THE EXTRACT OBLITERATION: A HAWKING-COOPER RADIATION

In “The Extract Obliteration,” Season 6, Episode 6, and other episodes, Sheldon rubs shoulders with Professor Stephen Hawking.

“The amazing thing is that every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust. You couldn’t be here if stars hadn’t exploded, because the elements—the carbon, nitrogen, oxygen, iron, all the things that matter for evolution—weren’t created at the beginning of time. They were created in the nuclear furnaces of stars, and the only way they could get into your body is if those stars were kind enough to explode. So, forget Jesus. The stars died so that you could be here today.”

—Lawrence M. Krauss, A Universe from Nothing: Why There is Something Rather than Nothing (2012)

Under a Starry Sky

Imagine Sheldon Cooper and Stephen Hawking are playing a game under a starry sky. In our dreamt-up domain beyond this world, Professor Hawking is gifted with divine powers. Exactly the kind of divine influence, in fact, of which the eminent Professor would strongly disapprove. Nonetheless, his imaginary powers suit our expository purpose. Not only has the Professor been able to make our sun a member of a young star cluster, but he’s also shifted time itself, so that our divine Professor, and his attentive student Sheldon, can be present on Earth from the very start. Nor is that the end of Professor Hawking’s powers.

Having wound time back to something of a beginning for the young star cluster of which our sun is a member, the Professor now speeds up time in the opposite direction, and ten billion years pass in a single night. Why the temporal trickery? Because this Hawking-Cooper Radiation game is an experiment to see what the evolution of stars would look like as a kind of fireworks display.

The Professor starts the cosmic clock ticking, and, almost at once, the giant stars explode as supernovae. The way stars evolve depends on their size. During most of their lives, stars burn hydrogen and turn it into helium. When they run out of hydrogen, they burn helium instead. Stars never die. Most change slowly into a different kind of star. But the biggest undergo huge explosions early in their evolution. When they run out of fuel to burn, they detonate in an enormous burst of light, more light than a small star gives out in its entire lifetime. So, on the Hawking-Cooper Radiation compressed time scale, where each hour is a billion years, all the spectacular stars blow out in the first few minutes.

The star cluster had formed from huge clouds of hydrogen gas. The gas clumped together, forming the star at the center, and a revolving disc that made the planets, moons, and other bodies. It’s possible that the explosions of the supernovae may now trigger any residue gas in the cluster into collapsing and making new stars. But the giant stars are done for, and the most fabulous part of the fireworks show is already over, before the Professor and his student have had time to settle down to watch the show (though no doubt with his newfound divine powers, Professor Hawking can conjure up a rerun).

The rest of the evening is an orchestrated light show, conducted by the steady engines of stellar nucleosynthesis. Successively less massive stars run out of hydrogen fuel as Hawking and Cooper watch them swell into red giants, expanding to two hundred times their normal size. Part of the red giant evolution spied by our pair of physicists is what’s known as the “planetary” nebula phase, though the shells of multicolored gas shed by the stars have nothing to do with planets, and the once-giants have to finally settle for an old age of dim and dwarf stardom.

The focus so far, in this game of Hawking-Cooper Radiation, has been on the speedier evolution of those relatively few stars in the cluster more massive than the sun. Sure, the events have been exceptional enough to hold the attention of our physicists. And yet, by dawn, ten billion years have passed. It’s our sun’s turn on the main stage. Suddenly, there’s something of a stellar quake of the sun’s core, and the solar atmosphere blows out into a diaphanous scarlet cloud, which easily engulfs the orbiting planets of Mercury and Venus, and moves swiftly to swallow up the Earth, but not so swiftly that the Professor is unable to repair the onlookers to a safer standpoint. From a distance, they watch as the scarlet cloud melts away to leave the naked core of the remnant sun, a helium-rich dwarf, a million times as dense as during its hydrogen-burning days.

Day has finally fully dawned, and the night of starlight is done. The game of Hawking-Cooper Radiation has only been the beginning. The created cosmos carries on. With most of the Professor’s pet cluster made of stars less massive than the sun, they continue to burn with a steady lemon light. Unspectacular in the extreme, this silent majority of modest stars has lives ahead of them longer than the universe itself. They will still be shining when the puffed-off atmosphere of stars like the sun has been gathered up into the medium between the stars and condensed to make another stellar generation. This game, says the Professor to Sheldon, has taught us one main lesson: that the meek shall inherit the galaxy.