Are cell mutations always bad? A mutation is a change in the genetic material of an organism. We are made from trillions of cells, each with a nucleus composed of DNA â a set of instructions that tells the cell what to do. Cells copy themselves with astonishing accuracy, but every now and then a piece of code is copied incorrectly.
Eclipses occur due to the special coincidence of the moon and the Sun being the same angular size. The Sun is 400 times wider than the moon, but it is also 400 times farther away, so they coincidentally appear to be the same size in our sky. This is what allows us the phenomenal beauty of the total solar eclipse.
Solar eclipses are relatively rare; they happen when the Moon moves directly and precisely in front of the Sun. Why are they so infrequent, and why do solar eclipses always come in pairs with lunar eclipses? It is all down to a mix of orbital alignments and cosmic coincidences.