According to tyson, what two ideas did people once think were impossible, even though they do not defy any laws of physics

Two ideas that people once thought imposible even if they didnt violate laws of physics were-

Idea of human flying Idea of breaking the sonic barrier

Explanation:

Neil Tyson says that the idea of flying and breaking of the sonic barrier was earlier considered impossible, even if they did not specifically violate any laws of Physics.

The idea of flying had grown as an envy component in humans on seeing birds fly. Kelvin in his essay had argued for a machine that could fly and was heavier than air.

Similarly, the idea of breaking the Sonic boom was earlier considered to be impossible, but no physics law prevented it from happening. E. g. The bullets fired from the guns were travelling at a rate faster than the speed of the sound. However, after the Bell aircraft broke the sonic barrier, it was widely believed that the barrier can be broken.