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, near the end
of “A Trip to Infinity,” a new Netflix documentary directed by Jonathan
Halperin and Drew Takahashi.
اضافة اعلان
When I heard that statement during a showing of the film
recently, it broke my heart. It was the saddest, loneliest idea I had ever
contemplated. I thought I was aware and knowledgeable about our shared cosmic
predicament — namely, that if what we think we know about physics and cosmology
is true, life and intelligence are 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 somewhere in the universe where there
will be a last sentient being. And a last thought. And that last word, 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 bits
of the physical universe go on sailing apart for billions upon billions upon
billions of lonely, silent years.
Will that last thought be a profound pearl of wisdom? An
expletive?
How did we humans get into this fix? The universe as we know
it 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 someday collapse again into a “big crunch”.
All that changed in 1998 when astronomers discovered that
the cosmic 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 a fudge factor 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.
In the end, if this dark energy prevails, distant galaxies
will eventually be speeding away so fast that we can’t see them anymore. The
more time goes on, the less we will know about the universe. 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.
Worse, because thinking takes energy, eventually there will
not be enough energy in the universe to hold a thought. 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. And then, more uncountable trillions of eons to
come, until there is finally no way to count the years, as Brian Greene, the
popular Columbia University theorist and author, so elegantly and devastatingly
described it in his recent book, “Until the End of Time.”
Lambda would be the most uninteresting answer to the dark energy puzzle!
It is hard not to want to scream at our own insignificance
in all of this. If this is, in fact, what the universe will come to. The
universe as we know it is now 14 billion years old, which seems like a long
time but is only an infinitesimal sliver of the trillions and quadrillions of
years of darkness to come. It will mean that everything interesting in our
universe happened in a brief flash, at the very beginning. A promising start,
and then an eternal abyss. The finality and futility of it all!
In short, a tale full of sound and fury, signifying nothing.
What do we do with a universe like this?
You may point out that it is way too soon to be prescribing
a future for the universe. New discoveries in physics could provide an escape
hatch. Maybe dark energy will not be constant; maybe it will turn around and
recompress the universe. In an email, Michael Turner, the cosmologist emeritus
formerly at the University of Chicago who coined the term dark energy,
referring to the Greek letter symbolizing Einstein’s cosmological constant
said, “Lambda would be the most uninteresting answer to the dark energy
puzzle!”
But for now, that is what we have to look forward to.
Our goose will be cooked a billion or so years from now,
when the sun boils away the oceans. A few billion years later the sun itself
will die, burning Earth and anything that remains of us to a crisp.
There is no escaping to space. The galaxies themselves will
collapse into black holes in about 10^30 years.
And black holes will finally release all that they have
imprisoned as a thin spray of particles and radiation, to be scattered into the
prevailing wind of dark energy whisking them apart.
In some variations on the story, known as the Big Rip, dark
energy could eventually grow strong enough to tear apart the tombstones that
mark your grave.
And so, just as there was a first living creature somewhere,
sometime, to emerge from the splendid blaze of the Big Bang, there will be a
last creature to die, a last thought. A last sentient being, as Levin pointed
out.
That idea is what stopped me short. It had never occurred to
me that some individual being would have the last word on existence, the last
chance to curse or be grateful. Part of the pain is that nobody will know who,
or what, had the last word, or what was thought or said. Somehow that notion
made cosmic extinction more personal, and I wondered what it would be like.
Rather than whine about the end of time, most of the
physicists and astronomers I talk to say the notion is a relief. The death of
the future frees them to concentrate on the magic of the moment.
The late, great astrophysicist, philosopher, and black hole
evangelist John Archibald Wheeler, of Princeton, used to say that the past and
the future are fiction, that they only exist in the artifacts and the
imaginations of the present.
According to that point of view, the universe ends with me,
and so in a sense I do have the final word.
“Nothing lasts forever” is a maxim that applies to the stock
market and the stars as well as to our lives and Buddhist sand paintings. A
whiff of eternity can illuminate an entire lifetime, perhaps even mine.
No matter what happens in the endless eons to come, at least
we were here for the party, for the brief shining sliver of eternity when the
universe teemed with life and light.
We will always have the Milky Way.
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