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Friskydingo

Would an object be invisible if traveling faster than light?

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If the object itself produced light, since light speed is constant and its speed is not increased by originating from a moving object, the object would arrive at us before its light was reflected into our eyes. If light from a source at our feet were to bounce off the object, it would again, still reach us before the light returned to us. So would it not be technically invisible?

Something else that has been on my mind, i find it troubling to think that the speed of light is constant. Light moves away from you at the same speed no matter how fast you are traveling, so that is never possible to catch up to its edge. However if we take a source of light that is flipped on while me and you stand at its source and you begin to travel at half the speed of light at the same time the light source is flipped on, how does light stay at a constant speed for us both? Your beam of light would have to be traveling faster than my beam in order to travel at its constant speed. For those who may know of the light horizon, i think that light is for the most part instant, that it has no speed in which it must travel. It simply fades out at different lengths depending on the strength of the source.

Edited by Friskydingo

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If the object itself produced light, since light speed is constant and its speed is not increased by originating from a moving object, the object would arrive at us before its light was reflected into our eyes. If light from a source at our feet were to bounce off the object, it would again, still reach us before the light returned to us. So would it not be technically invisible?

It's unclear what would happen to light crashing into such a fast object. I do get your logic, but light does have an identity, it can't just dissappear, and I don't know what would happen to it: so I've no idea.

Something else that has been on my mind, i find it troubling to think that the speed of light is constant.

Any arguments or reasons for this feeling of unease about a proven fact?

However if we take a source of light that is flipped on while me and you stand at its source and you begin to travel at half the speed of light at the same time the light source is flipped on, how does light stay at a constant speed for us both?

It doesn't stay at a relative constant speed. It stays at a constant speed period, but for the person moving, it would seem to have a different speed.

Edited by Jake_Ellison

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So would it not be technically invisible?

No, because sooner or later, the light emitted from it would reach your eyes.

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I suppose it could be considered effectively invisible, since it would pass you before you saw it.

A supersonic bullet serves as an analogy. If you were to be shot at by such a round, you'd first know you were shot, then you'd hear the bullet being shot.

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Would an object be invisible if traveling faster than light?

As relative velocity approaches light speed, an object's mass approaches infinity. Something "faster" than the speed of light would have "greater than" infinite mass. The concept doesn't make any sense.

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i think that light is for the most part instant, that it has no speed in which it must travel. It simply fades out at different lengths depending on the strength of the source.

The speed of light was first measured in 1676 by Ole Christensen Rømer, who was studying the motions of Jupiter's moon, Io, with a telescope. You can verify their results yourself by heating marshmallows in a microwave (they will show wavelength of the microwaves) or a cheap Walmart telescope.

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If the object itself produced light, since light speed is constant and its speed is not increased by originating from a moving object, the object would arrive at us before its light was reflected into our eyes. If light from a source at our feet were to bounce off the object, it would again, still reach us before the light returned to us. So would it not be technically invisible?

Something else that has been on my mind, i find it troubling to think that the speed of light is constant. Light moves away from you at the same speed no matter how fast you are traveling, so that is never possible to catch up to its edge. However if we take a source of light that is flipped on while me and you stand at its source and you begin to travel at half the speed of light at the same time the light source is flipped on, how does light stay at a constant speed for us both? Your beam of light would have to be traveling faster than my beam in order to travel at its constant speed. For those who may know of the light horizon, i think that light is for the most part instant, that it has no speed in which it must travel. It simply fades out at different lengths depending on the strength of the source.

If atoms could move faster than light then yes, you could be hit in the head with one before seeing it with your eyes. The supersonic bullet is a good analogy.

The reason you and your friend both calculate the same speed of light is very simple. Your friend, travling at 0.5*c relative to you, has a clock that physically ticks slower than yours. So you see the light beam traverse a meter in a single tick of your clock, your friend sees it traverse half a meter but also only sees half a tick of his clock. You both get c=1.

Any arguments or reasons for this feeling of unease about a proven fact?

This is a bit patronizing and heavy-handed. Frisky is trying to visualize and understand the situation from a rational, intuitive approach in hopes of reconciling it with observations.

It doesn't stay at a relative constant speed. It stays at a constant speed period, but for the person moving, it would seem to have a different speed.

No, light does not "seem to have a different speed" for the person moving. Light's speed is calculated exactly the same.

The speed of light was first measured in 1676 by Ole Christensen Rømer, who was studying the motions of Jupiter's moon, Io, with a telescope. You can verify their results yourself by heating marshmallows in a microwave (they will show wavelength of the microwaves) or a cheap Walmart telescope.

Yeah, I've heard the "light is instantaneous" argument before and I can't conceive of any way it could possibly be true. Not only do I have issues with "true instantaneity" but every experiment ever done summarily falsifies it. In particular, a very simple setup (done in high vacuum 10^-10 mbar):

Source S and detector D are separated by 1 unit distance. Turn on the source and a timer, D detects and turns off the timer. The time for this is t and the speed of light is 1/t. If light is "instantaneous" then t is the time for us to detect the change in D, which is essentially constant.

Now S and D are separated by 100 unit distances. Repeat the experiment. If light is "instantaneous" but only appears to have a finite velocity because it takes some time for us to detect it, then we will get the speed of light has 100/t, where t is essentially a constant temporal offset.

Thus, if light were "instantaneous" we would expect its calc'd speed to increase with the separation of source and detector. We do not observe this effect. Until the proponents of "instant light" can surmount this seemingly invincible empirical barrier, I do not know how anyone can take such an idea seriously.

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Another way to measure the speed of light is to measure the ping time between two internet connections with the same number of nodes but different distances. Most long-distance traffic is carried by fiber-optic cables, so the difference will the travel time of light.

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I propose that you find this theoretical faster-than-light object before you worry about what color it is. :confused:

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I propose that you find this theoretical faster-than-light object before you worry about what color it is. :confused:

Agreed, no object with any mass to it at all can exceed the SOL.

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Something else that has been on my mind, i find it troubling to think that the speed of light is constant. Light moves away from you at the same speed no matter how fast you are traveling, so that is never possible to catch up to its edge. However if we take a source of light that is flipped on while me and you stand at its source and you begin to travel at half the speed of light at the same time the light source is flipped on, how does light stay at a constant speed for us both? Your beam of light would have to be traveling faster than my beam in order to travel at its constant speed. For those who may know of the light horizon, i think that light is for the most part instant, that it has no speed in which it must travel. It simply fades out at different lengths depending on the strength of the source.

Look up Michelson-Morley and read Einstein's "On the Electrodynamics of Moving Bodies." (Special Relativity)

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No, light does not "seem to have a different speed" for the person moving. Light's speed is calculated exactly the same.

True, I misspoke there. In fact light would still seem to be moving at the same speed, even if you were moving very fast in the same direction as the light you're emitting. (That light would be blue-er though, right?)

The reason you and your friend both calculate the same speed of light is very simple. Your friend, travling at 0.5*c relative to you, has a clock that physically ticks slower than yours. So you see the light beam traverse a meter in a single tick of your clock, your friend sees it traverse half a meter but also only sees half a tick of his clock. You both get c=1.

That doesn't work out. Someone travelling at half the speed of light doesn't have time slow down by half:

post-5684-1240619305_thumb.gif

According to that formula, at 1/2 the speed of light t' = t * sqrt(1-1/4)=t * 0.866...

That's 866/1000th of a clock tick, for every tick of the stationary clock.

That leaves the original question unanswered. (That's the main reason why I revived the thread)

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That leaves the original question unanswered. (That's the main reason why I revived the thread)

Assume there's a test apparatus with a light source at x=0 and a light detector at x=1. Assume two observers, the first is stationary relative to the test setup, and the second is moving along the x-axis at speed v. The first observer sees light emitted at x1=0, t1=0, and sees it detected at x2=1, t2=1/c (where c is the speed of light). Special relativity states that the second observer will measure a different location of the detector relative to the source, and a different passage of time for the event, because he is moving relative to the apparatus.

The location of the detector will be:

0c6ee87a22e51e7957c20995931ba43a.png

The time of the detection will be:

c0ff5f091774a86621f711d11e7c0068.png

So, observer 2 sees the light emitted at x1'=0, t1'=0, and sees it detected at x2'=x', t2'=t'. To calculate the speed of light, both observers divide the observed distance between source and detector by the observed time between emission and detection.

Observer 1 finds that (x2-x1)/(t2-t1) = c.

Observer 2 makes a similar calculation: (x2'-x1')/(t2'-t1').

Since x1' and t1' = 0, this reduces to x'/t'.

You can see from the above equations that the term sqrt(1-v^2/c^2) cancels,

leaving (x-vt)/(t-vx/c^2).

Plug in x=1 and t=1/c, and this reduces to x'/t' = c. And everyone agrees on the speed of light.

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True, I misspoke there. In fact light would still seem to be moving at the same speed, even if you were moving very fast in the same direction as the light you're emitting. (That light would be blue-er though, right?)

That doesn't work out. Someone travelling at half the speed of light doesn't have time slow down by half:

post-5684-1240619305_thumb.gif

According to that formula, at 1/2 the speed of light t' = t * sqrt(1-1/4)=t * 0.866...

That's 866/1000th of a clock tick, for every tick of the stationary clock.

That leaves the original question unanswered. (That's the main reason why I revived the thread)

I shouldn't have stated that the "friend" was moving at 0.5*c. What I said wasn't meant to be taken quantitatively but rather qualitatively. When you move faster relative to your friend you both calculate the same speed of light, although you both perceive different distances-traveled and different "times".

So if you're moving toward the light source at .5*c and your friend is "stationary" s/he sees light going at a speed of 1/1. You see it going at 0.577/0.577 = 1. You will of course observe a doppler blue shift but a relativistic red shift. To know which way it goes you'll just have to calc it, wikipedia has lots of great articles on rel, here's the one on the relativistic doppler shift:

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

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i agreed light is a visible part but it also have a invisible part. see in light photon is an object which travel at speed of light define in the world but that object is move at that speed due to energy in photon and photon does not allow to them to release that energy in it. photon bound that energy in itself. one thing is here the speed of light is actually depend on photon energy at the speed of light photon does not allow to move more then at S.O.L because it a breaking point for photon and it maintain it continuously if it will break the photon is vanish light get speed more then S.O.L (speed of light )which is last define but it cant see so we cant proof till. 

IF it will see so it means the actual speed of light is 2 * (S.O.L)   i definitely sure it will and i try to see possible by good proof which clear all contains of it 

THE question is this

1.    what is the frequency of that light which is become invisible

2.    how to break the photon energy

and etc.

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