That doesn’t mean the matter and energy that makes up our human body can stay intact as a unit in any meaningful sense to claim existence of an afterlife, though.

For example, our brain houses our consciousness, our thoughts, and our memories. The electrical activity in our brains is an integral part of that. Energy is never created or destroyed. But that electrical energy created by the brain as part of our consciousness may just evacuate the body as heat. It doesn’t disappear, but it’s no longer in a form that could reasonably be called a soul or a consciousness that survives death. It’s just heat loss.

Our bodies fall apart and become parts of many different things, on a molecular level. We become part of a blade of grass, part of an earthworm, part of an amoeba or bacteria that makes up the soil, and so forth and so on.

When you think about it like that, you’re already immortal because the molecules that make up you have been around for all of time already. You’re housing stardust and dinosaurs. They’re part of you, right now You will become stardust and creatures of unimaginable magnificence again.

When we die, we cease to be alive and become part of life itself. We integrate into the entire web of life. We only become nothing because we become everything.