Universe is probably faster than the fastest proton in the Universe, even though we've (probably) never observed either.
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Old 07-18-2017, 08:38 PM
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Chronos, I know you're too smart to forget Gallilean relativity, so I'm puzzled by your statements about one thing being "faster" than another. In some reference frame the proton is faster than the neutrino, and in fact in some reference frame the neutrino is standing still. So how can you talk about one thing being absolutely faster than another thing?
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Old 07-18-2017, 10:15 PM
Chronos Chronos is offline
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Would you be happier if I said "in any reasonable choice of reference frame"? Or "Any reference frame that anyone would ever use for any purpose other than making the notion of 'motion' seem absurd"?
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Old 07-18-2017, 11:39 PM
Claude Remains Claude Remains is offline
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I think Chronos is post padding now that he's hit 70,000.

- Ducks and runs-

Last edited by Claude Remains; 07-18-2017 at 11:40 PM.
  #39  
Old 07-19-2017, 07:07 AM
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Note that beta decay and fusion aren't the only way to make neutrinos. Whatever cosmic furnace is able to churn out OMG protons will very likely churn out mesons that will decay to produce OMG neutrinos of similar energies and therefore much higher speeds. In other words, it is difficult to imagine making crazy high-speed protons without also making even crazier higher-speed neutrinos at the same time.
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Old 07-19-2017, 07:24 AM
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What is the 2nd fastest thing?

Bad news.
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Old 07-19-2017, 07:45 AM
Darren Garrison Darren Garrison is offline
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Originally Posted by Pasta View Post
and therefore much higher speeds
Well, not exactly "much." Shaving this close to the speed of light, we are arguing about speed differences of something like millimeters per second.
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Old 07-19-2017, 07:49 AM
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Well, not exactly "much." Shaving this close to the speed of light, we are arguing about speed differences of something like millimeters per second.
*shrug*. Relative terms are... relative. "s/speed/gamma/g" if you'd rather that.
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Old 07-19-2017, 07:53 AM
Chronos Chronos is offline
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Probably true, with the caveat that we have no idea what the OMG furnace is, or how it works. But whatever it is, that's certainly a reasonable guess.
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Old 07-19-2017, 07:56 AM
Chronos Chronos is offline
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Darren Garrison, put it this way: If you had an OMG proton and an OMG neutrino, emitted from the same source and traveling in the same direction, and if you were riding along in the proton's reference frame, the neutrino would still zip past you very quickly.
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Old 07-19-2017, 01:24 PM
Stranger On A Train Stranger On A Train is offline
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Of course, from the reference frame of the neutrino, the proton is moving at the same speed. It is probably more sensible to talk in terms of a maximum gamma (that is the Lorentz contraction factor for anybody who is confused) from an arbitrary reference frame, but as a practical matter, any no-zero-mass particle could be accelerated to any speed short of c by successive Penrose or other gravitational momentum transfer processes regardless of the energy it had when it was produced, so there is no upper infinitesimal ceiling to particle kinetic energy or speed short of conservation of the total momentum of the universe. There is probably a practical upper limit of potential momentum transfer given the mass of the 'local' universe and time, and it is statistically certain that the cosmic particles we have observed do not even approach that by many orders of magnitude.

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Old 07-19-2017, 02:04 PM
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  #47  
Old 07-19-2017, 02:29 PM
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I'm not very good at physics. So bear with me. I've read that some particles come in twins that have the same "spin" - and that each will maintain the same spin even if the particles are separated. As soon as the spin of one is affected, the spin of the other will be too. So wouldn't whatever force transmits the spin between the twin particles be the fastest thing?
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Old 07-19-2017, 02:40 PM
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There is no instantaneous force or transmission of information between separated particles. You are thinking of entangled states.
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Old 07-19-2017, 02:55 PM
Stranger On A Train Stranger On A Train is offline
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You are referring to the quantum entaglement, in which particles have innately complementary states regardless of the separation distance between them. The change of states is apparently instantaneous (if you observe the change of state of a local particle, you will see the complementary change with a delay appropriate to the distance it takes light to travel from the distant particle) but it is wrong to think of this as having a speed or rate, and there is no 'force' or other exchange between them. They're just tied together in an apparently nonlocal but causal fashion. Although there are various interpretations of quantum mechanics which attempt to rationalize this behavior there is as yet no falsifiable hypothesis for how it works other than that it is a characteristic of nature at the level of single particles and very small systems where quantum mechanics dominates.

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Old 07-19-2017, 03:24 PM
Really Not All That Bright Really Not All That Bright is offline
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Join Date: May 2003
Location: Florida
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That's the thing. So there is actually an appreciable delay before the change in the state of the distant particle?
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