Thanks God the real world is neither entirely classical nor quantum. On the “large” scale, the world seems to behave rationally according to the classical theory. However as you go “smaller”, it starts to act in a strange, peculiar way to save itself from
extinction.

Now what if we were living in an entirely classical (non-quantum) world?

The answer is simple. There would be no world, classical or other, to live in. In a purely classical world, the atoms would not exist as the electrons would be sucked into the nucleus, transforming the world into a concentrated, dense material, in a fraction of a second.


A purely "classical feather" would outweigh a whole city.