# Faster than the speed of light

Is it possible to go faster than the speed of light? And why do some scientists say you can't???
Thanks -_-!

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DaveC426913
Gold Member
Is it possible to go faster than the speed of light? And why do some scientists say you can't???
Thanks -_-!
Nothing with mass can accelerate to the speed of light. The closer you get to it, the more energy it will take to get closer. It is an asymptotic limit.

Nothing with mass can accelerate to the speed of light. The closer you get to it, the more energy it will take to get closer. It is an asymptotic limit.
Hence, anything without mass can be faster than light: velocity of phase/group of EM waves, gamma-ray burst, neutrinos, and also initial acceleration of light (m/s² → v/t ), light’s initial acceleration shouldn’t exceed an acceleration of c (v/t), but it exceeds because it has no mass.
Extending this thought, if something has no mass then it can be faster than light, hence I thought it is logic the theory, that is said already observed in practice, that static fields (magnetic and electric) are at least 20 billion times faster than light.
As well, http://www.youtube.com/watch?v=Z8Hwqg9_oA8", which can be mathematically verified (f≥c/L)

As far as I could understand, "Nothing can be faster than light", except if it has no mass or negative mass.
My question is, could phase-shifted oscillations produce a kind of negative mass effect?

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K^2
No. Anything with no mass travels AT the speed of light. E.g. light.

DaveC426913
Gold Member
Hence, anything without mass can be faster than light: velocity of phase/group of EM waves, gamma-ray burst, neutrinos,
No, this does not follow.

and also initial acceleration of light (m/s² → v/t ), light’s initial acceleration shouldn’t exceed an acceleration of c (v/t), but it exceeds because it has no mass.
Light does not accelerate. It is emitted at c.

Extending this thought, if something has no mass then it can be faster than light,
It can't.

hence I thought it is logic the theory, that is said already observed in practice, that static fields (magnetic and electric) are at least 20 billion times faster than light.
No. Fields are pervasive - as in: they already exist everywhere. Changes to those fields are propogated at the speed of light.

As well, http://www.youtube.com/watch?v=Z8Hwqg9_oA8", which can be mathematically verified (f≥c/L)
Certain groups of things, such as wave pulses can propogate faster than c, but these are a special case. Nothing real (mass or massless) is actually moving faster than c, and no information can be transmitted faster than c. It is much like sweeping a beam of light in an arc. The spotlight can be seen to be moving faster than c, but the spotlight is simply a group of things - no thing is exceeding c, including information.

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Yes, it is. Space does it all the time.

In quantum mechanics there are effects that can be described by assuming virtual particles traveling faster than light. Still these virtual particles transmit no information and cannot be used for communication.

Light does not accelerate. It is emitted at c.
Acceleration is the rate of change of velocity over time (∆v/∆t), hence, how could the light be emitted, with instantaneous speed up to c, without initial acceleration?

f95toli
Gold Member
Because light does not follow the usual "rules" that apply for e.g. footballs. Light just "is" and always travel at c.

(a more scientific answer is that a photon is just an excitation of a tempora-spatial mode, i.e. that mode -which "travels" at c- either is or isn't occupied)

Because light does not follow the usual "rules" that apply for e.g. footballs. Light just "is" and always travel at c.

(a more scientific answer is that a photon is just an excitation of a tempora-spatial mode, i.e. that mode -which "travels" at c- either is or isn't occupied)
From what I have understood, then, is there a kind of “slot” that always travels at c, independently whether it is occupied by a photon or not?

doesn't it depend where? I think I heard that apparently in this universe you can't travel faster than the speed of light whereas outside this universe you can, such as the 11th dimension (I think) that we are expanding in, didn't the universe start expanding faster than the speed of light?

p.s. im only 15

russ_watters
Mentor
Acceleration is the rate of change of velocity over time (∆v/∆t), hence, how could the light be emitted, with instantaneous speed up to c, without initial acceleration?
T=0 therefore v/t= undefined

Danger
Gold Member
I feel obliged here to point out, as Dave alluded to, that the speed limit of light applies only to a vacuum situation. All manner of things can exceed it in a medium. Even that is deceptive, though. Individual photons within media still travel at c, but their journey is interrupted so much that the overall signal proceeds much slower. (I think that such is called "group velocity".)
Check out Cherenkov radiation as an example.
Resident scientists, I have quite a record for using incorrect terminology when trying to express myself, so please feel free to correct such.

A friend of mine posed the question that if light is affected by the gravity of a black hole, couldn't the slingshot effect accelerate light?

DaveC426913
Gold Member
A friend of mine posed the question that if light is affected by the gravity of a black hole, couldn't the slingshot effect accelerate light?
Nope. Light does not accelerate when subjected to gravity; it simply curves along the geodesic.

A massive object can be placed stationary with respect to a gravitational object such as Earth or a BH. From that point, it will begin to accelerate, due to the curvature of space toward the object. But you cannot place a beam of light stationary wrt a gravitational object, thus it does not accelerate toward it.

DaveC426913
Gold Member
Yes, it is. Space does it all the time.
"Space" doesn't "do" anything, including "go" anywhere. Things in space do things and go places.

Even when the universe is expanding, there is no "fabric" that is moving. It is simply that objects far apart are getting farther apart.

DaveC426913
Gold Member
From what I have understood, then, is there a kind of “slot” that always travels at c, independently whether it is occupied by a photon or not?
No. Not sure where this slot came from.

Regardless, the photon moves at c and only c. Photons do not experience time.
However, observers experience time. Would an observer see an emitted photon as it had acquired instantaneous velocity c in a time close to zero, observing infinity acceleration?

DaveC426913
Gold Member
However, observers experience time. Would an observer see an emitted photon as it had acquired instantaneous velocity c in a time close to zero, observing infinity acceleration?
Yes (if an observer could "see" a photon emitted, which is challenging).

K^2
From what I have understood, then, is there a kind of “slot” that always travels at c, independently whether it is occupied by a photon or not?
In quantum electrodynamics, yes. The state of a traveling photon always exists. When you "create" a photon, you merely excite that state. That's called the second quantization of electromagnetic field. So in a way, looking at it as something that always travels at c and you simply flip it on and off is consistent with our understanding of electromagnetic wave.

Just keep in mind that you're getting very close to the slippery edge of a rabbit hole that is quantum gravity.

Danger
Gold Member
Just keep in mind that you're getting very close to the slippery edge of a rabbit hole that is quantum gravity.
:rofl:

That has to be one of the best statements that I've ever seen.

Light does not accelerate. It is emitted at c.

.
hmmmm, that's interesting. So if light is slowed down as it passes through a medium, does this mean that it isn't accelerating although there's a change in velocity? That's rather strange to me...

If light can't accelerate, then forces cannot act on light, is that true? The definition of a force (as I know it) is something that causes an acceleration...

Danger
Gold Member
hmmmm, that's interesting. So if light is slowed down as it passes through a medium, does this mean that it isn't accelerating although there's a change in velocity? That's rather strange to me...

If light can't accelerate, then forces cannot act on light, is that true? The definition of a force (as I know it) is something that causes an acceleration...
As I mentioned earlier, the individual photons still travel at c. Even during their absorption and re-emission, their acceleration is instantaneous. Because of those "detours", however, the group velocity of the light is lowered.