David Peat

12 From Certainty to Uncertaintyposition, or its speed, but never both at the same time without a measureof uncertainty or ambiguity creeping in. Quantum theory dictatesthat no matter how refined are the measurements, the level of uncertaintycan never be reduced.How does this come about? It turns out to be a direct result of MaxPlanck’s discovery that energy, in all its forms, is always present in discretepackets called quanta. This means a quantum cannot be split intoparts. It can’t be divided or shared. The quantum world is a discreteworld. Either you have a quantum or you don’t. You can’t have half or99 percent of a quantum.This fact has a staggering implication when it comes to our knowledgeof the atomic world. Scientists learn about the world around themby making observations and taking measurements. They ask: Howbright is a star? How hot is the sun? How heavy is Newton’s apple?How fast is a meteor?Quantum ParticipationWhenever a measurement is made something is recorded in some way.If no record were created, if no change had occurred, then no measurementwould have been made or registered. This may not be obvious atfirst sight so let’s do an experiment: Measure the temperature of a beakerof water. Put a thermometer in the water and register how high themercury rises. For this to happen some of the heat of the water musthave been used to heat up and expand the mercury in the thermometer.In other words, an exchange of energy between the water and thethermometer is necessary before a measurement can be said to havebeen recorded.What about the position or the speed of a rocket? Electromagneticwaves are bounced off the rocket, picked up on a radar dish, and processedelectronically. From the returned signals it is a simple matter todetermine the rocket’s position. These same signals can also be used tofind out how fast the rocket is traveling—the technique is to use whatis known as the Doppler shift—a slight change in frequency of thereflected signal. (This Doppler shift is the same effect you hear as a