Consider Open-Individualism. It's actually very difficult to make a philosophical case for Closed-Individualism (the common sense belief your post seems to espouse). You have to show why subjects would be particular to a group of atoms which are constantly changing. If not, the subject of all experiences is the same across space and time, and it's only the experiences which are different and constantly changing. If so, existence is eternal, which is what relativity suggests.

http://www.atheismandthecity.com/2016/02/does-special-relati...