HowDoWhy

After years of “close” estimates, the speed of light was nailed down to 299,792.458 kilometers per second or 186,282.397 miles per second in 1983. Previous estimates came surprisingly close to the mark given how difficult it must be to put a limit on something as fast as light. We also know that the speed of light is a constant (which will become important if anybody ever asks me about relativity). It’s also important to understand how fast light moves as it will become a relevant measure of distance in subsequent posts.

Some facts about light:

• It takes light leaving the surface of the Sun a little more than 8 minutes to reach the Earth.
• It takes light traveling from the center of the Sun about 1 million years to reach us. Not because it is moving any slower but because the Sun is so densely packed that a particle of light keeps getting bounced around rather than traveling in a straight line as it moves from the center outward.
• If you watch somebody bounce a basketball or clap their hands from far away, you’ll notice that the sound of the ball or clap is out of synch. That’s because the light that allows you to see the action of the clap or bounce travels MUCH faster than the actual sound of the event.
• A beam of light is made up of all the colors of the rainbow.
• Your eye sees colors because an object absorbs some of the color of light and reflects others. A lemon absorbs the yellow spectrum of light more poorly than other colors so you see a lemon as yellow because yellow is what is reflected off the lemon and towards your eye.