Lecture Videos

• Relativity, motion is always relative
• For relativity, point of view matters
• Reference frame is the point of view that is used to measure speed
• All motion is relative.
• Einstein's special relativity hinges on two postulates (ideas for testing a theory):

  1. All laws of nature hold true in all inertial reference frames.
  2. The speed of light is always measured to be the constant c.
• Inertial here means "moving at constant velocity relative to another inertial reference frame." Basically, that RF cannot be accelerating in any way, including increasing or decreasing speed, or changing the direction of its velocity. This means that a spinning RF is not inertial. The reason that I'm bringing this vocab word in now is because most folks use it to describe an RF with constant motion.
• The first thought experiment is simultaneity. The result of the thought experiment is that events that are simultaneous in one RF are not necessarily simultaneous in another RF.
• Two events that are simultaneous in one reference point are not necessarily simultaneous in another reference point.
• The faster something moves relative to you, the slower it's time ticks compared to yours. We did not get to talk about length contraction, but it is related to time dilation, as a faster object ticks for less time, then it cannot move as far because it experienced less time.
• The faster something moves relative to you, the slower it's time ticks compared to yours. We did not get to talk about length contraction, but it is related to time dilation, as a faster object ticks for less time, then it cannot move as far because it experienced less time.
• Kepler has three rules, one is fairly obvious, another is reasonable, but the other one seems made up and otherwise doesn't have an obvious reason to exist.
• Kepler's Laws

  • orbits are elliptical
  • the area swept by an orbit per unit time is constant
  • period sqare is proportional to the axis length cubed
• Fields are something we have largely avoided due to them being mathematical tools and our aversion to math. 
• Gravitational Fields -> force field
• Force fields are a description of a force over some space
• Gravity is an attractive force
• A force fields tells you what force would be felt at that location
• Causality, if event A is going to effect event B, they must be separated by less than 8 light minutes.
• Three dimensions (x, y, z)
• A black hole is what happens when gravity becomes so strong that not even light could escape.
• Conservation of energy, escape velocity