Let There Be Light … and Mass

“Science fails when scientists march in the same direction. It becomes an exercise in flogging the old instead of rushing forward with the new. For a true revolution you need contrarians, not conformists.” Ian Sample, Massive: The Missing Particle that Sparked the Greatest Hunt in Science 55 (2010).

When the Universe came into being, a sea of electromagnetic radiation (light) and protons, neutrons and electrons (plus their antimatter counterparts) made their appearance. Light is made of massless particles, known as Photons, which are the carriers of the electromagnetic force, one of the fundamental forces of nature. The other three are the Strong Nuclear Force (which keeps atomic nuclei together and is “carried” by Gluons), the Weak Nuclear Force (which is responsible, among other things, for radioactivity and is transmitted by the W and Z Bosons) and Gravitation (which, among other things, makes the existence of stars and of our planet possible and is presumably transmitted by Gravitons).

In the 1960’s, the work of several physicists turned the attention of their colleagues to the question, why is there mass? That is, why is not the Universe made up only of light and other non-massive stuff, moving perpetually at the speed of light? This question has to do with the concept of symmetry. The ultimate symmetry would be precisely a universe made only of photons and other equally mass-less particles. But that’s not the Universe we know, nor could we live in such a place.

The existence of massive stuff required a break in the symmetry of the very early Universe, and the theory proposed in 1964 by Peter Higgs (see his picture, above) and five other physicists includes the idea that a field pervading space did the trick by interacting with the until then mass-less particles. Photons, which do not interact at all with what we now call the Higgs Field, remained massless, while other particles’ interaction with the field did make them massive.

Think of the field as having the effect of decelerating the movement of the particles, like a swimmer trying to move through a denser-than-water liquid medium. Having mass is equivalent to that slowing-down of the particle’s motion through space. The development of these ideas and the subsequent search for experimental evidence of the Higgs Field and its particle counterpart, the Higgs Boson, is one of the most fascinating science stories of the last 50-plus years.

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