Science Memes

11148 readers

3252 users here now

Welcome to c/science_memes @ Mander.xyz!

A place for majestic STEMLORD peacocking, as well as memes about the realities of working in a lab.

Rules

Don't throw mud. Behave like an intellectual and remember the human.
Keep it rooted (on topic).
No spam.
Infographics welcome, get schooled.

This is a science community. We use the Dawkins definition of meme.

Research Committee

[email protected]

Other Mander Communities

Science and Research

Biology and Life Sciences

Physical Sciences

Humanities and Social Sciences

Practical and Applied Sciences

Memes

Miscellaneous

founded 2 years ago

MODERATORS

[email protected]

889

8 Minutes (mander.xyz)

submitted 3 months ago by [email protected] to c/[email protected]

100 comments fedilink hide all child comments

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 9 points 3 months ago (2 children)

I'm trying to understand how that reference frame works when you just just bounce a photon off a mirror and time how long it takes to come back? Like, light must have a non-infinite speed to the stationary observer, or it wouldn't take time to traverse the distance.

[–] [email protected] 13 points 3 months ago (2 children)

thats the thing, thats from your reference frame. From the photons perspective time stands still and everything happens at once

[–] [email protected] 2 points 3 months ago

Well, yes. Sorry, I thought the claim was that photons move at infinite speed, relative to a stationary observer.

[–] [email protected] 0 points 3 months ago (1 children)

But that also doesn't translate. If the moment the photon is created (from whatever reaction that caused the light source), to the moment it hit the person's eyes had no time pass (nothing in the universe moved) then it would be instantly created and observed by the observer. But the moment the switch turns on and the moment the photon hits the observer (as miniscule as this distance is) the eye of the observer has moved from A: switch goes on to B: observed.

Yeah no time passes for the photon I guess, but the universe still moved around the photons travel.

[–] [email protected] 8 points 3 months ago* (last edited 3 months ago)

Let's preface this, I'm no astrophysicist. but from my understanding:

That's just the thing, different speed observers do not agree on when things happen, or even the shape of the universe. The faster you go the more the universe compresses in front of you, making distances shorter from your frame of reference.

From the photons perspective it instantly moves through an infinitesimally thin sheet of universe. Everything that "happens around it" from our frame of reference all instantly happens at once if you ask the photon.

Here's a really good explanation from someone far smarter than me https://youtu.be/-NN_m2yKAAk

[–] [email protected] 1 points 3 months ago (1 children)

The observable effect is the same either way. If light is infinitely fast and causality propagates at c then it's still going to take (distance to the mirror / c) for the fact that you turned on the light to reach the mirror, and that same amount of time for the fact that the light reflected to propagate back to you.

[–] [email protected] 1 points 3 months ago (2 children)

Those two things don't square. If you're moving relative to the mirror when your fire the photon, it would hit in a different place than if you were stationary. The photon can't be moving infinitely fast in your reference frame for that to happen.

[–] [email protected] 4 points 3 months ago

Yeah I think infinite is the wrong word for them to use there. Maybe call it maximally fast? Like it goes as fast as possible no matter your reference frame, but that speed is limited by the speed of causality. The photon has 100% of its skill points in speed through space and 0% on speed through time.

[–] [email protected] 2 points 3 months ago (1 children)

Would it? What does "stationary" mean when discussing relative velocities? The mirror being stationary and the person firing the photon moving at a constant velocity is literally an indistinguishable scenario from a stationary person firing the photon at a moving mirror.

If I am moving relative to a mirror when I fire the photon, then the mirror is moving relative to me, and will be in a different relative position by the time the "event" of my firing that photon reaches it.

Also, the photon isn't moving infinitely fast in my (the firer's) reference frame. It's moving infinitely fast in it's own reference frame.

[–] [email protected] 2 points 3 months ago

Yeah I eventually picked up that that's what you meant in your original comment, not that photons move instantaneously and that causality somehow catches up later.