In Slaughterhouse-Five, Kurt Vonnegut had a fantasy that time and gravity could be reversed, and that the bombs rained down upon Europe in World War II could reassemble themselves. The billions of blasted fragments would magically recombine, rescinding the destruction they had done. The bombs, made whole again, would float up into the bomb bays of the planes that had dropped them, and the planes would fly backward, back home, where the bombs would be disassembled and all their metals and explosive powders redeposited in the earth so they would be harmless and all the death would be repealed.
If reality...