Escaping from quantum weirdness by watching TV
After breakfast and a game of cards (see “Escaping from quantum weirdness by playing cards”), we will move on to watching television. We will assume a live football game is being shown. From a distance, the picture looks just like the real thing. But if we choose to focus in on the details, we soon find that the picture is flickering and grainy. If we push our noses up to the screen, things appear now here, now there, and we can’t see what happens in between.
The flicker and graininess is not of course the result of fundamental physics, but of the technology being used – the camera and receiver will have a certain scan rate, pixel size, bandwidth, that sort of thing. We can reduce the flicker and graininess on our television by improving the technology – for example by changing to High Definition TV – but technology can only ever reduce the flicker and graininess; it cannot eliminate it.
The reason we can be so sure is because it is not a question of technology, or physics, but of information. If our age of IT has taught us anything, it is that information has size. Whether we are receiving photographs by email or loading songs onto our music players, we cannot escape the fact that an amount of information is involved. We measure it in bytes – these days in megabytes and gigabytes. No matter how clever we are at compressing the data, and however large the storage capacity, if you keep receiving photos or loading songs you will eventually end up running out of space – you can never handle an infinite amount of information.
For any real situation there is a minimum amount of information, a single yes/no answer called a “bit” (eight of which make the more usefully sized byte), and a maximum amount, fixed by the physical practicalities of the particular situation. This finite maximum size cannot contain an infinite amount of information, because you cannot reduce the size of a bit to zero. To make a very simple point, information can only come in finite amounts.
So we cannot, even in principle, imagine being able to build a television system that transmits arbitrarily small detail, because that would involve an infinite amount of information. Whatever the public demand for the perfect picture, there will always be flicker and graininess in the picture at some level.
Suppose we now get lucky and someone gives us tickets for the game, which we can watch live and in person for the second half. Free from the constraints of television transmission, we don’t notice any flicker or graininess. Actually this is an illusion, because our eyes cannot see infinite detail or very rapid changes, but our brains have learnt to fool us that they can. We can, however, give our eyes all kinds of help in the form of optical technology, and then we can see as much detail of the game as we want.
But suppose we become insatiably curious and choose to look in finer and finer detail. We would find that when we reached the scale of atoms, something interesting happens. At this point, we find that our view becomes flickering and grainy. We see things that are now here and now there, but we can’t see what happens in between.
This is very curious, because unlike with the television transmission, the graininess isn’t limited by technology, but by something more fundamental. It seems to show that not only is it impossible to handle an infinite amount of information, it is also impossible to extract an infinite amount of information from the world as well. Whatever physicists’ demands for complete instant by instant knowledge of the whereabouts of elementary particles, this would ultimately require an infinite amount of information, and we should not be too surprised that it just isn’t available. To put it another way, information always comes in discrete chunks, so why are we surprised that information about the physical world is only available in discrete chunks?
So is the weird discontinuous information we find at the quantum level really just the same as the flickering and graininess we see on a television screen? Actually, no, there is an important difference, and it brings us at last to the prime candidate for true quantum weirdness. The difference is this: with live television viewing there are gaps in the information we receive, but we can always work out what must have happened in the gaps. With quantum viewing, on the other hand, sometimes there are gaps in the information we receive where it is absolutely impossible to fill in the gaps with anything that makes simple logical sense. In the jargon of physics, it is not possible to explain what has happened in terms of local hidden variables. So surely something very strange must be going on.
And yet you may already be experiencing a sense of déjà vu. We have already recognised (for example in “If only ..”) that something strange must happen in the present, if one set of events is singled out from many possible versions of the future. This “happening” version of the future is not marked out in advance, because there are other genuinely possible versions. Precisely because of this, we will never be able to work out in detail what is about to happen next, and we may never be able to work out exactly why a particular thing happened as it did. It is surely not surprising that we are unable to fill in all the details of how we got here in a way that seems straightforward.
Aren’t the inexplicable developments as the quantum picture unfolds much like the inexplicable twists as our own future unfolds? Is this not why we like to watch football games in the first place?
Back to home page.