Understanding the Higgs 1: Frozen light

The discovery of the Higgs particle is one step further on a long road – the search for the nature of matter.

Our experience of matter starts in childhood, when we become familiar with objects and learn to live with them – how to pick them up when they’re useful and avoid bumping into them when they’re not. Our language is so attuned to objects that we speak in object terms even when the topic is highly abstract and insubstantial. Thus we talk about ‘giving time’ as if we were handing out sweets, and ‘having a point of view’ as if we had taken up ownership of a piece of ground on a hill.

Physics has developed our object-experience into a theory of matter, as a kind of common essence to the numerous objects we encounter. It speaks of mass – as the quantity of matter in a big object or a little particle.

But while our hands are learning about objects, our eyes are learning about light. And light seems to exist at a more fundamental level than matter.

To take one instance: while material objects move along at different speeds, light travels supremely fast – and at the same speed, however we measure it. Whether we try to keep up with it, or whether we approach from the opposite direction, the speed we observe is the same. The light continues on its way regardless of how we try to measure it. Its fixed speed seems to be something built into the fabric of the universe.

And again: nothing can travel faster than light, and strange things happen when we try. Somehow, as we travel faster, our clocks slow down in comparison with a clock that is left in a fixed place; and also lengths shrink. And further, as our speed increases, so too does our mass; and it does so at such a rate that at the speed of light our mass would rise to an infinite level.

How then can light do it? And the answer is that light has zero mass to start with, and so it doesn’t matter what factor its mass is multiplied by, at zero it will remain. But for us, with a finite amount of mass to start with, that option is forever closed off.

Another deep difference between light and us comes when we try to look at space and time in the way that light might ‘see’ these dimensions. Since moving faster means that clocks slow down and lengths shrink, it turns out that for anything travelling right up at the highest extreme, the speed of light itself, its internal clock would slow down to zero and stop completely; and internal lengths would also shrink to zero.

In terms of the beam of light racing through space, this stopping of the internal clock must mean that somehow there is no time passing along the beam. In other words, the two ends of the beam must have no time-interval between them, and also no distance-gap. Somehow they must be in immediate contact, in an internal world in which there is no flow of time and in which everything is somehow connected in an instantaneous whole.

The Russian mathematician Yuri Manin, with an elegant clarity, wrote: ‘In a world of light there are neither points nor moments of time; beings woven from light would live nowhere and nowhen; only poetry and mathematics are capable of speaking meaningfully about such things.’

Beings woven from light would indeed have developed a very different physics from us – one with no concepts of space, or time or matter.

But in our own development of a scientific picture of the universe, we have traditionally started with matter, and followed on to try to understand light. Newton’s laws of motion were published in 1687; Maxwell’s equations showing how light waves originate from electricity and magnetism were presented to the Royal Society in 1864.

We have also built in to our physics a picture of the way in which we ourselves interact with light, a picture in which we are very much in charge. We talk about switching on light or catching it on a screen, and it looks indeed as if we are making things happen. But such processes could be pictured in another way. It might simply be that what we are doing is simply opening a section of window from our own territory on to the world of light. Thus when we shine a light, the process is like drawing out a line on a scratchcard, scraping away along this narrow track the opacity which normally keeps the deeper world of light obscured from us.

But although that world and ours are so different, we also know that there is more than just a window between them – there is an actual door. We can convert matter into light. and light into matter. This is the meaning of Einstein’s equation E=mc2. A particle and an antiparticle meet and annihilate, to produce a burst of light-like energy. Conversely, there are situations where light will convert itself into a particle/antiparticle pair. So despite the deep differences between light and matter, there is some common essence that allows in certain circumstances a mutual transformation.

In fact we can picture matter as ‘condensed or frozen light’. Those are the words of David Bohm, who went deep into fundamental philosophical questions about the core concepts of physics.

‘All matter is a condensation of light into patterns moving back and forth at average speeds which are less than the speed of light,’ he said. ‘You could say that when we come to light we are coming to the fundamental activity in which existence has its ground, or at least coming close to it.’

Bohm worked closely with Einstein at Princeton, but was put under pressure in the McCarthy era, and moved to Brazil, then Israel, and finally the UK. He probed the logical structure of quantum theory and developed an alternative way to look at it, and is widely considered to have been one of the best quantum physicists of all time. His approach was to insist that there had to be meaning in quantum theory and in physics as a whole – which meant developing concepts and language to explain the mathematics.

In another very evocative image, he spoke of light as a vast ocean, with matter as ripples on the surface. The world of light is primary, with us somewhere much more superficial and ephemeral. And the quest for the nature of matter in which the Higgs particle plays such a significant part is the search to understand how the surface of the ocean of light gets trapped into the ripples of matter.

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