The cosmos is made of 92 natural elements. But only a few truly affect us.
When we gaze up, hydrogen dominates the scenery. Each puffy cloud is 67% hydrogen, nearly a million pounds of it per cloud. It makes up three-fourths of every star, too. When excited by the UV light from stellar neighbors, hydrogen glows red, explaining why crimson repeats like a musical coda throughout space and time.
The second most abundant cosmic element is helium. It’s a grouchy entity that never, ever combines with anything else. It just takes up space — the universe’s bubble wrap.
The third commonest element is fun-loving oxygen. It gregariously combines with almost anything. Look at the Moon and you basically gaze at an oxygen ball. Half its surface is this single substance, merged with mostly silicon or aluminum into various uninteresting gray solids. By weight, about two-thirds of your beloved body is oxygen, too, along with the furry bodies of all those coyotes you hear at night. When they howl at the Moon, it’s basically oxygen howling at oxygen.
The fourth most common element is durable, worry-free carbon. With the highest melting point of all common elements, its many structures like diamonds and charcoal will retain their familiar solid forms even when the rest of Earth turns into liquidy goo after the Sun’s surface expands all the way to here. While we’re waiting for that, we can observe carbon’s countless creative arrangements as it readily combines with oxygen and hydrogen to give us endless organic items from mosquitoes to Almond Joy miniatures.
But it’s nuclear fusion that will someday bring carbon to visual brilliance. That energy-producing process, revealed a century ago by British physicist Arthur Eddington, is what makes the Sun and stars shine. The Sun fuses six million tons of hydrogen into helium each second, and can keep doing this for another five-billion years. But eventually its core will be mostly helium, and then other fusion processes will gain dominance. Ultimately, these various fusion reactions will make the Sun expand and cool, then collapse and heat up, until we’ll end up forever orbiting around it when it’s shrunk to only the size of Earth. It will then be mostly oxygen and carbon along with some residual hydrogen — the same stuff that mostly comprises our bodies today.
The universe’s fifth most common element is nitrogen. It makes up 79% of our air, so that’s what you and I are mostly breathing. It doesn’t hurt us and it doesn’t help us — it’s like those optional car warrantees.
Since oxygen is a fifth of our atmosphere and nitrogen just shy of four-fifths, that leaves about one percent of the air unaccounted for. What is that one percent? What›s the third most common element we’re inhaling?
Good teachers ignite a love of such information. They make kids excited to hear that strange, distinct creatures with their own lifespans and separate DNA called mitochondria live within each of our cells, or that rain falls at 22 miles per hour, or that we breath three distinct components that each make up one or more percent of the air. Anyway, most people guess carbon dioxide is the third commonest air constituent, but actually that molecule makes up less than a twentieth of one percent! It’s a truly minor component despite its greenhouse notoriety. Few could correctly name the third atmosphere item. It’s argon.
Argon is the gas we put inside light bulbs, so we look at it a lot. Argon and the remaining seven dozen elements are almost an extravagance, a seasoning added to our existence. Yet all these collective 92 natural elements make up just 4% of the universe. There’s six times more dark matter, whose gravity dominates the cosmos even though its composition is an utter mystery. And what has nature fashioned out of that?
Alas, this is where we reach the edge of present understanding.
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