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Author Topic: can a body reach velocity of light ?  (Read 4444 times)

Offline bahesbesdk

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can a body reach velocity of light ?
« on: 04/08/2009 20:25:41 »
Hi ,

Is it possible to reach an object to the speed of light or exceed it ?


 

Offline HankRearden

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can a body reach velocity of light ?
« Reply #1 on: 04/08/2009 21:32:09 »
I'm by far, no expert on anything like that, I'm actually trying to brush up on some Einstein right now, because alot his work deals with the speed of light. I do not believe you can math or exceed the speed of light, and it has something to do with the fact that the universe seems to change to keep the speed of light constant. Again this is more of a layman's perspective, I had a physics teacher explain it to me once, but he's an engineer by trade, not a theoretical physicist.
 

Offline wanhafizi

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can a body reach velocity of light ?
« Reply #2 on: 05/08/2009 11:56:26 »
The LHC experiment we can't do that.

But, who knows, there could be particles smaller than photons, then this could be possible.
 

Offline LeeE

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can a body reach velocity of light ?
« Reply #3 on: 05/08/2009 13:14:07 »
There are some things that can travel faster than light but the phenomenon isn't very useful in itself.  Probably the easiest example to explain and understand is the speed at which a wavefront can intersect something.

The common illustration of this to imagine sea waves breaking upon a beach where the angle that the waves intersect the beach dictate the speed of the wavefront along the beach.  If the waves are moving parallel to the beach then the wavefronts move along the beach at the wave speed but as the angle changes and becomes more perpendicular to the beach the wavefronts will move along the beach faster than the wave speed.  When the waves approach the beach at 90 degrees the wavefront breaks simultaneously at all points along the beach, so the speed of travel along the beach is effectively infinite.

Iirc this has some relevance to radar waveguides, but I can't remember the details.
 

Offline Pmb

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can a body reach velocity of light ?
« Reply #4 on: 05/08/2009 14:34:12 »
Hi ,

Is it possible to reach an object to the speed of light or exceed it ?
No. To be precise, no object, which can be at rest in one inertial frame, can move at the speed of light or faster as observed in another inertial frame. The intersection of two waves/lines is not an object so it doesn’t pertain to your question.
 

Offline krytie75

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can a body reach velocity of light ?
« Reply #5 on: 10/08/2009 19:20:23 »
Further more, as the speed of an object approaches the speed of light, the amount of energy required to further increase it's speed exponentialy increases.  As far as I know, for any object to be propelled to the speed of light would take more energy than there is in the universe.  An infinite amount of energy.  How this works for the photon I have no idea.
 

Offline Stefanb

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can a body reach velocity of light ?
« Reply #6 on: 11/08/2009 03:45:51 »
No!  ;D
Because then the body would cease to move through time and then would either suddenly exist in all time, not exist in any of it, or- if time CAN after all by divided into a smallest possible unit- would only exist in the frame of time it reached the velocity of light speed.
 

Offline lightarrow

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can a body reach velocity of light ?
« Reply #7 on: 11/08/2009 12:39:43 »
Further more, as the speed of an object approaches the speed of light, the amount of energy required to further increase it's speed exponentialy increases.  As far as I know, for any object to be propelled to the speed of light would take more energy than there is in the universe.  An infinite amount of energy.  How this works for the photon I have no idea.
Because what you said is valid for objects which have non zero mass and a photon isn't such an object (it has zero mass).
 

Offline krytie75

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can a body reach velocity of light ?
« Reply #8 on: 11/08/2009 17:21:07 »
Because what you said is valid for objects which have non zero mass and a photon isn't such an object (it has zero mass).

Ah yes quite right lightarrow.

To elaborate on my previous post:

As an object with mass increases velocity, it also get's an increase in mass. By the time an object is moving at the speed of light it would have infinite mass.  An infinite mass requires an infinite amount of energy to change it's speed.

 

Offline Pmb

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can a body reach velocity of light ?
« Reply #9 on: 12/08/2009 16:56:51 »
Quote from: krytie75
How this works for the photon I have no idea.
One does not change the speed of a photon so it doesn't apply.
 

Offline lightarrow

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can a body reach velocity of light ?
« Reply #10 on: 12/08/2009 19:44:25 »
To elaborate on my previous post:

As an object with mass increases velocity, it also get's an increase in mass. By the time an object is moving at the speed of light it would have infinite mass.  An infinite mass requires an infinite amount of energy to change it's speed.

Probably Pmb won't agree with me, but mass doesn't change with velocity (of course I'm referring to invariant = proper mass).
 

Offline krytie75

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can a body reach velocity of light ?
« Reply #11 on: 16/08/2009 00:04:28 »
Quote
Probably Pmb won't agree with me, but mass doesn't change with velocity (of course I'm referring to invariant = proper mass).

Einsteins famours equation e=mc^2 says that as velocity increases, so does mass.  But you just said mass doesn't change with velocity.  Can you explain the conflict?
 

Offline lightarrow

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can a body reach velocity of light ?
« Reply #12 on: 16/08/2009 02:46:33 »
Quote
Probably Pmb won't agree with me, but mass doesn't change with velocity (of course I'm referring to invariant = proper mass).

Einsteins famours equation e=mc^2 says that as velocity increases, so does mass.  But you just said mass doesn't change with velocity.  Can you explain the conflict?
What is mass? How do you define it? What does that equation really mean?
In special relativity (that is, in a flat spacetime) there are just two kinds of mass: proper = invariant mass and relativistic mass. The second, however, is much less used now than in the past, because of various reasons. We are left with the first one, invariant mass (when physicist says "mass" they almost always mean that one).
Then, the correct equation which relates mass to energy is not the one you wrote, but:

E = Sqrt[(cp)2 + (mc2)2]

E = energy
m = mass
p = momentum

the one you wrote is then valid *only* at zero momentum, for example for a still body.

The term "invariant" means, in relativity "it doesn't change from a frame of reference to another one". Invariant mass is one of such quantities, so it doesn't change with speed. An electron has a mass of ≈ 9*10-31 kg, and it keeps that value whatever its speed (and the same for anything else).

What changes with speed is momentum and energy, not mass.
« Last Edit: 16/08/2009 02:49:07 by lightarrow »
 

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can a body reach velocity of light ?
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