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Modern Physics

Relativity, quantum mechanics, and the strange truths discovered when we looked closely enough at the universe.

The speed of light explained — a light beam crossing from Earth to the Moon, c = 299,792,458 m/s

The Speed of Light Explained

The speed of light (c) is exactly 299,792,458 m/s — the fastest anything can travel and the universe's ultimate speed limit. Here's what that means, why it's constant, and how to work with it.

Special relativity light clock diagram showing time dilation at near light speed

What Is Special Relativity?

Special relativity explains how time, length and energy change near the speed of light. Master Einstein's two postulates, the key formulas and the twin paradox — with worked examples.

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