I sometimes think about historically based films in which tragedies happen and deaths occur.  I know they’re highly fictionalized, but think of Braveheart and of Gladiator* and movies of that sort, where the loss of loved ones makes viewers sad but drives the protagonist to “great” deeds that change the course of local history‒or, well, that make the course of local history.  After all, one only knows history after it happens, and once it’s happened, one cannot change it.  One can be mistaken about it, one can misrecord it, one can lie about it, but one cannot actually change it.

Even if it were possible to time travel, going into the past to alter something, it wouldn’t change the history from which you came‒as even the Marvel movies have pointed out, you’d just have created a new future, a new history, local to you.  It wouldn’t change your previous one‒that would be paradoxical.

Yes, Back to the Future is bullshit.  This really shouldn’t surprise you.  It’s still a fun movie.

Anyway, that’s beside the point I planned to make.  I think of tragic deaths in historical dramas that we see and about which we feel heartbroken, or even about real historical horrors‒human made, like the vast slaughters of Genghis Khan’s hordes or natural, like earthquakes and volcanoes and tsunamis and the like‒and about all the deaths involved, and sometimes I think:  “They would all be dead now, anyway, no matter what.”

Not one single person who was born before 1900 is alive today, as far as I know.  If there is one, that human is an all-time record holder in longevity, and is unlikely to live much longer.  And I would probably bet my own life** on there being no one alive who was born before 1850.  Indeed, the majority of humans who have ever lived are dead.  It’s not as big a majority as it might be, given how long humanity has existed, but that’s only because of recent exponential population growth.

In principle, of course, with a fast enough exponential population growth, it would be possible for the majority of humans to be presently alive, even with current lifespans.  But that’s not sustainable in the real universe.  For it to be sustainable in the long run, eventually humans would have to expand their empire over matter and space at faster than the speed of light, and reach far beyond the cosmic horizon, which is impossible in principle, as far as we know.

I say “eventually”, but don’t let that mislead you.  It would happen with surprising speed.  There’s a well known fact that, given a typical doubling/generation time of about 20 minutes, and assuming enough resources, a single bacterium could multiply to a volume greater than that of the visible universe within a month.  I’ll try to check my math on that when I get to sit down with a pen and paper***, but whether the specific time of a month is not quite right, it’s in the right ballpark.

This is the sort of doubling that is thought to have happened‒at an even faster rate, of course‒during the “inflationary” stage of the universe, if inflation happened.  Of course, in a sense, if “dark energy” is really the cosmological constant, then we are still undergoing inflation even now, just with a slower doubling time.  That doesn’t help is with our exponentially growing human population, though; spacetime itself can expand at, functionally, faster than the speed of light****, but nothing travels through spacetime faster than light.

Anyway, we’re already slowing down our population growth rate, which is good, since Malthusian growth tends to be unpleasant for almost everyone.  Therefore, as time goes by, the fraction of all humans who are dead will probably more and more overtake the fraction who are living.  And all early deaths are, in hindsight, not too terribly early.

This is one reason I get slightly irritated by people who talk of “saving lives” or characterizing a person’s death, per se, as a tragedy.  If every death is a tragedy, then the anti-natalists are right, and each new life should be avoided.  But, of course, it’s not that death in and of itself is a tragedy‒or if it is, it’s an inevitable one that’s going to happen to us all, sooner rather than later.  Even a being that lived for thousands or billions or googols or googolplexes of years would come no closer to living eternally than does a mayfly.  This is a mathematical fact.

It’s suffering that is the tragedy, not death.  Death can be a decent shorthand, in certain circumstances, because‒as Carl Sagan pointed out‒if one is dead, there is very little one can do to be happy.  Then again, if one is dead, there is also very little that can happen to make one disappointed or sad or in pain or afraid.  And since these things are more common and sustainable, or at least more reliable, than joy is, life itself, as a shorthand, is at least as good an indicator of suffering as death is of loss of possible joy.

It’s possible, I think, to live without joy‒meaning that it can happen, not that it’s a state one can or should seek.  But I don’t know that it’s possible for any true living things, or at least any living things with any equivalent of a nervous system, to exist without suffering.

So, perhaps Dumbledore’s post-mortem***** admonition to Harry Potter could be truncated to “Do not pity the dead, Harry.  Pity the living.”  Full stop.

*Which should have been the title of the sequel to Jaws.

**That’s maybe not as impressive as it might seem, since much of the time I hate my life and myself.  But it’s the only life I have with which to bet.

***With a typical length of 1 micrometer (10^-6 meters) and a doubling time of approximately 20 minutes (leading to 72 doublings a day), after only one day, a colony of bacteria would be roughly 4700 cubic meters in size, a cube more than 16 meters (just over 50 feet) on a side.  After 2 days, its volume would be about 2 x 10²⁶ cubic meters, or a cube 280,000 kilometers long on a side.  That’s nearly the distance from the Earth to the Moon.  After the 2160 doublings involved in a month of doubling, that would yield a volume of 2 x 10⁶³² cubic meters, or with a side length of about 5 x 10²¹⁰ meters.  A light year is 10 trillion kilometers, or 10 quadrillion meters, which is “only” 10¹⁵ meters.  So that’s a cube with a side length of 5 x 10¹⁹⁵ light years‒waaaaaay more than a googol light-years.  Indeed, if you subtracted a googol from that number, it would not change it to any degree measurable by any means known to humans (5 x 10¹⁹⁵ minus 1 x 10¹⁰⁰ is still, basically, 5 x 10¹⁹⁵).  The visible universe is only about 92 billion light-years across, yielding a sphere with a volume of “only” 4 x 10⁸⁰ cubic meters.  It’s not even close to the order of magnitude of a volume of 2 x 10⁶³² cubic meters!  My estimate was far short of the mark.  But that only strengthens my point, doesn’t it?

****It doesn’t actually do so locally‒I suspect that is also impossible, since it would defy the speed of local causality.  It’s only the summation of all the local doublings spread across the entirety of space that can make distant points separate at faster than the speed of light.  Then again, can “traditional” inflation cause any kind of local superluminal expansion?  I don’t think so.  Could two points in space a Planck length apart separate at a local speed that exceeds c even during inflation?  I doubt it, though I’m not absolutely sure.  Of course, if space is mathematically continuous, then there are no two closest possible points, anyway.  Between any two points on the real number line, there exists an uncountable infinity of other points, no matter how arbitrarily close you make them.

*****Of course, if one can deliver admonitions, one is not really dead in any useful or meaningful sense.  But it’s fiction, and it’s magic within fiction, so leeway can be given.  We have no evidence nor have I encountered any even borderline convincing arguments for any “life after death” in the real world, unless you count things like multiverses or Poincaré recurrences or the like, and I don’t, since they really entail other versions of a person, not a continuity of personhood.