In physics we often work with very large and very small numbers. For example, the mass of the earth is about 6 000 000 000 000 000 000 000 000 kg and the mass of an electron is 0.000000 000 000 000 000 000 000 000 000 911 kg. In this form, numbers take up much space and are difficult to use in calculations. To work with such numbers more easily, you can write them in a shortened form by expressing decimal places as powers of ten (in the form m x10ⁿ ). This method of expressing numerals is called scientific notation.