Berman also described part of **special relativity** — Lorentz transformations (shown) — in his article. Special relativity tells us that no privileged reference frames exist. If I am traveling at 60 mph (100 km/h), and you are standing still, our difference in velocity is 60 mph. But I could just as well imagine that I am standing still, and you’re the one who is going 60 mph. Though this seems simple, it has significant consequences: The speed of light is the same all the time, and time moves more slowly and lengths contract for those traveling fast. If you apply special relativity to gravitation, you get **general relativity**.