The Sun is the ultimate source of all life on Earth. Without it and its energy, nothing you see around you would be possible; every atom in your body would still exist but be arranged in a very different way, drifting through space, one infinitesimally small part of one, or maybe even several, of the billions of cosmic clouds drifting through the vastness of the cosmos.

The Pillars of Creation are part of the Eagle Nebula, a cloud of space dust 70 light-years across. The scales are mind-boggling. Atoms in our bodies could once upon a time have been a part of something like this, and one day they will be so again.

But fortunately for us, many many years ago, one of these cosmic clouds, or nebulae, began to condense, collapsing at an exponential rate as it gained mass. Eventually, the pressures in the heart of that ball of matter became so great that something incredible happened: atoms, one of the smallest units of observable matter, began welding together to form completely new atoms with completely new properties, all in a process known as nuclear fusion.

Nuclear fusion occurs under intense pressure, crushing atoms together and releasing photons as a byproduct.

Now the really interesting part about this is that this process, besides creating all the building blocks of life (if that isn’t interesting enough), also creates light. The byproduct of the nuclear fusion of two atoms is the release of a single photon, a fundamental particle of light. That newly formed photon then embarks on a very long journey. It first needs to weave its way between the quinquagintillions (it’s a word; I looked it up) of other photons all trapped in the sun’s interior and somehow claw its way to the surface of the sun. This process can literally take millions of years. But from there, it’s smooth sailing – a straight shot out into the universe. And for a very very few, one of every two billion to be more or less accurate (that’s 0.00000005% of the total number of photons produced by the sun), it’s a brief 8-minute and 20-second hop across to reach the little blue dot that is our home, planet Earth.

8 minutes and 20 seconds. Light from our next closest star takes 4.2 years to reach us!

Waiting for those photons, plants, algae, and a few specialised bacteria. And they are hungry; a single blade of grass will absorb 10 quadrillion photons per second. All of these photons are just the raw material for the earth’s living refinery, an operation made up of every single photosynthetic organism scattered over the globe. Within these plants are specialised structures called chloroplasts, within which a green pigment called chlorophyll resides.

This chlorophyll absorbs the incoming photons, becoming excited and releasing electrons (later to be replaced by electrons from the hydrogen atoms in water molecules, hence the release of oxygen as a byproduct). These electrons drive the synthesis of adenosine triphosphate (ATP), a molecule that serves as the primary energy carrier in living organisms. This ATP powers the production of organic compounds from carbon dioxide and hydrogen (all three of these atoms, carbon, oxygen, and hydrogen, were originally formed in the cosmic fusion reactor of our or some “nearby” sun), to create cellulose, an extremely complex sugar that is the basic building block of a plant. The plant thus grows, reaching its tendrils out further and further to gather more and more sunlight, and so on and so forth.

And then along comes an impala, one of many animals adapted to the utilisation of this coarser source of nutrition. These animals are unable to do the work by themselves, however, and rely on a symbiotic relationship with certain bacteria, protozoa, and fungi, which do the work of breaking down the complex cellulose into simpler compounds that are able to be broken down further by the body’s enzymes and used in growth and energy production.

Along with many others, impalas are specially adapted to make use of the cellulose in the grass.

The Three Rivers Female then spies this particular impala walking through an open clearing. She notes the limp the animal is sporting and locks onto her prey. The stalk requires patience, but she has ample reserves, she is a master of her craft. Two hours later, the limping impala is only metres from the female, who lies flattened in the long grass. She makes her move, and the lights soon fade for the Impala. The commotion caused by the rest of the herd is sure to alarm any nearby predators, and the female immediately starts dragging her prey towards a marula tree.

Success.

She must hoist her kill as soon as possible. It is an energy-intensive process, but she will have the ability to restock her reserves if she can make this final push. Just as she reaches the base of the tree and glances up to plan her route, she hears the sounds of a hyena lumbering towards her. There’s no time to lose! She reaches for her kill and scrabbles madly up the trunk of the tree. The hyena leaps, and his jaws snap shut with only air between them; he’s missed. The female leopard can then sit and enjoy her meal in relative peace, with the only likely threat being a patrolling male leopard spying on her hard-won prize. She feeds.

Enzymes in the female’s stomach break down the proteins, fats, and carbohydrates into smaller molecules that can be absorbed into the bloodstream and used by the body for energy and other metabolic processes. These molecules, ultimately imbued with cosmic energy, enter the bloodstream and are fed into the cells of the body. Within these cells lie the mitochondria, the power generators of the body, and within each mitochondrion, an incredibly complex (and frankly barely understandable) process transforms these products of digestion into energy, pure adenosine triphosphate (ATP), which fuels every reaction in the body, including cellular generation and regeneration, i.e., growth and repair.

Finally, one day the Three Rivers Female will be lost to us and her body will be returned to the cosmos. The atoms she has borrowed will be released back into the earth by bacteria and microorganisms. Possibly she will feed a wandering hyena, and her energy will flow into that animal. Ultimately, all of her atoms will be returned to the ether to be recycled again.

Vultures may add another strand to the ecological web as the body below decomposes.

Perhaps some small part of her will escape the confines of earth and end up in one of the trillions of clouds of organic molecules that dot our universe; perhaps another part will sink deep into the earth, fusing to our core, only to be released upon the destruction of earth some 5 billion years from now.

Ultimately, everything on our beautiful planet is fueled by the sun, with its energy flowing through us all. So, the next time you feel that radiant warmth of our star on your bank, try to remember to be grateful; it is the only reason we are all here.