Does the parable cut closer to home than we might have thought? The discovery of the Higgs particle by the Large Hadron Collider in Geneva has convinced physicists that the answer is a resounding yes. Nearly a half-century ago, Peter Higgs and a handful of other physicists were trying to understand the origin of a basic physical feature: mass.
Push on a freight train or a feather to increase its speed, and the resistance you feel reflects its mass. But where do the masses of these and other fundamental particles come from? When physicists in the s modeled the behavior of these particles using equations rooted in quantum physics, they encountered a puzzle.
If they imagined that the particles were all massless, then each term in the equations clicked into a perfectly symmetric pattern, like the tips of a perfect snowflake.
And this symmetry was not just mathematically elegant. It explained patterns evident in the experimental data. The equations became complex and unwieldy and, worse still, inconsistent. What to do? Instead, keep the equations pristine and symmetric, but consider them operating within a peculiar environment.
Imagine that all of space is uniformly filled with an invisible substance—now called the Higgs field—that exerts a drag force on particles when they accelerate through it. Push on a fundamental particle in an effort to increase its speed and, according to Higgs, you would feel this drag force as a resistance. For a mental toehold, think of a ping-pong ball submerged in water. When you push on the ping-pong ball, it will feel much more massive than it does outside of water.
Its interaction with the watery environment has the effect of endowing it with mass. So with particles submerged in the Higgs field. In , Higgs submitted a paper to a prominent physics journal in which he formulated this idea mathematically. The paper was rejected. Not because it contained a technical error, but because the premise of an invisible something permeating space, interacting with particles to provide their mass, well, it all just seemed like heaps of overwrought speculation.
But Higgs persevered and his revised paper appeared later that year in another journal , and physicists who took the time to study the proposal gradually realized that his idea was a stroke of genius, one that allowed them to have their cake and eat it too.
The physics community had, for the most part, fully bought into the idea that there was a Higgs field permeating space. Why is it so special? How was its existence proved at the LHC? This video explains the basics of the Higgs boson and its associated field in 4 minutes with infographics.
Real CMS proton-proton collision events in which 4 high energy muons red lines are observed. The event shows characteristics expected from the decay of a Higgs boson but is also consistent with background Standard Model physics processes. Image: CERN. The Higgs boson Elementary particles gain their mass from a fundamental field associated with the Higgs boson.
The Brout-Englert-Higgs mechanism In the s, physicists realised that there are very close ties between two of the four fundamental forces — the weak force and the electromagnetic force. Physicists believe the Higgs field may be slowly changing as it tries to find an optimal balance of field strength and the energy required to maintain that strength. Right now the Higgs field is in a minimum potential energy state — like a valley in a field of hills and valleys. The huge amount of energy required to change into another state is like chugging up a hill.
If the Higgs field makes it over that energy hill, some physicists think the destruction of the universe is waiting on the other side. But an unlucky quantum fluctuation, or a change in energy, could trigger a process called " quantum tunneling.
This quantum fluctuation could happen somewhere out in the empty vacuum of space between galaxies and create an expanding "bubble," Lykken said. Here's how Hawking describes this Higgs doomsday scenario in the new book: "The Higgs potential has the worrisome feature that it might become metastable at energies above [billion] gigaelectronvolts GeV.
This could happen at any time and we wouldn't see it coming. The Higgs field inside that bubble would be stronger and have a lower energy level than its surroundings. The Standard Model successfully describes all of the elementary particles we know and how they interact with one another.
But our understanding of Nature is incomplete. In particular, the Standard Model as originally conceived cannot answer one basic question: Why do most of these elementary particles have masses? The symmetry responsible for electroweak unification requires the force-carrying particles involved to have no mass. The photon, carrier of the electromagnetic force, fulfils this requirement; however, the W and Z bosons, carriers of the weak force, have non-zero masses.
The fact that the W and Z are massive breaks the fundamental electroweak symmetry. Needing a way out of this conundrum, several physicists [1] proposed a mechanism to explain the broken symmetry.
Once it was incorporated into the equations, this electroweak-symmetry breaking mechanism would allow particles to have mass. The mechanism also explains why the weak interactions appear to be weak at low energies; the force carriers are massive and therefore the force is short ranged. Peter Higgs pointed out that the mechanism required the existence of an unseen particle, which we now call the Higgs boson.
According to our current understanding, all particles were massless just after the Big Bang. Particles such as the W and Z acquire mass through their interaction with this field — the more intensely they interact, the heavier they become. The existence of such a field preserves the underlying symmetry of the electroweak theory, whilst explaining the broken symmetry we observe in Nature today. Other force-carrying particles — the photon and the gluon — do not feel any interaction with the Higgs field and remain massless.
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