ELI5. Why to tiny flies swarm together in one place when they have the whole planet at their wing tips?

Question

We’ve all been there. Walking along and suddenly loads of tiny midges or flies, and after 2 or 3 steps they are all gone… Left behind in the same place. They don’t seem to be going anywhere or doing anything.

In: 2

Answer 1

Were the flies hovering around a street lamp?