Kepler-11

exploringthecosmos:

People generally have an intuition for what mass* is, but no one quite understands it to the level that we would like. You can easily distinguish between an object that has little mass, say an ant, and an object that is very massive, like an elephant. The order of magnitude difference between the mass of an ant and an elephant is equivalent to that of the span of all masses of fundamental particles; masses of fundamental particles span about eleven orders of magnitude, but why? Where does all this stuff come from? There are several mechanisms by which mass arises but we will only focus on one method: The Higgs Mechanism.

The Higgs Boson was originally suggested solely for mathematical purposes as it imposed consistency on the Standard Model of particle physics and it fit quite well. Interestingly enough, this Higgs mechanism acts like a fifth force of nature! The four current forces of nature, including (in order of increasing strength) the gravitational force, weak force, electromagnetic force and strong force, have associated vector fields.  The fact that these are vector fields means that the orientation of particles in corresponding fields is important to the force it feels. For example, gravity seems to always pull down; there is a direction associated with the gravitational force, and as it seems, to all of the fundamental forces of nature… except the Higgs Field. The Higgs field is a scalar field, which makes sense if we think about it for a second. A particle moving around doesn’t seem to instantaneously change mass. This scalar characteristic means that the Higgs Boson has zero spin (whereas vector bosons associated with the above mentioned vector fields, such as the photon, do have spin.) This suggests that the Higgs mechanism requires a new force; a fifth force of nature.

By now, you’re probably thinking, “But what is the Higgs Boson? and what about the Higgs Field?” Well, to understand this a little better, let’s use an analogy to start with the Boson. You are walking outside when you see someone famous (pick your favourite person, anyone will do.) People start to notice this person, and everyone crowds. This crowding effect slows down the celebrity which is analogous to them becoming “heavier.” This is how you can think of particles acquiring mass in the Higgs Field. As particles couple to the Higgs Field, they acquire mass. Different particles couple to the Higgs Field differently (massless particles, like the photon, seem to not couple at all.) The origin of why certain particles couple more to the Higgs Field than others is not understood, nor is it understood how the Higgs Boson acquires mass itself (although it is believed that it is self-interacting.)

To understand the Higgs Field a little better, we can use another analogy. Imagine a ball sitting at the top of a large, steep hill. The position at the top of the hill is unstable, and will eventually fall with the slightest nudge. As the ball settles near the ground, we can imagine a groove along the circumference of the bottom of the hill that the ball can settle into. This is very much like the energy state of the Higgs Field; the most stable energy state of the Higgs Field (being at the bottom of the hill) has a non-zero value which you can imagine as below the x-axis (note image above.) The position at the top hill is a particle without mass, and the more stable position at the bottom is the particle having mass. The careful reader may have noted that at the bottom of the “hill,” there is negative energy. This would result in a saddle-shape universe, so to correct for this, physicists proposed the vacuum energy of the universe being greater than zero to “flatten” out the universe.

The search for the Higgs continues and only time will tell whether it exists and if so, whether we have the ability to detect it or not.

*Please note that mass is not weight. An objects mass never changes, but its weight can indeed change. When you go up in an elevator, you haven’t acquired any more mass but you feel heavier; your weight increased. Weight is a function of acceleration whereas mass is an intrinsic quality of an object. Since force (F=ma) is measured in Newtons, your weight should be measured in Newtons whereas your mass is measured in kilograms. So the next time someone asks you your weight, tell them your weight in Newtons and enjoy the looks that follow.

Sources: 1, 2, 3.