The Last Word Of the Universe
The End is coming, in maybe 100 billion years. Is it too soon to start freaking out?
“There will be a last sentient being, there will be a last thought,” declared Janna Levin, a cosmologist at Barnard College in New York, near the end of “A Trip to Infinity,” a new Netflix documentary directed by Jonathan Halperin and Drew Takahashi.
When I heard that statement, it broke my heart.
I thought I was aware of our shared cosmic predicament — that if what we think we know about physics and cosmology is true, life is doomed. I thought I had made some kind of intellectual peace with that. But this was an angle that I had not thought of before. At some point in the future there will be a last sentient being. And a last thought. And that thought, no matter how profound or mundane, will vanish into silence along with the memory of Einstein and Elvis, Jesus, Buddha, Aretha and Eve, while the remaining
Our memories and achievements are destined to vanish.
bits of the physical universe go on sailing apart for billions upon billions of lonely, silent years.
The universe originated in a fiery burst 13.8 billion years ago and has been flying apart ever since. Astronomers argued for decades about whether it would go on expanding forever or collapse into a “big crunch.” Then in 1998, they discovered that the expansion was speeding up, boosted by an anti-gravitational force that is part of the fabric of spacetime. The bigger the universe gets, the harder this “dark energy” pushes it apart.
This new force bears a striking resemblance to the cosmological constant, a cosmic repulsion Einstein had proposed as an element of correction in his equations as a way of explaining why the universe did not collapse, but later rejected as a blunder. But the cosmological constant refused to die. And now it threatens to wreck physics and the universe.
If this dark energy prevails, distant galaxies will eventually be speeding away so fast that we will not be able to see them anymore. The stars will die and not be reborn. It will be like living inside an inside-out black hole, sucking matter, energy and information over the horizon, never to return.
In the end there will only be subatomic particles dancing intergalactic distances away from each other in a dark silence, trillions upon trillions of years after there was any light or life in the universe.
Maybe it will be like falling asleep. Or like Einstein mumbling his last words in German to a nurse who did not know the language. Or the computer at the end of time in Isaac Asimov’s classic “The Last Question,” finally figuring out the secret of the universe and declaring, “Let there be light.” I would like to think my last thought would be one of love or gratitude or awe, but I worry it would be an expletive.
There is an encouraging metaphor from Einstein’s equations: When you are inside a black hole, light pours in from the outside universe, which seems to speed up while you appear to be frozen. In principle, you could see the whole future history of the galaxy or even the whole universe speed past you as you fall toward the center, the singularity where space and time stop, and you die. Maybe death could be like that, a revelation of all of the past and future.
Rather than whine about the end of time, most physicists say the notion is a relief. The death of the future frees them to concentrate on the moment.
The late black hole evangelist John Archibald Wheeler used to say that the past and the future are fiction, they only exist in the artifacts and the imaginations of the present.
No matter what happens in the endless eons to come, at least we were here for the brief shining sliver of eternity when the universe teemed with life and light. We will always have the Milky Way.