Einstein realized that the speed of light—about 186,000 miles per second—is constant whether it comes from a moving source such as a speeding car's headlights or an unmoving source such as a ...

A new method for manufacturing lightsails that can reach up 20% of the speed of light is making the technology look more ...

A series of new animations by a NASA scientist show just how zippy — and also how torturously slow — the speed of light can be. Light speed is the fastest that any material object can travel ...

Forces and the final velocity of objects can be determined. The speed of light is constant but length and time can change when objects travel at close to the speed of light. These changes depend ...