(A short-short story I wrote recently. Too short to make an ebook in itself, but I’ll include it in a short story collection at some poin).

t was a fine romance. The finest in fact. Even though they never met each other.

Jerry Taylor knew he loved Linda Soames from the moment he first saw her. They were obviously meant for each other. She took a little longer to fall in love with him, but it was only a matter of weeks before the two were agreed that they’d never met anyone like the other, and that no-one else would ever do for them.

They were married within a year, and spent the rest of their lives together, happily. They had three lovely children, who went on to have jobs that brought them slightly more financial success than their parents had, but not enough that they lost sight of where they came from. They celebrated their sixtieth wedding anniversary on a cruise around Hawaii with their grandchildren and great-grandchildren all around them, and when they finally died, as people do, they did so only a few hours apart.

But technically, they never existed in the same universe at the same time.

The multiverse is a bigger place than we imagine, or indeed than we can imagine. The mathematician Max Tegmark says, in fact, that not only every possible physical universe exists in it, but every possible mental universe. Any self-consistent mathematical system is its own universe, equally real with our own.

Including the ones containing Boltzmann brains.

A Boltzmann brain is a brain that comes into existence in a universe which is otherwise at maximum entropy. There’s nothing else in the universe, and then, blip! – a brain appears, complete with memories of an entire life that never happened. It has time for one single thought, and then it disappears out of existence again.

Given enough time, enough trillions of years, a second Boltzmann brain will appear, identical to the first except it’s now had that extra thought. Over googolplexes of years, this brain would live a normal human life in nanosecond-long installments, all its awareness of its surroundings being just false memories, and with no connection between its existence in one subjective moment and the next. But it would have a real, long, fulfilling life. Just like Jerry did.

Linda, on the other hand, didn’t even have that much physical existence. She was an artefact of a computer program that was never run. A computer scientist worked out a starting state for a cellular automaton which, if run, would have implemented a Turing machine, which in turn would eventually (after several quadrillion iterations) have simulated Linda’s entire life and all her visible surroundings. Her entire life, everything she ever thought, felt or experienced, was implicit in the twenty lines of Perl code the scientist had written down, but no computer in the world had the memory to run it or ever would.

Coincidentally, the Boltzmann brains that were Jerry Taylor contained faked memories that matched exactly the parts of the Linda program where she would have spent time with the man she loved. And the Linda program would eventually have produced a bunch of cells that implemented instructions that produced a simulacrum of a man within Linda’s range of vision, and that simulacrum would have behaved in exactly the same way that the Taylor brains would have, had they been connected to a body.

The children, grandchildren and so on, of course, had no independent existence of their own, and winked out of existence every time they were not in the presence of Linda or Jerry. They were just a shared hallucination of the Boltzmann brains and the computer program that was never run. But their lives were happy enough, for what they were.

Somewhere out there, in a universe we can never access, Jerry’s brain is popping briefly into existence again. For him, it is currently 1952, and Linda and he are on their second date. It’s the only experience that brain will ever have, before dissolving back into the mass of superheated protons from which it came, but it’s a happy experience. That nanosecond isn’t a bad life, all things considered.

And Linda? No-one’s even going to get round to writing her program for at least another sixty years. She doesn’t exist yet, even though Jerry is looking at her right now and wondering if she’ll let him do more than kiss her this time. But those twenty lines of perl code contain, in their own way, a recipe for happiness, if only they were to be followed closely enough.

And if Jerry and Linda live their lives totally oblivious of the nature of the universe they’re living in, if they’re completely unaware of their own natures and deluding themselves into thinking they’re something they’re not, and if neither of them will ever share a second’s real communication with the person they love, doesn’t that just make them human?