Phone-ins and Quantum Physics

In recent months several British television companies have run into trouble over phone-in competitions. It turns out that they have been rather casual about allowing the public to continue calling in – and part with their money through the premium rate phone line – after the winner of the competition had already been decided. 

The offence is a rather curious one, because the effect on the victims is barely noticeable. The later callers had a zero chance of winning, unlike the earlier callers, who instead had a very small chance of winning. To put it another way, though, when the choice of the winner was still in the future, people phoning in had a chance, but when the choice of the winner was in the past, they didn’t. The philosophical position was clear enough for everyone to realise that the television companies had done something they shouldn’t have.  

Now it is possible I missed it, but I didn’t notice the television companies arguing that according to physics the past and the future are purely subjective concepts, and everything looked fine from where they were looking. Or that although nobody knew who the winner was before the decision was made, everything involved was inexorably following the laws of physics, so only one person was ever going to win, and the ones calling in late can’t complain.  

Nor did anyone argue that the moment of decision – before which many people were in with a chance, but after which these people became one winner and many losers – involves an amazing, instant reality shift for many widely separated participants. And this is something so incredible that there must be enough versions of the Universe for everyone who phoned in to be the winner in at least one of them. 

And yet physicists have been making very similar arguments, rather fruitlessly, for decades. A photon approaches a narrow slit, beyond which is an array of detectors. Which one will detect the photon? Before the photon is detected, many of them have a chance; after it happens, only one. Call it quantum physics and we are obliged to say that this is weird. Perhaps this Measurement Problem can be avoided by the Many Worlds Interpretation, we say; or, we cannot believe that the photon just arrives at a destination at random, it must be predestined to arrive somewhere, and there must be a Photon Conspiracy that means when many isolated photons arrive, one after another, they have agreed to form the right diffraction pattern.  

With hindsight, there is a very simple and common sense description for both situations, which is that there is a big difference between the future and the past – in the future there are many possibilities, but in the past there are not. One of the available possibilities happens in the present, with a probability that we can often calculate in advance very accurately, one way or another.  

There seem to be two main lines of reasoning made against this naïve but helpful description. Firstly, the prevailing philosophical fashion is to avoid any role for randomness. To say that there are many available possibilities, with one chosen randomly according to its probability, is to deny there is an unbroken chain of causes and effects. According to this reasoning there is only ever one possible version of the future, however much we may instinctively feel otherwise, however random radioactive decay may appear.  

The winner always being certain, or the destination of the photon always being fixed, before anyone has “observed” them, is deemed to be a necessary feature for “reality”, and abandoning reality is said to be a bad thing. Suitable responses to this are: it shouldn’t matter to us if the future, which we cannot observe even if we try, is not “real”; the idea of a fixed future is not an appealing one in the first place; and why does no one argue this when it really matters, like after a phone-in competition scandal? 

The second point made is that physics, specifically special relativity, has stopped “the past” and “the future” having any objective meaning. Since 1905 we have known that how we move in space affects how we move in time, so that not only is there no universal “now”, but different observers can disagree about the order of events.  For our purposes, however, we don’t need “the future” to apply to everywhere in the universe at once – we just need the future to be defined at any particular place and time, and that is not a problem. Indeed special relativity kindly clarifies this, separating events (and potential events) around us into ones in our past, ones in our future, and ones that might be in our past or our future, but which can’t have any influence on us thanks to the unbeatable speed of light. 

Of course, if we say that our future is a mixture of possibilities, but our past isn’t, we are saying that something very interesting is continually happening in the moments we call the present – there is something special about our here and now. But this should not come as a surprise to physicists or anyone else, especially people who play games of chance.  

The mysteries of quantum physics have been elevated to such rarefied levels for so long that it seems disrespectful to compare the collapse of the wavefunction with the outcome of a lottery. Indeed many people seem to enjoy emphasising the weirdness of the “quantum world”, but we should not lose the hope that physics actually describes the world around us after all.

Back to home page.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: