Although scientists are definitely NOT lazy in general, if there is a quick way of writing something down, then the average scientist - and the average person - will tend to use that quick way of doing things. It saves everyone's time in the long run.
That's why we have a system of prefixes that tell people the amount or size of something that we are talking about, quickly and concisely.
Below is a list of prefixes in the SI system. Some you may have come across, and some you may not have.
| Prefix | Factor by which unit is multiplied | Symbol |
|---|---|---|
| tera | 1012 | T |
| giga | 109 | G |
| mega | 106 | M |
| kilo | 103 | k |
| hecto | 102 | h |
| deka | 10 | da |
| deci | 10-1 | d |
| centi | 10-2 | c |
| milli | 10-3 | m |
| micro | 10-6 | µ |
| nano | 10-9 | n |
| pico | 10-12 | p |
| femto | 10-15 | f |
| atto | 10-18 | a |
A convenient way of measuring length on the Sun is the megametre, symbol Mm. The symbol for a megametre is formed by taking the symbol for mega - M - and the symbol for metre - m - and putting them together
Very easy!
But do you know.....
How many femtoseconds it was since you were born?
or,
How many gigametres tall you are?
Remember to write down the number AND the correct unit TOGETHER.
Notice anything about the number in front of the unit?
It's really not very smart to measure your age in femtoseconds or your
height in megametres because people aren't a few megametres tall or a
few femtoseconds old! We tend to use units that are around the size
of the thing we're looking at. Since things on the Sun tend to be at least
106m in size, it's convenient to use megametres.