B Time and Space Distortions of Photons: What Am I Misunderstanding?

[Involute]

TL;DR Summary

If photons are subject to SR spatial and temporal distortions, how are we able to see them move?

As I understand it, photons are subject to the same time and space distortions under SR as anything else, which is why they don't perceive time or space, since they travel at the speed of light. To an outside observer, then, they should appear stationary, immobile at their moment of creation. Of course, we perceive them as moving, or else we wouldn't be able to see anything. What am I misunderstanding?

 

[PeroK]

What am I misunderstanding?

One hypothesis of SR is that photons (light) move at the speed of light. That is incompatible with your hypothesis that they do not move. Experiment decides the issue. Photons (light) in a vacuum move at the constant and invariant speed denoted by $c$.

 

[Herman Trivilino]

since they travel at the speed of light. To an outside observer, then, they should appear stationary

By that reasoning, the faster something moves the slower it moves.

 

[PeterDonis]

they don't perceive time or space, since they travel at the speed of light.

This is a common pop science misconception, but it's still a misconception.

 

[Ibix]

As I understand it, photons are subject to the same time and space distortions under SR as anything else,

There are no space and time distortions in SR. All of the effects in SR are a result of different choices of how to divide spacetime into space and time - this does not involve anything being distorted or curved.

they don't perceive time or space,

What do you mean by "perceive"? Light doesn't perceive anything, any more than an electron does. Usually, what is meant here is that it isn't possible to construct an inertial frame of reference traveling at the speed of light, which is true, but that doesn't stop us describing light as moving in our frames of reference. Certainly the points along the path of a light ray are distinct.

To an outside observer, then, they should appear stationary, immobile at their moment of creation.

No. The problem is that the "distance" through spacetime along a lightlike path is zero, but the events along that path are distinct. When you are talking about "time for light" you are talking about that distance along its path, but because that is always zero you can't use it to distinguish between the events. You can, however, use other parameters (such as your own rest frame's coordinate time) to identify them.

 

[A.T.]

What am I misunderstanding?

Basically everything. You should look at what the math of SR actually says, instead of those vague natural language descriptions.

 

[Will Learn]

Hi.
You're doing well and taking an interest in Physics, we're all going to like that. You've stumbled on some Pop Sci articles and you are, quite correctly, identifying problems with what they've implied in their simplification.

As I understand it, photons are subject to the same time and space distortions under SR as anything else, which is why they don't perceive time or space

That's the bit I would suggest you focus on if you want to make sense of the various comments already received. Firstly, there isn't a good reason to assume a photon is a little person who can perceive anything but let's put that to one side for the moment. When people talk about what an observer perceives or can see then they are generally talking about what they will determine in their own rest frame using the natural co-ordinates of that rest frame. It's their own rest frame which is the key to what they will see.

There isn't any inertial frame in SR where a photon would be at rest. To say that more clearly: Photons do not have a rest frame. As a consequence it's a non-starter to ask what a photon can see or how it perceives the universe. You can't sensibly express anything that a photon can see in it's own rest frame.

You can ask other questions, such as how much proper time elapses for a photon (the answer is none at all). This is often carelessly used to suggest that time doesn't pass for a photon. It's careless because proper time isn't going to be the photons co-ordinate time in any inertial frame of reference you can use. To phrase that more clearly: It's never going to be just a time interval for anyone or anything in any sensible frame.

Best Wishes.

LATE EDITING: @Ibix has already written something about rest frames by the time I finished this post.