Level 1 · Foundations teaching kit · Grades 8–9
Space, time, motion, and reference frames
Use the learner record during the live investigation, then use the instructor guide to facilitate comparison, address misconceptions, and assess evidence-bounded reasoning.
Learner lab record
Two-frame light-clock record
How can laboratory time and distance change while the clock's own spacetime interval stays fixed?
Setup
Use the two-frame light-clock studio. Hold proper time fixed, vary v/c, and compare coordinate quantities with the recovered interval.
Predict first
- 1. Predict the laboratory distance at v=0.
- 2. Predict what happens to γ as v approaches c.
| Variable | Role | Unit |
|---|---|---|
| Relative speed v/c | independent | unitless |
| Clock proper time τ | controlled | µs |
| Laboratory time and distance | dependent | µs and km |
| Recovered interval cτ | invariant check | km |
Observation columns
Analyze
- 1. Which quantities depend on frame?
- 2. Which two columns should agree in every run?
- 3. Why is time dilation not an optical illusion?
- 4. State the model's inertial-frame limitation.
Conclusion frame
Although the laboratory measured ___ and ___, subtracting the spatial contribution recovered ___, equal to ___.
Instructor guide · 40–50 minutes
Teach the investigation, not the interface
Learning target: Learners distinguish coordinate descriptions from an invariant interval using a numerical light-clock model.
Prepare
- • Review events and reference frames.
- • Draw a stationary and moving light clock.
- • Prepare a low-speed and a high-speed comparison.
Facilitation moves
- • Ask what each clock directly records.
- • Keep c fixed in every explanation.
- • Return repeatedly to the same two endpoint events.
Accessibility and participation
- • Use a narrated triangle description instead of relying only on the SVG.
- • Offer a table with units preprinted.
- • Avoid rapid animation; the model is fully usable as static states.
Evidence of learning
- • Correct rest-limit prediction
- • Interval equality across at least three runs
- • Clear separation of coordinate and invariant quantities
Misconception checks
The moving clock only looks slow.
Different accumulated proper times between shared events are measurable and persist when clocks reunite.
Relativity means anything is subjective.
Observers disagree on coordinates while agreeing on invariant intervals and physical meetings.
Extension
Compare two piecewise-inertial paths and identify where acceleration enters a twin-style journey.