Twin Paradox and Other Relativistic Paradoxes
Paradoxes are usually frame mistakes
Twin paradox
In the twin paradox, one twin travels at high speed and returns younger than the twin who stayed on Earth. The situation is not symmetric because the traveling twin changes inertial frames during the turnaround.
Acceleration matters
Special relativity handles inertial frames directly, but acceleration breaks the symmetry. The traveling twin’s worldline contains a turn, so the elapsed proper time along that path is smaller.
Core resolution
The twin who experiences less proper time along their worldline ages less, even if each inertial segment can be analyzed separately.
Other paradoxes
Common paradoxes include ladder-and-barn, pole-and-barn, and simultaneity puzzles. Each is resolved by careful attention to which events are simultaneous in which frame.
Why is the twin paradox not truly symmetric?
The traveling twin accelerates during turnaround and therefore does not remain in a single inertial frame.
Correct answer: Because one twin changes inertial frames
What determines which twin ages less?
The twin with the smaller accumulated proper time ages less.
Correct answer: Proper time along the worldline
Apparent contradiction vs. actual resolution
Apparent contradiction
- Each twin may claim the other is time dilated
- This seems to imply symmetry
Actual resolution
- Worldlines are different
- The traveling twin has smaller proper time