How much of your body is stardust, and how did it get there?
You've heard it a million times: we are made of stars.
We're also made of light, but ... how, exactly? Where did the atoms in our body come from and how did they get in our blood and our teeth and our butts?
Here's what happened.
A long time ago — 13.7 billion years, to be exact — the universe expanded after the Big Bang for a count of three seconds. Directly afterwards, it cooled into a state where subatomic particles assembled into atoms. Hydrogen formed first. With only one proton, it was, and is, the simplest atom.
About 300 million years later, these hydrogen atoms started to clump together under the force of gravity. As these clumps grew in size, the pressure in the center of them grew larger, and increased the temperature to roughly 15 million degrees Fahrenheit, the equivalent of atomic swimsuit season. At that point, the hydrogen atoms started to fuse together and make helium, the second smallest atom. These two fused together to make lithium, the third, and beryllium, the fourth, and so on and so on until stars began to form from massive clouds of newly fused elements.
Inside these clouds, a new element formed with every increase in size, heat and pressure. Then, at iron, everything stopped.
Iron is the 26th element. It's the cutoff point for when the energy it takes to create new atoms surpasses the amount it releases so that no new atoms can form. The only way to make a new atom is to apply a force, temperature and pressure so great that it restarts the process from iron but ... it won't happen on its own. It needs some sort of energetic boost. This is basically the point where the universe says, "I'm tired, get me a Red Bull. Or some meth-coated cocaine."
A red giant is the Red Bull. It'll get us up to element 83, bismuth. Supernovas are the methy coke. Otherwise known as a batshit crazy exploding dying stars, we'll need them to get to anything higher are more rare; uranium, radium, ytterbium and what have you.
In a red giant, a star has burned up all the hydrogen in its center. When that happens, the star becomes, as the astrophysicist Craig Wheeler puts it, somewhat schizophrenic: The core loses energy, contracts, and heats up even as the envelope — the rest of the star outside the core — gains energy, expands, and cools (and appears redder). Gooey on the inside, crispy on the outside. The expansion is quite, well, expansive: When our sun becomes a red giant, it will grow so large that it will engulf and evaporate the inner planets, including the Earth.
Some red giants last long enough to create elements in their cores heavier than iron through something called the s-process, for slow. Over a time scale of thousands of years, the s-process can result in the manufacture of elements all the way up to bismuth (83). These get pulled to the star's surface by convection and sloughed off into space via the star's stellar wind. Some of that widely dispersed stardust is holding you up right now.
A supernova creates even rarer elements in a much showier fashion. After a star has created enough iron, the hot burning core begins to cool. Now that the star has cooled, the core no longer expands and gravity quickly collapses the star. The star implodes with enough energy to immediately fuse some of the atoms into higher elements like nickel, krypton, gold, etc. This quick and violent implosion releases an enormous amount of energy that explodes the star. That, ladies and gentlemen, is a supernova. And so is this:
What we're essentially saying here is that all the elements in your body below iron on the periodic table formed during the birth of a star, while all the elements heavier than iron formed during the death of one. The exploded remains from a red giant or supernova travel through out the universe only to either someday clump together with other stardust and give birth to a new star, or, in the case of Earth, form life.
According to National Geographic, approximately 40,000 tons of this exploded stardust rains down on Earth every year. Most of the time, we can't tell it's there, but it gets in our soil, our plants, our animals and eventually, us. The only time we're aware of it is when an extra large chunk of it, called a meteor, hurtles down into a small Russian village and creates a lot of really entertaining YouTube videos.
But now ... back to you. Let's get to how this all relates to your body.
Take your blood, for example. Your blood relies on iron to transport oxygen to the cells in your tissues. This iron was created during the formation of some star somewhere, probably pretty close to where David Bowie's form.
Your muscles. They move due to the electrical conduction of sodium and potassium across your nerve cell membranes. Same with your thoughts. You wouldn't even be able to read, interpret, or process this sentence right now if it wasn't for sodium and potassium. Star birth strikes again.
Most of your body is made up of elements below iron — in fact, 99 percent of you is made of hydrogen, oxygen, carbon, phosphorous, calcium and nitrogen. That's all from little baby stars.
But, you can't function without the atoms of now-dead stars. The remaining 1 percent of your body is made of atoms larger than iron like zinc, iodine, manganese, copper and chromium.
Your thyroid, for example. It excretes hormones which depend on the presence of iodine for synthesis. Without exploded star atoms, you can develop debilitating diseases like hypothyroidism. And your immune system; it's entirely dependent on zinc to function. When it's low, you're much more vulnerable to infection. It also plays a role in cell growth and healing.
There are even trace amounts of gold in each in every one of us. It's in our bones; in our bloodstream.
Let's take this one step further.
Now that we've established that every element in the periodic table aside from hydrogen is stardust, we can determine how much of our body is made up of this stardust. If we know how many hydrogen atoms are in our body, and we do, then we know the rest is star parts.
Our body is composed of roughly 7x10^27 atoms. That's ... a lot of atoms. Try writing that number out on a piece of paper: 7 with 27 zeros behind it. Now it turns out that of those billion billion billion atoms, 4.2x10^27 of them are hydrogen. Remember that hydrogen is Big Bang dust and not stardust. This leaves 2.8x10^27 atoms of stardust. Translation? Forty percent of our body is stars. Just think, long ago someone may have wished upon a star that you are made of.
There. Do you feel more connected to the cosmos now? Do you feel less small and insignificant?
If not, here's one more thing to blow your mind: Quantum Entanglement (aka Spooky Action). The basic idea this physical theory is that two particles can be intimately linked to each other even if they're separated by billions of light-years of space. If you induce a change in one, it will affect the other ... almost like atomic empathy.
That means that if an oxygen atom on planet X287 starts spinning counterclockwise, it's partner particle(s), wherever that may be, will do the same.
You can even have thousands of atoms entangled with a single photon, or thousands of photons entangled with a single atom, or any other particle for that matter. Do you realize what that means? If there's a photon out there in space and one of its atoms is in your knee, your knee atom will respond to that photon and vice-versa. You are very, very, very not alone.
Jesus H Christ.
Well, as Very Smart Man™ Carl Sagan once said, "The cosmos is within us." You could take that to mean you just ate Cosmo's pizza on the hill, or you could sit back and reflect on what that really means: you are nothing more than a sort of lumpy micro-star with a taste for fine boxed wines and a penchant for talking during movies.
If none of this makes sense to you, never fear. Instead of believing us, take it from somebody who really gets it: