Magazine article New Statesman (1996)

Harnessing the Light Fantastic

Magazine article New Statesman (1996)

Harnessing the Light Fantastic

Article excerpt

There's nothing like winter gloom to make you appreciate the qualities of light. But rarely appreciated is what a puzzle they present.

Physicists still don't know what light is. You can think of it as either a wave or a particle, because it is both and neither. A century of physics experiments has shown that it hits our eyes in packets of energy known as photons. More than too years of experiments have also shown, however, that it operates in continuous waves, like ripples on water. We have been trying to describe what light is since the days of Isaac Newton and we still have no clear understanding.

The quantum properties of light make things worse: they show that we really don't understand how the universe works. In Paris this month, at the opening ceremony for the Unesco International Year of Light, the French researcher Alain Aspect will explain how an experiment on light he first carried out in 1982 destroyed our conception of what is real.

Aspect's experiment led to two extraordinary conclusions. First, it showed that certain properties of photons are generated at random by the act of measuring them. The implication is that the universe is random at heart--not every effect has a cause. The second is that you can affect the properties of a distant photon in ways that defy all conventional notions of space and time.

For all the philosophical conundrums it creates, we have harnessed the strangeness of light with aplomb. Take the laser, which relies on the quantum properties of photons. Initially it was a means of "light amplification": adding energy for tasks such as cutting or burning. But, oddly, its most exciting application in physics now is in refrigeration.

When the Nobel laureate William Phillips gives his plenary lecture at the Paris ceremony, he will no doubt mention his work using laser energy to cool atoms down. …

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