Particle Physics Teacher Sheet

Particle Physics Teacher Sheet


Students can continue their investigation of modern atomic theory by exploring the history and science of particle physics and the advent of the quantized atom, leading to the recent theory of the Standard Model. This sheet provides answers to the questions they should answer.

A Summary of Particle Physics

What questions did scientists seek to answer about the fundamental structure of matter by the mid-1930s?
They wanted to know (1) what held the protons and neutrons together to form the nucleus and (2) what forces were involved in the radioactive decays of nuclei that make alpha, beta, and gamma rays.

How did the use of accelerators advance and propel the study of the subatomic world?
Accelerators were a tool that allowed scientists to go deep inside the tiny nucleus and study the interactions between protons and neutrons. Accelerator experiments also, surprisingly, uncovered a whole world of other subatomic particles.

What was significant about the quark proposal of 1964?
Gell-Mann and Zweig’s revolutionary proposal suggested that all the protons, neutrons, and other new particles could be explained by these smaller, electrically charged, “fundamental” objects. Quarks would become part of the Standard Model of Fundamental Particles and Interactions.

In terms of particle forces and interactions, why has gravitational forces been excluded from the Standard Model?
They have been excluded because their “effects are tiny in particle processes and, furthermore, physicists have not yet figured out how to include it.”

Why are strong and weak interactions important?
They hold quarks together and allow them to change and decay. This is very significant because quarks are fundamental, and we depend on their strong and weak interactions “for the existence of all the stuff from which the world is made, and for the decay processes that make some types of matter unstable.”

In what sense is today’s Standard Model incomplete? How do particle physicists plan to answer the questions that remain?
Accept all reasonable questions and answers from the “What Questions Remain” section of this resource. Scientists plan to build and experiment with bigger, better accelerators to answer the deeper mysteries on the particles, objects, forces, interactions, and patterns that remain in the lowest levels of the subatomic world.

Particle Physics Timeline

Which discoveries do you think are the most significant, interesting? Why?
Accept all reasonable answers.

Which discoveries do you think are the least significant, interesting? Why?
Accept all reasonable answers.

What inventions or benefits to society do you think subatomic discoveries like these are going to lead to?
Accept all reasonable answers.

What other kinds of subatomic discoveries do you think scientists might uncover in the years ahead?
Accept all reasonable answers.

What problems or dangers do you foresee coming from this level of high-powered, scientific investigation? Is the world better off not knowing how the subatomic world works? Why or why not?
Accept all reasonable answers.

How does learning the history of modern atomic theory help you in your scientific studies of the same subject?
Accept all reasonable answers.

This teacher sheet is a part of the The History of the Atom 5: The Modern Theory lesson.

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