# Does light have a terminal velocity? Is lights terminal velocity "the speed of l

1. 72
Mikel G Robertsposted 14 years ago

Does light have a terminal velocity? Is lights terminal velocity "the speed of light"?

If we held a race between two beams of light, one beam being on a moving object and one from a stationary object, would the beam of light from the moving object arrive first at the finish line?

2. 61
Dr. Marieposted 14 years ago

Mikel:
First of all, have you had a physics class yet? Have you read Einstein's theory of general relativity? Next, light does not and cannot have a "terminal velocity". It is not an object. It is electric and magnetic waves (thus electromagnetic). And lastly, no, the beam from the moving object would not arrive first. "The speed of light" in a vacuum is faster than anything else in our known universe. Therefore, whatever moving object you had, the light would leave it behind, just like the stationary object, and both beams would arrive at the same time, provided they were turned on at the same time. In theory.

3. 72
Mikel G Robertsposted 14 years ago

DR. Marie, Yes, I have studied physics. Yes, I have read Einstein's Theory of General Relativity, And yes I have been properly "put in my place". But my question remains...

If light does not have a terminal velocity (terminal velocity being the maximum speed it can obtain), then "lightspeed" isn't the fastest thing in our known universe, ACCELERATED light speed would be.

If light can be accelerated as you said it can (because it can't have a terminal velocity), then releasing light, at speed should accelerate the light beam...and it should arrive first.

If light has a terminal velocity (maximum velocity) and cannot be accelerated, then would not the ever shortening distance that beam had to travel factor into it's arrival at the finish line first?

I'm not sure I understand your lastly statement, Light being the fastest speed "in a vacuum"... therefore...??? What if the moving object was moving at the speed of light?

4. 68
diplessposted 14 years ago

Light cannot be "accelerated" in the sense of gaining more speed. Light only has one speed, for the type of medium it is in for example a vacum or glass or anything else it can pass through.

However, for a fixed observer (which is really impossible near a black hole), the "falling" into the hole will increase the energy of the light, making each photon more energetic (each photon will see its wavelength become smaller = blue shift).

Any gravity field does that. It is even possible to measure this on Earth. The first time it was done was in the elevator shaft of a university.

A light with a very precisely known wavelength was shining straight down from the top of the elevator shaft. Detectors at the bottom measured the wavelength that was received.

The emitter was then moved to the bottom, and the detector to the top. Same thing (but shining upwards this time). Wavelengths were measured both ways and the difference matched what the calculations had predicted.

(They used gamma rays, which is a form of light with very short wavelengths -- invisible to the eye, but it is still light)

So you can't accelerate light in the way you would accelerate an object of mass, but it's wavelength can be changed with appropriate forces.

With regard to your comment about terminal velocity; Terminal velocity requires object mass, aerodynamic properties, and resistance (drag). Without resistance, terminal velocity is infinite. Use of the term terminal velocity when referring to the Universe or light is not correct.

5. 52
R-Bonhartposted 10 years ago

Light from both sources will leave at the same time. At significant fractions of light-speed, time slows down and lenght shrinks in equal ratio  (distance/time). This causes compensation in moving objects and thus maintain the consistency of the speed of light.
Therefore, whether you are moving or stationary, if you flash a torch, light will always leave at the same speed.
In short, regardless of the motion of the observer or source, the speed of light, when measured, will always be the same, 300,000 km/s.

working