Question

What’s cosmology?

A consumer of big numbers.
1020 is only three or so orders of magnitude smaller than Avagadro’s constant, which is one of the bigger numbers (that I know) in everyday use.

If you want to keep adding text to a string, the String variable will do fine:

String buffer = ""; 
...later...
buffer=buffer+'a';
buffer=buffer+'b';
buffer=buffer+'c';
buffer=buffer+'d';
// buffer now has 'abcd' in it

You can read more here:

http://arduino.cc/en/Reference/StringObject