From the proton to the universe

Sizes in nature run from a proton to the visible universe. You will make the program find the order of magnitude of each size, sort the sizes, and count how many powers of ten lie between the smallest and the largest.

The idea. Write a number as $a \times 10^{n}$ with $1 \le a < 10$. The order of magnitude is $10^{n}$ if $a \le 5$, and $10^{n+1}$ if $a > 5$.

Your tasks.

1. Make order(x) return the power of ten of the order of magnitude.
2. Make smallest_first the names, sorted from the smallest size to the largest.
3. Work out how many orders of magnitude lie between the smallest and the largest.