When You Look at a Star, You Are Looking into the Past

Looking into space is nothing but looking back in time.

Don’t worry if you don’t understand the space technology; I’m here to explain everything in simple words. Keep reading! You are going to love this amazing space fact.

Go out and take a look at the stars tonight. The twinkling stars in the sky do look beautiful, but surprisingly, what you are looking at is not a live visual of the stars. You are looking at their past.

To help you understand this fact better, let me first explain about how light and human vision works.

When light rays reflect off an object, they enter the human eye via the cornea with pictorial information of the object, which then will be converted into neural impulses by the retina. The brain receives the impulses from the retina, and processes them to show us what we are looking at.

Light is a kind of electromagnetic wave that is made of photons. It always travels very quickly, and perhaps you know that. At a speed of 186,282 miles (299,792 kilometers) per second, light is fastest universal entity known to us.

The distance between celestial objects is often measured using a “light year” as a unit. A light year is nothing but the distance light travels in one year. 186,282 miles x 60 seconds x 60 minutes x 24 hours x 365 days = some 5.88 trillion miles. Hence, a light year is equal to 5.88 trillion miles (Don’t ask me about how many zeroes the number has!) That is some ridiculously long distance!

We see things around us, instantly – without an observable lag. However, when the distance between the light source and our eyes is very big, light travels for some time before it hits our eyes. The distance between Sun and Earth is 149.6 million kilometers or 92.96 million miles, and light generated on Sun takes approximately 8 minutes and 20 seconds to reach Earth. Now this means, we aren’t seeing a live copy of the sun! If Sun stopped burning right now, we would know about that eight minutes later! When you look at Sun (don’t do that please), you are looking back eight minutes into the sun’s past!

Getting back to the point – those stars we see in the sky are hundreds and thousands of light years away from Earth. Betelgeuse is one of the brightest stars in the night sky, and it is 642.5 light years away from Earth. It takes 642.5 years for light to travel from Betelgeuse to Earth, so when you see Betelgeuse in the night sky, you are actually looking at how it used to look 642.5 years ago!

Imagine there was a habitable planet revolving around Betelgeuse with intelligent life species like humans who could see Sun and Earth in their night sky. What the people on that planet would see right now was Earth during the 14th century AD!

Some of the stars that we see in the night sky may not exist in real time.

Hey, don’t forget to share this mind-blowing science fact with your friends!

Read a similar article on the NASA’s website.