## A (final) speculation from “The Hidden Reality”

I have just finished Brian Greene’s The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, so want to take this opportunity to once again endorse it and also to restate or reprise one of his speculations in the book: this time one grounded firmly in computing rather than string theory or conventional cosmology.

The key question at the heart of this speculation is this: do you think that, given we have seen computational power double every 18 – 24 months or so for around a century now, we will reach the point where we will be able to convince computer-based agents that they are in a physically real world when they are, in fact, in a computer-based simulation?

And if you answer yes to that question, do you realise that you are more or less forced to accept that you are one such agent and what you see around you as real is, in fact, a computer-generated “virtual reality”?

The reasoning is simple: once the technology to build a sufficiently convincing virtual world exists then such worlds are likely to rapidly grow in number and there will be far many more ‘people’ who are agents than people who are physically real. By simple averaging you and I are far more likely to be such agents than to be real.

It’s a truly mind-bending thought.

Saying ‘no’ to the question requires putting a hard limit on human progress in the field of computation. How can that accord with our experience of ever faster, more powerful and ubiquitous computing?

Well, there are some reasons – but even they are open to attack.

Reality appears smooth and continuous, but smooth and continuous numbers are not computable. Computable numbers are of finite extent – as otherwise the computer would never finish computing them. For instance no computer can ever compute $\pi$, only render an approximation. Indeed most numbers are “transcendental numbers” and inherently not computable.

But this argument – which sounds like a sure-fire winner for knocking down the idea that our reality is, in fact, a simulation, has a weakness: we cannot measure smoothness either. Our measurements are discrete and while it appears to us that the world is smooth and continuous, maybe it is not – it is just that the computed approximation is beyond our ability to (presently) measure it.

If, at some point in the future, we discovered a finite limit to measurement that was beyond physical explanation it would surely confirm we were in a simulation.

## Not even Newt could beat this one

I have no sympathy for the politics of Newt Gingrich, but do have a sneaking admiration for his willingness to flaunt his nerddom in public.

Warnings about electromagnetic pulse weapons and proposals for a Moon base have provided both interest and entertainment. Though I am not sure whether Newt has had much to say about the threat posed by the biggest EMP weapon in the region – namely the Sun.

But not even Newt could think of a plan to defeat one threat to humanity’s existence – a quantum tunnelling effect as part of our universe transforms from a “false vacuum” to a “true vacuum”.

The idea is that there is a scalar field (an energy field) pervading the universe that could could fall to a lower value, releasing its stored energy. If this were to happen in our universe then the released energy would be seen in the rapid (speed of light) expansion of the new, lower energy bubble. And as this bubble would hit us at the speed of light we’d have no warning at all – indeed we’d be here one second and gone the next.

Is it a real threat? Possibly – there is some evidence that our universe might be in a false vacuum (higher energy) state. Is there anything we can do about it? No. Is it worth worrying about? No.