> extraordinary claims require extraordinary evidence

I think you've got the sign on your skepticism reversed. The burden of proof is very much on those who claim that FTL travel is possible.

From Wikipedia:

    The special theory of relativity implies that only particles with zero rest mass (i.e., photons) may travel at the speed of light, and that nothing may travel faster.

    As of the 21st century, according to current scientific theories, matter is required to travel at slower-than-light (also STL or subluminal) speed with respect to the locally distorted spacetime region. Apparent FTL is not excluded by general relativity; however, any apparent FTL physical plausibility is currently speculative.

See https://en.wikipedia.org/wiki/Faster-than-light

The burden of proof for people making that claim is on the person making that claim. The burden of proof for making the claim that it’s “fundamentally impossible” is likewise on the person making that claim.

For all we know, our understanding of the universe could be at a stage of analogous to “there are four elements: earth, air, fire, and water”. Many things that we enjoy daily were once “fundamentally impossible”.

> Many things that we enjoy daily were once “fundamentally impossible”.

Not so. They may have been conceptually impossible but did not run into the "fundamental" laws of physics. FTL travel breaks physics. A lot abiut our observable universe would be different if it were possible.

The evidence that the universe obeys these laws is significant and, currently, not counter indicated.

> but did not run into the "fundamental" laws of physics

Those "fundamental" laws of physics didn't exist several centuries ago.

Yes they did, we just hadn't figured them out yet. If we were very wrong in them, we'd have to be wrong in a way that doesn't affect all the technology using the wrong theory - which is part of why we refined them, because shit didn't work.

That's what it means to be contradicting fundamental physics. It implies all of our other knowledge is wrong, but we are just lucky enough that our machines work anyway. Which, unless we see a phenomenon that we can't fit into our existing theories, seems unlikely

Let's invent new laws of physics and hope the universe adopts them.

> FTL travel breaks physics

Like quantum mechanics broke physics?

Quantum mechanics _fixed_ physics. Newtonian physics predicts that an electron will spiral into the nucleus of an atom within a few nanoseconds of the atom’s creation.

We observed quantum effects before the theory. We haven't seen any phenomena so far which require physics that could lead to FTL

By this standard, there is literally nothing that can be called impossible. Perpetual motion machines can't be said to be impossible because, who knows, maybe there is a God and tomorrow He could flip the switch for free energy from off to on.

It's simply the difference between claiming something is "impossible based on our current understanding/model of physics" and "impossible regardless of what we don't understand". Science gives us the first one, but the original commentator unambiguously claimed the second. Our models of the universe being wrong happens all the time, sometimes in significant ways, and even now there are plenty of unexplained things in our universe that have the potential to change our understanding. It seems pretty optimistic to assume our current models are guaranteed correct in every circumstance we haven't yet observed even when they can't explain everything we have actually observed.

So yes, perpetual motion could start working tomorrow, or could already exist for all we know. That doesn't mean it's wrong to say physics _currently_ says it's impossible and any claim better have some pretty good evidence to dispute it (which none currently do). But that also doesn't mean that if we're around centuries/millennia from now we won't have found a special case where our current understanding breaks down.

I don’t think that anyone made the claim that FTL travel is possible; they merely said that there’s still so much we don’t know about the universe, so definitely ruling something out is a bit rash.

With our current understanding of the universe, yes, indeed, FTL travel is not possible. But it’s naïve to think that our understanding of universe won’t change.

After developing some intuition for relativity you realize that asking whether FTL is possible is more akin to asking whether you can remain inside a circle after traveling radius + 1 from the center, than it is to asking whether a car can be modded to exceed its top speed. It is nonsensical, not logically coherent within all currently known physics and it goes to the fundamental nature of motion itself.

It can't be ruled out, but neither can Russell's Teapot.

"FTL is impossible" doesn't seem like an extraordinary claim at all, but actually quite an ordinary one. The natural world seems to obey a light-speed limit every time it's been tested.

Sure, it might be wrong, but as far as claims go it has a lot going for it, both experimentally and theoretically.