Heavier than air flight was never thought impossible, even the ancients knew birds, bats and insects could do it, it is only that humans were too heavy. It was an engineering problem, not a scientific impossibility. As soon as the engineering was available (the gasoline internal combustion engine) people all over the world started working on the problem.

The same thing applies to flight faster than the speed of sound. No one thought it was scientifically impossible, rifle bullets and artillery shells had exceeded that speed over a century earlier. It was just an engineering problem that had to be solved, not a new law of nature to be discovered.

Even space travel had been scientifically established early in the 20th century, although there was nothing in physics to forbid it once Isaac Newton developed the Laws of Motion in the 17th!

What we are discussing here is a scientific impossibility, that's a different kind of nut to crack altogether.

If there are things that happen in nature, we can say with a high degree (but not certainty) of confidence that someday we may find out how to do them too, given a continued development of our technology. But if nature can't figure out how to do something it's not likely we will.

Examples of engineering problems are Artificial Intelligence, Nanotechnology, Fusion, and sub-lightspeed interstellar flight. Some day we'll probably learn how to do these things.

Examples of scientific problems are FTL spacecraft, time travel, artificial gravity, and perpetual motion machines (the category this car falls into).
It's highly unlikely we'll ever learn how to do any of these things.

I hope you don't think I'm lecturing you on this, Lindy, but there is a distinct and very fundamental difference between these two types of problems. It is a distinction many otherwise intelligent and educated people don't seem to grasp