Matter breaking the speed of light? [Nope]

[phinds]

As if the moon is a flat surface with equal distance away from all angles, you make a pretty bad argument here.

Huh? Have you calculated what % of the distance from here to the moon is represented by the radius of the moon?

 

[TheScienceOrca]

Huh? Have you calculated what % of the distance from here to the moon is represented by the radius of the moon?

It doesn't even matter! Each single photon is traveling at the speed of light just because you have more doesn't mean you can count the "group" of photons as a single object moving over the speed of light.

 

[TheScienceOrca]

But yes due to the curvature some photons will arrive at slightly different times than others.

 

[PeterDonis]

The time it takes for the photon from the laser in your hand to the moon to register each new position is slower than the time it would take for light to travell from A to B on the surface of the moon.

Here's an explicit calculation to show that this is not necessarily true.

Suppose we have two photons: the first is aimed at point A at the left edge of the moon, and the second is aimed at point B at the right edge of the moon. That's a distance of about 3500 km (note that I'm ignoring the curvature of the moon's surface--if you include it it just makes the distance larger and strengthens my argument). Light travels that distance in about 0.012 seconds; so if the two photons are emitted less than 12 milliseconds apart, the second photon will arrive at point B faster than light could have traveled from A to B if it started when the first photon arrived at point A. Unless you're maintaining that it's impossible for the two photons to be emitted less than 12 milliseconds apart, then your statement is disproved by the above.

 

[Fredrik]

As if the moon is a flat surface with equal distance away from all angles,

If that bothers you (and it really shouldn't), you can choose A and B to be two points on the surface of the moon that are almost exactly the same distance from you. Then you can easily see that the time it takes for the dot to move from A to B is the same as the time it takes to rotate the laser. The fact that the surface is curved between A and B only means that the dot will have an even greater speed than it would have had if the surface had been flat.

 

[ComplexVar89]

Why do you keep equating an interval, a measure of time, with light-speed, a velocity? They just aren't the same thing, as has been pointed out to you a couple of time (and now once more).

This is exactly what I was wondering.

 

[TheScienceOrca]

If that bothers you (and it really shouldn't), you can choose A and B to be two points on the surface of the moon that are almost exactly the same distance from you. Then you can easily see that the time it takes for the dot to move from A to B is the same as the time it takes to rotate the laser. The fact that the surface is curved between A and B only means that the dot will have an even greater speed than it would have had if the surface had been flat.

I agree up until "The fact that the surface is curved between A and B only means that the dot will have an even greater speed than it would have had if the surface had been flat."

I disagree here, the photons will always move at the speed of light no matter the frame of reference. So the speed of them doesn't change only the time of arrival of the photons relative to the observer does.

 

[Fredrik]

I agree up until "The fact that the surface is curved between A and B only means that the dot will have an even greater speed than it would have had if the surface had been flat."

I disagree here, the photons will always move at the speed of light no matter the frame of reference.

That's not a disagreement. The speed of the dot has nothing to do with the speed of the photons. If you could change the speed of light, this would only affect when the dot starts moving. It would have no effect on its speed.

 

[TheScienceOrca]

That's not a disagreement. The speed of the dot has nothing to do with the speed of the photons. If you could change the speed of light, this would only affect when the dot starts moving. It would have no effect on its speed.

Thanks for the clarification, disregard my last post by dot I thought you were referring to a single photon, not the array of photons.

 

[Buckleymanor]

Here's an explicit calculation to show that this is not necessarily true.

Suppose we have two photons: the first is aimed at point A at the left edge of the moon, and the second is aimed at point B at the right edge of the moon. That's a distance of about 3500 km (note that I'm ignoring the curvature of the moon's surface--if you include it it just makes the distance larger and strengthens my argument). Light travels that distance in about 0.012 seconds; so if the two photons are emitted less than 12 milliseconds apart, the second photon will arrive at point B faster than light could have traveled from A to B if it started when the first photon arrived at point A. Unless you're maintaining that it's impossible for the two photons to be emitted less than 12 milliseconds apart, then your statement is disproved by the above.

It's certainly a good calculation.If there is a problem it's my interpretation of the video explanation.The film and it's soundtrack give the impression of a single dot traveling across the moon for the laser to travel A to B in 0.012 seconds the dot would be more likely to appear as a continuouse strip of scattered light.

 

[Dryson]

No.
An object with mass traveling at the speed of light would have infinite kinetic energy. It doesn't matter how long the rod or how stiff, if a part of that rod is to travel at the speed of light you will have to expend an infinite amount of energy to accelerate it to that speed. In your scenario that would mean applying an infinite torque to the end of the rod you are holding.

Formula's mean nothing unless you have a visual account of the test to either prove or disprove the theory. There is much about space that we do not know anything about or even aspects of space that Einstein didn't know about when he was formulating his math.

Has it been proven that an object traveling at the speed of light does in fact have infinite kinetic energy?

 

[PeterDonis]

Has it been proven that an object traveling at the speed of light does in fact have infinite kinetic energy?

How would you "prove" this, given that it's impossible to run the experiment?

A better question would be, "Have we taken objects with mass and accelerated them to very high speeds, and measured how much energy it takes vs. the final speed, and compared that to the predictions of SR?" The answer to that is yes, and the experiments match the predictions of SR: the energy required to accelerate an object of mass $m$ to speed $v$ goes up exactly in accordance with the SR formula. This has been done, IIRC, for speeds up to one part in a trillion or so short of the speed of light for electrons. So we can certainly extrapolate from this data that the energy required increases without bound as the speed of light is approached (which is what "infinite kinetic energy at the speed of light" really means).

 

[A.T.]

The film and it's soundtrack give the impression of a single dot traveling across the moon for the laser to travel A to B in 0.012 seconds the dot would be more likely to appear as a continuouse strip of scattered light.

To the naked eye it would appear like a line, just like in a laser projector, because the human eye is too slow. That doesn't change that fact, that there actually is a light dot moving across the surface faster than c.

Nothing in your posts so far indicated that you were talking about the limitations of human vision. It seemed that you were talking about an actual physical limitation of the dot speed.

 

[Borek]

continuouse strip of scattered light.

What is stopping you from using a high power laser which emits enough photons in between to produce a traveling dot?