Twin Paradox Clock

SPECIAL RELATIVITY

One twin stays on Earth. One twin flies to a distant star or galaxy near light speed, turns around, and comes home. Who is older?

MISSION SETUP (CHOOSE THEN PRESS BEGIN)
We ignore fuel, turning physics, and cosmic expansion for far targets.

Ship speed

v = 0.800 c

Time scale

1 sec = 1 year

Destination

Proxima Centauri — 4.24 ly

PREDICTION (BEFORE LAUNCH)

Destination

Proxima Centauri

Distance (one way)

4.24 ly

Earth frame: round trip

~? years

Traveler's own time

~? years

You come back younger by

~? years

Lorentz factor γ

1.6667

Time slowdown

Ship clocks tick 1.67× slower

Status

Idle / pre-launch

EARTH TWIN

00y 00d 00:00:00

Time that passes on (or near) Earth.

TRAVELER TWIN

00y 00d 00:00:00

Proper time experienced by the traveler.

MISSION STATE · OUTBOUND → TURN → INBOUND → REUNION

Phase: STANDBY Trip not started. Press BEGIN MISSION.

Current leg

STANDBY

Earth time elapsed (sim)

0.00 y

Age gap now

0.000000 years

Mission result

–

For very distant targets (millions+ ly), we pretend the universe does not expand and we allow perfect turnarounds. This is a teaching simplification.