Mind swaps have been a standard science-fictional prop for decades. Just wire up the brain in a tired old body to something new, turn on the magical mind-transfer machine, and your mind gets downloaded into a new body.

There could be any number of physical laws in place instead of the ones we know, some of them possibly even more probable than the ones we know. But if other laws existed, we as humans may not.

We’ve come a long way from cultivating a handful of cancer cells in a lab, and every day scientists learn more about the particular wants and needs of our tissues and organs.

Before you sign up for immortality, be forewarned: It isn’t all it’s cracked up to be. Even in the comparatively sweet world of fiction there are plenty of souls embittered by immortality.