Several apparent paradoxes thrown up by quantum theory still have currency today. Perhaps the most graphic is the 'thought experiment' known as Schrodinger's Cat. Erwin Schrodinger used it to highlight one of the unsatisfactory aspects of quantum mechanics. Suppose you take a cat and put it in a box with a vial of poison. The vial of poison is linked to a device such as a chunk of radioactive material that might or might not decay according to the rules of quantum mechanics. If the material decays, the cat will become exposed to the poison with fatal results. According to quantum mechanics, until the measurement or observation is made, i.e., someone opens the box and look at the cat, the poor animal is existing in both states, dead and alive at the same time!

Schrodinger, it should be said, did not believe this bewildering state of affairs. The point is - what's sauce for the goose is sauce for the gander. Quantum theory successfully accounts for the behaviour of atoms, electrons or sub-atomic particles by describing them as mixtures of states until the act of observation is carried out. Then why not a macroscopic object like a cat? There are several interpretations of this puzzle. The most pragmatic simply says that quantum mechanics should not be used for large objects like cats. Many physicists feel that this is a cop-out.

Another interpretation, the 'Many Worlds' interpretation, suggests that every time a quantum event occurs, the universe divides. Following the example above, there would be one universe with a live cat and one with a dead cat. This interpretation necessarily invokes countless zillions of universes. This view, though wild and wacky, is held by some distinguished scientists. Another reading would say that although the rules of quantum theory have been proven to be beautifully precise billions of times, there is something about the theory that is not known, some modification that needs to be made, because it cannot be successfully applied to macro systems yet.

Although scientists may argue over the correct interpretation of quantum theory, it has led to the most precise predictions in the history of science and is the basis of all modern electronics in the hi-tech world we live in. The accuracy of quantum theory has been compared with measuring the distance between Los Angeles and New York and achieving a result correct to a single hair's breadth!