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KiwasiGames t1_iyhbnod wrote

Reply to comment by JonesP77 in Scientists simulate ‘baby’ wormhole without rupturing space and time by Crazy-Sundae-5141

Because we like causality.

Faster than light travel plus relativity means time travel. You would literally be able to travel backwards in time. Full on Michael J. Fox fall in love with your mother time travel.

Time travel introduces so many logical paradoxes that most scientists reject it out of hand. Even if you don’t reject it and allow time travel to be a thing, every known law of physics breaks down.

It’s not just a “go faster” thing. The speed of light is a fundamental limit to the universe.

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Extension-Ad-2760 t1_iyhsslb wrote

See, the thing is, quantum physics and just relativity also introduces a heckton of things that humans would call logical paradoxes. These are actually real. How do we know what is a true paradox and what isn't? The universe doesn't care about our perceptions. Time travel could just create multiple realities. Moving at close to lightspeed already does similar things

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supercalifragilism t1_iyil0lx wrote

So there's no experimental results to clarify what's going on with quantum mechanics and gravity, but we've also never seen anything travel faster than the speed of light. It has never been observed, ever. Every time we think there's an FTL phenomenon, it turns out to not be FTL. Energy levels are vastly higher in cosmological situations, so it stands to reason that FTL, if possible, would occur in nature. While absence of evidence is not proof of absence, it informs theories. Likewise, proving a negative is difficult or impossible.

The real problem with FTL are the implications it has for the rest of physics. There's a saying: "FTL, relativity, causality, pick two." Built into the logic of relativity is the idea that <c is the maximum velocity for anything with mass, =c for massless particles and >c for negative mass. It's unclear if negative mass is physically meaningful, it has also never been observed.

More than that, built into the logic and math of relativity is the idea that information can only travel at speeds less than c; there are a number of situations in relativity that can arise with superluminal travel that would undermine causality completely; even at near c, time dilation will never alter the order of events, causes will never follow effects and information can never arrive at a listener before the speaker says it.

Relativity is a very well researched and experimentally supported theory. It's only exceeded in predictive power and experimental agreement by quantum mechanics. But neither of them is anywhere near as important to science, logic and reason as cause and effect.

Basically, without proof of FTL that is ironclad, there's every reason to believe that all the rest of science is more accurate, because thre's no explicit experimental proof of FTL and the implications of FTL conflict with all other observations of basically everything.

tl;dr because of the implication

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Extension-Ad-2760 t1_iyixd2t wrote

The specifics of causality were invented by humans. For example, we don't like the grandfather paradox, but a multiverse just ignores that problem.

Personally, I think that we assign too much value to our own human experience. In our own experience it is possible to exactly know the velocity and position of an object. In our own experience things are solid, not wavelike. In our own experience it is impossible for time to warp based on speed. And in our own experience it is impossible for cause not to follow effect.

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supercalifragilism t1_iyj54s1 wrote

I'm sympathetic to this interpretation, and I agree that human experience is centered too often when dealing with these kinds of notions. The trouble is that causality is necessary for any and all science, including the science that's leading you to doubt causality. The nice thing about experiment is that it can allow you to get out of the human experience.

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coffeecofeecoffee t1_iyiyozv wrote

I feel like "we like causality" is not good enough for me. Just because we can't understand a universe that breaks causality doesn't mean it doesn't exist. We know n o t h i n g.

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KiwasiGames t1_iyj9pqv wrote

Come on. This is a science sub.

We have never seen a FTL particle, ever. And we have looked for them.

We have no gaps in our theories of physics that would be effectively explained by allowing FTL.

And every known law of physics would turn out to be wrong if FTL was a thing.

None of that suggests that we will ever get to FTL.

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coffeecofeecoffee t1_iyjolmc wrote

Yes, but models aren't truths, they are tools. Velocity A + Velocity B = Velocity (A + B) was a good enough model until we needed a more complicated one to account for relativistic speeds.

It doesn't mean the first model is wrong, just that it's not the full picture. I refuse to believe that Einsteins theory of relativity is the full picture.

I wonder why the speed of light is the speed of light? I feel things that are once thought of as "physical intrinsic laws" are really just results of a more complicated mechanism. So what's to say the speed of light, and velocity and spacetime in general is just the observable symptom of something more fundamental?

I don't expect us to find something faster than light but I'm not convinced the entire concept of velocity and spacetime is as fundamental and solid as it feels now.

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odoc_ t1_iyhuxll wrote

Some theories suggest time doesn’t exist (Order of Time by Carlo Ravolli). The way we understand time is a human extrapolation, and fundamentally time in physics it is irrelevant. In such a case a time paradox would not be a paradox at all.

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