Sergey has a Masters in Biomedical Engineering and has taught science and mathematics courses at the University of Wisconsin-Madison.
Imagine taking a block of butter and cutting it in half. After doing that, you take one of the resulting pieces and cut that one in half, and then do it again for the smaller pieces that follow, over and over. For the purposes of this thought experiment, your knife is infinitely thin, and you can keep going for an indefinitely long time. Initially, you will see smaller and smaller chunks of butter, until they become invisible to the naked eye. As you keep going, you will get down to the level of molecules, individual atoms, and finally subatomic particles.
You may be familiar with protons, neutrons, and electrons, which are the basic constituents of atoms. The protons and neutrons make up the nucleus of an atom, while the electrons orbit around this nucleus. However, even protons and neutrons are made up of more elementary particles, called quarks, which you can think of as tiny entities that are among the most basic constituents of all matter.
Let's proceed to take a closer look at these particles.
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Quarks: A Closer Look
There are six types, also known as flavors, of quarks: up, down, strange, charm, bottom, and top. These flavors differ based on mass and electric charge. By the way, the electric charge property I just mentioned is the same one that exists in electric circuits or that causes a hair brush to attract small strips of paper after you brush your hair with it. The 'up', 'charm', and 'top' quarks have a positive charge of +2/3, while the 'down', 'strange', and 'bottom' quarks have a negative charge of -1/3. Don't worry about the numbers, but remember that opposite charges (positive-negative) attract, while like charges (positive-positive or negative-negative) repel each other.
The masses of quarks, from heaviest to lightest, are as follows: top (heaviest), bottom, charm, strange, down, and up (lightest). Keep in mind that since we are talking about elementary particles, you can think of their masses as just another property that characterizes them. After all, you can't really weigh quarks on your scale at home.
Another property of quarks is color, also referred to as color charge. In order to satisfy the Pauli Exclusion Principle, which asserts that no two quarks can exist in the same quantum state at the same time, the property of color was ascribed to quarks. Three colors could be assigned to individual quarks, and a common color scheme is red, green, and blue.
For the purposes of our discussion, it's important to mention that every quark has an antimatter particle associated with it, called an antiquark. You can think of antiquarks as quarks with opposite electric and color charges.
In nature, quarks and antiquarks are only found existing in groups of two or three. One type of composite particles that result from these groupings are called hadrons. Hadrons are categorized into baryons and mesons. Baryons include protons and neutrons, which are comprised of three quarks each. Protons are composed of one 'down' and two 'up' quarks, while neutrons are composed of one 'up' and two 'down' quarks.
On the other hand, mesons are made from quark-antiquark pairs. For example, a pion particle is composed of a 'down' antiquark and an 'up' quark. It's important to note that mesons are unstable and decay into other particles after a very short time.
To recap, quarks are considered to be among the most elementary particles in existence. They're the constituents of protons and neutrons, as well as other particles. In addition, quarks have properties such as mass, electric charge, color charge, and others. They even have antiparticles associated with them, known as antiquarks. Quarks also come in six types, also known as flavors, of quarks: up, down, strange, charm, bottom, and top, with top being the heaviest (or most massive) and up being the lightest (or least massive).
The property of color, or color charge, was also ascribed to quarks in order to satisfy the Pauli Exclusion Principle, which asserts that no two quarks can exist in the same quantum state at the same time. Quarks are also only found in nature in groups of two or three, and these groups form composite particles known as hadrons. Hadrons are made up of baryons, which include protons and neutrons, made up of three quarks each, and mesons, which are made from quark-antiquark pairs.
So the next time you're buttering your toast, remember how small you can go with your slices, and think of quarks.
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What is a Quark? - Definition, Structure & Uses
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