Fentometers are used as a unit of measurement in the atomic world. They're \(10^{15}m\).

For speed we use fractions of the speed of light c ~\(3*10^{8}m/s\)

Volts are used for charge.

Particle Masses can also be expressed in eV units. Particle masses are actually pretty large with the eV unit.

Planck Size is about \(10^{-35}m\)

Angular Momentum can be measured in h-bars which are Planck's constant divided by 2π

• The nucleus takes up a very small amount of a particle
  • Comparison drawn here is a basketball in an airport for a large nucleus and a golf ball for smaller ones
• Electrons occupy in a probability distribution the rest of the space more or less
• The only viable way to measure distances that small are through scattering experiments involving shooting electrons at say a proton and observing the scatter pattern
  • The diameter of 1 proton is approximately 1 fermi
• We live in a relative distance average
• Short Wavelengths can also be observed to estimate the size of such small particles
• The Planck size is the smallest meaningful distance before spacetime breaks down into quantum foam

• The fastest anything can go so far as we know is the speed of light
• It's hard to get anything close to the speed of light, but for stuff like particle accelerators and cosmic rays it isn't super uncommon to get close
• Mass being the reluctance to accelerate means that the mass-less photon should be the fastest particle requiring no energy to reach the speed of light. For anything to go faster would be difficult.
  • However, physicists have studied the Tachyon which is theoretically capable of doing so but has not been discovered and also creates strange circumstances

• The longest known time is the lifespan of the universe
  • This is currently estimated to be about 13.7 billion years
• The speed of light is the natural link between distance and time measurements

• Mass is a measure of inertia meaning how hard something is to accelerate
• We measure particle's speed by measuring their resistance to acceleration with knowledge of their speed
• With particle masses it becomes more sensical to use MeV instead of kg since the units make more sense

• Energy and its conservation make it perhaps one of the most important things in physics
• Kinetic energy and mass energy are the most important types when it comes to particles
  • Rest mas is different from mass
• Mass represents a highly concentrated form of energy
  • A little mass leads to a lot of energy while a lot of energy can yield a little mass
• In the subatomic world mass and energy are typically both measured using the electron volt

• Electric charge is that thing that makes a particle attractive to another type of particle
• If the Gluons are overcome by the repulsion of the protons a nucleus will break apart
  • This is why there is a cap for how large an atom can be realistically since it would require too much energy to keep together than the gluons can offer
• Negative and positive is entirely arbitrary they are just opposites

• Spin occurs with anything from the largest galaxies down to the smallest particles
• Angular momentum is used to measure both orbital motion and rotation on one's own axis
  • Fundemental particles have measurable angular momentum, but a rate of rotation cannot be specified
    • Planck's constant divided by 2π is the fundamental quantum unit of rotation
• Difference in spin is drastic enough for us to call particles with different spin new particles
• All electrons have the same spin
  • Spin is quantized and things such as electrons are either "up" or "down"