The Universe is very big;in fact,it is bigger than anything else we know about.We can see that it exists as far as about 13.7 billion light years(ly)from us.We also know there is more beyond the edge of the observable universe but we don't know how much.the universe is expanding all the time-it is bigger now than when you started reading this sentence.
RECORD BREAKER
The largest structure in the Universe is the sloan Great wall.About one billion ly way from earth,it is the stretches for 1.37 billion across the universe..
THE MOST DISTANT OBJECT THAT MOST PEOPLE CAN SEE IS THE TRIANGULUM GALAXY,3 MILLION LY AWAY
The universe is a big, big place. But how big? And how do we know?
Throughout history, humans have used a variety of techniques and methods to help them answer the questions 'How far?' and 'How big?' Generations of explorers have looked deeper and deeper into the vast expanse of the universe. And the journey continues today, as new methods are used, and new discoveries are made.
In the third century B.C., Aristarchus of Samos asked the question 'How far away is the Moon?' He was able to measure the distance by looking at the shadow of the Earth on the Moon during a lunar eclipse.
It was Edmund Halley, famous for predicting the return of the comet that bears his name, who three centuries ago found a way to measure the distance to the Sun and to the planet Venus. He knew that the planet Venus would very rarely, every 121 years, pass directly between the Earth and the Sun. The apparent position of the planet, relative to the disk of the Sun behind it, is shifted depending on where you are on Earth. And how different that shift is depends on the distance from both Venus and the Sun to the Earth. This rare event, the transit of Venus, occurred again quite recently, June 8, 2004.
It was knowing this fundamental distance from the Earth to the Sun that helped us find the true scale of the entire Solar system for the first time.
GALAXY
Beyond our own galaxy lies a vast expanse of galaxies. The deeper we see into space, the more galaxies we discover. There are billions of galaxies, the most distant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago. So we see them not as they are today, but as they looked long before there was any life on Earth.
Finding the distance to these very distant galaxies is challenging, but astronomers can do so by watching for incredibly bright exploding stars called supernovae. Some types of exploding stars have a known brightness - wattage - so we can figure out how far they are by measuring how bright they appear to us, and therefore how far away it is to their home galaxy.
