Quantum 1: Bemused? Bewildered? Me Too
Yet I Still Want to be a Catholic:Post 7
Quantum (1): Baffled? Bewildered? Me too.
For me my own struggles with quantum physics have been extremely important in my re-discovery of religion. I can’t understand it of course, but, to my relief, neither can the scientists. Even scientists share the bewilderment we all feel in face of the great mystery of the universe. A bit like finding out that Bach was a mysoginist and Mozart liked scatological jokes. I’m sure many people will feel this is all too scientific for them, but please stay with it. This is the profoundest level of nature that we know, and we all need to make the best of it that we can. The story begins with William Young’s experiments with light in the nineteenth century. Newton had thought that light leaves the sun in showers of tiny particles or corpuscles, as the scientists of that age called them. Young proved that, on the contrary, light travels in waves. He shone a light through a slit in a screen onto a further screen. As you would have expected, the light fanned out from the slit just as it does from your electric torch. He then shone the light through two slits and you would have expected two fans. But this is not what Young got. Instead the light fell onto the further screen in bright vertical strips separated by dark ones. Young realised that this was because the light was travelling in waves. Just as a wave of water can split as it passes through two gaps in a jetty and then, in what are now two waves, join on the other side, so with the light. When two peaks or troughs of the waves co-incided , just as a wave of water sometimes surges forward and at other times there are lots of froth and turbulence and bubbles, so in the case of the light. Sometimes Young got bright light and then when the peaks and troughs didn’t coincide they cancelled each other out and there was darkness. Newton, it appeared, had been wrong.
At the end of the nineteenth century most physicists thought the only major problem left to be solved was that of black box radiation. This wasn’t necessarily anything to do with being black. It meant any object that does not reflect light but absorbs it. If you heat a lump of iron it turns red and then when the heat increases it begins to glow white. Think of the comparison with something that reflects light rather than absorbing it, say a flower, say a calendula. It still glows orange on a hot day as it did on a cold one. Why then should changes in temperature affect the frequencies and therefore the colours of light in black boxes? According to classical physics as the heat increases even further the radiation should pass beyond white into violet and then into the invisible part of the spectrum. Scientists called the expected passing into the invisible spectrum the ultra-violet catastrophe, which always makes me think of the costumes Mrs Thatcher wore at Conservative party conferences. But it didn’t happen. These were problems classical physics had failed to solve.
In 1900 in Berlin Max Planck produced an equation that solved the problem, but only if the radiation increased not smoothly and continuously but in discrete jumps. I’ve absolutely no idea why light moving in jumps rather than smoothly solves the black box problem but all the scientists agree that it does so I’ll take their word for it. He called the jumps quanta.
Max Planck. radiation moves in jumps.
But how could radiation, let alone light, move in jumps if it travelled in waves? Few took Planck’s equation seriously but in 1905 Einstein did, during his annus mirabilis in which he also solved the problem of Brownian motion (let’s leave that one for now) and worked out special relativity while relaxing in his evenings after days spent in the Berne patent office.
Einstein: Worked out the photo-electric effect in his annus mirabilis
Another problem physics hadn’t solved was that of the photo-electric effect. If you shine light onto a metal sheet the energy of the light knocks electrons out of the sheet and according to classical physics the stronger the light the more energy it should impart to the departing electrons, just as on the sea shore the bigger the wave the further the pebbles it tosses up the beach will bounce. But this wasn’t how the electrons behaved. Why not? Einstein found that if he applied Planck’s idea of quantum leaps of radiation to light he could solve the problem. But this was back to Newton’s corpuscles. To make jumps light had to be composed of particles, just as pebbles aren’t themselves waves but bits of stone that stop where they are each time the wave recedes Yet both sets of equations worked. One set proved light travelled in waves, the other that it was composed of particles. How could light be both? Then in 1927 the same paradox was found to apply to the most elementary elements of matter, such as electrons. How could matter be composed both of tiny particles, bits of material stuff in a particular place at a particular time, yet also of immaterial waves that are everywhere and nowhere? Eventually the scientists had to accept the paradox. Matter looked at from one point of view is composed of particles, looked at from the other it is composed of waves. Yet how can this be? It is a paradox to which no-one has found a solution. Perhaps you can already see my direction of travel
Enter Niels Bohr, who incidentally had previously been goalkeeper for the Danish national soccer team.
Like a goalkeeper Bohr made an unbelievable save
Bohr’s solution to the paradox, or you might feel even more mysterious evoking of an even deeper paradox, was his emphasis on the importance of observation or measurement. In Bohr’s view, which became known as the Copenhagen interpretation, phenomena do not exist until they have been observed or measured in some way, either by the human eye or some kind of measuring device. Until that point phenomena are in a superposition as physicists call it, existing, or rather not yet existing, only on the level of waves and not in the particulated way in which we experience physical reality. But measurement, according to the Copenhagen school, “collapses the wave function” and calls what was non-existent into existence. In other words, everything that exists depends on our seeing, or at least instruments we have made measuring it. As you might imagine, this was too much for some. What about the history of the earth before humans evolved? Are we to say there were no mountains before the first human to see a mountain called it into existence? Or that once the first mountain had been seen the whole previous history of mountains suddenly became a reality? A bit much to swallow, but in the absence of any other explanation during the twentieth century most scientists swallowed it, though very much as code for don’t look, don’t ask. They preferred to concentrate on the extraordinary extent to which quantum physics has entered our lives practically – computers, mobile phones, lasers, TV and a host of other things we now take for granted depend upon it. But the paradox has not gone away. Other interpretations have also been offered, though it must be said equally speculative and bizarre, and I will try and discuss them in the next post.
Scientists are still puzzled.
It seems to me that there must be a dimension of reality underlying our own that is beyond our understanding and from our point of view irrationally nonsensical. But it can’t be, because it underlies and penetrates and explains the rational world we know. What are we to make of it all? Quantum physics makes the mysteries of religion appear like, well before 1900 and Planck we might have said physics.
