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The End of the Universe

Fire and Ice

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.

-Robert Frost

Today's two primary theories of physics both hold predictions for the end of the universe. Surprisingly, the possibilities they describe are very different.

General Relativity: The World Ends in Ice

At the time he published it in 1916, Einstein's theory of general relativity contained an odd term called the cosmological constant. This parameter was specifically put in place by Einstein so that his theory describing gravity could allow for a universe that is stationary. This was important to him; there was no evidence to the contrary at that time and it appealed to his powerful intuition. Without a cosmological constant with a certain numerical value, the theory would predict that our universe is continually and forever expanding. 

In 1929, Edwin Hubble discovered that the universe itself indeed is expanding. Peering through the world's largest telescope, everything he saw appeared red-shifted, and the further away the thing was, the more redshifted it was too. (Redshift is to light waves what the sound of a truck horn receding away from you is to sound waves: a drop in frequency as an object moves away. This is referred to as the Doppler effect.) This could only be explained by the spacetime fabric of the universe stretching and pulling everything within it further apart. 

At this point Einstein removed the cosmological constant from his theory, calling it his "biggest blunder." Interest in the idea persisted for decades however, and in 1998 it was actually observed that the cosmological constant does exist, though its value is incredibly small-- almost zero, but slightly greater than zero.

Including this tiny value and what we know about the cosmos, general relativity predicts just what Einstein did not want: a universe that will expand forever, gradually growing thinner and thinner, colder and colder. Stars will burn out, galaxies will spin apart, matter will become less and less dense until, in many billion years, everything is at nearly absolute zero. Death by ice.

The Standard Model: The World Ends in Fire

Preliminary results announced this week give a different possibility for the end of the universe as we know it. The mass of the Higgs boson, discovered at the LHC last summer, have been plugged into the Standard Model to calculate something called vacuum instability. This is an esoteric possibility of quantum mechanics, where space might actually not be a true vacuum. Eventually, some part of the universe would quantum mechanically jump (or be pushed by tremendous energy) into the true vacuum state, and the entire rest of the universe would be sucked in too. The universe would "explode" into the new state at the speed of light, destroying everything that currently exists in an enormous runaway flash.

This theory is still being investigated, and no one is sure how realistic this possibility is. (It's probably theoretically possible, but extraordinarily unlikely.) 

Personally, I'd prefer to have billions of years to prepare for the ice. A chance explosion would confirm my fears-- before death no time to make nice.

(Photo: Universe via Wikimedia Commons)

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Tom Hartsfield
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