4 ms·
Not an expert, but can't resist chiming in anyways... One thing to think about it what exactly is causality? There'll be tons of different definitions, but they
by squeaky-clean 3y ago
Not an expert, but can't resist chiming in anyways... One thing to think about it what exactly is causality? There'll be tons of different definitions, but they'll all have one thing in common, events that cause "later" events, and/or events that depend on "earlier" events.
And in a physics sense what is an event? An interaction between two things, right? And since there doesn't exist any force that can interact instantaneously across distance, the speed limit of causality is equal to the speed of our fastest forces.
If we discovered some scifi-esque Tachyon particle that traveled at 2C, we could no longer say the speed of light is the speed of causality.
- someplaceguy 3y agoI'm not an expert either, but I like to think that the speed of causality is the speed at which a piece of information (e.g. a particle, a gravity wave, etc) is traveling through space. So the speed of light / gravity is essentially the maximum speed of causality, because nothing can travel faster than that. EDIT: Or you can think in terms of how information propagates through spacetime. In this point of view, the speed of causality is always the speed of light, for everything, including particles with mass.
- squeaky-clean 3y agoYeah that's what I was trying to work towards. Basically that causality is an abstraction, or at least a "higher level" idea. And if we look at the components of it, we can see that interaction between two things is a central part of it. And an interaction between two things in our universe has a maximum bound of the speed of light (and gravity and so on). The speed of causality is just the speed of the fastest thing.
- anon291 3y agoIt's the reverse. Light and gravity travel at c because they (at least light) are mediated by particles / systems that have no mass. Mass is what slows the speed of causality for certain particles. For example, while the photons I emit may travel at C, the massive particles that make up 'me' cannot.
- mr_mitm 3y agoI'm an expert, and an event is just a point in spacetime.
- squeaky-clean 3y agoSure, but events have a causal future light cone which can have a causal relationship with future events, and a past light cone with the inverse.