Here's a question ....... How Long Does It Take Sunlight To Reach Earth? Though it sounds a bit strange but, it's worth thinking. We all know that the sunlight travels at the speed of light (obviously). The photons emitted from the surface of the Sun needs to travel through the vacuum of space and Earth's atmosphere to eventually reach our eyes.
The short answer is that, on an average it takes sunlight 8 minutes 20 seconds to reach Earth.
The speed of light is 299,792,458 meters per second. (299,792.458 kilometers per second!)
At the same time, the distance between the Earth and Sun on average is 149.6 million kilometers. We all know that the Earth revolves around the Sun in an elliptical orbit. As a result the distance between the Sun and Earth is not constant. The distance varies between 147 million kilometers to 152 million kilometers.
When Earth is at perihelion (closest to the Sun) the sunlight takes 8 minutes 10 seconds (490 seconds) to reach Earth. And when at aphelion (farthest from the Sun) the sunlight takes 8 minutes 27 seconds to complete the same journey.
If the Sun disappears suddenly (don't panic, this will not happen while you are reading this) then it will take us 8 minutes to realize that the brightest object in the sky just vanished. The same happens with other objects. For instance, the light from your screen on which you are reading this, actually was emitted few nanoseconds or less ago! Everything we see in the night sky, the stars, planets, galaxies, we see them as they were in the past!!
However, the journey of light is even more interesting inside the sun.
The photons that reach us are not 8 minutes 20 seconds old! The photons are created inside the Sun's core by fusion reactions. They initially start as gamma rays and during their journey from the Sun's core to surface, they are absorbed and emitted innumerable times as they wander for the path inside the huge star to reach the surface.
Once they reach the surface, they reach Earth in just matter of minutes.
However, you may not know ...... it ACTUALLY requires a photons Tens Of Thousands of years to reach the surface of the Sun!
All these efforts for just a 8 minute short journey to our eyes!!!
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