Can something move faster than light?

[C1ay]

Because the universe is expanding it has to be expanding relative to something...

 

Why does that something have to be anything other that itself? When a balloon expands each oh the points on it moves away from all of the other points on it regardless of it's surroundings. There does not need to be some external measure of expansion for expansion to occur.

[NomadaNare]

I saw somewhere earlier that if something moved faster than light it would observed as moving backwards. Well I've heard descriptions of positrons being just "electrons moving backward in time" and they are almost massless so... :friday:. I have often pondered this question though. But what Im wondering is what if there is something already moving faster than light and we just can't detect it. Maybe "dark light" having something to do with dark matter. idk just random spouts of me brain.

[Tormod]

Welcome, NomadaNare. Very nice avatar! :friday:

[maddog]

I saw somewhere earlier that if something moved faster than light it would observed as moving backwards. Well I've heard descriptions of positrons being just "electrons moving backward in time" and they are almost massless so... :friday:. I have often pondered this question though. But what Im wondering is what if there is something already moving faster than light and we just can't detect it. Maybe "dark light" having something to do with dark matter. idk just random spouts of me brain.

NomadaNare, I think you are talking about Positrons. It is these particles that would behave as you

say. A Positron is actually the Antimatter partner of an electron. Were an positron and an electron to

meet they would annilhilate each other and produce two Gamma Rays moving away from the center of

the explosion in opposite directions. :)

 

Maddog

[NomadaNare]

I was also thinking about the question on my way home. Doesn't E=mc^2 imply that if something has energy is has mass? Well, light is energy, which implies that it has a mass even if it is a miniscule amount, right? My insight into the equation is very limited so if one could clear up this misconception, i would appreciate it. O and thanx tormod.

[Jimoin]

A modification on the pole question, instead of pushing it, how about spinning it?

 

If I had a really long pole, were able to pick it up like a baseball bat and spin around, what's stopping the end of it breaking c? It doesn't rely on collision effects because each particle is only moving in relation to each other, not space.

[maddog]

I was also thinking about the question on my way home. Doesn't E=mc^2 imply that if something has energy is has mass? Well, light is energy, which implies that it has a mass even if it is a miniscule amount, right? My insight into the equation is very limited so if one could clear up this misconception, i would appreciate it. O and thanx tormod.

This is one of the many odd things about QM. Yes light or particle version called a

photon has energy. Yes, a photon is a massless particle (no mass). Yes, E = mc^2.

Yes, this doesn't agree. I know it is odd. The mass you would be thinking of in the

above equation is a "rest mass" or the mass at rest. Well, the photon or wave of

light is always in motion and never still. This is called propagation or radiation of

the light. I hope this clears it up. :friday:

 

Maddog

[maddog]

A modification on the pole question, instead of pushing it, how about spinning it?

 

If I had a really long pole, were able to pick it up like a baseball bat and spin around, what's stopping the end of it breaking c? It doesn't rely on collision effects because each particle is only moving in relation to each other, not space.

The problem is here you "pole" is made up of atoms. Atoms are only loosely bound

together even for a solid. Stresses on the pole will prevent the pole from being very

long at any speed let alone relativistic ones. :friday:

 

Maddog

[Jay-qu]

Yet another mod to the pole question...

 

What if it was a disk? :friday:

[Qfwfq]

Pole or disk, even if you avoid breaking it, even if you recite the right mantra, to get the furthest parts of it moving at a velocity approaching c you would have to supply a kinetic energy approaching infinity, wich means you would have to do an amount of work approaching infinity.

[Qfwfq]

Doesn't E=mc^2 imply that if something has energy is has mass? Well, light is energy, which implies that it has a mass even if it is a miniscule amount, right?

Unfortunately NomadaNare, there has been a lot of confusion around since Einstein's pubblication of 100 years ago. It is, to a great extent, a matter of terminology.

 

Think of mass as being energy, not as what something has besides energy. In modern terminology, mass is a shortcut for saying "rest energy". When moving, a body will have a kinetic energy as well as the rest energy and the total of these is often called the mass of that body at that velocity, but this type of statement is a misconception that has created a lot of confusion.

 

A photon has no mass and therefore it has only kinetic energy, which also bears the consequence of its velocity being exactly c. This kinetic energy is proportional to frequency, a fact that had been gleaned from the photoelectric effect not long before SR was worked out.

 

If the moving body is part of a composite object, this will have a mass (rest energy) which includes the moving part's kinetic energy, just as it will include potential energies of forces between its parts. Only in this way it makes sense to regard the kinetic and potential energies as also being mass; they contribute to the rest energy of the composite body. Not to the rest energies of the single bodies that are moving, or attrating and repelling each other.

 

The misconception of mass = m_0 over gamma was introduced the year following Einstein's publication when these things were still poorly understood, it should be considered a relic of history, a half baked thing, neither fish nor fowl. Instead it is still taught, all to much, as being an essential fact of SR.

 

In the appropriate Lorentz-covariant way of things a body has a mass, which is a scalar quantity not dependent on its motion but I won't go into detail because I don't know if you are familiar with the 4-vector formulation of these things.

[Qfwfq]

I was forgetting...

I saw somewhere earlier that if something moved faster than light it would observed as moving backwards. Well I've heard descriptions of positrons being just "electrons moving backward in time"...

Both of these are not to be taken too literally. They are often erroneously put this way but I'll try to say them a bit less loosely. In any case these two things are quite separate, they don't mean that electrons go faster than light.

 

The first is that if something is going ftl then it has a space-like trajectory and for some observers it is going one way, for others it's going the opposite way and for some observers the motion will be instantaneous. From this follows that if causality could go ftl then it could also go backwards in time.

 

The second sentence is the matter of PCT in field theory. In Feynman diagrams, the same line, with an arrow from A to B, is used to represent either an electron going that way or a positron going the opposite way. In both cases the particle has a time-like trajectory so either A is previous to B or vice versa, for all observers. Obviously, if B is previous to A, the line represents a positron going from B to A.

[ShaoLinBastard]

i may regret to say this..

 

time is marginal in aspects such as tense and age+duration.

if something is faster than light, to our reality, wouldn't it

appear to be non-existent? therefore, time would change or stop.

my point is, it can. :)

[Jay-qu]

Im not sure i understand what you are trying to say... Eienstien already showed us that time slows down as you approch c, is that what you are reffering to?

[UncleAl]

Massed bodies cannot propagate at lightspeed. Unmassed bodies cannot propagate at any speed other than ligthspeed. Can anything be superluminal?

 

1) The mathmatics of tachyons is perfectly reasonable and utterly non-physical.

 

2) Let's do the experiment! Reaching Absolute Zero is forbidden for the same reason as reaching lightspeed - division by zero is undefined. Negative temps absolute are all over the place - every lasing medium is at negative degrees kelvin, as are the human volumes being imaged in MRI machines. One simply goes the long way around, from positive infinite temp to negative infinite temp and back on the other side. Doing the analogous finesse with Special Relativity is left as an exercise for the alert reader.

 

3) Internal inconsistencies in Special Relativity (meaning inconsistencies of a purely mathematical logical nature) automatically lead to contradictions in number theory, itself, and arithmetic, since the mathematics of Minkowski geometry is equiconsistent with the theory of real numbers and with arithmetic.

[Qfwfq]

One simply goes the long way around, from positive infinite temp to negative infinite temp and back on the other side. Doing the analogous finesse with Special Relativity is left as an exercise for the alert reader.

Find a way to do it experimentally and then next week you send me a message so that I recieve it by tomorrow, with the right numbers. That jackpot currently stands at €57.500.000.

 

Lorentz and Boltzman are two quite different things. Of course, could we only but reverse all the momenta, we could even un-mix the two mixed gasses!

 

The only way I can get your point in 3) as being relevant is as a long way around of saying that Lorentz isn't a statistical matter.

[lindagarrette]

i may regret to say this..

 

time is marginal in aspects such as tense and age+duration.

if something is faster than light, to our reality, wouldn't it

appear to be non-existent? therefore, time would change or stop.

my point is, it can. :)

When a particle is accelerated, instead of travelling faster than light, it gains mass and therefore, its inertia increases, which stops it from passing the speed of light. If we are observing from a relatively fixed platform, we perceive events pertaining to the object to happen in slow motion. We can say time slows down but time is not a thing. It is a way to measure sequences of events, Beyond max speed we would perceive a motionless particle of infinite mass.