Universe
From the Simple English Wikipedia, the free encyclopedia that anyone can change
In astronomy, the universe is "everything out there". It contains the sun, all the planets including Earth, all of our galaxy, plus many other galaxies, and all of outer space. It is so huge that scientists measure its size in billions of light years - the distance light travels in a whole year. To travel in a spaceship, using today's knowledge, to even the nearest star would take centuries. In between the stars and galaxies, it is mostly empty and very cold.
Cosmology is the science studying its origin, how it changes, and its future. Through history, different theories about it have been made, but the theory accepted by most scientists today is called the "Big Bang". It tells us the universe was once very dense, and then began expanding ("bang") a long time ago.
Across history, many people have come up with ideas explaining how the universe came to be. Explanations involving gods or deities are called religions. We are still unsure of the answer, and this question is one that is the subject of much interest amongst mankind.
