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What happens to the electrons, protons, neutrons and photons that exist in living beings when they die?

Pat French
Telford, Shropshire, UK

Short answer 鈥� nothing. It is the molecules that are made up of atoms that change after death. The atoms are simply rearranged in less ordered ways. This is called decay and, ultimately, entropy.

Atoms will remain practically unchanged for much of the life of the universe. They will quite possibly become parts of other molecules, only to break down and combine yet again.

For example, a potato contains billions of carbon atoms. It dies when you fry it in your chip pan. Your body then breaks it down into simpler nutrients that you absorb, most of which include carbon atoms. You also produce waste substances, which may contain carbon, that you excrete and then might compost. You also breathe out carbon dioxide, which green plants can use to make sugars and grow. You die, and your carbon atoms help something else grow. Through it all, those carbon atoms are still carbon atoms.

Atoms are built from protons, neutrons and electrons. Protons and neutrons are built from quarks. Only in the final stages of entropy in the cosmos, many billions of years from now, might an atom鈥檚 component quarks drift apart in the 鈥渉eat death鈥� of the universe 鈥� if that is indeed how it shall end.

Herman D鈥橦ondt
Sydney, Australia

Let鈥檚 have a look at the past lives of the atoms in our bodies. For a start, all hydrogen was created around the time of the big bang. That means all the hydrogen atoms in our bodies are the same age, some 13.8 billion years old. These make up 62 per cent of a person鈥檚 atoms.

Most of the other atoms within us were created through nuclear fusion in dying stars. As Carl Sagan said, 鈥淲e are made of star stuff鈥�. Hence, all our atoms are at least as old as Earth, i.e. 4.6 billion years.

When we die, our atoms will become incorporated in the environment and eventually in other living beings. It is estimated that every glass of water we drink contains some water molecules that went through a dinosaur and were expelled in its urine. Living bodies may recirculate atoms, but the atoms themselves persist.

How long can we expect these particles to last into the future? Unconfined neutrons undergo beta decay, with a half-life of about 610 seconds, but inside a nucleus they are stable. Electrons may be immortal, as they are the least-massive carrier of electrical charge and hence can鈥檛 decay under current theories. Some theories suggest that protons may have a limited life. This has been tested experimentally, and so far we have found that, if protons do decay, they won鈥檛 do so for at least 10³⁴ years. That鈥檚 100 trillion times as long as the current age of the universe, so not something most people would worry about.

Andrew Murray
Moore, South Carolina, US

All Yorkshire people know that 鈥渢鈥檞orms鈥檒l come an鈥� eyt thee oop鈥�. So no atomic particles are lost, just recycled.

To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.

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