The sun is a star, just like the thousands of others we see in the sky each night. But it looks so very big. Is it the biggest star? No. The only reason the sun appears so big is because it is closer to us than any other star.
The sun is just 93,000,000 miles (or 14,88,000,000 km) away from the earth. That seems an awful lot of distance, but light can travel so quickly that the sun’s rays reach the earth in a little more than eight minutes! That is the wonder of light.
Many of the stars that we see at night, are more than 1000 times farther away than the sun. Obviously, this means that their light, too, would take 1000 times more time to reach the earth. And most stars are so far away that their light takes hundreds or even thousands of years to reach us.
The distance travelled by light in a year, is called a light year (for those who have a head for figures, one light year is 58,780,000,000,000,000 miles).
Therefore, if light takes 100 years to travel from a star to the earth, we say that the star is 100 light years away (100 x 58,780,000,000,000,000 miles.)
Some of the stars we can see in the night sky are so far away that it takes thousands and thousands of years for their light to reach us.
Scientists have only been able to see some nearby stars. One of them is Alpha Centauri, which is 4.35 light years away.
Yet another star, Alpha Canis Majoris, or Dog Star, which is the brightest star in the sky, is 8.48 light years away.
A look into the heavens or a plunge into the past
Here is something interesting to think about. If it takes 8.48 years for us to see the Dog Star, then doesn’t it mean that we are looking at it the way it looked 8.48 years ago? So, in that sense, aren’t we looking back into history?
By this logic, if the Dog Star were to die today, when would we come to know about it? Only 8.48 years later, as we humans would continue to see the star till then.
The deeper we look into the universe, the farther away we go both in time and space. And that is why scientists believe that if they could see the centre of the universe, then they would actually be able to see the events that led to the creation of the universe.
So the next time you watch a movie by the name of Back to the future, you would surely know time travel is as simple as a peep into the night sky!