The Speed of light
Speed of light (in a vacuum) -
c = 299,792,458 m/s
This number is a physical constant, believed to be true everywhere in the universe. The letter c is used to represent the value being of constant celerity (speed).
By the way, it's hard to remember this exact number, and I wouldn't expect you to. However, here are some approximations that may make it easier to keep it in mind. The speed of light is approximately:
- 300,000,000 meters/sec
- 186,000 miles/sec
- 7 times around the Earth's equator in 1 second
- Out to the Moon in around 1 second (1.3 seconds is closer) - so, the Moon is approximately 1.3 "light seconds" away (on average)
- To the Sun in about 8 minutes - so, the Sun is approximately 8 "light-minutes" away (on average)
- To Mars in about 13 minutes, though this varies depending on the relative locations of Earth and Mars in their respective orbits
- To the nearest (non-Sun) star, actually a 3-star system (Alpha Centauri A and B, and Proxima Centauri) in 4.3 years. Yes, YEARS. So, that 3-star system is around 4.3 "light years" away from us. And that's our closest neighbors!! See why we don't get too far in space travel?
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