Excuse me, when people die, is there really an underworld and a dead world?

I think from the law of conservation of energy (the basic law of physics), no matter what is dead, there should still be some energy that we can't detect now, which may be called ghosts or souls. Because, for example, people will have biological energy such as blood pressure energy and bioelectricity when they are alive. When the body is dead, this substance has not changed for the time being, but these biological energies are gone. But the total energy of nature should be conserved. Where did this energy go? I think it should have a soul, so as to conform to the basic theorem.