Everyone has mentioned how software is deterministic.
Hardware RNGs sometimes rely on thermal noise (which is really random) but there are sometimes flaws with how that noise is sampled and de-skewed. Also, they need to be monitored to cope with hardware failure. Be aware, especially if you're using them for cryptography, that they might be a poor fit for your purpose.
And surely everyone on HN knows that part of the "snow" noise displayed on an untuned TV is cosmic background radiation, ie "afterglow" of the big bang. I still find that amazing.
Hardware RNGs sometimes rely on thermal noise (which is really random) but there are sometimes flaws with how that noise is sampled and de-skewed. Also, they need to be monitored to cope with hardware failure. Be aware, especially if you're using them for cryptography, that they might be a poor fit for your purpose.
Testing Hardware RNGs
(http://www.robertnz.net/true_rng.html)
EDIT:
Descriptions of various forms of noise:
(http://www.eie.polyu.edu.hk/~ensurya/lect_notes/commun_cir/C...)
And surely everyone on HN knows that part of the "snow" noise displayed on an untuned TV is cosmic background radiation, ie "afterglow" of the big bang. I still find that amazing.