If you shined the light backwards,would anyone ever see it?

22 by I.R. Brainiac - 6/11/2004 12:24:22 AM So where does the light go?

Well the headlights would shine, it just can''t travel no farther or faster than you.


[Message Edited]

So what happens to it?

Backwards of what????

Also images are made of light hitting the eyes...at the speed of light...why are not your eyes overwhelmed by the light?(they cant disapate light that fast)

Just a few questions to ponder...gotta go to bed...night people

I.R.

Lots of questions!

According to the theory of relativity, no matter what your particular frame of reference, you will always measure the velocity of light to be 'c', or approximately 300 million centimeters per second. How fast you're travelling doesn't make a difference in this context. From your viewpoint, shining the flashlight would look just like it would if you lighted it at *any* other speed.

As for light hitting your eyes, it isn't a matter of dissipation. The photons of light that hit your eyes are absorbed by the atoms in the light receptors in the retina, causing the electrons of the atoms in question to increase its energy level, which indirectly triggers an electrochemical reaction in the nerve connection to the retina. This electrochemical reaction travels down the optic nerve and triggers a response in the visual cortex of your brain.

The energy content of a photon is directly proportional to the frequency of the radiation, not its velocity. Red light has less energy (lower frequency) than blue light (higher frequency). Since photons have a proper mass of zero, they don't have momentum as such (although there is a recoil effect when the electron in an atom absorbs a photon, and an equivalent recoil when the electron releases a photon).

Simple answer, light photons are absorbed, not dissipated (the contained energy is applied to the system, but it is quite small overall, but it can be overdone, as evidenced by the fact that viewing the sun without protection will destroy your retina (energy overload)).

So if you can get a car to go at the speed of light and turned on your headlights, from your vantage point, it would look perfectly normal (actually, you can get close to the speed of light, but you can't actually reach that speed, as the energy required to accelerate you would be infinite, relativity again).

From the viewpoint of a distant observer, if you were moving away from him, and your headlights were aimed in the direction of your motion, he would see nothing, as the photons from your beams would be outside of the scope of his observable viewpoint. If your headlights were aimed at the observer, and you were travelling away from him at near the speed of light, the frequency of your light beams would be 'red-shifted' or lowered in frequency probably to the point where they would now be identified as radio waves in the very low frequency band.

If your headlights were aimed at the observer, and you were travelling toward the observer at near the speed of light, the frequency of your light would be 'blue-shifted' or raised in frequency, and would probably be identified by the observer as gamma radiation. You would also reach the observers location shortly after your light beams do.

If you were travelling at right angles to the observer, and were aiming your light at the observer, he would see it at the same frequency that was emitted.

The above is a very simplistic description of the events, doing the explanation justice would require a substantially longer post.

And if you think relativity is weird, you should try quantum physics

Well you've settled that argument... Now then, is ice cream a liquid or a solid?

Proper ice cream is chocolate

Aleatoric....good try...but if the source of light emission is travelling at the speed of the emission nothing will be emitted at all.

Call it phase shifting or doppler effect, but the perception of light emitted from a moving source comming towards you will still reach you at the same speed...that of light...but subsequent emissions will appear 'sooner'...and phase-shift to a shorter wave frequency....same speed.

Assuming light-speed is reached the photons will not 'project' from the source faster than the source moves ...at which point the light will be 'black'.

If it can be shown that this is not particle theory but wave theory where it can be argued that there is a 'back pressure' projecting the light the light will be 'pushed' at the speed of the object emitting it....in other words light speed and look entirely normal....that is, until you have that automobile square between your eyeballs and it ALL goes real black for a real long time....

head .... hurts .... mmm, ice cream

You would be crushed by the force of traveling thru air molecules at some speed well before reaching light speed. I'm guessing the speed of sound so you don't hear your head implode.

Armadillo's is speedbumps. We got moose

If you stand at a perpendicular angle to a light beam passing thru a vacuum, can you see it?

No, because it is flat.

Jafo,

Actually, while there are a couple of unique characteristics for an object travelling *at* the speed of light, the theory of relativity still holds.

I had reframed I.R.'s question to take the case of an observer with a flashlight travelling at some speed close to the speed of light (since an object with mass cannot actually reach the speed of light.

However if we want to actually consider the behaviour of some object that is actually at the speed of light, we can solve Einstein's equation using c as the objects velocity.

In that case, solving for t (time) gives us an answer of zero, and the Lorentz contraction frame also reaches zero. What this means is that if an observer could actually *reach* the speed of light, both time and distance would be zero and the observers frame of reference would be as if he were everywhere at once (in other words, from the observers perspective, it would take zero time to travel any distance).

Also, there is no difference in the behaviour of light at relativistic speeds (or even at light speed), regardless of whether you treat it as a particle or a wave. That's just a fundamental characteristic of quantum physics. The equations solve the same regardless (actually, the equations state that the photon exhibits both characteristics).

As for the doppler effects, from a wave standpoint, the frequency of the emitted light is changed by the motion of the source, from a particle standpoint, the energy of the emitted light is changed by the motion of the source. Since the frequency of the light is isomorphic to the engery of the photon (E=hf, energy = frequency times Plancks constant), the result of the emission is the same whether taken as a particle or a wave.

It's all about the decision of whether the speed of light is an absolute....a range that cannot be exceeded...in which case the projector's speed cannot be added to the light's speed....wave, or particle.

Simple math...when accepting theorems relating to absolutes...infinity, etc....

It's all about the decision of whether the speed of light is an absolute....a range that cannot be exceeded...in which case the projector's speed cannot be added to the light's speed....wave, or particle.

Actually, that's correct, as far as it goes. The interesting bits happen because relativity states that there's no privileged frame of reference (for all observers, the speed of light will be measured the same, no matter how fast one observer may be travelling with regard to some other observer).

At relativistic velocities, the math is not merely additive.

Anyway, this could be a book (and has been several ) and I'm sure no one really wants to see a 30,000 word post on relativity and quantum physics Suffice it to say that the universe is fascinatingly strange, and it's a lot of fun playing with it

Two Zen monks were arguing about a flag waving in the breeze, and whether it was the flag or the wind that was moving. The Sixth Patriarch of Zen, Hui Neng, overheard "I suggested it was neither, that what moved was their own mind."

/me ponders and scatches head at above conversation.

Ice cream is still liquid, just frozen. And proper ice cream is in my tummy

*Hides in the closet with a flashlight and a mirror...crams the flashlight in her mouth....turns it on and looks in the mirror......



Heckuva way to get rosey cheeks!!!

UBoB,

You're making the unwarranted assumption that I *have* a mind

Or ..

I have a mind like a steel trap. There's a dead raccoon stuck in it

Ice cream is still liquid, just frozen.

If it is frozen, then isn't it a solid?

Is glass liquid or solid?  (that's an odd one)

Jell-o is a colloidal suspension

Glass is an amorphous solid (i.e. non-aligned crystalline structure).

As for ice cream, if you don't think it's a solid, you've never tried to spoon it out right from the freezer

Glass is an amorphous solid (i.e. non-aligned crystalline structure).

Actually, that is just one side of the debate:
"Glass is a liquid," and "Glass is an amorphous solid," and "Glass is neither a solid nor a liquid." There is not a lot of consensus.

A lot of scientists just put it in its own category as "glass".

ponders the deeper meaning of 'glassy eyed'