The vagaries of the alphabet mean that sometimes you have to make the choice between really fiddling the title of a piece to make it fit where you want it to fit in the sequence, or just accepting it and cracking on. In an ideal world, I would probably have gone with the former option: today’s ‘A’ is just too perfect an opportunity to miss out on, but it is also quite exotic and pushes us in a particular direction sooner than I had planned. My AtoZ for 2017 is a look at the materials found in fiction from the perspective of a Materials Scientist (see welcome post). As a quick reminder, that means we’re interested in Properties, Processing, Performance, microstructure and how we characterise these different things.
Why is today’s exotic in that context? Well, A is for Antimatter – and surely for that we need an anti-materials expert? In practice we’re interested in the same things, but it’s just a bit more nervous because matter and antimatter are not happy playmates. This is absolutely true, but if you’ve read Angels and Demons, Dan Brown’s first Robert Langdon Novel, you might be wondering why on Earth scientists are allowed to investigate antimatter at all. Firstly, antimatter-matter reactions are seriously energetic. A mass of ~1 g of antimatter reacting with the equivalent mass of matter would cause an explosion on the scale of small/medium sized nuclear bomb. On the other hand, the total mass of antimatter created by scientists to date weighs in at a few billionths of this: I’d be more worried about the bananas in your fruit bowl.
Wait: what? Yep. Bananas. I never did trust them. A quick chemistry refresher: elements have a unique number of electrons and protons, and in addition a number of neutrons. So for example hydrogen, the lightest element, has one electron orbiting one proton. But hydrogen has three isotopes. The first we’ve just met, the second sees one neutron join the proton (to give deuterium) and the third sees two neutrons join the proton (tritium). Deuterium and tritium are still hydrogen, just special forms. This occurs for a number of different elements, although not usually in this specific pattern. What we do know is that a) different isotopes are usually present in very specific proportions and that radioactive isotopes decay at known rates. This is the principle behind radiocarbon dating – the number of 14C atoms compared with 12C and 13C can be used to give an indication of the age of an organic or other carboniferous object. What has that got to do with bananas? Well as any sportsman will tell you, bananas are high in potassium. Potassium has a radioactive isotope, 40K (no, not a rapper). When 40K decays, one of three things happens: i) it emits an electron and an antineutrino and decays to 40Ca, ii) it captures an electron and emits a gamma ray and a neutrino and decays to 40Ar or iii) it emits a positron and a neutrino and decays to 40Ar. The latter is the least likely, occurring about 1 time in 100,000. But there are around 6.6 x 1021 (or 6,600,000,000,000,000,000,000) atoms of potassium in a banana (on average, your mileage may vary etc), so what you find is that a positron is released every 75 minutes or so. It reacts almost instantly with surrounding matter, to be obliterated. To round off this point, don’t forget that you yourself contain around 2.2 x 1024 (or 2,200,000,000,000,000,000,000,000) of potassium.
Other uses of antimatter abound – in fiction, at least. One of my favourites is in Peter F. Hamilton’s Night’s Dawn Trilogy. This is a sprawling space opera that, over the course of ~1 million words, takes in philosophy, ethics, sociology, psychology – in short, what it means to be human, not forgetting architecture, biology, evolution and dozens of other concepts – oh, and the odd bit of engineering and physical science, of course. It also contains a great piece of set-up, which we might dub Chekov’s Antimatter. Crucial to the dénouement is the ability of Lady McBeth, the spaceship of key character Joshua Calvert, to travel at much faster speeds than are normally possible. The roguish Calvert inherited his ship from his equally roguish father. The ship includes an antimatter drive, i.e. one which uses the reaction of matter and antimatter to create energy to propel the ship. Where it all gets interesting is that owning such a drive is not illegal, but the use of it is – because of the potentially devastating military applications of antimatter, its use is completely proscribed and there is a dedicated Navy force tasked with finding and destroying illegal antimatter production facilities. Calvert comes in for a great deal of attention from the authorities when he redeems the ship from the creditors and has it repaired and refurbished, including the antimatter drive which his father had put into the ship ‘just in case’, and before the disapproval for the technology coalesced into legislation.
For all sorts of reasons that only really work because it’s a novel, Calvert is, of course, the only person in a position to save the day, and it so happens he needs the antimatter drive that is already installed, which necessitates laying hands on some highly illegal antimatter. Cue a sanctioned, military supported raid on a pirate production facility… As we’ve already established, the energy from a matter-antimatter reaction is potentially huge and it is this that they’re relying on to provide enough thrust, sustained over a long enough period to accelerate/decelerate the ship across the cosmos in order to complete the mission in the time available, before – well, let’s not dwell on what is going to happen if they don’t succeed…Suffice it to say, that the science is credible, even if the story is out on several limbs.