Twin paradox
A thought experiment on relativistic time dilation and aging.
The twin paradox is a thought experiment in special relativity involving twins, one of whom takes a space voyage at relativistic speeds and returns home to find that the twin who remained on Earth has aged more. This result appears puzzling because each twin sees the other as moving, leading to an incorrect naive application of time dilation and the principle of relativity. However, the scenario can be resolved within the standard framework of special relativity, as the travelling twin's trajectory involves two different inertial frames or acceleration, breaking the symmetry between the twins' spacetime paths.
- field
- Physics
- known_for
- Thought experiment in special relativity illustrating differential aging
- first_described_by
- Albert Einstein (1905)
Lore & Background
In his 1905 paper on special relativity, Albert Einstein deduced that a clock moved from point A to B would lag behind a stationary clock at B, and considered this a natural consequence, not a paradox.
Reader's Guide
The twin paradox has been central to understanding special relativity, demonstrating that time dilation is not symmetric between observers who follow different spacetime paths. However, it has been proven that neither general relativity nor acceleration is necessary, as the effect still applies if two astronauts pass each other at the turnaround point and synchronise their clocks. The paradox is not a logical contradiction but a consequence of the asymmetry in the twins' trajectories.
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