This is an open-source, modern physics textbook typically for the third semester students majoring in engineering, physics or chemistry. An emphasis is placed on fundamental principles as well as numerical solutions to equations where no analytical solutions exist. The content begins with optics and uses that as a stepping stone to wave phenomena and quantum systems.
Quantum Field Theory is generally accepted as an accurate description of the subatomic universe. However until recently this theory had one giant hole in it. The particles it describes had no mass! The Higgs field and the Higgs mechanism were proposed long ago in order to give particles mass, but it was only in 2012 that the existence of the field was proved with the discovery of the Higgs boson by the Large Hadron Collider.
But this intuitive, mechanical reality is emergent from underlying reality in which the particles that form matter arise from of the combination of an infinity of possible properties. And forget matter – the vacuum itself is the sum of infinite possible particles. If we fully unravel this idea we’ll be on the verge of tackling things like Hawking radiation. But as you’ll see today, in that unraveling we are led, unavoidably, to Heisenberg’s uncertainty principle.
Let’s talk about vacuum energy from a theoretical standpoint. From the perspective of quantum field theory, every point in space is represented by a quantum oscillator; one for each elementary particle type. Higher energy oscillations represent the presence of real particles. However even the lowest possible energy oscillation – the one corresponding to the absence of particles – has some energy.
How do we study nothing? An empty jar still contains something: molecules of air and a bath of infrared light from its warm environment. But what if we suck out every last molecule of air, chill the jar to absolute zero, and shield it from all external radiation? The jar would contain only empty space, but it turns out that empty space is far from nothing.
Many experimental physicists have spent their careers trying to cool things to absolute zero. This state of absolute cold is the zero-point on the Kelvin temperature scale, corresponding to -273.15 Celsius. Using lasers and magnetic fields, we’ve now managed to cool certain substances to less than a billionth of a Kelvin. Doing so has revealed some bizarre quantum states of matter. But quantum mechanics may also prevent us from ever reaching absolute zero.
One-Electron Universe idea: that there exists only one electron, and that electron traverses time in both directions. It bounces in time, eventually traversing the entire past and future history of the universe in both directions, and interacting with itself countless times on each pass. In this way it fills the universe with the appearance of countless electrons. And when the electron is moving backwards in time it is a positron; the antimatter counterpart of the electron.