![]() ![]() If aliens lived in those galaxies, and had strong enough telescopes, they would see the Earth as it looked in the past. For example, the galaxy M109 is located about 83.5 million light-years away. There are galaxies millions of light-years away, which means the light we're seeing left the surface of those stars millions of years ago. And so, if the light from the nearest star (Alpha Centauri) takes more than 4 years to reach us, we're seeing that star 4 years in the past. The Sun is more than 8 light-minutes away. The light reflected from the surface of the Moon takes only a second to reach Earth. ![]() The light you see from your computer is nanoseconds old. Once they escaped the surface, it was only a short 8 minutes for those photons to cross the vast distance from the Sun to the EarthĪs you look outward into space, you're actually looking backwards in time. What you probably don't know, is that these photons striking your eyeballs were ACTUALLY created tens of thousands of years ago and it took that long for them to be emitted by the sun. They start off as gamma radiation and then are emitted and absorbed countless times in the Sun's radiative zone, wandering around inside the massive star before they finally reach the surface. You probably know that photons are created by fusion reactions inside the Sun's core. ![]() And then at the most distant point, it takes 507 seconds for sunlight to make the journey.īut the story of light gets even more interesting, when you think about the journey light needs to make inside the Sun. At its closest point, sunlight only takes 490 seconds to reach Earth. Remember, the Earth follows an elliptical orbit around the Sun, ranging from 147 million to 152 million km. Divide these and you get 500 seconds, or 8 minutes and 20 seconds. ![]() Light moves at 300,000 kilometers/second. We orbit the Sun at a distance of about 150 million km. ![]()
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