Question

Why dont we measure all lengths in meter ,but its multiples or sub multiples

Answer 1

Explanation:

we know we can measure length of smaller particles(microscopic particles)

and the length of larger bodies(planets, galaxies)

think what would happen if we express their units in metre. it will become challenging to do this.for example if we will measure the average distance between earth and sun in metres that will be

149597870700metres which is is too hard to write so simply we will write this as 1AU(astronomical unit).

similarly it is hard to write the average radius of a hydrogen atom which is 5.29177 X 10-¹¹m

so we express this in nanometre as

0.529nm