> Hydrogen (fusion) on the other hand, pretty much defines the useful lifetime of the universe. That's how I define "sustainability". That's true! That's true

> Hydrogen (fusion) on the other hand, pretty much defines the useful lifetime of the universe. That's how I define "sustainability". That's true! That's true and funny! Hydrogen fusion does define the "useful" lifetime of the universe (ie: the interval before the entire universe becomes mainly full of cold heavy metals), but the stars are going to be burning for a few more billion years because fusion is an "unlikely" process. Yes! The solar system is still as we know it, with the planets well separated from the Sun and not yet conglomerated into a big red giant, for the same reason for which we are struggling to get fusion in our labs: because that's difficult! You need enormous temperatures to convince hydrogen atoms to come together and mix their nuclei, and so you get a lot of problems in controlling the overall process. Sure, we can try with cold fusion, but unfortunately we have not yet got a useful result. But we can insist. Actually, I think we must insist! I can't imagine a better source of energy than cold fusion, if we ever get there. Yes, we must definitely insist!