Coyotes and Cats

If a tree falls in a forest and no one is around to hear it, does it make a sound? If Wile E. Coyote runs off a cliff chasing Roadrunner but doesn't look down, will he fall?

Today two cosmologists from respectable American universities claimed that man may be significantly shortening the life of the universe by observing Dark Matter as a consequence of an effect predicted by a thought experiment involving a cat -- Schrödinger's cat.

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Schrödinger's cat is an imaginary experiment — a thought experiment — devised by Erwin Schrödinger, which is often described as a paradox. It attempts to illustrate what he saw as the problems of the Copenhagen interpretation of quantum mechanics when it is applied to systems large enough to be seen with the naked eye, and not just to atomic or subatomic systems.

It is accepted that a subatomic particle can exist in a superposition of states, a combination of possible states. According to the Copenhagen Interpretation, the superposition only settles into a definite state upon observation. This is known as collapse or measurement.

Which would seem to suggest that in the subatomic world, an event only becomes definite when it is observed. Wile E. Coyote only starts to fall when he looks down. There is lively debate over the "meaning" of certain aspects of quantum theory. Two scientists, Profs Lawrence Krauss of Case Western Reserve University and James Dent of Vanderbilt University seem to applying the Copenhagen Interpretation of quantum theory to the consequences of measuring dark matter.

"The intriguing question is this," Prof Krauss told the Telegraph. "If we attempt to apply quantum mechanics to the universe as a whole, and if our present state is unstable, then what sets the clock that governs decay? Once we determine our current state by observations, have we reset the clock? If so, as incredible as it may seem, our detection of dark energy may have reduced the life expectancy of our universe."

It is widely believed that large objects do not exist in a state of superposition and so why the measurement of Dark Matter have any perceptible effect on the lifespan of the universe is an obvious question to raise. Einstein in considering the question asked himself if the moon only existed when he looked at it. But the respectability of the institutions with which the two professors are associated probably guarantees they have already considered these objections and still believe there is a legitimate concern. I leave it to the readers to consider this interesting topic on the day after Thanksgiving as an entertaining alternative to the problem of concocting recipes for leftovers. And while we are on the subject of Thanksgiving, have you considered the possibility that there may be many more in store for you in the world of Quantum Immortality?

In quantum mechanics, quantum suicide is a thought experiment which was independently proposed in 1987 by Hans Moravec and in 1988 by Bruno Marchal, and further developed by Max Tegmark in 1998, that attempts to distinguish between the Copenhagen interpretation of quantum mechanics and the Everett many-worlds interpretation by means of a variation of the Schrödinger's cat experiment. The experiment essentially involves looking at the Schrödinger's cat experiment from the point of view of the cat. Quantum immortality is a metaphysical speculation derived from the quantum suicide thought experiment. It states that the many-worlds interpretation of quantum mechanics implies that conscious beings are immortal.

A physicist sits in front of a gun which is triggered or not triggered depending on the decay of some radioactive atom. With each run of the experiment there is a 50-50 chance that the gun will be triggered and the physicist will die. If the Copenhagen interpretation is correct, then the gun will eventually be triggered and the physicist will die. If the many-worlds interpretation is correct then at each run of the experiment the physicist will be split into one world in which he lives and another world in which he dies. After many runs of the experiment, there will be many worlds. In the worlds where the physicist dies, he will cease to exist. However, from the point of view of the non-dead copies of the physicist, the experiment will continue running without his ceasing to exist, because at each branch, he will only be able to observe the result in the world in which he survives, and if many-worlds is correct, the surviving copies of the physicist will notice that he never seems to die, therefore "proving" himself to be immortal, at least from his own point of view.

Another example is where a physicist detonates a nuclear bomb beside himself. In almost all parallel universes, the nuclear explosion will vaporize the physicist. However, there should be a small set of alternative universes in which the physicist somehow survives (i.e. the set of universes which support a "miraculous" survival scenario). The idea behind quantum immortality is that the physicist will remain alive in, and thus remain able to experience, at least one of the universes in this set, even though these universes form a tiny subset of all possible universes. Over time the physicist would therefore never perceive his or her own death.