The Infinite Monkey Cage – How to Build a Universe. Robin Ince

ordered structure, just like a teacup. This is not all that happens, however. The plant radiates heat out into its surroundings, which is in turn radiated into the coldness of space. Heat is also a stream of photons, but they are lower energy and more numerous than those in the incoming sunlight. Heat is a highly disordered form of energy, and when all the sums are done, it turns out that this more than compensates for the increase in order during the formation of sugars and the other intricate structures of the strawberry. We might say that the strawberry increases the amount of disorder in the Universe quicker by the very fact of its existence, thus hastening the demise of all of creation. It borrowed order from the Sun, but increased the disorder of the rest of the Universe as a result.

      The moment that the strawberry’s metabolism grinds to a halt, it can no longer function as a little machine sitting between the cascade of ordered energy from the Sun and the coldness of space, and the Second Law reasserts its grip. This is death.

      The seeds inside the ovaries attached to the fruit are a different matter, however. They are alive if they are capable of germinating. Seeds can stay dormant for very long periods of time; many decades in some instances, and there are different types of dormancy in the plant kingdom. The strawberry seed exhibits physical dormancy, which means that the seeds’ outer casing, being impermeable to water, prevents the embryo within germinating – germination is defined as the sprouting of the seedling from the seed. When the strawberry is eaten by an animal, the seeds pass through the digestive tract and the outer casing is damaged such that it becomes permeable to water. This begins the germination process. In other species, the outer casing can be damaged by fluctuating temperatures, freezing and thawing, drying, or even fire. The evolutionary advantage of delayed germination is clear; there is a selective advantage to delaying germination until the onset of the rainy season in the tropics, for example. Awaiting dispersal via consumption by an animal can also be seen to offer a selective advantage. Precisely how physical dormancy evolved, however, is a matter of ongoing research.

      Some seeds exhibit a different form of dormancy known as physiological dormancy, in which embryo growth is prevented by inhibiting chemicals. All gymnosperms – of which conifers are the most common group – exhibit physiological dormancy. Unlike physical dormancy, physiological dormancy can be reversible.

      The definition of a dead strawberry is therefore a slippery one, and depends on whether you mean the strawberry itself (which is not a berry), or the seeds it contains. In the simplest terms, Professor Nick Lane, from University College London, stated that if the strawberry is not continually harnessing energy to maintain being alive, it’s dead. Seeds can continue to metabolise, albeit extremely slowly, whilst dormant. They are therefore alive, until they stop.

      Brian noted that our understanding of the plight of a strawberry might be further complicated by taking quantum theory into account, extending the discussion to Schrödinger’s Strawberry.

      R: I’ll tell you what, we’ll put a strawberry in a box and we won’t observe it and it can be both.

      Katy: I love the idea of Shrödinger’s Strawberry.

      R: The whole of Wimbledon changes.

      B: I’m thinking about how you’d write down the wave function of a strawberry.

      R: When are you not thinking of a wave function…?

      Series 7, Episode 2 (26 November 2012)

      Consider a strawberry in a sealed box with a small thermonuclear bomb triggered by the decay of a single radioactive nucleus sufficiently powerful to completely vaporise the strawberry, but not the box. Quantum theory allows us to calculate the probability that at a given time after the box is closed, the radioactive nucleus will have decayed, thus triggering the death of the strawberry.

      Until we observe the nucleus (although see below), quantum theory informs us that we are to treat the nucleus as being in a mixture of both ‘decayed’ and ‘not decayed’. Physicists call this mixture a linear superposition. The amount of ‘decayed’ and ‘not decayed’ changes over time in a way that we can calculate using the Schrödinger Equation, but crucially this is all we can do. The nucleus hasn’t decayed or not – it is simply in a linear superposition.

      Since the decay of the nucleus determines the fate of the strawberry, we should also say that the strawberry is in a linear superposition of alive and dead before the box is opened, just like the nucleus. In the form of an equation, a physicist would write:

      There appear to be two problems with this description. Firstly, we need to be clear what we mean by ‘observe’. What is so special about observation that it reduces the linear superposition to the certainty of one outcome or another? Why does the strawberry’s experience not count as an ‘observation’ of whether the radioactive nucleus has decayed? What if we replaced the strawberry by Robin Ince? Would he remain in a superposition of alive and dead until we opened the box?

      Secondly, the idea that a strawberry can only be in some combination of alive and dead in such an experiment and not one or the other doesn’t correspond to our perception of reality; surely the strawberry cannot be simultaneously both alive and dead before we open the box?

      There is an interpretation of quantum theory known as the Many Worlds Interpretation that addresses both these issues. It is the simplest interpretation of the theory, and states that the superposition is never broken. All that happens when we open the box is that we enter a superposition with the strawberry and the nucleus. We might say that there are ‘worlds’ in which we see a vaporised strawberry and ‘worlds’ in which we don’t, but this language is really misleading. Reality is a superposition of all possibilities – and the interesting question becomes why our experience is of a reality consisting of only one set of possibilities. The answer is that the two ‘branches’ of reality following our interaction with the strawberry box evolve separately to each other; they do not interfere and nothing in the future of each branch is contingent on things happening in the other branch. In the Many Worlds Interpretation of quantum mechanics, however, both branches are equally real. The terminology that has developed is to refer to these branches as ‘different worlds’, but that’s misleading. There is only one ‘world’, and it is a world in which everything that can happen does happen and everything is in a superposition with everything else. There are parts of reality in which we opened the box and saw a strawberry, and parts of reality in which we opened the box and saw only vapour. The reason we are unaware of the true ensemble of alternative possibilities in practice is because they have no discernible influence on our experience in a particular branch.

      In response to the Great Dead Strawberry Debate, Monkey Cage regular Professor Nick Lane sent us this contribution:

      Strawberries really are in a superposition of states, although unlike Brian I’m not thinking about quantum states: parts are alive and parts are dead. We tend to think of death as a digital process: we are either alive or dead. But even when a person dies, many