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 occur at New Moon, when the Moon is between Earth and the Sun. Lunar eclipses occur at Full Moon, when Earth is between the Sun and the Moon. Eclipses do not take place every month because the orbits of the Moon and Earth are tilted at an angle. Most of the time, the line- up is not precise enough for an eclipse. However, there are more eclipses than people are generally aware of: There are at least two eclipses of the Sun each year, though most are partial.