Nothing New Under the Sun, or in It

“Don’t pick that up!” our mothers used to scold. “You don’t know where it’s been!”

Our mothers wanted everything their children encountered in this world to be somehow shiny and new, untouched by other human hands, unsullied and pure.

These days, of course, almost everything we pick up has had some previous incarnation somewhere else: We walk around on rubber soles that were formerly parts of tires, write on stationery that was once paper money (or even old jeans), wear fuzzy fleece jackets recycled from plastic soda bottles.

Even yesterday’s banana peels and coffee grounds get born again as next spring’s begonias.

Like Buddhist souls, everything seems to have at least one past life.

One of the great surprises of 20th century science was the discovery that what is true of fleece jackets and rubber soles is true of nearly everything in the universe.

Consider the solid ground on which you stand. It’s made of rock that’s been recycled many times, melted down and remade in that great churning pressure cooker that simmers constantly beneath the deceptively cool surface of the Earth. One day, your backyard will sink back under the ocean, to be cooked down as scrap, perhaps to emerge again as the outpouring of some volcano.

Or take a deep breath. Do you know where it’s been? Almost certainly, it has been inhaled and exhaled by someone else. According to some estimates, at least a few of the molecules we suck up in every breath almost certainly spent some time in the lungs of Cleopatra or Napoleon.

And so it goes. No matter where you look, the stuff of Earth has been there, done that, somewhere, somehow, before.

One of the most spectacular products of recycling is our solar system itself--that neat assemblage of fierce central sun with its well-behaved family of nine circling planets. Where did it come from? Where has it been? Where were elements that make up our sun and planet before they were part of us?

Physicists have known for some time that all elements heavier than helium are cooked inside exploding stars, or supernovae. Therefore, everything we are today must at some point have been “star stuff,” as Carl Sagan so famously put it. Our sun and planetary system condensed like globs of cold soup out of the hot, gaseous breath of some now long gone supernova.

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The question is: Where did the stuff of that supernova come from? Did the star that exploded also condense from the debris of some previous explosion? If so, what formed the elements that went into making that star? And how long does our lineage go back? How many times have the elements now in our solar system been swallowed up by some star, digested and regurgitated? A few times? Hundreds of times? Thousands?

This is the question that astronomer Alan Dressler and his colleagues at the Observatories of the Carnegie Institution, based in Pasadena, would like very much to answer.

“The history of chemicals in this galaxy is the history of chemicals that produced our bodies,” said Dressler. “But the details of that aren’t known.”

That history is hard to sort out, in part because so much recycling has mixed everything up. “It’s like adding salt and sugar to your coffee and then trying to separate them out,” said Dressler’s colleague, astronomer Wendy Freedman.

And the mixing never stops.

“Things are constantly sloshing around in the galaxy,” said Gus Oemler, director of the Carnegie observatories. Sometimes, smaller galaxies fall in, adding their ingredients to the brew.

To get a handle on the problem, astronomers go back to a simpler time--which in astronomy, of course, means looking out into space with high-powered telescopes. Specifically, astronomers are searching out relatively virgin stars--stars, that is, that have gone through very few recyclings. These stars stand out because they are only slightly contaminated with elements produced in previous stellar explosions. In other words, they are mostly just hydrogen and helium.

Alas, such stars are rare objects--only about one in every 10,000. Enormous new twin telescopes going up now at Carnegie’s site in Chile will help the search.

The 6.5-meter Magellan scopes--the first should be operational early next year--will help the astronomers do what Oemler calls “archeology on our own galaxy.” Among other things, they will be looking for the traces of the very first stars, composed of the pure, unadulterated ingredients that ultimately got recycled into us.

It’s an astonishing thought: to be able to look back to a time when nothing in the universe had been used before.

Not even the elements.