Moving clocks run slow, moving rulers shrink

Science · Quantum & Modern Physics · ages 18-19

Name ______________________ Date ____________

What is gamma at rest?
- 0
- 1
- Infinite
Why does the ground judge the ship clock slow?
- Its light traces a longer zigzag path
- Mirrors slow in space
- Ship time stops fully
Each frame sees the other clock run fast.
Circle one: True False
Gamma is 2 and the ship clock ticks 10 seconds. What time does the ground measure in seconds?
Answer: ______________
A fast rod flies past. What shrinks?
- Every direction equally
- Width across motion only
- Length along motion only
How does the ground frame explain muon landings?
- Muon clocks run slow so they live longer
- Muons outrun light
- Air stops all decay
A student contracts the rod width across motion. What is the error?
- Gamma only widens rods
- Rods cannot move fast
- Transverse sizes never change
How does the muon frame explain the same landing?
- Earth clocks run fast instead
- The air layer is contracted, shortening the trip
- Muons teleport downward

Answer key

For grown-ups. Fold this page away before handing over the rest.

1 · Zero speed leaves the square root at one.
Its light traces a longer zigzag path · A longer light path at fixed light speed means longer ticks.
False · The effect is symmetric, and each side sees slow.
20 · Ground time is gamma times ship time: 2 times 10 is 20.
Length along motion only · Contraction squeezes only the line of travel.
Muon clocks run slow so they live longer · Dilated lifetimes bridge the fall that should kill them.
Transverse sizes never change · Only the travel direction feels the squeeze.
The air layer is contracted, shortening the trip · In the muon rest frame the air rushes past, squeezed thin.