| Earth and Beyond |
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| Measuring distances in space | |
Distances in space are so great that when we measure them in kilometres the number is very large. Light years are often used to measure distances in space. A light year is the distance that light travels in one year. Light travels 300 000 kilometres in one second and so in a year it travels
300 000 × 60 × 60 × 24 × 365.25 = 946 728 000 000 kilometres
The Sun is 150 million kilometres from the Earth. It takes light 8 minutes to travel that distance, so the Sun is 8 light minutes from the Earth. The next visible star is Alpha Centauri and that is 4.3 light years away from Earth. We really are seeing stars and galaxies as they were when the light that enters our eye started its journey, years ago. If a distant galaxy disappeared it could be millions of years before anyone on Earth knew about it.
| Planet | Distance from the Sun (million kilometres) |
Scaled distance from the Sun (sheets of toilet paper) | Scaled Diameter mm 600mm (size of a beachball) |
Relative gravity Earth = 1 |
Description |
| Mercury | 57.9 | 1 | 2 | 0.37 | Hot and dry. Suface pock marked like the Moon |
| Venus | 108.2 | 2 | 5 | 0.88 | Surrounded by dense clouds that reflect sunlight making Venus the brightest planet. Venus is very hot and its dry ground is covered with loose rocks |
| Earth | 149.6 | 2.6 | 5.5 | 1 | The Earth has one moon. It has land, oceans and an atmosphere |
| Mars | 227.9 | 3.9 | 3 | 0.38 | Called the "red planet" because it shines with a reddish glow. It is cold and has violent wind storms. |
| Jupiter | 778.3 | 13.4 | 63 | 2.34 | Jupiter has 16 moons. Jupiter is a huge ball of liquids and gases. It has a red spot which scientists think is a violent storm that has been going for hundreds of years. |
| Saturn | 1427.0 | 24.6 | 53 | 1.15 | Saturn is a ball of liquids and gases. It has a colourful thin, ring made of rocks and pieces of ice. |
| Uranus | 2869.6 | 49.5 | 20 | 1.17 | So far away that scientists do not know much about it |
| Neptune | 4496.7 | 77.5 | 20 | 1.18 | So far away that scientists do not know much about it |
| Pluto | 5899.0 | 101.5 | 1 | Difficult for scientists to calculate from data currently available | So far away that scientists do not know much about it |
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