This article explores from a scientific perspective how the atoms that make up the human body were created in space, brought to Earth, and how they return to space after death, emphasizing that we are part of a cosmic cycle.
“Where do we come from and where are we going?” This question has piqued human curiosity throughout time and place. Humans have attempted to answer this question since the dawn of time, and the greatest philosophers and thinkers have come up with plausible answers. This question goes beyond the question of our origins and end, and leads to a deeper exploration of the meaning and purpose of existence. In other words, why are we here, and what direction should our lives take? It’s a question that people still ponder at least once in their lives, and it’s a question that’s hard to answer.
How would a scientist answer this question? Unlike philosophical and religious discussions, science provides us with a more concrete and clear answer to the question of material origins and fate.
Every object we encounter in life is made up of atoms. An atom is an unimaginably small particle, and there are more than 100 different types of atoms in nature that come together in different ways to form the countless objects in the world. They’re nature’s Lego blocks, so to speak. Atoms are made up of a nucleus and electrons orbiting around the nucleus, which in turn are made up of protons and neutrons. The number of protons determines the type of atom: atoms with one proton are hydrogen, atoms with two protons are helium, etc. The different types of atoms form matter in different ways, giving rise to the countless beings in the universe. Naturally, our bodies are no exception. The human body is made up of about 100 trillion atoms, and different atoms like hydrogen, oxygen, carbon, and nitrogen combine to form even more different substances. Each of these substances plays a role in our bodies, and it’s what keeps us alive.
But where and when did the atoms that make up our bodies come from? To answer this question, we need to look beyond Earth. The centers of self-luminous stars like the sun are so hot and pressurized that two atoms can collide, causing the nuclei of the two atoms to clump together into a single, larger atom. This is called nuclear fusion. Stars shine because the energy released from nuclear fusion is released in the form of light. Nuclear fusion is important in the history of the universe because at the beginning, there was only hydrogen in our universe. All other elements were created through nuclear fusion from hydrogen, the smallest element with only one proton. And the only place in the universe where nuclear fusion occurs is in stars. Carbon, which has six protons, oxygen, which has eight, and iron, which has 26 protons, were all created sometime in a star.
And these new elements are spread throughout the universe when the star dies and explodes. Every atom on Earth (except for hydrogen) was made in a star once upon a time, and flew into the solar system with the star’s death. They then spent 4.5 billion years on Earth, cycling through air, rocks, plants, and animals, until they formed the bodies we have today. The hydrogen and oxygen atoms in your body probably came from the water you drank a few weeks ago, and the nitrogen came from protein foods like meat and beans. Naturally, our bodies are not the end of this vast cycle. The tons of carbon dioxide in your exhaled breath, which you’re constantly exhaling right now, is made up of carbon and oxygen atoms that you took from outside your body sometime ago. This carbon dioxide may dissolve into the ocean, or it may one day be absorbed by a tree and form leaves or branches, where it will begin its endless journey around the globe.
We often feel that human life is finite, but from a scientific perspective, we realize that we are part of a cycle that goes on forever. In five billion years from now, the sun will no longer shine. As the sun expands in its final days, the material on Earth will not be able to support it, and it will bounce off into the distance, scattering to the far reaches of space. The hydrogen that makes up your body could end up in a star somewhere in the universe, far away, long after the end of time, and become the material for nuclear fusion. Maybe the carbon atom you just exhaled will one day travel to another planet and form the body of a living being on that planet.
Our bodies come from other bodies and go back to other bodies, and they are no different from the other materials that make up the universe. The atoms that make up my body are not my own. There are countless beings before me who held them, and countless beings after me. Think of it this way, and you’ll realize that all life on Earth, and indeed the entire universe, is not isolated from each other.
