Crux introduces some new science, and in particular, “uploading”. The Su-Yong Shu we see in Crux is not a flesh and blood person. Instead, she is a computer program, a vast mathematical construct of electronic neurons that initially mirrored the precise neural map of the original Su-Yong Shu’s brain. For every neuron the original Su-Yong Shu had, her upload had a digital counterpart. For every synapse connecting two neurons, the upload also started with a counterpart.

The idea of uploading sounds far-fetched, yet real work is happening towards it today. IBM’s “Blue Brain” project has used one of the world’s most powerful supercomputers (an IBM Blue Gene/P with 147,456 CPUs) to run a simulation of 1.6 billion neurons and almost nine trillion synapses, roughly the size of a cat brain. The simulation ran around six hundred times slower than real time – that is to say, it took six hundred seconds to simulate one second of brain activity. Even so, it’s quite impressive. A human brain, of course, with its hundred billion neurons and well over a hundred trillion synapses, is far more complex than a mouse brain. Yet computers are also speeding up rapidly, roughly by a factor one hundred times every ten years. Do the math, and it appears that a super-computer capable of simulating an entire human brain and do so as fast as a human brain should be on the market by roughly 2035–2040. And of course, from that point on, speedups in computing should speed up the simulation of the brain, allowing it to run faster than a biological human’s.

Now, it’s one thing to be able to simulate a brain. It’s another to actually have the exact wiring map of an individual’s brain to actually simulate. How do we build such a map? Even the best non-invasive brain scanners around – a high-end functional MRI machine, for example – have a minimum resolution of around ten thousand neurons or ten million synapses. They simply can’t see detail beyond this level. And while resolution is improving, it’s improving at a glacial pace. There’s no indication of a being able to non-invasively image a human brain down to the individual synapse level any time in the next century (or even the next few centuries at the current pace of progress in this field).