Sparks

The paradox of the cat-bacteria

 By Eniday Staff

It’s like an experiment out of a science fiction movie, but don’t tell Erwin Schrödinger, who came up with his famous feline paradox in 1935…

Schrödinger’s stupefying paradox is back – and this time seems to be telling us that the cat, which continues to be simultaneously alive and dead, simply started dancing with the uranium atom that was supposed to decide its fate.
Setting out to prove this new paradox, this time using bacteria, is a team of researchers at the University of Sheffield, in the United Kingdom.
The researchers sequestered several hundred very small, light-hungry bacteria – Chlorobaculum tepidum – in a cavity made from a system of infinite mirrors. When they injected light into the cavity, it bounced between the mirrors and began to act as a stationary wave at a certain frequency. They then found that the bacteria started pulsing in unison, occasionally absorbing and re-emitting light. In other words, for a moment, a living being assumed a quantum type of behaviour, simultaneously acquiring two states that in each bacterium’s normal life are opposed and irreconcilable. Who knows what Schrödinger and his old cat would think of the use of quantum mechanics to describe living systems, which are accordingly far more complex than individual elementary particles?

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Chlorobaculum tepidum bacteria

To be or not to be?

But what exactly does this mean? What does it change for all of us? First let’s answer the second question – and in the process, reassure all the cat owners out there. The experiment is about the temporary conditions of microscopic organisms and we – like our feline friends – are anything but microscopic.
To answer the first question, however, it is worth taking a step back to 1935 and the famous paradox of Erwin Schrödinger. Basically, you take a cat, a uranium atom (radioactive and destined to disintegrate sooner or later) and a Geiger counter. Put them all in a sturdy box and wait for the atom to disintegrate. This triggers a mechanism that will release a lethal dose of cyanide into the box. So is the cat alive or dead? The surprising answer is that it is as much alive as it is dead because the state of the radioactive atom is not predictable – except statistically – so according to quantum physics it has both disintegrated and not disintegrated.
The paradox tells us two things: first, quantum physics states that it is not possible to describe an electron or a proton in the same way that we describe an apple or the moon. We cannot define its position, but only the probability that it is in one position rather than in another, or yet another.
When we decide to check where it actually is, here comes the game changer: by intervening, we immediately stop the object in the position in which we observe it and all our conjectures and measurements come to nothing.

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Diagram of Schrödinger's cat thought experiment. Apparently, the cat can be both alive and dead at the same time (Dhatfield, Wikimedia)

The limit of quantum physics rules

The other moral of Schrödinger’s cat paradox is that these rules of quantum physics apply only to tiny, atomic and sub-atomic entities. A molecule – even one as simple as water, for example – will abide by the rules of classical physics and not by those of quantum physics. The same quite obviously applies to a cat.
So, thinking back to the experiment on bacteria by researchers at the University of Sheffield, is this a revolution in our way of thinking? It’s probably still too early to say. First of all because the time in which the bacteria interacted with the quanta of light was incredibly short, in the order of one millionth of a billionth of a second, and secondly because the change involved the chloroplasts and probably not the whole bacterium.

 Unexpected results

But there are also two positive outcomes that give hope to the British researchers. The first is that the experiment took place at room temperature, which is unusual since quantum physics experiments normally require temperatures close to absolute zero. The other – not to be underestimated – is that it seems that the poor bacteria were still in excellent health after this nasty little episode. So they’re doing better than the cat anyway!

READ MORE: Sticky bacteria make better biofuel by Benjamin Plackett

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Eniday Staff