Author: Haroon Khalil
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The Weak Interaction
The fact that some nuclei are unstable. These are called radioactive nuclei, and their state and even identity can change spontaneously. These changes occur by the absorption and emission of energy in the form of alpha particles, electrons, positrons, and gamma rays. Radioactive nuclei that have too many neutrons compared to protons emit electrons in…
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The Strong Interaction
Ernest Rutherford’s nuclear model of the atom, consisting of a tiny massive nucleus surrounded by a cloud of electrons. With the discovery of the neutron in 1932 by James Chadwick it became clear that the nucleus is really formed of protons and neutrons. So a natural question would be, given the electromagnetic repulsion between the…
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The Electromagnetic Interaction
The physics of electromagnetic phenomena is governed by the electromagnetic interaction, which includes both electricity and magnetism. It is based on a quantity called charge, of which there are two varieties–positive or negative. Of course, not all particles are charged in the first place, and so-called “neutral” particles couldn’t care less about the electromagnetic interaction.…
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The Gravitational Interaction
Gravity was not only the first of the fundamental interactions we introduced in this book, it was also the first recognized by scientists. As far back, even, as Aristotle. We described gravity as an attractive force between all particles with mass, whether they are charged or not and whether they are big or small. Gravity…
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From Galaxies to Quarks
The universe is big. So big that we don’t really know precisely how big it is. The most recent estimates, based on scientific observations, give a radius of about 46 billion light years. (A light year is the distance that light, with all of its speediness, travels in a year.) While the universe contains mostly empty space,…
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Introduction
Nature presents us with the macroscopic world, everything we see about us on Earth, but also everything above us, in our solar system and beyond. Nature also presents us with microscopic entities such as atoms, which are made of nuclei and electrons. Nuclei are themselves composed of protons and neutrons. But is this the end…
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Why Bother Trying to Interpret Quantum Physics?
As we have seen, trying to explain the meaning of quantum physics can lead us far afield in many different directions. A lot of it sounds like science fiction, or just wild speculation. As we’ve mentioned, a lack of answers in this area doesn’t stop physicists from doing physics, especially in the microscopic realm. In…
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Free Will and Determinism
A lot of the difficulty in understanding quantum physics hinges on the question of free will. We’re confused because it seems that we can decide to measure either the wave properties or particle properties in the same system, and our decision determines whether wave properties or particle properties are seen. But does free will truly…
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Von Neumann’s Chain
The Schroedinger’s Cat Gedankenexperiment helped us appreciate the measurement problem by bringing superposition up from the microscopic world to the more familiar macroscopic scale. But it raised the problem of what we would see if we could see inside the closed box. If the very act of seeing always and immediately gets rid of the…
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The Role of Consciousness
Classical physics made great progress for many years, all the while insisting on a total separation between observers and the reality they observed. Objective reality was everything that existed apart from the observers, stuff that would exist and would have the same properties whether or not anyone was around to see it. But with quantum…