>mentioning the second law of thermodynamics
The second law of thermodynamics applies to closed systems. It implies the Sun will run down eventually if let it continue shining. The Earth isn't a closed system, since it receives sunlight, and your body isn't a closed system because you eat.
But I agree with the other posters, anxiety about the prospect of dying is more of a problem than the specific scenarios. I have had luck with "Unlocking the Emotional Brain", but I stopped reading at their summary of EMDR because it seemed ridiculously optimistic.