There is a Facebook post saying there is a really bright big comet that will appear in the sky tonight. I do get annoyed with these sort of posts because they are so illogical.

I decided to reply: If it was in the sky we would have seen it coming. It wouldn’t just appear. It might be travelling at a few hundreds or thousands of miles an hour but it wouldn’t appear instantaneously. There is a comet called Atlas (not sure of the full name) that is in the southern sky after recently passing the sun. It’s only a low visability comet and is starting to fly out of the solar system. Visible with binoculars just before sunrise. Gradually dimming as it becomes more distant.