The Solar System
- There are eight planets orbiting the Sun in almost circular paths; Mercuy, Venys, Earth, Mars, Saturn, Uranus, and Neptune.
- There is also asteroids, dwarf planets, comets and dust orbiting the Sun.
- The Solar System is about 5000 million years old.
- Made from clouds, dust and gas. One day it all collapsed in on itself. The centre of the collapse formed a protostar. As the temperatures increased fusion started. Hydrogen nuclei joined together with helium. Fusion gives out massive amounts of heat and light, giving birth to the Sun.
- All heavier atoms than helium and hydrogen were also formed.
- Material from the surrounding cloud clumped together to form planets.
- The oldest rocks (meteorites) are around 4500 million years old.
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Beyond the Solar System
- Our sun is one of thousands of millions of stars which form the Milky Way galaxy- about one in 10^11
- Every galaxy is made up of thousands of millions of stars, and the universe is made up of thousands of millions of galaxies.
- A light year is the distance that light travels through a vacuum in a year.
- Earth and Sun- 5000 million years old
- Universe- 14000 million years old
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Looking into space
- Stars emit electromagnetic radiation.
- To work out the distance of nearby stars you can use parallax. This is when Astronomers take pictures of stars six months apart. The apparent movement of the star between the photos lets you work out how far away it is.
- Stars further away appear to move less.
- Another way to work out the distance of a star is the brightness.
- However the atomsphere and light pollution can cause some problems.
- We see stars and galaxies as they were in the past. This is because they are so far away, and the light takes a really long time to reach us.
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The life of the universe
- Distant galaxies are moving away from us.
- When a galaxy is moving away from us the wavelength of the light form changes and becomes redder. This is called red shift.
- The greater the red shift the faster it is moving away.
- According to the Big Bang theory all the matter and energy in the universe was once compressed into a very small space. Then is exploded and started to expand, This expansion is still going on.
- The amount of dark matter in the universe, and also what it actually is, is unknow. It can only be detected by the way that it affects the movement of the things that we can see.
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The changing Earth and Wegner's theory
- Rocks provide a record of changes in the Earth.
- Wegner hypothesised that Africa and South America had previously been one continent.
- There was matching layers in the rocks on different continents, and similar fossils.
- Wegner's theory of continental drift said that 300 million years ago there had been one super continent - Pangaea.
- The theory wasn't first accepted as Wegner couldn't explain how the drifting happened. He was a meteorologist. And other scientists were hostile and didn't like it.
- The sea floor is spreading. As magama rises up, solidifes and creates mountains.
- The magnetic orientation of rocks change. As the magma contains iron particles which align themselves with the Earths magnetic field, magma soldifies.
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- Earthquakes cause different types of seismic waves. There is two different types that travel through the Earth; P-waves and S-waves.
- P-waves travel through solids and liquids, they travel faster than S-waves, and are longitudinal.
- S-waves only travel through solids, they are slower, and are transverse.
- When they reach a boundry between different layers of the Earth some waves will reflect. They can also change speed as the properties of the mantle and core change.
- The change in speed causes the waves to change direction, which refraction.
- The fact that S-waves are not detected in the core's shadow, tells us that the outer core is liquid.
- P-waves travel slightly faster through the middle of the core, which suggests a solid inner core,
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Waves- The basics
- Waves carry and transfer energy is the direction that the waves travel.
- The amplitude is the distance from the rest position to the crest of trough. The bigger the amplitude the more energy the wave has.
- The wavelength is the length of a full cycle of the wave e.g. from crest to crest
- Frequency is the number of complete waves passing a certain point per second, it is measure is hertz (Hz). 1Hz is 1 wave per second
- Distance(m) = speed(m/s) X times(s)
- Waves can be Transverse of longitudinal.
- In Transverse waves the vibration are at 90' to the direction of travel of the wave.
- In Longitudinal waves the vibrations are along the same direction as the wave it's travelling.
- Speed(m/s) = frequency(Hz) X wavelength(m)
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