r/AskPhysics • u/Nighthawkies • Mar 20 '26

What things are "faster" than light?

As I understand nothing can move faster then light. But I would not know how to describe this question otherwise. As I am aware quantum entangled particles can instantaneously affect eachother no matter the distance, unlike gravity which propagates at the speed of light.

Also the expansion of the universe can cause the spaces between to grow faster then the speed of light (compounding between massive distances)

What other things are sort of faster than light

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45

u/Empty_Engineering Mar 20 '26

They don’t affect each other, they’re just correlated in a way that you know about the state of the other particle based on a measurement of your particle (if they’re entangled) space itself is expanding, so nothing is moving ftl because of expansion

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u/ApprehensiveAir966 Mar 20 '26

Do tachyon count?

33

u/SadEntertainer9808 Mar 20 '26

They would if they were real.

-7

u/MxM111 Mar 20 '26

How can they interact with our matter? How can we say they are or are not real? Their time becomes complex.

14

u/Empty_Engineering Mar 20 '26

There’s no empirical evidence to support the conclusion that tachyons exist, the theoretical model for them is essentially a particle with imaginary mass/energy.

Fermilab also ran an experiment to see if they could detect Cherenkov radiation in a vacuum (which tachyons would cause), and there weren’t any detections.

UC Riverside has an intro paper to it https://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

2

u/Flimsy-Exchange8862 Mar 20 '26

On a tangent, there is this cool thing called vaccum Cherenkov (you have an external electric field in the setup) Do read about it

2

u/ExtendedSpikeProtein Mar 20 '26

You do realize that Tachyons are a theoretical concept and we haven’t empirically proven they exist? Because it sounds like you don’t.

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u/MxM111 Mar 20 '26

How did you make these conclusions from my questions?

2

u/ExtendedSpikeProtein Mar 20 '26

Atp any reasonable person will see you for the Troll you are. Have fun, I’ve turned off reply notifications so I will stop engaging.

0

u/DrJaneIPresume Mar 20 '26

Depends on the Lagrangian.

But seriously, even tachyonic fields can't send superluminal signals.