No-one's celebrating "December" because Christmas is too offensive. If anyone's celebrating December, it's because there are three major holiday celebrations in December. It's why we've been saying "vrolijke feestdagen" foor ages now.

Columbus wasn't all that different from anti-vaxxers. The idea that the Earth was round was widely accepted at the time. However, Columbus recalculated the circumference of the Earth and came to the conclusion that it was smaller than everyone else thought. He was, of course, quite wrong. We've known the general size of the Earth pretty accurately since ancient times.

Part of that... whatever it is can also be seen on Google Sky.

Of course not, but that is why we don't work with ordinal numbers when talking about decades.