Why the universe is heavy: how symmetry breaking creates matter
In short: According to the equations of the Standard Model, all fundamental particles should technically be massless. If they were, atoms could not form and life would be impossible. The reason you have weight is due to a profound cosmic event where the laws of physics broke their own rules.
In quantum mechanics, symmetry refers to properties that remain unchanged under specific transformations, such as the fact that physical laws are identical in different locations (space translation symmetry). These symmetries are responsible for the three fundamental forces: electromagnetic, weak, and strong. However, a perfect universe of pure symmetry would be devoid of mass. To create the world we inhabit, nature had to undergo 'symmetry breaking,' where the underlying rules shift into a state that favors specific outcomes over others.
The Higgs mechanism provides a primary example of this process. Imagine a 'Mexican hat' potential: a ball placed at the very center represents a symmetric state with maximum energy. If the ball rolls into one of the surrounding minima, it settles into a lower energy state where symmetry is lost. In our universe, the Higgs field is unique because its lowest energy state is non-zero even in empty space. As fundamental particles move through this field, their interactions with it grant them rest mass. Particles that do not interact with it, such as photons, remain massless.
While the Higgs field explains the mass of fundamental particles, it does not account for all the weight in the universe. The majority of the mass in protons and neutrons actually originates from binding energy within the nucleus. This is governed by chiral symmetry breaking. A chiral-symmetric theory would treat left-handed and right-handed particles identically; however, the Standard Model does not. Because the model breaks this symmetry, quarks (like the left-handed up quark with a mass of about 2.3 MeV) gain mass through gluon interactions associated with the strong force.
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Sources
- Summary by Intellect · source: What is the ORIGIN of all MASS in the Universe? Physics of symmetry breaking
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