Why is it not easy to describe the Universe?

When you hear the word ‘Universe’, what do you think of? You think of a large and unimaginable expanse of dust, gas, stars, clouds, galaxies, and life. It is difficult to describe it exactly, because no one knows what it actually consists of. There may be many distant worlds in the Universe about which we know nothing. Even every empty space is part of the Universe, and so are matter, time, and energy.

Some scientists say that if you could look at the entire universe at once, it would look like a giant spider web, made up of billions of galaxies, and trillions and trillions of stars. If you find this a bit too much to grasp, don’t worry! Even the greatest scientists have not yet solved the mystery of the Universe!

 
It is difficult to say how big the Universe is, because we can’t even imagine how big it might be. Our Earth is only a tiny, tiny part of our solar system, and our solar system a tiny part of another system called the ‘galaxy’. Beyond our own galaxy lies a vast expanse of galaxies. There are billions of galaxies, the most dist ant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago!

Perhaps, all these billions of galaxies put together are still only a tiny part of a larger system.
So, we know that the Universe is bigger than what anyone can imagine, but how much bigger is a quest ion that Man has been asking himself since the beginning of time. The answer is still beyond our grasp, especially as scientists believe that the Universe is still expanding! 

Why is It Possible to Measure Distances From The Stars?

Scientists cannot Stretch a measuring tape from the Earth to a nearby star, so how do they know how far away they are? It’s always been known that the stars are very remote, but it was not until 1838, that the first Star-distance was measured, using the method of parallax by F. W. Bessel.

 A star, viewed from different Points in the Earth’s orbit will shift against its background of more distant stars the deviation in the angle can be used to calculate the distance. Today, scientists use Special cameras fitted into some special types of telescopes to calculate distances. Special types of telescopes are used to Photograph large areas of the sky. Scientists also use instruments like a spectroscope radio telescope, etc. to determine how far a star from Our Earth is. 

Light years are the unit of distances in Space. This sounds like a unit of time, but a light year is actually the distance that light travels in one year Light travels 299 792 km per second. So, a light year is about 9 460 700 000 000 km. It has been calculated that the nearest galaxy is the Andromeda, which is at a distance of 2.2 million light years, from Earth. Did you know that the Sun is positioned only 8 light minutes away from Earth? This is called the light speed. Light takes only 8 minutes to travel to our earth from the sun.