Dr Johnson famously settled an argument on the existence or non-existence of the physical universe by kicking a heavy stone and saying “I refute it thus”.

But when it comes to the science of the micro-universe, the quantum world, no heavy stones seem to be around to be kicked.

I have been thinking about this since I posted a blog about Antony Valentini‘s idea that we could use some very rare particles to communicate at a speed faster than the speed of light.

Valentini’s challenge is to the “Copenhagen interpretation” of what quantum mechanics appears to tell us.

The fundamental difficulty with quantum mechanics is that it says we cannot know, with total accuracy, the position and momentum of a particle. This “uncertainty” is what creates the “spooky interaction at a distance” – because if we measure the momentum of one paired particle then uncertainty and energy conservation laws “appear” to make the other particle assume a certain state instantaneously.

In the “Copenhagen interpretation” we are essentially asked to accept that this is due to an instantaneous “collapse” of the physical laws we have been using to this point. It’s as if our quantum rules are just a window on to a “real” physical world and that our poking shakes up what is going on behind the scenes in ways we cannot hope to understand.

That’s not very convincing, though (even if it “works”).

So, what are the alternatives?

Valentini is reviving an idea of Louis DeBroglie that was rejected in favour of the “Copenhagen interpretation”: namely that our paired particles remain linked by a “pilot wave” that communicates the state change instantly.

That, though, appears to offend against the physics of the world of general relativity – we are conditioned to think such instant communication is impossible because our physics tells us that we need infinite energy to move a massive body at the speed of light: hence making that an unbreakable speed limit.

And then there is the “many worlds” interpretation – namely that all that might happen does happen and so there are an infinite number of those paired particles and “our universe” is just one of an infinite number.

None of them really seem that satisfactory an explanation.

## One response to “The trouble with Copenhagen”

>The fundamental difficulty with quantum mechanics is that it says we cannot know, with total accuracy, the position and momentum of a particle.

Could take it at face value, that the product of the position and momentum uncertainty is a constant. Basically we have our preferred math we like to use to describe things, and unfortunately the universe doesn’t work like that at small scales. You can’t find a way to peek behind the curtain and catch small particles in bed with our familiar scalar vectors.