Neutrino speed

Old but meh.
As some may remember last year a team of scientists recorded neutrinos going faster than light. Leading to a ton of poorly written science articles and this picture making the rounds.

Anyhow new tests were run which were unable to reproduce the results. Analysis of the initial test area found error sources + Show Spoiler +

http://www.wired.com/wiredscience/2012/02/neutrinos-faulty-cable/

A few days ago those errors were confirmed.

Physicists at the CERN laboratory have put the final nail in the coffin for the idea that neutrinos can travel faster than the speed of light. They also confirmed that the groundbreaking results from 2011 can be blamed on faulty equipment.

http://www.wired.com/wiredscience/2012/06/neutrinos-cant-beat-light/

cliffs: neutrinos don't go faster than light, Einstein wins.

[x] did read that before
[ ] profit

tesla is a fckin badass

whats the point of this thread again?

So some scientists concluded that there are particles with speed higher than that of light, then they said they were wrong and that is enough for you to conclude that they are now correct? Don't you think that they might be wrong a second time? Not that I know what's the truth here but quantum particles are proven to communicate instantaneously, surpassing the speed of light - Quantum Entaglement. It's not said that they communicate via a sent and received wave of energy such as light but quantum physicists believe they are "teleporting" information (lol there should be a better way to explain it i'm sure). So I guess if that is possible, it might be possible that there are particles we cannot detect that are faster than light. I dunno, just food for thought.

What is also important, is that this scientific community faced a problem for which they had no explanation and they decided to reveal all the data they had to the public in order to let people to try to explain it.
So they had no problem saying : "we don't understand", which doesn't happen very often in other fields.

On June 11 2012 08:55 D_smart_S wrote: So some scientists concluded that there are particles with speed higher than that of light, then they said they were wrong and that is enough for you to conclude that they are now correct? Don't you think that they might be wrong a second time? Not that I know what's the truth here but quantum particles are proven to communicate instantaneously, surpassing the speed of light - Quantum Entaglement. It's not said that they communicate via a sent and received wave of energy such as light but quantum physicists believe they are "teleporting" information (lol there should be a better way to explain it i'm sure). So I guess if that is possible, it might be possible that there are particles we cannot detect that are faster than light. I dunno, just food for thought.

There is something quite different between you and those scientists. They don't conclude as fast as you can, they don't assert things just saying "that are proven".
So, no, they never said they demonstrated (or concluded) that there were particles with a speed higher than the one of light. They just said : "here is the experiment we made. Results are odd, and we can't explain it, let's check again, and if you want, do it with us". Next, they tried to repeat the experience and did not find the same results, and in the meantime found an explanation for the first odd results.

On June 11 2012 08:58 kingpowa wrote: What is also important, is that this scientific community faced a problem for which they had no explanation and they decided to reveal all the data they had to the public in order to let people to try to explain it. So they had no problem saying : "we don't understand", which doesn't happen very often in other fields.

what also makes this such a travesty is that the lead researcher of the faulty experiment resigned. He did everything 100% right by the scientific method and ideology he shouldn't be punished when errors were found in his experiment.

@dsmart...entanglement doesn't actually transmit information faster than light, it's a common misconception. Entanglement can roughly be explained as the following. You take a red rock and a blue rock. Put both rocks in a bag, close ur eyes and mix the bag. Then with ur eyes still closed take a rock out and throw it across the solar system. When u check the rock in the bag u instantly know the color of the rock that is at the other side of the solar system. That's, roughly, entanglement. No information was transferred faster than light.
More/better info http://plato.stanford.edu/entries/qt-entangle/

I felt cool when this first happened many months ago, a mate told me, they just found some thingys that go faster than light. And I told him, no, it's wrong calculations, they don't go faster. Really felt it in my gut, they don't.

Remeber I saw a talk about a recent supernova, and they had calculated when the light came and the neutrino's. There's no way they would come when they did unless they were travelling at the same speed, the difference would be mindboggling.

yay, think it was on Sixty Symbol channel, they also interview the Professors there when the news came about the speed thingy, and they're really skeptic, saying it's prolly not the case, and after it's debunked, ye, kinda like we suspected.

Yeap

On June 11 2012 09:29 palak wrote: Show nested quote + On June 11 2012 08:58 kingpowa wrote: What is also important, is that this scientific community faced a problem for which they had no explanation and they decided to reveal all the data they had to the public in order to let people to try to explain it. So they had no problem saying : "we don't understand", which doesn't happen very often in other fields. what also makes this such a travesty is that the lead researcher of the faulty experiment resigned. He did everything 100% right by the scientific method and ideology he shouldn't be punished when errors were found in his experiment. @dsmart...entanglement doesn't actually transmit information faster than light, it's a common misconception. Entanglement can roughly be explained as the following. You take a red rock and a blue rock. Put both rocks in a bag, close ur eyes and mix the bag. Then with ur eyes still closed take a rock out and throw it across the solar system. When u check the rock in the bag u instantly know the color of the rock that is at the other side of the solar system. That's, roughly, entanglement. No information was transferred faster than light. More/better info http://plato.stanford.edu/entries/qt-entangle/

man, I don't want to argue but Quantum Entanglement has nothing to do with what you just said, absolutely nothing. If I take a hair from ur hair and put it a 1000 miles away and I put you under some stress and measure your reaction ( I can't remember which factors are measured, I think it's the electrical discharge or stg like that) the cells in the hair that is 1000 miles away from you will give out the exact same signal you did at the exact same time to the tiniest fraction of time we can measure - in other words instantly. The reading of the two signals are graphs that match 100% ( like a sharkscope graph). That's the way quantum particles communicate, that's a very basic fact but I will not bother arguing about it. It's an instant transfer of information but not by means of a wave of energy. That's the fascinating side of Quantum Physics.

On June 11 2012 10:48 D_smart_S wrote: man, I don't want to argue but Quantum Entanglement has nothing to do with what you just said, absolutely nothing. If I take a hair from ur hair and put it a 1000 miles away and I put you under some stress and measure your reaction ( I can't remember which factors are measured, I think it's the electrical discharge or stg like that) the cells in the hair that is 1000 miles away from you will give out the exact same signal you did at the exact same time to the tiniest fraction of time we can measure - in other words instantly. The reading of the two signals are graphs that match 100% ( like a sharkscope graph). That's the way quantum particles communicate, that's a very basic fact but I will not bother arguing about it. It's an instant transfer of information but not by means of a wave of energy. That's the fascinating side of Quantum Physics.

No you idiot, you can't put the hair you have under stress and make the hair far away change, you can merely observe the hair you have and know the state of the other one.

In other words: You can not use it to transfer data. Information can not be transferred faster than c.

Just because you read ridiculously sensationalized articles like this one: http://www.nature.com/news/2008/080813/full/news.2008.1038.html
doesn't mean information can actually be transferred faster than c, although you can measure something and get a response instantaneously (have them tangled)
doesn't mean you can devise a way to transfer information that way.

^transfer of information between any 2 particles is forbidden by relativity, which yes does still apply to quantum mechanics.
Edit: meant to apply to dsmart, not taco

google "instant transfer of information" , pretty sure it's contrary of being a "fact". But i guess Illuminati owns that site too.

http://www.physicsforums.com/showthread.php?t=472775

On June 11 2012 08:55 D_smart_S wrote: So some scientists concluded that there are particles with speed higher than that of light, then they said they were wrong and that is enough for you to conclude that they are now correct?

Yeah, fuck the scientific method. Once is good enough for me. I love the fact that you attempt to explain how a key scientific concept has nothing to do with this, yet you don't even understand why it was necessary for the experiment to be repeated.

screw you tesla, talking all that smack, albert wins again

There is a reason for Telsa making a car, he is so behind in coolness to Einstein that they try to make up for it with an e-car.

On June 11 2012 10:48 D_smart_S wrote: Show nested quote + On June 11 2012 09:29 palak wrote:   On June 11 2012 08:58 kingpowa wrote: What is also important, is that this scientific community faced a problem for which they had no explanation and they decided to reveal all the data they had to the public in order to let people to try to explain it. So they had no problem saying : "we don't understand", which doesn't happen very often in other fields. what also makes this such a travesty is that the lead researcher of the faulty experiment resigned. He did everything 100% right by the scientific method and ideology he shouldn't be punished when errors were found in his experiment. @dsmart...entanglement doesn't actually transmit information faster than light, it's a common misconception. Entanglement can roughly be explained as the following. You take a red rock and a blue rock. Put both rocks in a bag, close ur eyes and mix the bag. Then with ur eyes still closed take a rock out and throw it across the solar system. When u check the rock in the bag u instantly know the color of the rock that is at the other side of the solar system. That's, roughly, entanglement. No information was transferred faster than light. More/better info http://plato.stanford.edu/entries/qt-entangle/ man, I don't want to argue but Quantum Entanglement has nothing to do with what you just said, absolutely nothing. If I take a hair from ur hair and put it a 1000 miles away and I put you under some stress and measure your reaction ( I can't remember which factors are measured, I think it's the electrical discharge or stg like that) the cells in the hair that is 1000 miles away from you will give out the exact same signal you did at the exact same time to the tiniest fraction of time we can measure - in other words instantly. The reading of the two signals are graphs that match 100% ( like a sharkscope graph). That's the way quantum particles communicate, that's a very basic fact but I will not bother arguing about it. It's an instant transfer of information but not by means of a wave of energy. That's the fascinating side of Quantum Physics.

You talk about a difficult subject that you don't even slightly understand. And btw a hair is not a quantum particle lol, no quantum effect on such a huge object...

a hair consists of cells which consist of atoms and subatoms and quantum particles. It's the electrical charge of a cell that's measured I think but whatever the details, the thing is that quantum particles communicate instantly.

my balls can go faster than the speed of light

Thoughts are faster than light, they can go from the sun to planet earth in less than 8 minutes, and they can even reach the furthest galaxies and beyond.

lol

There are a number of things which can go "faster than light" without breaking relativity. http://en.wikipedia.org/wiki/Faster-than-light

Also, I did 10% of my third year Physics degree on a report about the OPERA faster than light experiment - so it's cool to see you guys talking about it here. :D

^theoretically things may be able to go faster than light, however they would not be able to carry or transmit information at FTL speed

On June 11 2012 20:21 palak wrote: ^theoretically things may be able to go faster than light, however they would not be able to carry or transmit information at FTL speed

They would be able to carry and transfer information. They can not transfer this information to subluminal/slower than light particles though, only to other superluminal particles. A particle in itself is transferring and carrying information by its very existence , if it can be seen by an observer.

^if/could be true would be wonderfully hard to prove experimentally

On June 11 2012 20:41 palak wrote: ^if/could be true would be wonderfully hard to prove experimentally

If the particle exists and can be observed by someone/something, then it is carrying and delivering information by its very existence alone.

Maybe the particle would travel slower than light in a certain medium, just like light needs a vacuum to travel at full speed. Then perhaps we could observe them.

^once you are over c, you can't drop back below c, at least not with physics as we know it.

One curious effect is that, unlike ordinary particles, the speed of a tachyon increases as its energy decreases. In particular, approaches zero when approaches infinity. (For ordinary bradyonic matter, E increases with increasing speed, becoming arbitrarily large as v approaches c, the speed of light). Therefore, just as bradyons are forbidden to break the light-speed barrier, so too are tachyons forbidden from slowing down to below c, because infinite energy is required to reach the barrier from either above or below.

http://en.wikipedia.org/wiki/Tachyon

On June 11 2012 20:58 palak wrote: ^once you are over c, you can't drop back below c, at least not with physics as we know it. Show nested quote + One curious effect is that, unlike ordinary particles, the speed of a tachyon increases as its energy decreases. In particular, approaches zero when approaches infinity. (For ordinary bradyonic matter, E increases with increasing speed, becoming arbitrarily large as v approaches c, the speed of light). Therefore, just as bradyons are forbidden to break the light-speed barrier, so too are tachyons forbidden from slowing down to below c, because infinite energy is required to reach the barrier from either above or below. http://en.wikipedia.org/wiki/Tachyon

But the speed of light is not a constant in every medium, in a different medium the FTL speed may be slower than the speed of light outside that medium. Thus in a different medium, FTL particles may be observable from the outside, because the particle still travels faster than light in that specific medium.

"Light, which normally travels the 240,000 miles from the Moon to Earth in less than two seconds, has been slowed to the speed of a minivan in rush-hour traffic -- 38 miles an hour. "

http://www.news.harvard.edu/gazette/1999/02.18/light.html

http://en.wikipedia.org/wiki/Slow_light

c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second

On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second

If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster.

someone make a troll physics comic of slowing down light so we can travel faster than light.

On June 11 2012 21:31 Zorglub wrote: Show nested quote + On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster.

it may travel slower than it normally would and if you want to say pretend world of say tachyon 1,2,3 where 3=6c faster than 2=4c faster than 1=2c in a vacuum there could be a medium where tachyon 1 would travel faster than tachyon 3...so say tachyon 3 would get slowed to 1.5c while tachyon 1 continues on at 2c...but all 3 would need to always travel faster than c at all times

On June 11 2012 21:44 palak wrote: Show nested quote + On June 11 2012 21:31 Zorglub wrote:   On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster. it may travel slower than it normally would and if you want to say pretend world of say tachyon 1,2,3 where 3=6c faster than 2=4c faster than 1=2c in a vacuum there could be a medium where tachyon 1 would travel faster than tachyon 3...so say tachyon 3 would get slowed to 1.5c while tachyon 1 continues on at 2c...but all 3 would need to always travel faster than c at all times

Why is that? C is the speed of light in a vacuum, it is not some magical number. If you run a light particle and a tachyon through a "slowing medium", the tachyon would remain at the relativistic faster than light speed (in that medium). The tachyon stays the same compared to light in that medium. Speed and velocity are dependent on reference frames, they are "nothing" on their own, they are only meaningful if you compare them to something else.

On June 11 2012 21:56 Zorglub wrote: Show nested quote + On June 11 2012 21:44 palak wrote:   On June 11 2012 21:31 Zorglub wrote:   On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster. it may travel slower than it normally would and if you want to say pretend world of say tachyon 1,2,3 where 3=6c faster than 2=4c faster than 1=2c in a vacuum there could be a medium where tachyon 1 would travel faster than tachyon 3...so say tachyon 3 would get slowed to 1.5c while tachyon 1 continues on at 2c...but all 3 would need to always travel faster than c at all times Why is that? C is the speed of light in a vacuum, it is not some magical number. If you run a light particle and a tachyon through a "slowing medium", the tachyon would remain at the relativistic faster than light speed (in that medium). The tachyon stays the same compared to light in that medium. Speed and velocity are also dependent on reference frames, they are "nothing" on their own, they are only meaningful if you compare them to something else.

C is a constant number that doesn't change. Something that lowers lights speed to v=C/n may slow a tachyon from v'=xC to v'=xC/n but x/n will still always need to be >1 so the tachyon speed is above 1 so v'>C always.
Think about it how the wiki article says...or well my simplified version...
A normal particle you add energy to speed it up, in order to speed a particle with mass up to C you need to add an infinite amount of energy to it (impossible to duo), to slow it down you obviously remove energy from it (which can be done to zero)
A tachyon as above C to begin with has the effects of energy addition reversed...as you remove energy from a tachyon it speeds up, in order to slow down a tachyon you need to add energy to it, slowing the tachyon down to C requires the addition of infinite energy (impossible to do)

longer explanation + Show Spoiler +

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

On June 11 2012 22:18 palak wrote: Show nested quote + On June 11 2012 21:56 Zorglub wrote:   On June 11 2012 21:44 palak wrote:   On June 11 2012 21:31 Zorglub wrote:   On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster. it may travel slower than it normally would and if you want to say pretend world of say tachyon 1,2,3 where 3=6c faster than 2=4c faster than 1=2c in a vacuum there could be a medium where tachyon 1 would travel faster than tachyon 3...so say tachyon 3 would get slowed to 1.5c while tachyon 1 continues on at 2c...but all 3 would need to always travel faster than c at all times Why is that? C is the speed of light in a vacuum, it is not some magical number. If you run a light particle and a tachyon through a "slowing medium", the tachyon would remain at the relativistic faster than light speed (in that medium). The tachyon stays the same compared to light in that medium. Speed and velocity are also dependent on reference frames, they are "nothing" on their own, they are only meaningful if you compare them to something else. C is a constant number that doesn't change. Something that lowers lights speed to v=C/n may slow a tachyon from v'=xC to v'=xC/n but x/n will still always need to be >1 so the tachyon speed is above 1 so v'>C always. Think about it how the wiki article says...or well my simplified version... A normal particle you add energy to speed it up, in order to speed a particle with mass up to C you need to add an infinite amount of energy to it (impossible to duo), to slow it down you obviously remove energy from it (which can be done to zero) A tachyon as above C to begin with has the effects of energy addition reversed...as you remove energy from a tachyon it speeds up, in order to slow down a tachyon you need to add energy to it, slowing the tachyon down to C requires the addition of infinite energy (impossible to do) longer explanation + Show Spoiler +   It is a well known fact that nothing can travel faster than the speed of light. At best, a massless particle travels at the speed of light. But is this really true? In 1962, Bilaniuk, Deshpande, and Sudarshan, Am. J. Phys. 30, 718 (1962), said "no". A very readable paper is Bilaniuk and Sudarshan, Phys. Today 22, 43 (1969). Here is a brief overview. Draw a graph, with momentum (p) on the x-axis, and energy (E) on the y-axis. Then draw the "light cone", two lines with the equations E = ±p. This divides our 1+1 dimensional space-time into two regions. Above and below are the "timelike" quadrants, and to the left and right are the "spacelike" quadrants. Now the fundamental fact of relativity is that E² &#8722; p² = m² where E is an object's energy, p is its momentum, and m is its rest mass, which we'll just call 'mass'. In case you're wondering, we are working in units where c=1. For any non-zero value of m, this is a hyperbola with branches in the timelike regions. It passes through the point (p,E) = (0,m), where the particle is at rest. Any particle with mass m is constrained to move on the upper branch of this hyperbola. (Otherwise, it is "off shell", a term you hear in association with virtual particles — but that's another topic.) For massless particles, E² = p², and the particle moves on the light-cone. These two cases are given the names tardyon (or bradyon in more modern usage) and luxon, for "slow particle" and "light particle". Tachyon is the name given to the supposed "fast particle" which would move with v > c. Tachyons were first introduced into physics by Gerald Feinberg, in his seminal paper "On the possibility of faster-than-light particles" [Phys. Rev. 159, 1089—1105 (1967)]. Now another familiar relativistic equation is E = m[1&#8722;(v/c)²]&#8722;½. Tachyons (if they exist) have v > c. This means that E is imaginary! Well, what if we take the rest mass m, and take it to be imaginary? Then E is negative real, and E² &#8722; p² = m² < 0. Or, p² &#8722; E² = M², where M is real. This is a hyperbola with branches in the spacelike region of spacetime. The energy and momentum of a tachyon must satisfy this relation. You can now deduce many interesting properties of tachyons. For example, they accelerate (p goes up) if they lose energy (E goes down). Furthermore, a zero-energy tachyon is "transcendent", or moves infinitely fast. This has profound consequences. For example, let's say that there were electrically charged tachyons. Since they would move faster than the speed of light in the vacuum, they should produce Cherenkov radiation. This would lower their energy, causing them to accelerate more! In other words, charged tachyons would probably lead to a runaway reaction releasing an arbitrarily large amount of energy. This suggests that coming up with a sensible theory of anything except free (noninteracting) tachyons is likely to be difficult. Heuristically, the problem is that we can get spontaneous creation of tachyon-antitachyon pairs, then do a runaway reaction, making the vacuum unstable. To treat this precisely requires quantum field theory, which gets complicated. It is not easy to summarize results here. However, one reasonably modern reference is Tachyons, Monopoles, and Related Topics, E. Recami, ed. (North-Holland, Amsterdam, 1978). However, tachyons are not entirely invisible. You can imagine that you might produce them in some exotic nuclear reaction. If they are charged, you could "see" them by detecting the Cherenkov light they produce as they speed away faster and faster. Such experiments have been done but, so far, no tachyons have been found. Even neutral tachyons can scatter off normal matter with experimentally observable consequences. Again, no such tachyons have been found. How about using tachyons to transmit information faster than the speed of light, in violation of Special Relativity? It's worth noting that when one considers the relativistic quantum mechanics of tachyons, the question of whether they "really" go faster than the speed of light becomes much more touchy! In this framework, tachyons are waves that satisfy a wave equation. Let's treat free tachyons of spin zero, for simplicity. We'll set c = 1 to keep things less messy. The wavefunction of a single such tachyon can be expected to satisfy the usual equation for spin-zero particles, the Klein-Gordon equation: (&#9633; + m²)&#966; = 0 where &#9633; is the D'Alembertian, which in 3+1 dimensions is just &#9633; = &#8706;²/&#8706;t² &#8722; &#8706;²/&#8706;x² &#8722; &#8706;²/&#8706;y² &#8722; &#8706;²/&#8706;z². The difference with tachyons is that m² is negative, and so m is imaginary. To simplify the math a bit, let's work in 1+1 dimensions with co-ordinates x and t, so that &#9633; = &#8706;²/&#8706;t² &#8722; &#8706;²/&#8706;x². Everything we'll say generalizes to the real-world 3+1-dimensional case. Now, regardless of m, any solution is a linear combination, or superposition, of solutions of the form &#966;(t,x) = exp(&#8722;iEt + ipx) where E² &#8722; p² = m². When m² is negative there are two essentially different cases. Either | p | &#8805; | E |, in which case E is real and we get solutions that look like waves whose crests move along at the rate | p/E | &#8805; 1, i.e., no slower than the speed of light. Or | p | < | E |, in which case E is imaginary and we get solutions that look like waves that amplify exponentially as time passes! We can decide as we please whether or not we want to consider the second type of solution. They seem weird, but then the whole business is weird, after all. (1) If we do permit the second type of solution, we can solve the Klein-Gordon equation with any reasonable initial data — that is, any reasonable values of &#966; and its first time derivative at t = 0. (For the precise definition of "reasonable", consult your local mathematician.) This is typical of wave equations. And, also typical of wave equations, we can prove the following thing: if the solution &#966; and its time derivative are zero outside the interval [&#8722;L, L] when t = 0, they will be zero outside the interval [&#8722;L&#8722; | t |, L + | t |] at any time t. In other words, localized disturbances do not spread with speed faster than the speed of light! This seems to go against our notion that tachyons move faster than the speed of light, but it's a mathematical fact, known as "unit propagation velocity". (2) If we don't permit the second sort of solution, we can't solve the Klein-Gordon equation for all reasonable initial data, but only for initial data whose Fourier transforms vanish in the interval [&#8722;| m |, | m |]. By the Paley-Wiener theorem this has an odd consequence: it becomes impossible to solve the equation for initial data that vanish outside some interval [&#8722;L, L]! In other words, we can no longer "localize" our tachyon in any bounded region in the first place, so it becomes impossible to decide whether or not there is "unit propagation velocity" in the precise sense of part (1). Of course, the crests of the waves exp(&#8722;iEt + ipx) move faster than the speed of light, but these waves were never localized in the first place! The bottom line is that you can't use tachyons to send information faster than the speed of light from one place to another. Doing so would require creating a message encoded some way in a localized tachyon field, and sending it off at superluminal speed toward the intended receiver. But as we have seen you can't have it both ways: localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal. futher note...when the paper says   | p/E | &#8805; 1, i.e., no slower than the speed of light he has already set c=1 during the derivation so the answer with c set to a constant is c*|p/E| > c http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

Yes I am aware of that simplified explanation, but C is only a constant from a specific reference frame or point of view. If you are a photon yourself, the speed of light is not 299,792,458 metres per second. If you are travelling towards the light at high speed, the speed of the photons hitting you would be more than 299,792,458 metres per second and vice versa if you travel away from it. (Redshift/Blueshift). If you are moving at close to the speed of light, a tachyon travelling at say 1½ times the speed of light passing by you from behind, would not travel faster than 299,792,458 metres per second from your point of view, because of your already inherent speed compared to that particle.

Na Tesla still rules. Turn on a light and you'll see I'm right.

On June 11 2012 22:50 Zorglub wrote: Show nested quote + On June 11 2012 22:18 palak wrote:   On June 11 2012 21:56 Zorglub wrote:   On June 11 2012 21:44 palak wrote:   On June 11 2012 21:31 Zorglub wrote:   On June 11 2012 21:22 palak wrote: c is not "speed of light"...c is the speed of light in a vacuum, the absolute max speed of any known particle...saying a particle can't go below c means no matter what it will be traveling above our current maximum speed limit of 299,792,458 metres per second If light is travelling slower in some media compared to others, why would this not be the case for a tachyon also? It would still remain at the same relativistic speed compared to light. Maybe a tachyon only would be able to travel faster. it may travel slower than it normally would and if you want to say pretend world of say tachyon 1,2,3 where 3=6c faster than 2=4c faster than 1=2c in a vacuum there could be a medium where tachyon 1 would travel faster than tachyon 3...so say tachyon 3 would get slowed to 1.5c while tachyon 1 continues on at 2c...but all 3 would need to always travel faster than c at all times Why is that? C is the speed of light in a vacuum, it is not some magical number. If you run a light particle and a tachyon through a "slowing medium", the tachyon would remain at the relativistic faster than light speed (in that medium). The tachyon stays the same compared to light in that medium. Speed and velocity are also dependent on reference frames, they are "nothing" on their own, they are only meaningful if you compare them to something else. C is a constant number that doesn't change. Something that lowers lights speed to v=C/n may slow a tachyon from v'=xC to v'=xC/n but x/n will still always need to be >1 so the tachyon speed is above 1 so v'>C always. Think about it how the wiki article says...or well my simplified version... A normal particle you add energy to speed it up, in order to speed a particle with mass up to C you need to add an infinite amount of energy to it (impossible to duo), to slow it down you obviously remove energy from it (which can be done to zero) A tachyon as above C to begin with has the effects of energy addition reversed...as you remove energy from a tachyon it speeds up, in order to slow down a tachyon you need to add energy to it, slowing the tachyon down to C requires the addition of infinite energy (impossible to do) longer explanation + Show Spoiler +   It is a well known fact that nothing can travel faster than the speed of light. At best, a massless particle travels at the speed of light. But is this really true? In 1962, Bilaniuk, Deshpande, and Sudarshan, Am. J. Phys. 30, 718 (1962), said "no". A very readable paper is Bilaniuk and Sudarshan, Phys. Today 22, 43 (1969). Here is a brief overview. Draw a graph, with momentum (p) on the x-axis, and energy (E) on the y-axis. Then draw the "light cone", two lines with the equations E = ±p. This divides our 1+1 dimensional space-time into two regions. Above and below are the "timelike" quadrants, and to the left and right are the "spacelike" quadrants. Now the fundamental fact of relativity is that E² &#8722; p² = m² where E is an object's energy, p is its momentum, and m is its rest mass, which we'll just call 'mass'. In case you're wondering, we are working in units where c=1. For any non-zero value of m, this is a hyperbola with branches in the timelike regions. It passes through the point (p,E) = (0,m), where the particle is at rest. Any particle with mass m is constrained to move on the upper branch of this hyperbola. (Otherwise, it is "off shell", a term you hear in association with virtual particles — but that's another topic.) For massless particles, E² = p², and the particle moves on the light-cone. These two cases are given the names tardyon (or bradyon in more modern usage) and luxon, for "slow particle" and "light particle". Tachyon is the name given to the supposed "fast particle" which would move with v > c. Tachyons were first introduced into physics by Gerald Feinberg, in his seminal paper "On the possibility of faster-than-light particles" [Phys. Rev. 159, 1089—1105 (1967)]. Now another familiar relativistic equation is E = m[1&#8722;(v/c)²]&#8722;½. Tachyons (if they exist) have v > c. This means that E is imaginary! Well, what if we take the rest mass m, and take it to be imaginary? Then E is negative real, and E² &#8722; p² = m² < 0. Or, p² &#8722; E² = M², where M is real. This is a hyperbola with branches in the spacelike region of spacetime. The energy and momentum of a tachyon must satisfy this relation. You can now deduce many interesting properties of tachyons. For example, they accelerate (p goes up) if they lose energy (E goes down). Furthermore, a zero-energy tachyon is "transcendent", or moves infinitely fast. This has profound consequences. For example, let's say that there were electrically charged tachyons. Since they would move faster than the speed of light in the vacuum, they should produce Cherenkov radiation. This would lower their energy, causing them to accelerate more! In other words, charged tachyons would probably lead to a runaway reaction releasing an arbitrarily large amount of energy. This suggests that coming up with a sensible theory of anything except free (noninteracting) tachyons is likely to be difficult. Heuristically, the problem is that we can get spontaneous creation of tachyon-antitachyon pairs, then do a runaway reaction, making the vacuum unstable. To treat this precisely requires quantum field theory, which gets complicated. It is not easy to summarize results here. However, one reasonably modern reference is Tachyons, Monopoles, and Related Topics, E. Recami, ed. (North-Holland, Amsterdam, 1978). However, tachyons are not entirely invisible. You can imagine that you might produce them in some exotic nuclear reaction. If they are charged, you could "see" them by detecting the Cherenkov light they produce as they speed away faster and faster. Such experiments have been done but, so far, no tachyons have been found. Even neutral tachyons can scatter off normal matter with experimentally observable consequences. Again, no such tachyons have been found. How about using tachyons to transmit information faster than the speed of light, in violation of Special Relativity? It's worth noting that when one considers the relativistic quantum mechanics of tachyons, the question of whether they "really" go faster than the speed of light becomes much more touchy! In this framework, tachyons are waves that satisfy a wave equation. Let's treat free tachyons of spin zero, for simplicity. We'll set c = 1 to keep things less messy. The wavefunction of a single such tachyon can be expected to satisfy the usual equation for spin-zero particles, the Klein-Gordon equation: (&#9633; + m²)&#966; = 0 where &#9633; is the D'Alembertian, which in 3+1 dimensions is just &#9633; = &#8706;²/&#8706;t² &#8722; &#8706;²/&#8706;x² &#8722; &#8706;²/&#8706;y² &#8722; &#8706;²/&#8706;z². The difference with tachyons is that m² is negative, and so m is imaginary. To simplify the math a bit, let's work in 1+1 dimensions with co-ordinates x and t, so that &#9633; = &#8706;²/&#8706;t² &#8722; &#8706;²/&#8706;x². Everything we'll say generalizes to the real-world 3+1-dimensional case. Now, regardless of m, any solution is a linear combination, or superposition, of solutions of the form &#966;(t,x) = exp(&#8722;iEt + ipx) where E² &#8722; p² = m². When m² is negative there are two essentially different cases. Either | p | &#8805; | E |, in which case E is real and we get solutions that look like waves whose crests move along at the rate | p/E | &#8805; 1, i.e., no slower than the speed of light. Or | p | < | E |, in which case E is imaginary and we get solutions that look like waves that amplify exponentially as time passes! We can decide as we please whether or not we want to consider the second type of solution. They seem weird, but then the whole business is weird, after all. (1) If we do permit the second type of solution, we can solve the Klein-Gordon equation with any reasonable initial data — that is, any reasonable values of &#966; and its first time derivative at t = 0. (For the precise definition of "reasonable", consult your local mathematician.) This is typical of wave equations. And, also typical of wave equations, we can prove the following thing: if the solution &#966; and its time derivative are zero outside the interval [&#8722;L, L] when t = 0, they will be zero outside the interval [&#8722;L&#8722; | t |, L + | t |] at any time t. In other words, localized disturbances do not spread with speed faster than the speed of light! This seems to go against our notion that tachyons move faster than the speed of light, but it's a mathematical fact, known as "unit propagation velocity". (2) If we don't permit the second sort of solution, we can't solve the Klein-Gordon equation for all reasonable initial data, but only for initial data whose Fourier transforms vanish in the interval [&#8722;| m |, | m |]. By the Paley-Wiener theorem this has an odd consequence: it becomes impossible to solve the equation for initial data that vanish outside some interval [&#8722;L, L]! In other words, we can no longer "localize" our tachyon in any bounded region in the first place, so it becomes impossible to decide whether or not there is "unit propagation velocity" in the precise sense of part (1). Of course, the crests of the waves exp(&#8722;iEt + ipx) move faster than the speed of light, but these waves were never localized in the first place! The bottom line is that you can't use tachyons to send information faster than the speed of light from one place to another. Doing so would require creating a message encoded some way in a localized tachyon field, and sending it off at superluminal speed toward the intended receiver. But as we have seen you can't have it both ways: localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal. futher note...when the paper says   | p/E | &#8805; 1, i.e., no slower than the speed of light he has already set c=1 during the derivation so the answer with c set to a constant is c*|p/E| > c http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html Yes I am aware of that simplified explanation, but C is only a constant from a specific reference frame or point of view. If you are a photon yourself, the speed of light is not 299,792,458 metres per second. If you are travelling towards the light at high speed, the speed of the photons hitting you would be more than 299,792,458 metres per second and vice versa if you travel away from it. (Redshift/Blueshift). If you are moving at close to the speed of light, a tachyon travelling at say 1½ times the speed of light passing by you from behind, would not travel faster than 299,792,458 metres per second from your point of view, because of your already inherent speed compared to that particle.

This is part of the fun of relativity, relativistic velocity and independence. The speed of light in a vacuum,c, is independent of the observers reference frame. If you are traveling at 5 mph in a vacuum you will see light pass you at 299,792,458 m/s, if you are going 299,700,000 m/s you will still observe light passing you at 299,792,458 m/s. This is extremely counter-intuitive.
you are doing this exact problem

It is tempting to extrapolate one or other of these results to light: if light is like little arrows, Jasper should measure v+c. If light is like sound, and if its medium is stationary with respect to Jasper, than Zoe should measure its speed as c−v. (We discuss the possibility of a medium for light later.) If we are really careful in our thinking, however, we should also say that light may be neither like arrows nor like sound. The extrapolation mentioned above is tempting, but it would be a huge extrapolation: light travels nearly a million times faster than sound. And extrapolations are always dangerous. For instance, very near where you are now, the temperature and other physical conditions are (I hope) fairly comfortable. But the further you go from your familiar surroundings - suppose for instance you go 20 kilometers up or down - the more likely things are to be different in surprising ways. The further you go from the familiar, the more likely we shall be surprised. And the speed of light is a very unfamiliar speed. Indeed, the speed of light (about 300,000 km/s - over a billion k.p.h.) is so great that our intuition is of little use. All the observations about speed that you have ever made, all of the experience upon which your common sense is based, are in a tiny area of physical reality that we could label "extremely low speed" compared with light. It is often the case that one can make approximations that apply over a limited region of reality, but that fail when we examine a larger range. For instance, objects fall at 9.8 metres per second per second in the lab. Also in the basement or on the roof. But this is not true in high orbits, or at the centre of the Earth.

furhter explained y that is wrong http://www.phys.unsw.edu.au/einsteinlight/jw/module3_weird_logic.htm

Another assumption on the laws of physics made by the SI definition of the metre is that the theory of relativity is correct. It is a basic postulate of the theory of relativity that the speed of light is constant. This can be broken down into two parts: The speed of light is independent of the motion of the observer. The speed of light does not vary with time or place.

http://math.ucr.edu/home/baez/physics...vity/SpeedOfLight/speed_of_light.html
experiment done http://www.phys.unsw.edu.au/einsteinlight/jw/module3_is_it_true.htm

Even if you are traveling in a vacuum at say 99999% the speed of light and an object if fired directly at you going 99999% the speed of light by Einein velocity addition you would only observe the object flying at you as going 9999999999499994% the speed of light, still not 100% the speed of light.

Relativistic velocity calculator (note the blank boxes need a decimal place since you are going at a percent of c, so .5 for 50% c instead of putting 50 http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel2.html#c2

Key is no matter what reference frame or objects, a person will never observe an object going faster than light in a vacuuum and a person will never be able to slow the speed of light in a vacuum relative to themselves.

Palak is right 200 000 km/s + 200 000 km/s =/= 400 000 km/s, that is relativity.

On June 11 2012 08:55 D_smart_S wrote: So some conspiracy theorist concluded that there will be a new disaster soon and nothing happens[b], then they said they were wrong and that is enough for you to conclude that they are now correct [b]on their new conspiracy theory ? Don't you think that they might be wrong a second time?

fyp

Interesting. I dont quite get that Einstein Velocity Addition though. It seems to me in the explanation they talk about velocity, which has a vector and thus it is able to be negative. Speed on the other hand has no vector and is therefore not negative. A photon at negative speed would be travelling back in time.

The speed of an object is the magnitude of its velocity (the rate of change of its position).

Now this confuses me, they write: "How will A and B measure their relative speeds? This is an example of Einstein velocity addition. In the calculation below, velocities to the right are taken as positive." They write how will A and B measure their relative speeds, yet they go on by calling it velocities instead and naming one of them negative. I don't see the logic in that. How would one of them suddenly have a negative velocity, when they talk about relative speeds?

I understand that the speed of light is fixed due to time dilation for the observer.

B is moving to the left therefore it's velocity vector is taken to be negative. Instead of saying it's coming at you with speed x, they just rephrase it as "it's traveling at -x velocity" since there is no worry of the problem situation changing they are lazy w/ exact wording. Speed and Velocity are used nearly interchangeably in the problem since it's just a 1 dimensional example problem.

Also a photon (or any object) traveling faster than light under relativity is also going backwards in time

Nice, but a bit confusing An object travelling at negative velocity equals an object travelling faster than light equals an object going back in time.

yep...relativity and quantum mechanics is confusing but awesome

On June 12 2012 21:02 palak wrote: yep...relativity and quantum mechanics is confusing but awesome

But does it make any sense saying that speed is independent of the observer, if time is dependent on the observer, and time is used to measure the speed?

"Nature can produce even larger particle energies. Some particles striking the Earth's upper atmosphere have energies that exceed 2*1020 eV. If such particles are protons (with mass of about 1 GeV), their speeds would be 0.999 999 999 999 999 999 999 995 c. For them, γ is 1011. Now the age of the universe is about 13 billion years for us, but for such particles, the age of the universe would be about (13 billion years/1011), ie about a month. Such a particle could cross the visible universe in a matter of months (their time)."

amount at which spacetime is warped changes based off a persons speed...by some math i don't feel like understanding right now..it happens that objects going at light speed will warp spacetime in the observers reference frame in such a way that it always appears to be traveling at c

The consequence of Einstein's two postulates are radical: time and space become intertwined in surprising ways. Events that may be simultaneous for one observer can occur at different times for another. This leads to length contraction and time dilation, the slowing down of time in a moving frame. Every observer has her own personal time, caller proper time. That is the time measured by a clock at the observer's location. Two observers, initially the same age as given by their proper times, could have different ages when they met again after traveling along different spacetime paths. ... Proper Time of Moving Observers As noted above the proper time is the time measured by a clock at an observer's location. So far we have considered the proper time of a special class of observers, namely, those who are in a fixed spatial location relative to a coordinate system; that is, those for whom dl = 0. But what about the proper time of observers who are moving relative to the coordinate system. How do we compute their proper times? Let's start with the formula for the spacetime interval ds2 = (cdt)2 - dl2 By dividing throughout by c2 and pulling out a factor of dt2 on the right-hand side we can re-write the interval as ds2/c2 = dt2[1 - (dl/dt)2/c2]. But, by definition, v = dl/dt is the observer's speed, relative to the coordinate system; so we can write ds2/c2 = dt2[1 - (v/c)2]. We assume observers can travel only along timelike intervals; therefore, their speed v is always less than the speed of light, c. So in the above expression (v/c)2 is always less than 1. We now take the square root of that expression to obtain: ds/c = dt[1 - (v/c)2]1/2. The spacetime interval between two nearby points along the worldline of our moving observer is, by definition, just ds. The latter has the dimensions of distance; but when we divide it by the speed of light we convert ds to a quantity dt = ds/c that has the dimensions of time. Notice that dt = ds/c is always less than or equal to dt. It is only equal to dt when our observer is at rest in the coordinate system. This is the case we considered earlier, when we identified ds/c as the proper time of an observer fixed relative to the coordinate system (that is, dl = 0). By continuity, we conclude that, in fact, dt = ds/c is the proper time not only for observers at rest in the coordinate system but also for moving observers, provided that they move only along timelike worldlines. This then gives us the rule for computing the proper time of any observer, whether at rest, or in motion, relative to our (arbitrarily chosen) coordinate system: the elapsed proper time between any two nearby events, along the worldline of an observer (regardless of their state of motion) is just the spacetime interval between the nearby points divided by the speed of light: dt2 = (ds/c)2 = dt2 - (dl/c)2 By adding up (that is, integrating) all the small elapsed proper times dt along the worldline we can compute the total elapsed proper time measured by a clock attached to any observer. The formula that relates dt to dt shows that the former is always less than or equal to the latter: the clocks of moving observers run slower relative to a clock that is stationary in the coordinate system. This is the famous time dilation effect of relativity theory. Observers that are fixed in space (dl = 0) have particularly simple worldlines; this makes it easy to compute their elapsed proper times. For more complicated worldlines the calculation is not quite as easy because we then have to worry about displacements both in coordinate time dt as well as in coordinate space dl.

http://www.physics.fsu.edu/courses/sp...3033/Relativity/GeneralRelativity.htm

also see
http://en.wikipedia.org/wiki/Time_dilation
http://en.wikipedia.org/wiki/Length_contraction#Paradoxes

On June 11 2012 18:25 D_smart_S wrote: a hair consists of cells which consist of atoms and subatoms and quantum particles. It's the electrical charge of a cell that's measured I think but whatever the details, the thing is that quantum particles communicate instantly.

Could we please just ban this annoying troll already?

Nobody is that stupid.