The Last Physics Question - Hopefully

[cabinetman]

Lets pretend you are driving your car at night at the speed of light (neat huh), and turn on your headlights. Will they do anything?



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[gjat]

What do you mean 'do'? Illuminate 1,000 feet ahead, or 'light up' by having electricity travel through the tungsten and create heat energy?

Yes, the lights would light up, but you would be traveling faster than what they illuminate ahead. If you turn a flashlight on inside, it would seem normal because the objects are moving just as fast relative to the light source.

[JBCrooks]

I have an unfair advantage on this one. (Just finished reading Einstein's Relativity). To make it more real, lets say the car was going 90% the speed of light when you turned on the headlights. You would see the beams of light moving out from you at the full speed of light (~300,000 km/s). A static observer would also see the beams moving at the speed of light. The difference is due to time and distance being variable with speed.

[jwaterdawg]

A static observer would also see the beams moving at the speed of light.

Not to pick semantics but there is no such thing as a "static observer". Any other observer would see the photons moving at the speed of light relative to them.

[cgallery]

I have an unfair advantage on this one. (Just finished reading Einstein's Relativity). To make it more real, lets say the car was going 90% the speed of light when you turned on the headlights. You would see the beams of light moving out from you at the full speed of light (~300,000 km/s). A static observer would also see the beams moving at the speed of light. The difference is due to time and distance being variable with speed.

R U sure that is right? Light would be traveling at 300,000km/sec + 300,000km/sec(.90). Or am I totally wrong on this?

[dlminehart]

Totally wrong. That's the weird thing, why it took hundreds of years after Newton for an Einstein to figure it out. The trick is that neither time nor space are absolutes. 300,000km/sec is how fast light goes in a vacuum, but the km and sec stretch or compress depending on the objects' speed relative to the observer.

For example, if you were moving 90% as fast as light, space would be relatively compressed around you, but to you it would look normal. Therefore, for you, the light moving away from you in this compressed space would seem to be going through the usual number of (squeezed) kms, looking like it was going 300,000km/sec relative to you. For the (relatively) static observer, the light would also seem to be going at 300,000 (relatively unsqueezed) km/sec, but you'd be going 270,000 km/sec, almost keeping up with it.

That's why it's called the Theory of Relativity. Dimensions of time and space depend on the relative speeds of observers. The constant is the speed of light, with the distances and times adjusting accordingly.

[jseklund]

I have a feeling someone else will be better able to answer this, but the answer is that nothing spectacular would happen. Everything would appear to be the same as if you were driving at 60 MPH and turned on your lights. The reason is that TIME is relative (Thanks Einstein). Time is a fourth dimension of space in this instance. Since Speed = Distance/Time, if time is relative to my position in space, then speed is also relative.

For instance- if I am standing across the room from you, and throw a lightbulb at you at 5 mph, assuming it stays lit, the light is not moving towards you at the speed of light + 5 mph. It is moving towards you at the speed of light still.

The lights would travel out from my position at the speed of light, and my position would be changing at the speed of light.

[Stytooner]

If I was traveling the speed of light at night, I would not worry about the headlights, but rather my reaction time to the brake peddle. Better yet, the reaction time from my eyes to my brain. At that speed, these times would be critical in light or dark.
But to answer the question, the head lights are probably mounted about 6 foot in front of you. This is how far I think the beam would shine out.
No wonder Star Trek has sensors that sense thousands of kilometers away. They need to know when to put on the brakes.

[DJehlik]

Does the Doppler Effect play a part in this scenario?

[dlminehart]

I believe the Doppler Effect only refers to sound, which is generated at a particular frequency but the movement of the generator changes the frequency relative to a stationary listener. Requires a medium (air). No Doppler Effect in space.

[BigguyZ]

I believe the Doppler Effect only refers to sound, which is generated at a particular frequency but the movement of the generator changes the frequency relative to a stationary listener. Requires a medium (air). No Doppler Effect in space.

Not true. The doppler effect, or Doppler Shift, is used to determine the distance of a star away from us. The more shift, the further the distance. It can also be used to determine other factors as well.

Due to time and space dialation, the obverser in the car would see the project forward at the speed of light.

[Kristofor]

Doppler shift would apply to things (like stars) outside of your inertial reference (ie any stars you don't happen to be taking with you in your car). Stars you're approaching would appear shifted toward the blue, and those you're traveling away from would shift red.

[big tim]

I guess the headlight light would travel at twice the speed of light.

[onedash]

Some of this science stuff I wonder about. The whole doppler effect about color shift and they can tell if the start is moving towards or away etc....I just seen in the news a black hole ate a star.....More mumbo jumbo...Most of the people making these claims think we came from monkeys and the big bang created the universe..No offense if you believe that....
Now as far as some of this stuff they claim to "see" is just an ultraviolet burst in the case of the black hole eating a star....
Even carbon dating....If we have a machine that can carbon date something you calibrate it.....You take something a known age and if it measures correctly I assume it would pass...well whats the oldest known sample age we can use to calibrate the machine??? And I know carbon deteriorates at a certain rate (so they say) but how do we know it always has??? Maybe God changed something along the way..Why did people stop living hundreds of years? I dang sure don't believe the earth or universe is trillions of years old......
Anyhow I don't think the headlights would produce light like they do on the at highway speeds (overdriving your headlights) just like a jet flying faster than the speed of the bullets from their guns..They can fire them but they better move or they will fly into them..But then again bullets slow down....Light doesn't..It just reflects or gets absorbed unless it changes medium at which point it can change speed..Right???

[Otter]

Part 1: the first question.

If you were traveling at the speed of light and turned on your head lights you would not see the beams. the light would come into being (here is where things get tricky, is light a wave or a particle, if it is both, then where dose the photon come from?) but it and you would be traveling together.

Part 2: The observer.

As much as light as a wave has been popularized it is part of the idea of dilatation and if you believe light to be a wave then Doppler plays here as well. The observer in the car would see the standing person as frozen, where the stander would only see a blue shifted streak as the car approached and a red one after it passed.

If you really want to play lets whip out Heisenberg, Schrodinger and Maxwell and throw them in the mix….Who wants to play.