When we look up at the sky, we see the moon and billions of stars, thinking this is how they look like at the moment. However, what we are actually seeing is past and how the sky objects have looked minutes, hours or even years ago.

Sound travels about a kilometer every three seconds, whereas light travels 300,000 kilometers every second, hence we see lightening first and then hear the thunder, but even when we see a flash of lightning 3km away, we are actually seeing it happened a hundredth of millisecond ago.

But these time differences stretch more to seconds, minutes, hours, and even years into the past as seen with our naked eye. Seeing it with a telescope makes us travel way back in time, according to The Conversation.

Starting with the moon which sits about 380,000km away from Earth, it takes 1.3 seconds for travel from the moon to us, hence the way we see the moon is actually how it was 1.3 seconds ago. Moving on to the Sun that is about 150 million km away, we see it as it was eight minutes ago. We even see our neighboring planets, Venus and Mars, as they were minutes ago. Moreover, Saturn is seen as over an hour ago.

The distance stretches to years when talking about stars, since they are really distant. The stars are measured in light years that mean the distance traveled by light in one year, which is about 9 trillion km.

The nearest star system visible, Alpha Centauri, is at a distance 270,000 times the distance between Earth and Sun, which equals to four light years. Hence, the star system is seen as it was four years ago. Another star system Betelgeuse is about 640 light years away, thus if it exploded tomorrow, we won’t know about it for another 640 years, detailed The Conversation.

These distances stretch more to over millions of years that we can see in the past with just our naked eye. Using telescopes will help us see the skies as they were billions of years ago. Hence, it is interesting how we look up at the skies and think of the mesmerizing objects as present, but in fact we have traveled to the past.