(455) HL Special relativity introduction [IB Physics HL]

Definition: A theory developed by Albert Einstein applying to non-accelerating reference frames moving at constant velocity.
Meme Reference: "Bad puns make me relatively angry."

First Postulate: The speed of light (C) is constant in all inertial (non-accelerating) reference frames.
- Implication: Closure speed does not exceed the speed of light. Example of two cars both driving at 100 km/h coming towards each other appears as 200 km/h from one car's perspective but does not apply at speeds approaching C.
Second Postulate: The laws of physics are the same in all inertial frames.
- Example: Tossing a ball in a moving vehicle or standing still produces the same outcome as long as there's no acceleration.

Gamma (γ): A useful tool in relativity representing time dilation and other phenomena.
Formula: γ = 1 / √(1 - v²/c²) where v is the velocity of an object and c is the speed of light.
- Behavior: As velocity (v) approaches the speed of light (C), gamma approaches infinity, leading to strange time behaviors.

Used to convert measurements from one inertial reference frame to another.
Synchronization of clocks occurs at T=0 in two frames (S and S prime).
Agreements on measurements of Y and Z, but not on positions or time—indicating the relativity of time.

Applies to different references: speed of a moving frame with respect to a stationary observer.
- Example: When observing two spaceships approaching each other at 7C as seen from Earth, the observed speed from one spaceship's perspective is calculated using U' = U - V formula, demonstrating closure speed remains less than C.
- Closure speed of approaching spaceships calculated as 0.94C, not exceeding the speed of light.

Special relativity showcases how measurements, time, and speed are relative depending on the observer's frame of reference, challenging classical assumptions about speed and motion.