Physics Speed of Light and car Question

• 22-16
In summary, the question of whether light would project from a car traveling at the speed of light and turning on its headlights is a thought experiment that led to the development of Einstein's theory of relativity. According to this theory, the speed of light is constant in a vacuum, and any object moving at the speed of light would experience time dilation and length contraction. Therefore, it is impossible for a car to achieve such a speed, but a similar situation can be observed
22-16
If a car was traveling at the speed of light, and it turned on its headlights, would light project from the car[?]

Originally posted by 22-16
If a car was traveling at the speed of light, and it turned on its headlights, would light project from the car[?]

Probably since the photons weren't generated until the headlights were turned on. But I think the car woul have been long incinerated if you accelerated close to the speed of light so there would be no headlights to turn on.

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Greetings !

Welcome to PF 22-16(are you a Borg unit ? ) !
Originally posted by 22-16
If a car was traveling at the speed of light, and it turned on its headlights, would light project from the car[?]
To the passengers in the car everything
will "look" normal - the light will move
from them at c. To the outside relativly
stationary observer everything will also
"look" normal - he/she'll see the light
moving slowly ahead - just a bit faster
than the car (the car can not reach c, it
can only come close to it).

I said "look" because the only way for you
to know that the light is there is for some
of it to get reflected towards you by
particles. (In the vacuum of space, that's
a problem.)

Live long and prosper.

First of all, it is important to note that no material object can travel at the speed of light in a vacuum) It will always travel at some speed just slighty less. In which case, the answer Drag gave is correct.

It also is useless to ask, "But what if the car could travel at the speed of life".

Because that would mean that the rules which we need to use to answer the question have been broken and no longer apply to the question. (All bets are off in that case, and anything could happen.)

This is actualy an interesting question when broken down. Light doesn't always travel at c, in some materials it moves much slower than c, but in this same situation another object could in theory not only move at the same speed of the light, but even faster than the speed of the light. So if the car was moving just slightly slower than the light, then the light would slowely move away from the car, but beyond that I don't know what would happen. You would assume that the same thing that happens to sound abouve the sound barrier, only you would have to work out the equations for the "Chandrikara"<spelling is off, can't think of how to spell it right now> would have to be applied, but I would assume the passangers would see some sort of strange doppler lighing effect, would be cool to see, and mabey even more interesting to think more on.

^^^ The trick is "if the car was moving just slightly slower than the light." According to who?... some second observer; they would see light just barely getting away from the car. The people in the car would see their light moving away at normal speeds, and the outside world squished and sped-up.

Originally posted by 22-16
If a car was traveling at the speed of light, and it turned on its headlights, would light project from the car[?]
Yes ... the fundamental postulate to special relativity is that light always travels at the same speed in a vacuum ... no matter who you are (providing all individuals concerned are traveling at a constant velocity). When the equations are worked through you find that the car can not travel at a velocity of c because the equations reach a singularity which is not something you want.

A variant on this theme was proposed by Einstein himself ... if myself and a mirror are traveling (in a vacuum) at a the speed of light would I see my reflection in the mirror?

As per SR, if we assume u r able to get velocity slightly slower than c, then according to ur dilated time of 1 sec the relative velocity of light is c with respect to u ( c is constant in any frame of reference ).

It also is useless to ask, "But what if the car could travel at the speed of life [sic]".
Agreed.

If black was white what color would it be?

Such questions are utterly meaningless.

I think your missing the point, the car can't move at the speed of light in a vacum, but a car could move at the speed of light in another medium, and that is what poses the interesting question.

yes

i think the answer is yes
this question make Einstein create the theory of relativity
for the theory
the light will never change it speed...
no matter the source of the light moving with wat speed...

I think your missing the point, the car can't move at the speed of light in a vacum, but a car could move at the speed of light in another medium, and that is what poses the interesting question.
Not correct. The speed of light through a medium is APPARENT speed, not actual speed. It only appears to be traveling faster because it stops every now and then. Photons ALWAYS travel at C.

Originally posted by russ_watters
Not correct. The speed of light through a medium is APPARENT speed, not actual speed. It only appears to be traveling faster because it stops every now and then. Photons ALWAYS travel at C.

but, charges moving through water (say) at less than c_water(~c/1.3?) produce cherenkov radiation, a neat blue glow that is used to detect all sorts of things (famously neutrinos, recently).

per SR,

imagine fast car traveling through medium akin to water.
to ourside observer, car is nearly keeping up with it's beams - neat

to inside observer, length contraction should make the water seem much much denser - which will make the beam in the car frame travel very slowly.

this, coupled with time dilation should make things work out consistently.

(an interesting thought - beams (as apposed to light - the distinction between "classical beams" and photons is important) can be slowed to ~0m/s (in BEC's at harvard and elsewhere?) so one could almost preform this experiment!)

Joe

Originally posted by russ_watters
Not correct. The speed of light through a medium is APPARENT speed, not actual speed. It only appears to be traveling faster because it stops every now and then. Photons ALWAYS travel at C.

This is true, but your missing the point of the question, in another medium the car would be able to "out run" its headlights.

Originally posted by MrCaN
This is true, but your missing the point of the question, in another medium the car would be able to "out run" its headlights.
Indeed, fascinating isn't it...

Originally posted by drag
Indeed, fascinating isn't it...
...nope.

1. What is the speed of light in a vacuum?

The speed of light in a vacuum is approximately 299,792,458 meters per second, or about 186,282 miles per second.

2. How does the speed of light affect a car's speed?

The speed of light does not directly affect a car's speed. The speed of light is a constant and does not change, while a car's speed can vary depending on factors such as acceleration and friction.

3. Can a car ever reach the speed of light?

No, according to Einstein's theory of relativity, it is impossible for any object with mass to reach the speed of light. As an object approaches the speed of light, its mass increases infinitely and would require an infinite amount of energy to accelerate further.

4. How is the speed of light related to time and space?

Einstein's theory of relativity states that the speed of light is a fundamental limit for the speed at which all particles and information can travel. This means that as an object approaches the speed of light, time slows down and space contracts.

5. Why is the speed of light considered a universal constant?

The speed of light is considered a universal constant because it is the same for all observers, regardless of their relative motion. This is one of the fundamental principles of Einstein's theory of relativity.

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