Scientific notation is really just a shorthand version of writing really big or really small numbers. No working scientist uses scientific notation for every number -- numbers like 1,000 or 0.01 are small enough and simple enough to write that they would be written just like that. But a working scientist would certainly not write out 40,700,000,000,000 kilometers in a paper -- it's just too long! Instead, she would write the number as kilometers -- which is easier to write. (In fact, she'd probably write km, since ``km'' is the abbreviation for kilometers.) Similarly, she wouldn't write out 0.000000000000000002356; again, it's just too long. She would instead write out , which again is easier on everyone. And scientific notation can make some kinds of math problems more manageable. Doing arithmetic on really big or really small numbers is much simpler, once you know how to use scientific notation.