Why is a Telescope Like a Time Machine?

Short Answer: Although light is fast, it is not infinitely fast. It takes time for the light of objects to reach us. Therefore, we see the previous states of the objects.

Are you ready to look back in time?

Since the speed of light has an enormous speed of 300,000 km/s, we do not notice this delay effect in daily life. But the universe is BIG and there are huge distances. It takes time for light to come to us from celestial bodies.

It is impossible to know what a celestial body looks like now. We only know what it looks like when its light on the road. Let’s give a few examples;

Let’s start with the Sun, the star of our Solar System. The distance from the Sun to the Earth is 149,600,000 km and we know that light travels about 300,000 km per second. Dividing the distance by this speed makes 8.3 minutes. So it means When we look at the Sun, we actually see it as it was about 8 minutes ago.

The light covers a distance of 1 AU in about 8 minutes.

We see the moon, which is our satellite, as it was 1.3 seconds ago. We see the red planet Mars as it was 4.2 minutes ago. Jupiter is at a distance of 4.2 AU and we see it as it was 33.6 minutes ago.

Let’s get a little further away. We see Proxima Centauri, the closest star to us after the sun, as it was 4.2 years ago. And we see our neighboring galaxy, Andromeda, as it was 2.5 million years ago.

So, when we look at the sky, the stars we see may not be alive anymore. The situation is the same for distant galaxies. We see them as they were ten billion years ago. As they were long before the Earth was born…

The most distant past we can see with light is 13.7 billion years. That is, 630 million years after the Big Bang, the beginning of our universe! 13.7 billion years of light is the remnant of the big bang.

In conclusion; The further away the object is, the more history we see. So the telescope is actually a “time machine”. 🙂

Thanks to the light, we can take a journey into the past of the universe and discover how it all started. The story of our universe is actually our story.

– Prof. Brian Cox