2. The Size of the by The Dark Side Universe

3. It takes 16 hours to fly from Alaska to Chile in a 747 going 900 km/h. It would take two years to walk it.

4. BUT IT’S NOT AS BIG AS THE SUN

5. If the Earth were the size of a large sand grain (3 mm across), the sun would be the size of a basketball. The sand grain would be 50 m from the basketball. Earth Sun

6. Pluto would be 2 km from the basketball.

7. How far from the basketball would the nearest other star be? Have a guess!

8. 14 000 km Pluto might be a long way away, but it is very close compared to even the closest star.

9. That nearest star is Proxima Centauri. Light travels 300 000 km in one second. A light year is how far light travels in a year. So a light year is about 10 000 000 000 000 km and Proxima Centauri is about 40 000 000 000 000 km away. It is 4 light years from our Sun.

10. The Sun and Proxima Centauri are two of the 200 billion stars in our galaxy, the Milky Way. The Milky Way is 100 000 light years across.

11. There are about 100 billion galaxies in the part of the universe we can see. They form clusters, strings and sheets surrounding big empty bubbles up to 200 million light years across. The universe is a bit like an Aero bar.

12. The most distant galaxies observed are about 40 billion light years away. But there are lots of galaxies beyond them. It is possible that they go on for ever.

13. The part of the universe we can see is 3000000000000000000000000 0000000000000000000000000 times as big as the Earth.