The story of an atom
13.798 ± 0.037 billion years ago (or thereabouts), something happened. A tiny thing that we call a singularity, for reasons we still don’t understand, began to expand. Inside this singularity, conditions were almost unimaginable; incredibly high energy densities, temperatures and pressures existed and pretty much nothing else. After about 10^-37 seconds, this expansion appeared to increase exponentially. At 10^-32 seconds, this inflation slowed down and the now baby universe continued expanding, but at a more stately pace.
At this point the energy density, temperature and pressure had cooled off enough to allow a collection of particles to appear - the bits that make up the bits that make up atoms. But there were no atoms yet. These particles were so hot and energetic, they whizzed around and bounced off each other too fast for anything to stick together. The motions of these particles were at speed of lightish speeds, and particles of all kinds were being continuously created and destroyed. Then, something happened; somehow, ‘normal’ particles dominated over their ‘anti’ particle brethren somewhere in the region of one particle in about 30 million.
Fast forward in time to 10^-6 seconds after the beginning of the expansion, these tiny particles had slowed down and cooled off enough to begin combining into more familiar things - neutrons and protons. The temperature was now no longer high enough to create new ‘normal’ and ‘anti’ particles, so a mass cancelling out of these opposing particles immediately followed. After this battle for particle dominance, the remaining protons, neutrons and electrons were no longer moving relativistically and the Universe was essentially populated by photons with a few neutrinos thrown in for good measure.
Over the next couple of minutes, the universe expanded and cooled even further; protons and neutrons began to join together to form deuterium, helium, some lithium and a few other unstable nuclei. The leftover protons (or as we call them, hydrogen nuclei) formed the rest of the matter in the now toddler universe.
This was the state of things for the next 379,000 years or so. Expansion, cooling and particles whizzing about. By then, temperatures had dropped sufficiently that the electrons, protons and neutrons could finally bind together into fully formed atoms. This produced mostly hydrogen, some helium and a smattering of lithium.
Eventually, these atoms began to clump together under mutual gravitational attraction to form vast clouds of gas. These vast clouds of gas, which, under their own gravitational influence, would occasionally grow denser, begin to compact and get hotter and denser in certain regions. Once a pocket of this gas was hot and dense enough, nuclear fusion would occur in the centre of this pocket and the first stars were born. Massive, hydrogen rich beasts of stars these were, lighting up the teenaged universe for the first time, but they were destined to live short lives, burning through their hydrogen fuel in only a few million years before exploding as supernovae and seeding their local neighbourhoods with the contents of their outer shells.
This now dramatically enriched cosmic medium (containing such exotic atoms as oxygen, neon, carbon, iron and silicon) eventually underwent its own gravitational collapse and formed the next generation of stars. These enriched stars were smaller than their forebears, lived slightly longer and, upon their demise and supernova, further enriched the cosmos with even more exotic atoms. Finally, we get to the birth of the third generation of stars (of which our sun is one), and the birth of a small planet that orbits it in a celestial gravitational embrace.
Temperatures in the cores of stars are not hot enough to fuse anything but hydrogen into helium during the majority of their lives. But as a star ages and runs out of hydrogen fuel, the delicate balance between forces that try to blow the star apart and try to collapse it down as small as possible begin to destabilise; the star begins to shrink. As the star contracts, the core heats up more and reaches temperatures at which it can fuse helium into heavier elements. The star ‘puffs out’, getting even bigger, becoming a red giant and can last this way for a few more million years before it uses up its supply of helium. Then it contracts again until it can fuse the carbon in its core. This process continues, with the successive stages being fuelled by neon, oxygen, and silicon. Near the end of the star’s life, fusion continues along a series of onion-layer shells within the star. Each shell fuses a different element, with the outermost shell fusing hydrogen; the next shell fusing helium and so on inwards. Finally, when the core has worked its way to iron, this process finally comes to an end. Iron, unlike the elements that precede it, requires more energy to fuse into heavier elements than you get out of it, so the process essentially ceases. The star begins its collapse again. If the star has enough mass, the outer layers come crashing inwards, the core begins to collapse in on itself and creates pressures and temperatures hot enough to create an explosion so titanic that every element heavier than iron (uranium, gold, platinum, etc) are created.
Virtually every element in your body (with the exception of some of the hydrogen, helium and lithium) was created from this 13.798 ± 0.037 billion year process. Stars lived and died as spectacular explosive fireworks to seed the universe with the elements that your body now uses with such abandon. Every time you look up at the night sky and see the stars, you can think to yourself that some of these stars will provide creatures in the far distant future with the raw materials to make iPods (or whatever these creatures will use for personal entertainment).
So the next time you blow your nose and examine the content of the tissue, it’s not mucus and snot that you’re examining, it’s the ashes of your long dead stellar parents.
