Most of the atoms in your body are 13.7 billion years old, and being you is just the latest page in the incredible story of their life.
There’s no doubt that they’ve been inside of stars, and floated suspended in outer space for far longer than our species has been around.
They’ve washed through the chemical cycles of the Earth countless times, which might have included being frozen to the top of a mountain in one eon, to stomping through dense jungles as part of the thigh bone of a brontosaurus in the next.
It’s like looking in a mirror right? Image source: Wikipedia Commons
But how is this possible? Don’t atoms break down eventually? And how can they move from the top of a mountain to a prehistoric jungle?
We can use modern science to answer these questions and see the story of us from its true beginning. Along the way we will discover how we are born of the universe, not separate, like a wave that emerges from an ocean.
Atoms are the minuscule LEGO blocks of everything we see around us. They are so tiny that they’re as small to a quarter as a quarter is to the United States.
They make up the cells that make up our bodies, and although cells have a lifespan of a few days to a few years, most atoms will coast around the universe for 10 million billion billion billion years before they break down. They are practically immortal.
To find out where their story starts, the lens we have to use is a field of science called astrochemistry, which is the study of molecules in the universe.
The different types of atoms (called elements) have slightly different but parallel stories, though they all begin in the same place; the Big Bang.
Part One. The Giant Plasma Storm.
While the nature of the Big Bang itself remains one of the greatest unsolved mysteries in science, we do have a fairly good grasp on what happened afterwards.
From a microscopic point, the universe erupted outwards in a condition of unimaginable heat and pressure. From the sheer amount of energy coursing through the fabric of reality, the first quarks seared into existence like waves erupting from a turbulent ocean.
Within minutes, quarks joined together to form protons and neutrons. They formed an opaque cloud of plasma so vast that it stretched across the entire universe. It rippled with light and electricity, and may have looked something like a combination of being inside a plasma globe and a lightning storm.
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The universe passed 240,000 years in this dense, violent plasma storm, a time so extraordinarily long on human timescales that it would have encompassed the entire history of our species.
But the same explosive force of the Big Bang that creates the plasma storm kept the universe expanding, and eventually, it started to cool off.
The electricity which rippled through the cloud began to combine with its protons and neutrons to form the transparent gasses hydrogen and helium, and thus the first complete elements to exist in the universe.
About 60% of the atoms in our bodies are directly descended from this hydrogen and helium.
The plasma storm began to fade and was replaced by this new, transparent cloud, and the universe began to resemble space as we now know it.
Part Two. Inside a Star.
In the cold silence of space, your atoms would have been witness to one of the most sublime visions in the universe: the formation of the Milky Way galaxy through a veil of a nebula.
They started to feel the pull of gravitation. First subtly and slowly, but soon like a colossal riptide, they were pulled into the gravity well of a still-forming giant star, one of the ancestors of our Sun.
As more material fell into the growing star, the pressure felt by your atoms climbed to over 250 billion times the pressure of our atmosphere. A dull glow began as the star ignited, which soon became a heat and light hotter and brighter than anything we could imagine.
Your atoms spent hundreds of millions of years here, adrift in the ebb and flow of the internal storms of the star.
Some fell deep into the star’s core. Here they were subject to pressure that was extreme compared even to the rest of the star, and in this furnace atoms of hydrogen and helium fused together to become oxygen, carbon, iron and other elements, releasing bursts of heat and light as they merged.
The light from the Sun that warms your skin during the day, and the flickering of light from the stars at night originates from the same brutal process of fusion.
Although it would have seemed like an eternity, after hundreds of millions of years the giant star began to run out of its hydrogen and helium fuel.
At the same time, its waste products of oxygen, carbon, and iron began to build up, and its light began to dim.
It erupted in a supernova explosion, a blast so violent that it would have been visible from across the other other side of the Milky Way galaxy, if there was anyone there to see it.
The searing explosion fused other atoms, creating more oxygen and carbon, as well as rarer elements like silicon, neon, and sodium.
The shockwave pushed the newly formed elements back into what was left of the original hydrogen and helium cloud, disrupting it and seeding it with countless new types of atoms.
As the shockwave impacted surrounding gas, it compressed millions of miles of hydrogen and oxygen together to form icy water.
Disrupted from the blast, the gas cloud began to once again feel the pull of gravitation.
This cycle repeated many times, in many different stars. But each time, the surrounding cloud became populated with more ice and new rocky elements. which clumped together and grew larger and larger.
From the cloud hundreds of new, smaller stars formed. Eventually, one of them was our Sun.
In the small part of the cloud that our Sun occupied, remaining hydrogen and helium, and now other elements too, were once again felt the pull of gravity and were destined to be set adrift in the internal stellar storms all over again.
But some of the gas and rocks found themselves not being pulled in to the star, but held in orbit around it in a vast ring called an ‘accretion disc’.
Over time they collided with each other, forming larger and larger balls of rock and gas in a series of impacts until they grew to the size of planets, which were bombarded by asteroids for hundreds of millions of years.
When it ignited, the Sun released a series of immense shockwaves that impacted the new planets and determined the shape of the new ‘solar system’.
It pushed most of the gas outwards, towards the outer planets, where it formed the gas giants Jupiter, Saturn, Neptune, and Uranus.
The heavy, rocky material closest to the Sun was left behind by the shockwave, and it formed the small, rocky planets Mercury, Venus, Earth, and Mars, with a thin remnant of gassy atmosphere for each of them.
One of the main scientific goals of the manned missions sent to the Moon and the robots sent to Mars was to gather and analyse their soil, in order to discover the composition of the accretion disc that formed the planets.
Information like this helps us determine if the conditions on Earth are in some way unique, and if this could account for why there is life here. As it turns out, if there is something unique about the Earth, it’s not the soil.
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Over time the asteroid bombardments slowed down, and one hundred percent of the atoms that would eventually form you found themselves in one place; Earth.
Part Three. The Cycles of Earth.
Here on Earth, your atoms began to cycle through the air, land, and water.
At this point, it’s hard to track exactly where your atoms went, but we do know that they have been very well recycled.
By the way, the average person is made of seven octillion atoms! (7,000,000,000,000,000,000,000,000,000!)
Just for reference if you had seven octillion standard sized bricks, they’d fill the volume of the planet Jupiter… four times over.
They no doubt combined into different molecules and broke down again billions of times, but the atoms themselves, once formed after the Big Bang and fused inside of a star, never degraded.
”Every atom you possess has almost certainly passed through several stars and been part of millions of organisms on its way to becoming you. We are each so atomically numerous and so vigorously recycled at death that a significant number of our atoms — up to a billion for each of us, it has been suggested — probably once belonged to Shakespeare. A billion more each came from Buddha and Genghis Khan and Beethoven, and any other historical figure you care to name. (The personages have to be historical, apparently, as it takes the atoms some decades to become thoroughly redistributed; however much you may wish it, you are not yet one with Elvis Presley.) So we are all reincarnations — though short-lived ones. When we die, our atoms will disassemble and move off to find new uses else-where — as part of a leaf or other human being or drop of dew. Atoms themselves, however, go on practically for ever.Bill BrysonA Short History of Nearly Everything
A handful of your atoms may have been used in one of the very first molecules of DNA at the birth of life on Earth.
Others may have been used in one of the mandibles of a five-eyed Opabinia regalis, a tiny three-inch predator during the Cambrian Explosion.
Image credit: Dotted Yeti / Shutterstock
Others may have been part of both the muscle tissue of a Tyrannosaurus, and of its prey.
In the chaos of Earth’s ever changing chemistry, it seems like our seven octillion atoms have truly been everywhere.
Eventually, through your food, they came together to create your hands, heart, and the eyeballs you’re using to read these words.
One thing we know for sure though is that your carbon atoms were very recently part of a plant, and considering our modern diet, it was probably corn or wheat. It pulled carbon dioxide molecules floating in the air and using the Sun’s light as a catalyst, the green cells of the plant combined them into a long carbohydrate molecule. You recently ate it as part of bread, corn starch, or sugar.
The last glass of water you drank has also gone through a monumental process. It’s in a constant cycle of rain and evaporation driven by the heat of the Sun, while occasionally getting diverted through the belly of a plant or animal.
You might have seen a diagram of the water cycle like the one below in school, but what it doesn’t make clear is the scale of this process. Water is exchanged across the entire surface of the Earth, for billions of years at a time.
Your atoms might have been a wave that pushed Christopher Columbus’ Santa Maria across the the Atlantic, or an avalanche that toppled one of Hannibal’s elephants down the Alps, or part of the iceberg that sank the Titanic.
The water cycle. Image credit: NASA
But the atoms that we have now are not the atoms that we’ll keep. In fact, they are completely replaced once every ten years.
Steve Grand in his book Creation: Life and How to Make It points out that because our atoms are in constant flux, we are more like a wave than a permanent thing. He invites us to do a quick thought experiment.
”Think of an experience from your childhood — something you remember clearly, something you can see, feel, maybe even smell, as if you were really there.
After all, you really were there at the time, weren’t you? How else would you remember it?
But here's the bombshell: You weren’t there.
Not a single atom that is in your body today was there when that event took place.
Matter flows from place to place and momentarily comes together to be you. Whatever you are, therefore, you are not the stuff of which you are made.
If that doesn’t make the hair stand up on the back of your neck, read it again until it does.Steve GrandCreation: Life and How to Make It
To put it another way, the atoms that comprise your mind and body don’t belong to you; you are just borrowing them.
“The very dust that blows along the street
Once whispered to its love that life is sweet.”Hallam HawksworthThe Adventures of a Grain of Dust
Part Four. After Earth.
After another 5 billion years of cycling around the Earth, all atoms on the Earth will be scorched by the Sun as it expands into the final stage of its life, a red giant.
The Sun’s outer layers will expand until they engulf Mercury, Venus, and finally the Earth. Any life that has not found a way to leave the Earth by this point will be, in a word, completely cooked.
The Sun will swell into a red giant, scorching then engulfing the Earth. Image credit: James Gitlin
Eventually like the ancestor stars that preceded it, the Sun will explode, returning new atoms to the cold, dark cloud in space. Then the star cycle begins anew.
Hundreds of new stars will form, and your atoms will be split amongst a new set of planets, moons, and maybe new forms of life.
Cosmologists believe that this cycle of death and rebirth of the stars will repeat about one hundred times, before the final star in the universe exhausts all the remaining hydrogen and helium, and the galaxies will go dark.
What will follow is an era of black holes. All matter, including your old atoms, will either be consumed by them or flung into deep space from their gravity.
After countless ages, where the time scales are so long that time begins to lose its significance, even the black holes disappear, evaporating into nothing but radiation.
This is the end of the line of what scientists know what will happen for sure.
But there is some speculation about what happens next.
One possibility is that, after any surviving atoms and radiation have spent an eternity travelling through the cold, dark remnants of the universe, they will decay into the quarks that they consist of.
These particles will fill the universe in a ‘thermal equilibrium’, where every place in the universe is barely above a temperature of absolute zero, and no further exchange of energy becomes possible.
This means no stars, life, or intelligence will be possible. It may remain in this state for all of eternity. This is called the heat death of the universe.
A second, more hopeful possibility is that the expansion of the universe itself slows, and is reversed by the pull of its own gravity.
After hundreds of billions of years, every atom and flash of radiation are first slowly, and then rapidly brought back together until they rush to collapse into a single point. This is a reversal of the Big Bang, called the ‘Big Crunch’.
Many scientists believe that the Big Crunch will be the end of our universe, but it may be followed by something spectacular.
A new Big Bang that creates a whole new, different universe, which may one day have new stars, new planets, and new life.
In this distant universe, the energy that was once you may one day cycle through a planet once again, and it’s creatures.
It may form the light of a distant star that impacts the retina of a scientist or storyteller who wonders about the universe, and where her own atoms came from.