THE STRANGE WORLD OF QUANTUM PHYSICS by Mathew Fr Joseph

Author:Mathew , Fr Joseph
Language: eng
Format: epub
ISBN: 9789391399320
Publisher: ATC Publishers
Published: 2022-03-31T00:00:00+00:00

Figure 17. Annihilation of electron-positron pair

The figure above is a Feynman diagram of the collision of an electron and a positron. An electron on left side approaches a positron which is coming from right side. At their point of contact at the center, they mutually annihilate each other, and two photons (marked by broken lines) are created which depart in opposite directions at the speed of light. In fact, this unceasing dance of creation and annihilation ever goes on among subatomic particles.

However, this process of quantum fluctuation involving the creation and annihilation of particles and anti-particles apparently violates one of the most fundamental laws of classical physics, namely, the law of the conservation of energy. This law states in effect that the quantity of energy in the universe remains constant; and that the total amount of energy is preserved even though its spatio-temporal distribution changes. This means that “no quantity of energy in the world can arise out of nothing, but only from the transformation of a previous energetic equivalent” and that “no particular quantity of energy can disappear without being transformed into its equivalent.”132 In other words, energy cannot be created or destroyed. Now, let us imagine that this law of energy conservation is checked by an energy accountant who keeps track of the total energy of physical interactions in the universe. The accountant's ledger records energy incomes and energy expenses in two columns, and both columns have to balance exactly. For example, the chemical energy stored in petroleum can be transformed into heat and motion of cars. There should be an exact balancing of energy on both sides in this process. In this way, an energy balance sheet would account for all the transformations of chemical energy and all other forms of energy. That is the requirement of the law of conservation of energy. Thus according to this law, energy is neither created nor destroyed but rigorously conserved, merely being converted from one form to another.

Now, if according to the law of energy conservation, energy is neither created nor destroyed, how then can we explain the creation and annihilation of particles and anti-particles in quantum vacuum fluctuation? Heisenberg's uncertainty principle provides us the answer. This principle can suspend the law of conservation of energy for an extremely short period of time; and this is the consequence of uncertainty relation between energy and time. Accordingly, there is an uncertainty in the measurement of the conjugate quantities of energy and time. If we know the energy state of a particle with precision, then we are not certain about the amount of time it is likely to remain in that state. Conversely, if we know precisely the length of time a particle has been in that state, we would be uncertain about the energy needed to remain in that state. Hence, there is a limit to the accuracy with which we can measure energy of the quantum state of a particle within a given interval of time. Such uncertainty between energy

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