1. Revision Guide. Physics – Space. By Sian Lowry

2. Contents Page. Introduction How to remember the order of the planets Positions of the planets Facts about the solar system Facts about space Facts about the planets (sections 1,2 and 3) Key words and definitions Quiz

4. Introduction. This GCSE revision guide will tell you many things that you need to know about space. It will make studying seem fun and it will help you to remember information that you need to know. As well as revising the information that you enjoy and like, make sure that you revise the information that you don’t like.

5. How to remember the order of the planets. There are many different ways of remembering the order of the planets. There are 8 planets altogether in the solar system and they include; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto doesn’t count as a planet anymore because it is a dwarf planet. Even though it may seem hard to remember the order of them, it’s pretty simple. If you keep on repeating this, you wont forget the order of the planets.

6. Positions of the planets. In the centre of the solar system, there is the Sun. The Sun isn’t a planet, however, all of the planets orbit it. The first planet, the planet which is closest to the Sun, is Mercury. The second planet, one of two planets which is closest to Earth, is Venus. After Earth there is Mars. The fifth planet is Jupiter and after Jupiter comes Saturn. Uranus is the seventh planet and Neptune is the last. No one counts Pluto as a planet anymore because it is a dwarf planet.

7. Facts about the solar system. The solar system consists of a star (the Sun) with lots of planets orbiting it. The 8 planets orbit the Sun in circular paths. In between the inner planets (the first 4 planets) and the outer planets (the last 4 planets) is the asteroid belt. Also, dwarf planets, dust and comets orbit the Sun. The planets in the solar system are much closer to us than any of the stars, except the Sun. The oldest rocks on the Earth are meteorites, which are rocks from space that crashed into the Earth. The meteorites were said to be formed not long after the solar system was formed. These are about 4500 million years old, so the solar system is at least 4500 million years old.

8. Facts about space. The inner planets are; Mercury, Venus, Earth and Mars. The outer planets are; Jupiter, Saturn, Uranus and Neptune. Asteroids and comets are made from the left overs from the formation of the solar system. The rocks between Mars and Jupiter didn’t form a planet, they stayed as small lumps of rubble and rock, we know these as asteroids. Comets are balls of rock, dust and ice which orbit the Sun. They often orbit the Sun in different paths from the planets. As a comet approaches the Sun, its ice melts. This causes the comet to leave a bright tail of gas debris which can be millions of kilometres long. We can see these from the Earth.

9. Facts about the planets – Section 1. Mercury: It is the smallest of the 8 planets in the solar system. It is the closest planet to the Sun, so it orbits the Sun faster than all of the other planets. It is 57,910,000km away from the Sun. Its surface area is 74,800,000km squared. Mercury's orbital period is 88 days. Its radius is 2,440km and its mass is 328.5E21kg (0.055 Earth mass.) It has a diameter of 3,031 miles. Mercury has a rocky surface and is covered with many craters. Venus: Venus is named after the Roman goddess of love and beauty. It is 108,200,000km away from the Sun and its surface area is 460,234,317km squared. Its orbital period is 225 days. Venus’s radius is 6,052km and its mass is 4.867E24kg (0.815 Earth mass.) Also, it has no natural satellite. Earth: Earth is also known as the world, Terra and Gaia. It is the densest planet in the solar system and it’s the third nearest planet to the Sun. It is 149,600,000km away from the Sun and its radius is 6,371km. Its mass is 5.972E24kg. The Earth is 4.54 billion years old and the population of Earth is around 7.125 billion. It has one moon, called the Moon.

10. Facts about the planets – Section 2. Mars: Mars is the second smallest planet in the Solar System. Its surface area is 144,798,500km squared and its orbital period is 687 days. The radius of Mars is 3,390km and its mass is 639E21kg (0.107 Earth mass.) Its gravity is 3.711 m/s squared. It has two moons, called Phobos and Deimos. Jupiter: It is the largest planet in the solar system and it is a gas giant with two and a half times the mass, bigger than all of the planets put together.. Jupiter is 778,500,000km away from the Sun and its surface area is 61,418,738,571km squared. Jupiter’s radius is 69,911km and its mass is 1.898E27kg (317.8 Earth mass.) Its gravity is 24.79 m/s squared. Jupiter has many moons, such as, Lo, Europa, Ganymede, Callisto, Amalthea, Adrastea, Metis and many more. Saturn: It is the second largest planet in the solar system and it was named after the Roman god of agriculture. Its astronomical symbol represents the god’s sickle. Its orbital period is 29 years. It is 1,433,000,000km away from the Sun and its surface area is 42,700,000,000km squared. Saturn’s radius is 58,232km and its mass is 568.3E24kg (95.16 Earth mass.) Saturn has many moons, such as, Titan, Enceladus, Mimas, Dione, Rhea, Tethys, Lapetus, Pan and many more.

11. Facts about the planets – Section 3. Uranus: Uranus is the seventh planet away from the Sun and it was discovered on the 13 th of March 1781. Its surface area is 8,083,079,690km squared and its orbital period is 84 years. Its radius is 25,362km and the mass of Uranus is 86.81E24kg (14.54 Earth mass.) Uranus has many moons such as, Miranda, Titania, Oberon, Ariel, Umbriel, Puck, Cordelia and a few more. Neptune: Among the gaseous planets in the solar system, Neptune is the most dense. It is 4,503,000,000km away from the Sun and its surface area is 7,618,272,763km squared. Its orbital period is 165 years and its radius is 24,622km. Neptune's mass is 102.4E24kg (17.15 Earth mass.) It has many moons such as, Triton, Nereid, Proteus, Naiad, Thalassa, Galatea, Larissa, Despina, Psamathe, Neso, Sao, Laomedeia and Halimede.

12. Key words and definitions. Comets – Comets are balls of rock, dust and ice which orbit the Sun in ellipses, often in different planes from the planets. Asteroids – Asteroids are small lumps of rubble and rock. Light year – A light year is the distance that light travels through a vacuum (like space) in one year. Light pollution – Light pollution is when the light from street lamps, etc… is thrown upwards and it makes it harder to see dim objects. Red shift – Red shift is when a galaxy moves away from us and then the wavelength of the light from it changes, the light then becomes redder. The Big Bang – The Big Bang was a theory that was said why the Universe was expanding.

13. Quiz. How many planets are in the solar system? 10 6 8 12

14. Quiz. 1.What is the order of the planets? 2.What are the oldest rocks of the Earth called? 3.How old are meteorites? 4. Which planets are the inner planets? 5. Which planets are the outer planets?

15. Quiz. Which planet is the largest? MarsJupiter Saturn

16. Quiz. 1.What are comets? 2.What are asteroids? 3.Which planet only has one moon? 4.Which planet is covered with craters? 5.Which planet has only one moon?

17. Quiz. 1.Which planet in the solar system is the most dense? A) Saturn B)Earth C)Neptune D)Mercury 2.Which planet has 13 moons…can you name them? 3.Which planet has an orbital period of 84 years? 4.How far away is the Earth from the Sun?

18. Quiz. What are the definitions of the following words? The Big Bang…The Big Bang was a theory that was said why the Universe was expanding. Light pollution… Light pollution is when the light from street lamps, etc… is thrown upwards and it makes it harder to see dim objects. Comets…Comets are balls of rock, dust and ice which orbit the Sun in ellipses, often in different planes from the planets. Light year…A light year is the distance that light travels through a vacuum (like space) in one year. Asteroid…Asteroids are small lumps of rubble and rock. Red shift…Red shift is when a galaxy moves away from us and then the wavelength of the light from it changes, the light then becomes redder.