03/11/2015 The Earth in the Universe M Barker Shirebrook Academy (OCR 21 st Century)

03/11/2015 P1.1 The Earth in the Universe

03/11/2015 The eight planets of our Solar System Mercury Mars Jupiter Saturn Neptune Uranus Venus Earth As well as the eight planets, the solar system is also made up of asteroids, dwarf planets, comets and moons

03/11/2015 Different Orbits Mercury Mars Jupiter Saturn Neptune Uranus Pluto Venus Earth Mercury = 88 days Mars = 687 days Pluto = 90,500 days

03/11/2015 The Earth’s Orbit Ellipse

03/11/2015Asteroids An “asteroid belt” lies between Mars and Jupiter. But what is an asteroid?

03/11/2015Comets Comets are balls of dust and frozen gas. They have very elliptical orbits: Notice how the tail always points away from the sun!

03/11/2015 The Solar System summarised What makes up our solar system? Complete the following mind map with what you now about each object: The solar system

03/11/2015 Solar systems, galaxies and the Universe OUR SUN (100 times wider and 4.6 billion years old), which is small compared to… THE MILKY WAY, which contains at least 200 billion stars and is 100,000 light years across, which is small compared to… Our planet (around 13,000km diameter and 4500 million years old) is pretty small compared to... THE UNIVERSE, which contains billions of galaxies and is 14,000 million years old.

03/11/2015 How to make a solar system

03/11/2015 Stage 1: Nebulae A nebulae is a collection of dust, gas and rock. Some examples of nebulae…

03/11/2015 Dark nebula

03/11/2015 Emission nebula

03/11/2015 Planetary nebula

03/11/2015 Reflection nebula

03/11/2015 Gravity will slowly pull these particles together… As they move inwards their gravitational potential energy is converted into heat and a big object (PROTOSTAR) or smaller objects (planets, asteroids etc) are formed Stage 2: Throw the nebula together

03/11/2015 Stage 3: Make a star Any element in space that is heavier than helium is thought to have been made in a star. In a star the forces of gravitational attraction pulling the particles inwards are _________ by forces acting outwards due to the huge __________ inside the star. Stars are basically ________ reactors that use _______ as a fuel. During its main sequence a star will release energy by combining hydrogen and helium nuclei (light elements) into _________ elements. Words – heavier, balanced, hydrogen, nuclear, temperatures

03/11/2015 Observing the Universe All of these methods rely on detecting radiation from stars.

03/11/2015 The Light Year Distances in space are so big that they are measured in units called “light years”: 1 light year = the distance travelled by light in one yar Q. If light travels through space (i.e. A vacuum) at 300,000 km/s how far is one light year? Because of this, when we see stars in the night sky we are actually seeing them as they were in the past.

03/11/2015 Distances in space 03/11/2015 The Sun, our closest star, is 1.6x10 -5 light years away from us. The Andromeda Galaxy (our closest galaxy) – approximately 2.5 million light years away The next closest star, Proxima Centauri (4.2 light years away) The centre of our galaxy, the Milky Way, is around 26,000 light years away.

03/11/2015 Measuring distance using brightness The sun looks very bright. But, to be fair, it’s very close to us so it should look bright!

03/11/2015 Measuring distance using brightness When I look at these stars some appear brighter than others. This because they are either brighter stars or closer to me. For example, the star Antares is 10,000 times brighter than the sun but it is 500 light years away from me, so it is only the 15 th brightest star in the night sky.

03/11/2015 Measuring distances to stars Distant stars Nearby star 1) Relative Brightness The further away a star is the dimmer it is. Simple. 2) Parallax Parallax is the apparent change in position of closer stars due to the Earth moving around the sun.

03/11/2015 Problems in Measuring Distances 1) Light pollution and other atmospheric conditions can interfere with observing stars: 2) Stars are simply very far away so the angles involved in using techniques like parallax are very small:

03/11/2015 How our Earth and the Sun compare to others… 03/11/2015

How did the universe begin? Scientists believe that the universe began by a “big bang” around 14 billion years ago:

03/11/2015 Evidence about the origins of the universe…

03/11/2015 Source of light “Spectra”

03/11/2015 If you pass the light through a gas something different is seen… helium Some wavelengths of light are absorbed by the gas – an “absorption spectrum”.

03/11/2015 After helium If the light source is moving away the absorption spectra look a little different… helium Before

03/11/2015 The absorption lines have all been “shifted” towards the longer wavelength end (red end)… After Before A similar effect happens with sound – this is called “The Doppler Effect” This is called red shift. The faster the light source moves the further its light will be “shifted”

03/11/2015 Red Shift simplified Basically, if I walk towards you I’ll look slightly more blue. Then, if I walk away from you, I’ll look slightly more red!! Let’s try it…

03/11/2015

Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point. This is the BIG BANG theory

03/11/2015 Red shift summary Light from other galaxies has a longer _________ than expected. This shows that these galaxies are moving ____ from us very quickly. This effect is seen to a greater extent in galaxies that are _______ away from us. This indicates that the further away the galaxy is, the ______ it is moving. This evidence seems to suggest that everything in the universe is moving away from a single point, and that this process started around 15 _____ years ago. This is the ____ ________ Theory. Words to use – faster, away, big bang, billion, wavelength, further

03/11/2015 Hubble’s Law Edwin Hubble The speed at which galaxies are moving away from us is proportional to their distance from us. In other words, the further away they are, the faster they go.

03/11/2015 Big Bang Theory 03/11/2015 Some scientists have explained that red shift can actually be used to support the Big Bang Theory – this explanation is based around the rates of expansion and contraction of different galaxies. If our neighbouring galaxy is expanding at a different rate to the Milky Way then it will appear red or blue-shifted. Stephen Hawking, So Mr President, red shift shows us that galaxies are moving and therefore we assume that space itself is expanding. Elementary!

03/11/2015 The end of the Universe There are some theories about how the universe will end but its difficult to tell due to difficulties in measuring objects that are so far away: “The big crunch” – if there is too much mass (i.e. too much matter) the universe will collapse under its own gravity. It may then do another “big bang” – this is the “oscillating universe” theory. “Expanding Universe” – if there isn’t enough mass in the universe then it will just keep on expending forever. If there is just the right mass in the universe then it will reach a fixed size.

03/11/2015 The End of the Universe Stephen Hawking Basically, how the universe will end depends on its “energy-mass density”. Size of universe Time Open universe Closed universe Critical density Now

03/11/2015 P1.2 The Changing Earth

03/11/2015 Evidence for the age of the Earth Scientists once thought that the Earth was only 6000 years old. Rocks have provided lots of evidence for the world being older. 1) Erosion 2) Craters 3) Mountains 4) Fossils 5) Folding 6) Radioactive dating The Earth’s age must be older than the oldest rocks, which are around 4,000,000,000 years old.

03/11/2015 Continental Drift Look at the coastlines of South America and Africa. I wonder of they used to fit together… Alfred Wegener I’m going to call this my Theory of Continental Drift

03/11/2015 Tectonic theory What’s my evidence for this? Three things: 1)The “jigsaw fit” 2)Each continent has similar rocks and fossils 3)Each continent has similar animal species

03/11/2015 Another Example of Continental Drift The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India: This is where India is now This is where India was millions of years ago If it wasn’t for processes like this then, if you think about it, continents would eventually disappear due to erosion. Fascinating.

03/11/2015 Tectonic theory The Evidence: 1)Some continents look like they used to “fit” together 2)Similar rock patterns and fossil records The Problems: Wegener couldn't explain how continental drift happened or provide evidence so nobody believed him. Also, he wasn’t a geologist so he had no credibility and there were other explanations for the same evidence. Conclusion – scientists now believe Wegener’s Tectonic Theory The Answer: Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move.

03/11/2015 Movement of the Lithosphere The Earth’s LITHOSPHERE (i.e. the _______) is split up into different sections called ________ plates: These plates are moving ______ from each other a few centimetres every _______. They can slide past each other, move apart from each other or move towards each other, causing volcanoes and _________. Words – earthquakes, crust, apart, tectonic, year

03/11/2015 Sea Floor Spreading Oceanic Crust Mantle Magma Earthquakes and volcanic eruptions can be common here Igneous Rock Convection Currents

03/11/2015 Magnetic Patterns in Sea Floor Spreading The Earth’s magnetic field swaps poles every million years. The above picture shows those changes recorded over time in rocks on the sea floor and provides evidence for long-term sea floor spreading.

03/11/2015 More on Plate Movements Convection Currents Thin, dense oceanic plate Thick, less dense continental plate Subduction

03/11/2015 The Structure of the Earth A thin crust km thick and not very dense A mantle – extends almost halfway to the centre, hot and dense A core – made of molten nickel and iron. Outer part is liquid and inner part is solid. Gets hot due to radioactive decay. How do we know? A lot of the evidence for these facts comes from studying earthquakes (seismic waves)…

03/11/2015 An introduction to Waves A Wave is a “movement of energy” but NOT a transfer of matter

03/11/2015 Transverse vs. longitudinal waves Transverse waves are when the displacement is at right angles to the direction of the wave. Longitudinal waves are when the displacement is parallel to the direction of the wave… Displacement Direction Displacement Examples – light, other EM waves, some seismic waves Examples – sound, some seismic waves

03/11/2015 Seismic waves Earthquakes travel as waves through the Earth – we call them SEISMIC WAVES. There are two types: P waves: 1)They are longitudinal so they cause the ground to move up and down 2)They can pass through solids and liquids 3)They go faster through more dense material S waves: 1)They are transverse so they cause the ground to move from right to left 2)They ONLY pass through solids 3)They are slower than P waves 4)They go faster through more dense material

03/11/2015 Seismic waves These P waves travel through the Earth and are refracted when they pass through a medium These P waves are being reflected at the crust These S waves cannot travel through the outer core as they only go through solids – this tells us that the outer core is liquid The paths of these waves are all curved because density is gradually changing

03/11/2015 Locating Earthquakes By measuring the time it takes the wave to travel to these locations the location of the earthquake can be found.

03/11/2015 Wave definitions… 1) Amplitude – this is “ how high ” the wave is: 2) Wavelength ( ) – this is the distance between two corresponding points on the wave and is measured in metres: 3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz) 4) Speed – this is how fast the wave travels and is measured in metres per second (m/s)

03/11/2015 Distance, Speed and Time for waves Speed = distance (in metres) time (in seconds) D TS 1)A water wave travels 200 metres in 40 seconds. What is its speed? 2)Another wave covers 2km in 1,000 seconds. What is its speed? 3)Sound travels at around 330m/s. How long does it take to travel one mile (roughly 1,600m)? 4)Light travels at a speed of 300,000,000m/s. How long would it take to travel around the world if the diameter at the equator is around 40,000km?

03/11/2015 Drawing waves 1) Low amplitude, low frequency: 2) Low amplitude, high frequency: 3) High amplitude, low frequency: 4) High amplitude, high frequency:

03/11/2015 The Wave Equation All E-M waves obey the Wave Equation: Wave speed (v) = frequency (f) x wavelength ( ) in m/s in Hz in m V f Notice that frequency is inversely proportional to wavelength – if wavelength goes up, frequency goes down

03/11/2015 1)A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? 2)A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? 3)The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 4)Purple light has a wavelength of around 6x10 -7 m and a frequency of 5x10 14 Hz. What is the speed of purple light? Some example wave equation questions 0.2m 0.5m 0.6m/s 3x10 8 m/s