User blog comment:Pgrobban/Computers and random numbers/@comment-24956068-20160118202922/@comment-25968376-20160118203809

The way I understand is that you can have basically anything as atmospheric noise. It could be temperature, pressure, voltage in a current and so on. When you measure these with a sensitive enough instrument, you will see that there are huge variations. These are also deterministic, but in order to accurately predict these, you have to study the position and speed of every molecule in the universe, which is quite difficult...