If you're in a vehicle going the speed of light, what happens when you turn on the headlights? ?

Question

Just curious.

Answer 1

This is a matter of applying Einstien's special theory of relativity. In the driver's reference frame, traveling at constant speed of 0.99 c, of course (it's not possible to travel at c), it does not matter how fast he is traveling, since all the laws of physics are the same at any speed, and light will be reflected back to him accordingly. However, objects will appear extremely contracted, Doppler shifted toward the red, and rotated.

Anthony

Answer 2

The speed of light in a vacuum is the universal speed limit. No object can go at that speed.

For an object to reach light speed would require infinite energy because it's mass would be infinite. Relativistic mass is given by:

m' = m / √(1 - (v²/c²))

As v approaches c the denominator approaches 0, so at v = c the relativistic mass is infinite.

Now, if you were traveling near the light speed, the headlights would work as normal. However, everything coming toward you would be blue-shifted, and everything to the sides of you red-shifted. Also, every thing would appear contracted, like a pancake, in the direction of motion.

You're clock also slows down by:

t' = t / √(1 - (v²/c²))

At .95c, you would age 3.20 times slower than someone you left behind.

Take a look at this video buy Carl Sagan:

http://www.youtube.com/watch?v=6Vpu6yJPR...

Answer 3

why worry about this you most probably can't calculate the distance a projectile will cover launched at 20 degrees with an inital velocity of 50 meters per second

Answer 4

You can't travel at the speed of light since it would take an infinite amount of energy... but if you could the light would emerge from your headlights at the speed of light.  All inertial observers see light travel at the speed of light in their inertial reference frames.

Answer 5

Strange as it may seem, time stops at the speed of light for your reference - and you would not have any time to turn on the headlights or perform any other tasks for that matter.

Other than that, and a few other quirks, from your reference inside the vehicle, nothing strange would occur on your way up to this speed - the lights would work the same as if you were at rest.

Answer 6

Wow...  interestingly that many have misunderstood Einstein's Special Relativity.

1.  When you travel very fast, time slows down for you RELATIVE to others NOT moving with you.  But if you're on that space ship, travelling very fast, then you would perceive time to tick as NORMAL... so you would be able to turn your lights on just like normal...

2.  To simply answer the question... Light always travels at speed 'c' irrespective of source or observer speeds.  So if you turn your head lights on, while travelling at 'c', then your headlights' beam would still travel away from you at a speed of 'c'.

If you've learn't about Relativity... Try the maths... Velocity addition... V = (u + v ) / (1 +uv/c^2)

(all this is of course is hypothetical, coz no mass could ever accelerate to speed 'c')

Answer 7

You got an the same question there maybe 130 years ago, it was first ask by einstein when he was 16years old, but when as he go deepen onto it, he had been analyse that there is no such thing that can travel more the speed of light... because speed of light would mean an infinity of time and mass.. and travelling in the speed of light and try to turn on your light would mean that the headlight will be the in the same point  with you....

Answer 8

Maybe you slow down to catch up with the light??

Answer 9

you are going the speed of light with your headlights on :-)

what's up with the thumbs down? How am I wrong??? :-(

Answer 10

This answer requires some of Einstein's Theory of Relativity.  

Your headlights will seem to move at the speed of light.  This can occur because from your perspective time speeds up to everyone not moving with you while those not moving with you see your time move slower (time dilation).  

You can see an example of this at:

http://www.pbs.org/wgbh/nova/einstein/ho...

Answer 11

u won't c the light from d headlight

Answer 12

You can't go the speed of light.

But lets say hypothetically you were able to go the speed of light, 186,000 miles per second.  When you turn on your headlights, you would not see them because you are going the same speed as the light.

Answer 13

First thing, you would never be traveling the speed of light in the first place.  It's impossible, and you get a lot on nonsense if you try to describe what would happen, because it's a nonsense, impossible thing.

However, we can pretend you are going a TINY bit slower than the speed of light, and it will help you understand.  There's a couple ways we can explain what would happen.  They both involve dilation - time dilation, distance dilation.

In the time dilation explanation, we know that time slows down the closer you travel to light speed, and it stops when you reach light speed.  With time ALMOST frozen for you, but passing VERY slowly, it would take you billions of years to actually flip the lights on, and billions of more years for the light beam to shoot out in front of you.  However, since your brain is slowed down along with everything else, you wouldn't think it was happening any slower than normal.  You'd feel like you reached up and flipped the lights on just like normal, and they lit the road ahead of you just like normal.  To you, it looks like everything else is going SUPER fast, aging billions of years in the time it takes you to turn the lights on.

To you, you flip the lights on just like normal, but the rest of the universe is moving really fast.  To the rest of the universe, you flip the lights on very slowly and the light comes out of the headlight very slowly.  

Who's right?  Well, you both are.

In the distance dilation explanation, we know that distances get shorter the closer you come to light speed.  If you're going a TINY bit slower than light speed, 100 miles becomes only a fraction of a centimeter long.  But since you yourself are also shrunk down in the direction of motion, you still think it's 100 miles.

So you see yourself flip the lights on and they shoot out and light up the road a mile ahead of you just like normal.  To someone else, they see you flip the lights on and the light moves out very slowly in front of you, and takes a minute or two just to light up the first half an inch.  And they see it takes a billion years for the light to light up that mile.

Who's right?  Again, you're both right.

And if you'll think about those two scenarios, time and distance dilation, you'll see they're the same.  In both cases, you see the light move out in front of you like normal, but everyone else sees it move really slow.

This is what we call the Theory of Special Relativity.

And from here, you can also see why you get impossible nonsense at the speed of light.  At the speed of light, time is frozen and distance is shrunk down to zero.

Answer 14

1. you can't travel at the speed of light, but only close to it

2. the speed of light is allways the same, so you would see it as you do when not travelling fast

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

Answer 15

You would see the lights turn on, just the same as you see the vehicle, which you see because of light reflecting off of it.