(spaceships) rocket (super)science

[Johnny1A.2]

Originally Posted by malloyd

This is a popular take on this that is actually sort of false.

Bronze age guys don't know *how* to move that fast, but they have no reason to think it is impossible, and indeed have excellent evidence it probably *is*, in that the sun manages to circle the Earth in a day, and you can see things apparently about as high in the sky (like clouds) outrace the sun all the time.

But in their ways of conceptualizing the world, the movements of the sun and the clouds are irrelevant to what is possible for mortals.

We on the other hand have a pretty good reason for concluding that things can't go faster than light (essentially the same one the Bronze Age guys have for concluding things you do now can't change the past)

Which is loaded with overt and hidden assumptions that we take on faith, because that's all we can do. The most science can ever say, as far as it can legitimately go, is 'as far as know now'.

A lot of the difference is just difference in how interconnected the things we know are. Bronze Age facts largely aren't very connected - being wrong about the speed of the sun doesn't imply you are wrong about anything else. But being wrong about relativity basically breaks all of modern science and engineering in very central ways, and there is a [lot] more evidence it is at least broadly right (among other things it implies everything we know about electromagnetism is wrong, and yet generators and radios do work....)

Which proves nothing about what is possible or not possible. The impossible always seems clearly impossible until it isn't, and there's no way to know what will hold up and what won't. It really doesn't matter how interconnected what we think we know is, as far as assessing it's reliability. We cannot go beyond 'as far as we know'.

There's a reason FTL proposals are always way out on the edges of known energies or require material properties we can't prove exist - if it could happen in the range of materials or energies we can regularly observe, we should have already seen evidence. One important corollary to that which I think deserves more attention is that if FTL were somehow possible, it is likely to be useless. We've can already see something of an example - hydrogen fusion - that's blindingly common in the universe but almost useless to us because it's so far from achievable conditions, FTL would presumably be much worse.

non sequitur. If it's possible at all, it means there's something basically wrong with out view of How Things Work, which means we can't make any meaningful predictions about how useful it will be or won't be. We're in the same position there that predictions about the utility of atomic energy once were. Or someone in 1930 pondering the precision of engineering necessary to create something like a modern processor chip.

For that matter, we can't say that fusion will remain useless to us with any confidence. Only that we can't do much with it (other than weapons) right now. It was known that flying machines and horseless carriages were possible long before they were practical, there was a long, long legacy of failed attempts before it all finally came together and worked. Ditto practical submarines.