# If you are in a vehicle going at a speed of light, what happens when you turn on your head light?

Relevance

According to relativity, if you're going at the speed of light and you switch on the headlights, you'll see the light going away from you at...The speed of light! This makes sense, because you know if you throw a rock out of your car at twenty miles an hour, you'll see the rock moving away from you at twenty miles an hour. No matter how fast your car is going relative to the ground.

A better question would be to ask "what would someone standing next to my car see when I switched on the headlights?" Since according to relativity, all observers measure the same speed for light.

WELL in the car u actually feel urself at the rest and other things moving wrt u at a speed of light backwards.but the light will not behave this way even in Ur hypothetical car.when U turn on the headlights light will still be found to travel at a speed 'c'.

and any observer outside the car also notice light as going at the 'speed of light'.

this is because light is postulated to travel at same speed from any reference frame,be the frame is moving at 20m/s wrt some observer or 10km/s or even at speed of light.(but it is a fact that at least till date our scientists do not have any way to accelerate a frame up to speed of light,and this is theoretically impossible also)

this is very hard to believe as it is against our everyday experiences.but it works in exactly that way!!!!!!!

This is purely a hypothetical question and a popular one! looks like.

Examine the the Lorenz factor

r=1/sqrt[1-u^2/c^2]

m=m0*r

mo is the rest mass. m is the mass at any speed. Please note that the Lorenz factor becomes infinite when u the speed of the vehicle approaches speed of light c. In other words the mass gives enormous resistance and it becomes infinite when u approaches c the velocity of light. In very simple words nothing can ever approach the speed of light. So switching on the lights just does not arise. It is based in error.

the head light will be going at the same speed of the vehicle. so you can't see any light at the front

Lv 7

Let's get this straight. All of the energy in the universe isn't enough to accelerate one electron to the speed of light. Matter can't exist at that speed. It ain't gonna happen Nancy.

I would say that the light would still light up the area in front of the vehicle for the same distance as at a lower speed.

But because of the speed of the vehicle at the speed of light moving so fast the beam of light would appear to be shorter.(From inside )

What you see would be coming in to view so fast that you wouldn't be able to focus on very much. ( You wouldn't focus on things father away from you.) (So beam would appear shorter.)

• Holden
Lv 5

The reason that one cannot travel the speed of light is that no matter how fast you travel, your headlights travel away from you at the speed of light in your reference frame.

That light is also travelling at the speed of light in anyone elses point of view, regardless of their speed.

Since you are going slower than your headlights you are travelling less than the speed of light.

• Anonymous

You will be in the dark, because wherever you go, the leading edge of the wave of light from your headlights will be passed by the front of your vehicle.