It's been said that SARS-CoV-2 can remain on surfaces up to 9 or 10 days. While I read that smallpox can survive out of a host even for years.
As much as I know, since viruses are only protein capsules around RNA strands, thus they are comparable to rocks or metals. Why do they die out of a host?
What happens to them that causes them to die? Do they consume energy and run out of fuel? Do they have mysterious half-life as in chemical elements? Do they have predators in food- chain and get eaten by something else?
Why a surface diagnosed with a virus today, is clean after X daya/months/years? What happens to viruses on that surface?
I searched this and I couldn't find answera for why. They only say how long it survives.