A while ago I read Max Tegmark‘s “Our Mathematical Universe” (Amazon link) – which introduced me to the concept of “Quantum Suicide” and the idea that if the “many worlds” interpretation of quantum physics is correct then, if death is a result of quantum processes (e.g., does this particular atomic nucleus decay, releasing radiation, causing a mutation, leading to cancer and so on), then, actually, we can expect to live forever – in the sense that our consciousness would continue on in that universe where all the quantum randomness was for the best.
It’s a powerful, if quite mind-bending idea, and it had quite a profound effect on me.
Until, that is, at the end of January, when I slipped on a London street, smashed my face on the pavement and swallowed the broken piece of tooth. Three months later the pain in my upper left arm – with which I tried to break my fall, is a constant reminder that maybe Niels Bohr and the Copenhagen Interpretation was right after all.
So, let us conduct a thought experiment that might suggest “you” can live forever.
In this world we assume that you don’t do anything dangerous – such as commute to work. The only factors that could kill you are the normal processes of human ageing (and related factors such as cancer): your fate is completely determined by chemical processes in your body.
And we accept the “many worlds” view of quantum mechanics – in other words all the possible quantum states exist and so “the universe” is constantly multiplying as more and more of these worlds are created.
Now, if we accept that the chemical processes are, in the end, driven by what appears to us as stochastic (random) quantum effects – in other words chemicals react because atoms/electrons/molecules are in a particular range of energies governed by the quantum wave equation – then it must surely be the case that in one of the many worlds the nasty (to our health) reactions never happen because “randomly” it transpires that the would-be reactants are never in the right energy state at the right time.
To us in the everyday world our experience is that chemical reactions “just happen”, but in the end that is a statistically driven thing: there are billions of carbon atoms in the piece of wood we set fire to and their state is changing all the time so eventually they have the energy needed to “catch fire”. But what if, in just one quantum world of many trillions, the wood refuses to light?
So, too for us humans: in one world, the bad genetic mutations that cause ageing or cancer just don’t happen and so “you” (one of many trillions of “you”s) stays young for ever.
The obvious counter argument is: where are these forever-young people? The 300 year olds, the 3000 year olds? Leaving aside Biblical literalism, there is no evidence that such people have ever lived.
But that is surely just because this is so very, very rare that you could not possible expect to meet such a person. After all, around 70 – 100 billion humans have ever been born and each of them has around 37 trillion cells, which live for an average of a few days (probably) – so in a year perhaps 37 billion trillion cell division events – each of which could spawn a new quantum universe – take place. That means the chances of you being in the same universe as one of the immortals is pretty slim.
Yet, on the other hand, we all know someone who seems to never age as quickly as we do…
…I’d be really interested in hearing arguments against the hypothesis from within the many worlds view of quantum physics.
I haven’t quite finished it yet – so I’ll do a fuller review when I do (and there were good bits too), but what I want to take issue with here is his case (or, perhaps more accurately, the cases he quotes with approval) against the idea that we live in some sort of great computer simulation.
I am not arguing in favour of such a view of our universe – but it certainly has its strengths – if you think computer power will keep on growing then it is pretty difficult, if we apply the basic “Copernican” principal that we are nothing special, to avoid the conclusion that we are in such a universe.
Tegmark uses two major arguments against this idea that I want to take issue with.
The first, I think, is not an argument against it at all – namely that we are more likely to be a simulation within a simulation if we accept this basic thought. Well, maybe – but this is completely untestable/falsifiable and so beyond science. (In contrast the basic idea that we are in a simulated universe is testable – for instance if we find that our universe has a “precision limit” that would be a strong pointer.)
The second is the degree of complexity of simulating a many worlds quantum multiverse. But, of course, the simulator does not need to actually “run” all those other quantum worlds at all – because it’s not a physical reality, merely a simulation. All it has to do is leave the signs (eg the traces of superposition we can detect) in our environment that such alternate universes exist, but once “decoherence” takes place those alternate universes go straight to your garbage collection routines. So too for more anything much beyond the solar system – all the simulation has to do is provide us with the signals – it doesn’t have to actually, for instance, “run” a supernova explosion in a distant galaxy.
I wonder if there is any major part of physics that has changed so fundamentally in the last thirty years as cosmology.
Back in 1987 cosmology was more or less the last module we were taught as part of the astrophysics degree. But what we were taught then seems like basic arithmetic compared to today’s differential calculus.
But what is really shocking is Tegmark’s – convincing – argument that what we already knew supports inflation and inflation means we must live in an infinite multiverse. Moreover he completely clobbers the idea that multiverses are unscientific speculation: the evidence, he says, is all around us and the theory fully falsifiable in Karl Popper’s sense.
The book is an easy read – it is semi-autobiographical – and I have made a lot of progress with it in just a couple of days. Certainly recommended.