Lightspeed and your headlights

Lets say we have a spacecraft travelling at light speed. Ok we flip on the headlights... what would happen? Would there be no light? Would it reach a certain point and stop? Or would the lights work in a normal fashion?
......What if we flipped on headlights in the rear in the opposite direction???
If the forward headlights worked normally, would the light be travelling twice lightspeed??? Any thoughts and opinions greatly welcomed.

Very interesting thought brought up by my 7 year old cousin

Well if the car travels at the same speed as the light from the headlights, you wont probably see the light. Light would only travel faster if your car travels faster than the speed of light.

well what ive read and seems to be popular thinking is that

u in the ship wouldent see the light becouse its travelling the same speed as the ship

but an observer outside would see the light emitting from the ship
becouse its all rellative.

but that would mean from the observers point ov view the beem of light would be travelling twice the speed of light wich i think is impossible

if i thrust a torch forward it doesent make it come out faster
same as a hair dryer wouldent

im confused now

I have wondered some thing like that.


On star trek and other sci-fi movies you have a ship traveling faster than light and it shoots another ship also traveling faster than light with a laser beam.

If you are going faster than light wouldnt you shoot yourself?

You, in the ship, would see the light move out in front of you just like if you were sitting still.

Anyone outside would see the light and you at the same moment. It wouldn't go faster, time would just be distorted.

That's the thing about relativity, it is all relative. No matter your speed, light speed is still light speed.

You, in the ship, would see the light move out in front of you just like if you were sitting still.

Anyone outside would see the light and you at the same moment. It wouldn't go faster, time would just be distorted.

could u explain how this works viendin? please

i know its reletive but does the light go twice the speed or does it just look that way

How could someone on the outside observe something travelling at light speed??? Unless the time distortion was suffiecient enough.

If the speed of light were fixed no matter what the speed of the object emitting it, I wonder what would happen if you pointed a laser straight ahead of you while you travelled at the speed of light.

Seems like more and more light would build up in a single spot. (Since you are constantly emitting light in the same spot where the other light beams currently are).

The speed of light is relative to space/time. Look at is this way:
(1) The Earth spins at 0.5 km/sec.
(2) The Earth is revolving around the sun at 29.77 km/sec.
(3) Our solar system which is located in the outer edge of the Orion arm of the Milky Way completes one rotation around the galaxy every 225 million years or at a speed of 250 km/sec or 155 miles/sec.
(4) Our galaxy is moving relative to the other galaxies in our neighborhood at the incredible speed of 185 miles/sec or 300 km/sec.
(5) The speed of light in a vacuum is 299,792 km/sec or 186,000 miles/sec.

Even though the galaxy is traveling at 300 km/sec or 1/1,000 the speed of light when you point a laser in one direction, measure the time it takes the light to travel a specific distance, turn the laser around 180 degrees pointing it in the other direction, and measure the speed to and equally spaced mirror, it is the same relative to the distance of the equally spaced mirror in that opposite direction.

So if you were on a ship flying through space at half the speed of light then you fired a laser in front of your ship and behind the ship according to the discription above it would still go at the speed of light relative to your ship right? It would go at a speed of 1 1/2 times the speed of light from the point of view of an off ship location when pointed forward right? Now this is where it really gets weird. Nothing is supposed to go faster than light right? Due to the speed of light being relative to space/time, what would happen to the light? Would it go forward in time as seen from a point other than the ship and would it stay in the same time as the ship because it didn't go faster than the speed of light relative to the ships speed? This is what I think. Scratching head!

The problem I think is, Time Dilation.

If you travel the speed of light, time = 0. So the question of what happens when you hit the headlights on is "moot" because there is no time to do anything, you can travel 1 billion light years instantly.

Of course when you arrive at your destination, the Universe has aged a billion years, along with your world and the place you were going.

But you? You haven't even aged a nano-second, time literally equals zero at the speed of light.

So basically, if you were to reach the speed of light with say head lights on, you and the head lights become light...and all the head lights are is a "distortion" a different wave-length than yourself to an observer observing you and the head-light.

The head-light would be in the very very cosmic-ray section of the spectrum, you would probably be say...bluish, if you were moving towards the person measuring you.

Now if you were travelling .99 speed of light, the same thing should be the case, to you the light travels from you normally, however it only travels for say a million years, when the rest of the universe has changed by a billion.

So the wave-length is distorted. But the head light will only reach its destination by a million years faster than you (1 billion to cover 1 billion light years instead of 1.1billion for yourself at .99 light speed: not accurate calculation but you get the idea.) that is from a stationary realative position.

Yourself the trip would be say...a million years. The head light, instant.

Your wave length woudl be bluish, it more cosmic-ray spectrum.

Does that kinda explain things? I'm not sure of its accuracy, but from what I remember, this does cover the general concepts.

In the end though, this is just presenting another idea.

So if you were travelling at .99 speed of light, as you were saying, wouldnt the light very slowly travel ahead of you, increasing in distance as you stay at a constant .99 speed???

Still stumped on what would happen if you shone a light through the rear of the craft.

[edit on 18-7-2004 by jrod8900]

Still scratching head. Now picking hair off of the floor.

So at the speed of light my body would convert to two dimensional (no mass) energy from 3 dimensional matter because nothing in material space can go faster than light so I could not exist in three dimensional form and I could zip a billion years into the future?

No jrod, if you shone the light, to you it would travel the speed of light...after all you are not going anywhere, in a sense, it is the rest of the universe moving and you are standing still. So the light would leave your craft at "light speed". However, to an observer in the universe, the light is travelling the same speed, and you are not....you are travelling .99 the speed. So you'll arive after the head light.

The reason you both can see the speed of light travelling the same speed, even though one of you is travelling .99 the speed of light, is time dilation.

To the stationary observer, you on the craft is going much slower. (as in your movements...not your speed away from the stationary person).

See to us, at such low speeds, we throw a ball ahead of us, and see it is going faster than us.

And someone off the train sees it going faster.

But at near light-speeds, this changes, and the speed difference is not distinguishable, until finally at the speed of light, there is no speed difference.

That is what I'm purporting...because time dilation says that there is no time at the speed of light, you both reach the "destination" at the same time, you reach the "end" at the same time as your head light.

Thnx freemason i think i understand now

I cannot throw a fastball... but, put me in a car going 90 miles an hour, and I launch the ball ahead of me at, say... 60 miles an hour, in essence, the ball is traveling at 150 miles an hour. The speed of the ball is relative to its source, ie, the car.

Same with speed of light/headlamps.

You, in the car, are traveling at speed of light, and turn on the highbeams... and you can see ahead of you. Why? Even though the light is now traveling at twice the speed of light, it is only traveling at the speed of light relative to its source.

true, but it is beleived that the speed of light is the universal 'speed limit'. but still theres that underlying thought that you can exceed it, which i believe is very possible.

If you travelled faster than light you would not be able to see the headlights. Of course you would have to be in space and if you are in space it dosn't matter because light wouldn't really anything to reflect you. This might be theory as no one has travelled the speed of light. It's just my opinion.

math.ucr.edu...

"Sadly this question and all others about experiences at the speed of light do not have a definitive answer. You cannot go at the speed of light so the question is hypothetical. Hypothetical questions do not have definitive answers. Only massless particles such as photons can go at the speed of light. As a massive object approaches the speed of light the amount of energy needed to accelerate it further increases so that an infinite amount would be needed to reach the speed of light."


I say nothing would happen......cause as mentioned before...you are already going the speed of light, and as far as earth science is concerned nothing can exceed the speed of light, so you (in the car) would see nothing

www.newton.dep.anl.gov...

Here is a different approach to the question

www.windows.ucar.edu...=/kids_space/light_car3.html&edu=elem

And another here

www.theanswerbank.co.uk...

[edit on 18-7-2004 by NetStorm]

Soothsayer, Light doesn't work the same way your baseball does. The speed of light is the universal speed limit, the light from the headlights of the spaceship won't be seen cause they are going the same speed as you.

Even though the galaxy is traveling at 300 km/sec or 1/1,000 the speed of light when you point a laser in one direction, measure the time it takes the light to travel a specific distance, turn the laser around 180 degrees pointing it in the other direction, and measure the speed to and equally spaced mirror, it is the same relative to the distance of the equally spaced mirror in that opposite direction.

So then how do you explain this?