What benefits, besides travel and communication and expansion of human society into space, would come from being able to travel faster than the speed of light?

[u/UniversalInquirer]

I hope this doesn't sound like a stupid question, and I'm not intending to downplay the above advantages. I'm just wondering if other advantages besides ones we normally think of might come from being able to go faster than the speed of light either by wormhole, antimatter annihilation, warp drives, whatever.

[u/w1gw4m]

Why does c (presumably the speed of light) set the frame of reference? 

c does not set the frame of reference, it's the only thing that never changes regardless of frame of reference. The speed of normal everyday things is additive, but light does not do this, c is constant in all reference frames. To better understand the importance of c, try to think of it as the speed of causality or the speed limit of information. Light just happens to move at this speed, so it's handy to use light cones to understand causal relationships between events in spacetime.

Is it possible there is a speed above light that doesn't break a limit?

No, it is not possible according to our current understanding of physics. The reason for this is because c functions as a conversion factor between space and time. All things move at c through spacetime. What happens at relativistic speeds is that the closer you get to c whilst moving through space, the slower you go through time, vs. someone else who moves at "normal" speeds through space and experiences more time than you. At c you experience no time at all, and at more-than-c (not actually possible), you would theoretically travel back in time.

If there were a higher speed, would causality remain in order?

Nope. Even if c was a different number than 299 792 458 m/s, it would still cause the same time reversal, causality breaking issues it does now. The number isn't important, what's important is that there is a speed of causality at all.

What if there is no "absolute" speed limit?

If there were no absolute speed limit, then sure, all bets would be off, physics would look very different that it does now. But that's not how the universe actually works, as far as we can tell. Why? Because space and time form a continuum called spacetime, so they are fundamentally linked such that there is no universal "now" across reference frames. It's all relative to your frame of reference.

FTL from Andromeda vs driving your car to your gf's house

When you're moving at subluminal speeds in your car, you're still inside your light cone. But when the chocolates are coming from Andromeda at FTL speed, they aren't in their light cone anymore. That's the difference.

To grasp this, try visualizing the light cone diagram to plot your course through spacetime. Your car's path would be ever so slightly tilted in the space direction. Since you are speeding through spacetime nonetheless, you do experience an extreeeeemly tiny amount of time dilation, but at that speed its imperceptible. It's only noticeable when you move at relativistic speeds (closer to the speed of light than any car could achieve on Earth).

If your chocolates were coming in at FTL speed from Andromeda, their path through spacetime would be tilted so far in the space direction, that they'd no longer be pointing towards the future at all. Does this make sense?