Time Dilation

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Time Dilation

Time dilation causes a moving clock to run slower.

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Time dilation

  • Time is different at different velocities within an inertial frame of reference.
  • As velocity increases, time will run slower:
    • t=t01v2c2t = \frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}}
    • t is the moving time.
    • t0t_0 is the time at rest.
    • v is the velocity of the mover.
    • c is the speed of light.
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Lorentz factor

  • The factor by which time dilates is called the Lorentz factor.
    • γ=11v2c2\gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}
  • This determines how much time will differ.
  • As velocity approaches the speed of light, time will slow down.
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Proof of time dilation

  • Muon decay provides proof of time dilation.
  • Muons have a very short half-life, and should decay before they get through the atmosphere.
    • However, muons are still detected on the surface of Earth.
  • This is because muons travel so quickly, that time dilation provides them with more time to move.

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1Measurements & Errors

2Particles & Radiation


4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

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12Option: Turning Points in Physics (A2 only)

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