Universe [comprehension quiz]

Most astronomers [scientists who study stars, planets and galaxies] think that the Universe was formed during an event called the Big Bang. This was a giant explosion which occurred between 10 and 20 billion years ago. This giant explosion hurled matter in all directions and caused space itself to expand. As the Universe cooled, the material in it combined to form spinning, swirling disks of material we call galaxies. At the centre, gravity [the force by which a planet or other body draws objects toward its centre] pulled more material in. As these bodies smashed into one another they formed larger and larger galaxies. Earth is located in an outer spiral arm of one of the galaxies called the Milky Way.The Milky Way is one of perhaps 100 billion galaxies in the universe. So we live on a planet in our own Solar System with a star at its centre. Most of the hundreds of billions of stars in our galaxy are thought to have planets of their own. Here you can just see where our Solar System is within the Milky Way galaxy.

1. What is an astronomer ? someone who tells a persons fortune someone who has been into space someone who studies the stars, planets and galaxies 2. How do astronomers think the Universe was formed ? when two galaxies smashed together during an event called the Big Bang gravity pulled a lot of matter together 3. When do they think this event occured ? between 10 and 20 billion years ago between 100 and 200 billion years ago between 1000 and 2000 billion years ago 4. Where is Earth in all of this ? in an outer spiral arm of the Milky Way in a dense cloud of interstellar gas and dust in a solar nebula 5. How many stars are in our galaxy ? hundreds of millions hundreds of billions hundreds of thousands

There are 9 pictures in a grid. As you hover over each picture a blue screen appears on which there is some information about what is being shown in the picture. Read this information and look at each picture to make sure you understand what is being shown. If you want to check how much you understand try the quiz on the right hand side. To start the activity again just refresh the page.