Brady F. Anderson

Six Easy Pieces: Essentials of Physics Explained by Its Most Brilliant Teacher

My Notes

General Knowledge

Each law is only an approximation of the complete truth. These laws are necessarily approximations because we don’t know all the laws yet. We face an expanding frontier of ignorance.

The fundamental principle of science: the test of all knowledge is experiment.

However, experiment isn’t sufficient. We need imagination to bridge the gap between experimental hints and the brilliant generalizations that end up becoming our laws.

How to tell whether a rule is correct:

  1. A situation is, or may be arranged to be, so simple that we can predict what will happen and thus check our rule.
  2. See if we can prove less specific rules that would follow from our rule. E.g., If bishops move diagonally is our general rule, then a less specific rule is bishops will always be on the same-colored square.
  3. If you can approximate what will happen next, even though we don’t understand why everything happens the way it does, then we have a functional rule. E.g., A new viewer doesn’t understand why football players run or pass the ball but can interpret that the purpose of each play is to help move from one side of the field to the other.

Tycho Brahe decided that to find out the motions of the planets the best method would be to measure the actual positions of the planets. This was revolutionary: instead of engaging in philosophical debates prevalent at the time, Brahe decided experiment was a better pathway to truth.

Specific Knowledge

The “law” mass is constant, independent of speed, has ended up being false. Mass increases with velocity, but this effect only becomes noticeable near the speed of light. Even though the first intuition is true in most situations we will encounter, the newer finding requires us to make a profound change in our idea to arrive at truth.

How to think of atoms: “If an apple is magnified to the size of the earth, then atoms in the apple are approximately the size of the original apple” (5).

A hypothesis that always feel weird to think about: everything that living creatures do, atoms do. Philosophers of the mind have struggles with this subsequent question: is conscious experience caused by the particular, neurological, atomic arrangement of our brains or is conscious experience merely that arrangement?

Tyco Brahe’s data was foundation for Kepler’s laws:

  1. Each planet goes around the sun in an ellipse, with the sun at the focus of the ellipse.
  2. Planets move faster when they are near the sun, and slower when they are farther away.
  3. The time it takes a planet to go around the sun is proportional to the size of its orbit.

Quantum mechanics: The description of the complete behavior of matter, in particular on an atomic scale.

The Uncertainty Principle: it is impossible to measure both momentum and position at the same time. No one has yet found a way around this problem. This is a crucial hypothesis of quantum mechanics: we will never have a complete description of the behavior of matter that is accurate.

A huge Implication of quantum mechanics: “it is impossible to predict exactly what will happen in any circumstance” (35). This means that if we set up the same conditions for an experiment, it is not the case that the same experiment will always yield the same results. We can only find the statistical average as to what will happen.