Subatomic Particles: The Quantum Realm

From the Lecture Series: Understanding the Misconceptions of Science

By Don Lincoln, Ph.D., University of Notre Dame

Inside an atom is mostly an empty space, a dense nucleus with the greatest force ever known, and particles called quarks that have not yet been seen. In fact, the quarks might have zero size, while they zoom around neutrons and protons nearly at the speed of light. The electrons are also everywhere they can be, simultaneously. Well, the quantum realm is a strange place.

Particle, quantum entanglement (quantum correlation). Quantum mechanics . 3d illustration
There is a world of considerable energy in the heart of an atom, creating most of the mass of all objects. (Image: Jurik Peter/Shutterstock)

Quarks inside the protons and neutrons are so small that they have not yet been spotted by any equipment. The strongest device in this regard is a particle accelerator in Europe called the Large Hadron Collider, which lets us resolve the size of objects as small as 5*10-20m, i.e., 1/2000 size of a proton. Anything smaller than that might go unnoticed, and quarks might be smaller.

How Big Are the Quarks?

The quark does not necessarily have a size of 5*10-20m. It might even have zero size, but that is also a theory. Considering this theory as reality, the proton can be as big as a basketball and the three quarks as small as three small grains of sand, or even smaller. Quarks move around the proton or neutron nearly with the speed of light. Just like the atom, the proton and neutron are also made essentially of empty space.

However, the forces that keep the quarks together are massive. Unlike on Earth, there is no field and no gravity inside the proton.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, on The Great Courses Plus.

Forces in the Quantum Realm

Things in the world of subatomic particles are not as easy to imagine and comprehend as things happening on Earth. In the 1940s, American physicist Richard Feynman began to investigate subatomic forces. He found out that there was no gravitational field in a, say, proton. Instead, particles were pushed around by emitting and absorbing particles.

Quark Fusion - Quark Power - Abstract 3D Illustration
The movements and forces inside the atom nucleus are not easily describable through gravitational fields and laws. (Image: GiroScience/Shutterstock)

Imagine shooting a rifle: as the bullet leaves the gun, the one who has shot feels the recoil. When the bullet hits an object, the object will go flying as a result of the force. The same happens in a proton.

In a proton or neutron, there is a particle carrying the force and keeping the proton together. It acts like glue and is thus called the gluon. The gluon is what the quarks are emitting and absorbing. Hence, inside a proton, there are not only the quarks zooming around. There are also the gluons jumping back and forth between the quarks, and some gluons are even interacting with other gluons. The empty space in the protons, neutrons, and the atom still remains. So, where does mass come from?

Learn more about untangling how quantum mechanics works.

Mass and Energy

Everything is made of atoms, and everything has a mass. However, the atom is essentially empty space. Protons and neutrons have almost the same mass and are called nucleons, in general. A nucleon’s mass is about 1836 times that of an electron. If the mass is rounded up to 2000, the electrons can be ignored. The mass of an object is almost equal to the sum of the nucleons’ mass, creating that object. But the nucleons also have a considerable empty space inside.

The gluons are massless, so each quark must have a mass equal to one-third of the nucleon, but they do not. The sum of the mass of all quarks in an object is around only 2% of the total sum. The speed of the quarks is close to the speed of light, which means they contain considerable kinetic energy. Quarks zoom around in the space of 10-15m across, and keeping such a fast object in such a small place requires enormous forces, hence, creating massive potential energy.

Learn more about untangling what quantum mechanics means.

Relativity in Subatomic Particles

Quarks are made of 2% mass and 98% potential and kinetic energy. Einstein’s relativity equation, i.e., E=mc2, claims that energy and mass are equivalent. Thus, 2% of any object’s mass is the mass of quarks, and the remaining 98% is solely energy. Essentially, everything is mainly force fields, not ‘stuff’ that has mass.

Image of color atoms and electrons. Physics concept
About 98% of the mass of everything is made up of the extreme energy in protons and neutrons, not the mass of quarks inside them. (Image: ESB Professional/Shutterstock)

There is more in the atom: virtual particles of matter and antimatter that last only a moment. They add to the complexity of the image, as they appear everywhere in the universe, from the deep space to the core of atoms

The final image of an object would be mainly energy held together by force fields in the protons and neutrons, nuclei, atoms, and molecules creating the object. This is explainable in the quantum realm. Science has a considerable lot to do to complete that image and know what really happens in any scale of the world around, or in, us.

Learn more about how relativity is misunderstood.

Common Questions about Subatomic Particles

Q: How many subatomic particles are there?

So far, 36 confirmed fundamental particles are discovered. They include anti-particles as well. Subatomic particles are of two types: elementary and composite particles. They can last as short as a moment and be found everywhere in the universe, not just inside the atom nucleus.

Q: What type of forces hold subatomic particles together?

Subatomic particles are held together by two types of forces: the nuclear force and the electromagnetic force. This is the strongest force known so far to mankind. It has to keep particles moving at nearly light speed in an extremely small space, so it is the strongest force discovered so far.

Q: What are the 12 fundamental particles?

There are more than 12 subatomic particles, but the 12 main ones include six quarks (up, charm, top, Down, Strange, Bottom), three electrons (electron, muon, tau), and three neutrinos (e, muon, tau).

Q: What is a quark?

A quark is a subatomic particle found inside the protons and neutrons. They are considerably smaller than the protons, leaving much empty space inside the protons and neutrons. Quarks are 2% mass and 98% energy, but they create the heavy mass of the nucleons, based on Einstein’s relativity theory.

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