Learning

The universe is the total of all the space, matter, and energy that exists. It includes everything - our earth, the sun, stars - everything, whether we can see them or not.

A long time ago, people thought only about Earth, the Sun, and the Moon. They believed these were the main things in the universe. But now, we know that there is a very huge space outside the earth. Our earth moves continuously around our sun. Other bodies similar to our earth also move continuously around our sun. And a lot more can be found even far away from the sun which is the star of our small part of the Universe.

Telescopes are used to look far away from earth into parts of the Universe which can not be seen by our naked eyes.

When we use a telescope to look into the space away from the earth, what we can see or observe is called the "observable universe." 

Starting from Earth, we first see our neighbours like the Moon and other neighbour planets like Mars, Venus, Jupiter & Saturn. As we look farther, we see further into our galaxy, called the Milky Way. And beyond that, groups of more stars and galaxies. There are estimated to exist over a hundred billion galaxies in the observable Universe. And each galaxy is estimated to contain hundreds of billions of stars.