Rest Frame of a Photon - FAQ by Forum Members

In summary, the concept of a rest frame for a photon in special relativity is not possible because it would require the photon to be both at rest and moving at the speed of light, which is contradictory. While there are non-inertial coordinate systems where light can have constant coordinates, this is different from a reference frame (tetrad) where the photon is at rest. It is important to understand the distinction between these two concepts.
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D H
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I've read that in relativity the concept of the rest frame of a photon doesn't make sense. Why is that?

A rest frame of some object is a reference frame in which the object's velocity is zero. One of the key axioms of special relativity is that light moves at c in all reference frames. The rest frame of a photon would require the photon to be at rest (velocity=0) and moving at c (velocity=299792458 m/s). That of course is contradictory. In other words, the concept doesn't make sense.The following forum members have contributed to this FAQ:
D H
Dale
Fredrik
Pallen
 
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One thing to add to this is a brief comment that while it is not possible to have a reference frame (tetrad) where light is at rest, it is possible to have a non-inertial coordinate system where some light rays have constant coordinates. Light cone coordinates are one such example. This is one place where it is important to understand the subtle distinction between reference frames (tetrads) and coordinate systems.
 
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1. What is the rest frame of a photon?

The rest frame of a photon is a theoretical concept used to describe the perspective of an observer who is traveling at the same speed as the photon. In this frame, the photon has zero velocity and all of its energy is in the form of electromagnetic waves.

2. Why is the rest frame of a photon important?

The rest frame of a photon is important because it allows us to better understand the behavior of light and its interactions with matter. It also helps us to explain phenomena such as the Doppler effect and relativistic effects.

3. Can we ever observe the rest frame of a photon?

No, it is not possible for us to observe the rest frame of a photon because it would require us to travel at the speed of light, which is impossible according to the theory of relativity. However, we can use the concept of the rest frame to make predictions and calculations in physics.

4. How does the rest frame of a photon relate to the speed of light?

The rest frame of a photon is a frame of reference in which the photon has zero velocity. This means that in this frame, the speed of light is always constant and equal to its maximum value, which is approximately 299,792,458 meters per second in a vacuum.

5. Are there any exceptions to the rest frame of a photon?

Yes, there are a few exceptions to the rest frame of a photon. For example, the rest frame of a photon can change if it interacts with matter or is affected by gravitational fields. In these cases, the photon's energy and velocity may change, and its rest frame would also change accordingly.

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