⚡ The Golden Rule: The speed of light (c) is exactly the same for every observer, no matter how fast they are moving. This forces time and space to behave strangely.
Welcome to this interactive journey through Einstein's Special Relativity. You'll witness one of physics' most mind-bending phenomena: time dilation.
The Setup:
Observer 1 (Blue) stands on the ground next to the train tracks.
Observer 2 (Orange) stands at the rear of an ultra-long train stretching 200 light-hours in front of them.
At the front of the train is a powerful lamp. At ground time t = 0 (Observer 1's start), the train will be moving at 0.999c (99.9% the speed of light), and the lamp emits a pulse backward.
Both observers measure the speed of this light as exactly c. But something extraordinary must happen to their sense of time...
Phase Title
Special Relativity — Time Dilation
Train at v = 0.999c · Lorentz factor γ ≈ 22.37 · Rest length = 200 light-hours
📱 Tip: Rotate your phone sideways for the best view!
Observer 1 · You, standing on the ground
Ground (stationary) reference frame
00:00:00.000
Your clock ticks normally. This counts how much time has passed for you since the lamp fired.
Observer 2 · Passenger at the rear of the train
Moving train reference frame
00:00:00.000
This clock runs ≈22.4× slower as seen by you. The passenger ages more slowly. This is proper time t′ = t ÷ γ.