2013-12-31 18:58 - The Science of Expiration Day

Science Fiction is the literature of the “what-if”. Change some aspect from the world today, and in theory, you have a science fiction story. That doesn’t exempt you from the requirement for a decent plot, and characterisation, without which you don’t have a sale, but the “what-if” is key.

If that “what-if” is a simple extension of our current understanding of the universe, then the science fiction is “hard”. So “what if we had a colony on Mars?” is essentially an engineering “what-if”, or a financial “what-if”, rather than requiring new physics.

At the other end, “what if there were elves?”. Probably magic. Probably fantasy. But possibly “soft” SF, or even “hard” SF if it’s just a matter of DNA.

So where does Expiration Day fit in this spectrum? How much of my speculation has some kind of basis in early twenty-first century science? Or is it just magic?

Let’s start with the fertility problem. When I began writing the novel, back in 2006, I set the start of the fertility problem in 2010, and imagined an unexplained fall, that by 2049 meant that few human children were being born. In 2010 the population actually reached 6.9 billion, and then I demanded that within a year the number of successful births would just tumble off a cliff. I carefully avoided giving a specific cause in the novel, though I kicked out a few suggestions:

• Radiation of various sorts – there’s plenty of it about, whether from the sun, or from our own obsession with ever-faster communication. Who’s to say that such-and-such a frequency wouldn’t resonate unpredictably with some delicate stage in the reproductive process?
• Some biological agent. Terrorism, perhaps. A rogue state, such as the USA. Or just natural mutation. Our bodies are full of odd bits of life and near-life that don’t cause any known diseases, or haven’t been linked to any. Just a little mutation is all that’s needed.
• Auto-immune problems are on the increase. We’re making lots of new, big molecules, and discovering that familiar substances in nano-particle form have very different properties. Our body sees a molecule it doesn’t like, constructs a new antibody, and sends it hunting. We trust that the antibody only hunts the intended target, but sometimes it also accidentally targets unrelated cells, like bone marrow, or the pancreas.

For it to strike everywhere practically simultaneously isn’t difficult. Anything wind-borne can circle the globe in less than a week. Anything a human can catch and then sneeze out again can get from London to Sydney in a day, with a stopover to to let some bugs off at Singapore. And if whatever-it-is only attacks the reproductive system, we’d never detect the vector in time to quarantine it.

So, we notice that the birth rate plummets – what does humanity do then? We can’t have children – but what do we do? Assume that the world is not full of patient saints, who will wait calmly for scientists to find a cure. A few authors have had a crack at this - read The White Plague or The Children of Men . Humans fight. My neighbour’s wife has just had a kid, but my wife can’t. So if I want offspring, maybe I just need to impregnate someone who can have kids. Kidnapping and vigilantism at the local level. Populist politicians blame the neighbours and find they’ve got a tiger by the tail. That’s the Sabine Wars – the premise of “The White Plague” raised to international level.

So now Oxted invents the neurotronic robot. Actually, I think he needs to already have some experimental models prior to the crisis - the brain at least - and be using them to solve all the engineering problems around building robot bodies to emulate human children. Even so, this is the what-if that significantly transcends the state of the art. Robotics and AI aren’t really very close yet, at least not in the science journals I’ve seen.

In the novel, I assert that the existence of child substitutes is a significant contributor to ending the violence, with the use of nuclear weapons on civilian populations being the other. Stick and carrot, punishment and reward. I guess it also depends on how bad the Sabine Wars were – I suggest that if they were to wipe out 90% of the world’s population, you might reach a point where you just want the slaughter to stop. Maybe.

The Uncanny Valley. A robot that’s not quite human feels scarier than a clunky robot. Definitely good science that’s well-documented.

Using exotic matter with negative mass to achieve light-speed travel. I mention this in passing as being how Zog’s people travel about the galaxy. I didn’t want to create a race of superbeings. Giving Zog’s people FTL travel and near-immortality would have done that. So I made Zog’s people long-lived, but limited them to travelling the galaxy at light-speed, and worse, to having to live through every minute of the hundreds of years it takes light to travel the distances between stars. And a galaxy that was devoid of life, save for a single, tantalising hint of a now-defunct civilisation. But special relativity tells us that travelling at light-speed takes lots of energy, and you get time dilation. Besides, it’s been done before, lots of times- the classic novel here is Poul Anderson's Tau Zero . I wanted to do something different, to reduce the energy cost of interstellar travel, but not at the price of slowing or stopping time.

So, things with zero mass can travel at the speed of light. Photons are the classic example. Ergo I need to give the ships zero mass. Fred Pohl’s Gateway uses an unexplained mass cancellation device for his mushroom ships, but I wanted to stay closer to known physics. Instead, we shroud ordinary matter with exotic matter with negative mass, so that it exactly cancels out. Think of the rubber-sheet universe, where masses distort the rubber sheet. Photons, being massless, don’t bend the sheet, and they move unimpeded at light-speed. Current physics says that’s the normal (or only, or at least the default) speed for zero-mass particles. Likewise my exotic matter shrouded ships. But photons don’t age, says the theory. I suggest that’s because a photon is a point, so there’s no “inside” where time can have meaning. The shrouded ships carry their own internal “rubber sheet” – a little mini-universe, separate from the outer universe, a bit like a black hole, but with “ordinary, positive” masses inside. So a photon inside the shell has its rubber sheet to travel across, bounded by the shell of exotic matter, but this means that you can have space-time events inside the shell, with photons that define the ordering of those events, and so time flows “normally”.

That all depends on Zog’s people finding or creating the right kind of exotic matter to have negative mass. A bit difficult, for many reasons. For starters, standard model physics doesn’t suggest the need for any particles of negative mass. Then, the consequence of Newton’s Law of Gravitation is that negative-mass particles will accelerate towards positive-mass particles (though the positive-mass particles will accelerate away from the negative-mass particles, while the overall momentum and energy of the system stays unchanged). So you need to create equal amounts of negative-mass matter on the left and on the right of the positive-mass payload you want to move, probably in the form of a solid shroud that you can close into a sphere. Still, that’s an engineering problem, once you accept the existence of negative mass particles.

And how would you make negative-mass particles? Probably quite cheaply, because Einstein’s E = mc2 tells us that negative mass can be created out of negative energy. So it might even become a neat power source, better than fusion. Start with zero energy, separate out equal amounts of positive and negative energy (so no net change), use the negative energy to make negative-mass particles and use the positive energy to light and heat your cities. Might need a Maxwell’s Demon to bat all the positive energy one way and the negative energy the other way, but how hard can it be? How’s that for some really off-the-wall speculation?

Hmm... That’s a lot of explanation for a throwaway line in the novel, but I wanted a very specific universe for Zog’s people to live in, as the backdrop for my vision of Tania’s future. That story is in my head, being transferred to paper (or at least, a Word document). Let’s see if I can sell the notion to Tor…