🕰️ Relativity — Intermediate#

Scope — Special relativity, spacetime structure, and measurable relativistic effects.

Key concepts#

• Time dilation — moving clocks run slower relative to stationary observers.
• Length contraction — objects shorten along the direction of motion at high speeds.
• Spacetime — unified four‑dimensional framework combining space and time.

Seed Q&A triads#

• Q: How does time dilation arise?
  A: From the requirement that light speed remains constant for all observers.

• Q: What is length contraction?
  A: The shortening of objects measured in the direction of relative motion.

• Q: Why combine space and time into spacetime?
  A: Events are best described by coordinates that mix space and time consistently across frames.

Short exercises#

• Calculate time dilation for a fast‑moving spacecraft relative to Earth.
• Analyze the ladder–barn paradox using relativity of simultaneity.