Murray Gel-mann

The Scientists Behind the Atom:

Murray Gell-Mann

Scientists had once thought that the atom's protons, neutrons and electrons were not composed of any smaller particles. However in the late 1960's Gell-Mann proposed that particles like protons and neutrons were created by a combination of different types of even smaller particles named "quarks".

THE END!

Who is he?

Gell-Man and the Atomic Theory

Personal Life

What are Quarks?

Types of Quarks

The Discovery of Quarks

Gell-Mann was born in Manhattan into a Jewish family on September 15, 1929. As a child, he had a keen interest for mathematics and nature. He graduated high school as the class valedictorian and entered Yale at age 15. He later attended MIT for his PhD and received the 1969 Nobel Prize physics award for his work on elementary particles.

Quarks combine in groups of three to give their hadron a net charge with their fractional charges. Therefore, there are different quark flavours (types). Each one of them has a unique mass. Scientist classify them as such:

Murray Gell- Mann performed a series of inelastic electron neutron scattering experiments between 1967 and 1973 to prove the theory of Quarks as the true elementary particles.

Quarks are the building blocks of neutrons and protons and therefore one of the elementary particles that make up everything around us. Protons and neutrons are both hadrons. Hadrons are particles that interact by strong interaction. The atom's protons and neutrons classify as hadrons because they are composite particles that are given their net charge because of bundles of two or three quarks. Individually, quarks have a fractional charge, however they combine as such to give particles like protons and neutrons their net charge.

It has now been proven that atoms are made up and can emit many types of subatomic particles. However, the reason why electrons are not made up of quarks is becuase they do not classify as a hadron but as a lepton instead. This means that electrons like other leptons are solitary particles unlike quarks which are always composite.

The 'flavours' of a quark can also change from on to the other like so:

up (u) -> down (d)

charm (c) -> strange (s)

top (t) -> bottom (b)

Some people didn't believe his theory because they are located inside particles like protons and neutrons and can't be isolated. Therefore, they cannot be seen through a microscope or brought out to be examined.

The different flavours of quarks combine with each other to make the different types of hadrons - baryons and mesons . Baryons are made up of three quarks whereas mesons are composed of two quarks- a quark and an anti-quark. Protons and neutrons both fall under the baryons category as they are made of three quarks instead of two.

Matter is ultimately made of quarks

Diagram of the quarks in the neutron and the proton

Gel-Mann teaching about quarks

The Eight-Fold Theory

The Standard Model

The standard model is a collection of theories, including Gel-Mann's contributions, that represent the elementary particles. The model classifies all of the subatomic particles known to man and regards all of their nuclear interactions.

To prove that quarks existed, Murray Gell-Mann proposed the eight-fold theory. He realized that many of the known particles could be fit into a series of families based on an abstract mathematical construct. He called his theory the Eightfold Way. In other words, he organized subatomic baryons and mesons into octets.

Baryon octet

Meson octet

Standard model of elementary particles

Explained standard model

Quiz

1. In which subatomic particle(s) can you find a quark?

2. How many types of quarks are there?

3. What type of quark is a proton?

4. Why didn't people believe Gel-Mann's quark theory at first?

5. What does the standard model classify?