Fifteen facts about the Universe

1. The matter in the universe is so thinly dispersed that the universe can be compared with a building twenty miles long, twenty miles wide, and twenty miles high, containing only a single grain of sand.
2. The word Universe derives from the Old French word Univers, which in turn derives from the Latin word universum.
3. The three most common elements in the universe are 1) hydrogen; 2) helium; 3) oxygen.
4. No one knows the exact number of galaxies in the universe, but it is estimated that there are more than 170 billion galaxies in the Universe.
5. As late as 1820, the universe was thought to be 6,000 years old. It is now thought to be between 15 and 20 billion years old.
6. A "light year" is a measure of distance, it is the distance that light travels in a year and is equal to about 9.5 trillion kilometres, or about 6 trillion miles.
7. Scientists believe that hydrogen comprises approximately 90 to 99 percent of all matter in the Universe.
8. While astronomers used to believe that galaxies were distributed more or less evenly through space, they have now found regions where galaxies are rare or absent.
9. Astronomers believe that the universe contains one atom for every 88 gallons of space.
10. It is possible that many planets in the galaxy may not orbit around stars. Recent work by Kailash Sahu found six gravitational lenses in the star cluster M22 from objects smaller than brown dwarfs, the smallest type of star. Only one gravitational lensing event by a star was found in the same work.
11. About 25% of the universe consists of "dark matter", and about 70% consists of "dark energy", leaving only about 5% of the universe visible to us.
12. According to the scientists our solar system was formed about 5 billion years ago.
13. Most scientists think that the universe began 13.7 billion years ago (that is 1,370 million years ago). But there is not much differece as other scientists say that the Universe is 10 to 20 billion years old.
14. Astronomers believe that the universe contains one atom for every 88 gallons of space.
15. The Earth was formed about 4.5 billion years ago.