What article should I use right after "the enigma of"? Should it be "the enigma of the" or "the enigma of a(n)"?
Please, look at these pictures. Can you guess what all these pictures are about? Rain? Well, not only rain. Storm? Well, it's closer, but still not fully there yet. What? Right - ball lightning. The enigma of ball lightning has bothered scientists for centuries. On one hand, it is known that it is nothing else than a big bunch of energy, but on the other hand, it can easily change its size - from a big ball by the size of a zeppelin or a hot air balloon to a small ball by the size of an egg or even a marble...