Category Archives: Universe

The smuggest of all quarks, the charm quark was given such a fancy name because the physicists that discovered it were delighted with the symmetry it brought to their models.

The strange quark, ostracized by the other, more normal quarks, almost had an even weirder name — because the different kinds of quarks are also called “flavors,” the three initial quarks were originally known as vanilla, chocolate and strawberry.

Down quarks are the second-lightest particles of the bunch, and that’s about all they have going for themselves. Still, things wouldn’t work out without them: One up quark and two down quarks make a neutron, while two up quarks and one down quark make a proton.

Quarks are the “nuclear” family of particles. They exist at a scale where the strong nuclear force dominates. It glues these particles together into groups called hadrons; trying to separate them just creates new hadron groups through a process called color confinement. The most common hadrons in the Universe are the protons, made of two up quarks and one down quark, and the neutron, mode of two down quarks and one up quark. Quarks don’t have a true size, since they are wave—like and the wavelength is determined by their energy and what they are doing. The sizes we used here are typical for the bundles we find them in.

The quark with the lowest mass of all quarks, the up quark, is also the most common quark in the Universe: two up quarks are found in every proton and one in every neutron. Because of their abundance, up quarks are responsible for most of the mass of atomic matter in the Universe.

Many subatomic particles are highly partisan: they like to think in black or white and want you to pick a side, negative or positive. Neutrons skip the drama and keep to a neutral charge. While they don’t affect an atom’s atomic number or electrical charge, they do affect its mass.

Just how small is a proton? A proton is to a grain of sand what a grain of sand is to the Sun. Thinking about it that way, it’s incredible that we even know about protons. Imagine a species of giant humans so big that our Sun was the size of a grain of sand in their hand and our Earth would only be visible to them under a microscope. Now imagine that that species knows how to study grains of sand on that microscopic Earth. That’s what it’s like for us to study protons.

You might not think much about the helium nuclei. But it’s specifically their creation that powers the Earth and everything on it. When four hydrogen atoms are squeezed together tightly enough in the center of the Sun, they combine into a helium nucleus. This is the process of nuclear fusion that gives the Sun its energy.

Chlorine is the third most abundant element in the ocean after oxygen and hydrogen. 1 liter of ocean water has 19 grams chlorine. You might know that chlorine is the stuff we put in swimming pools to kill germs but we have it diluted to no more than 3 milligrams per litre, over six thousand times less than in ocean water! If so, how come the oceans aren’t immensely toxic pools of death, but filled with living things? Well, the chlorine for killing germs in pools is free chlorine (hypochlorite, ClO-), the highly reactive form ready to kill nasty germs. In the ocean, chlorine floats around as chloride ion (Cl-) which is coming from the dissolved salts and not in its killer reactive state. Very good for all the living things in the ocean!

Uranium is pretty stubborn: its half-life — that means the time it takes half of its atoms to decay — is a whopping 4.5 billion years. Uranium is the main source of heat inside the Earth, but its power can also be harvested artificially through fission: a much faster way to split uranium isotopes.

If you think a supernova explosion is bright, you don’t even know half of it! When a star’s core collapses to make a neutron star, almost every single electron gets converted to a high energy neutrino. In fact, only 1% of the energy of a supernova is in light — the other 99% is invisibly carried away by neutrinos. The Universe is teeming with neutrinos from past supernovae, with so much energy that they can cause nuclear reactions on the rare occasions they interact with atoms on Earth.