P1

Making the Solar System

• Planets are smaller than stars & much closer
• Clouds started to get squeezed
• Particles close, gravity pulled things togehter, cloud collapsed
• At the centre particles formed a protostar
• Hydrogen nuceli joined to make helium (fusion) when temp v high
• Fusion gives out a lot of heat & light, made the Sun
• Material containing helium, hydrogen & heavier elements clumped to form planets

Asteriods & Comets

• Made of stuff left over from the making of the Solar System
• Asteroids = lumps of rock
• Comets = balls of rock, dust & ice that orbit in boomerang
• As the comet reaches the sun, ice melts forming a tail

Milky Way Galaxy

• Galaxy = thousands of millions of stars, Universe = thousands of millions of galaxies
• Sun is about half way on one of the sprial arms of the Milky Way

Space Distance

• Light year = distance that the light travels through a vacuum in one year
• Light years are distance not time

Relative Sizes, Distances & Ages

• Small - large = diameter of : Earth, Sun, Earth's orbit, Solar System
• Small - large = distance  of : Sun to nearst star, Milky Way, Milky Way to nearest galaxy
• Milky Way's diameter 600 billion x bigger than Sun's diameter about 100x bigger than Earth's
• Age of (millions years) : Earth = 5000, Sun = 5000, Universe = 14000

Measuring Distance of Stars

• EM shows a star's colour (temperature) 
• Parallax = when something appears to move when you look at it from different places
• Stars further away appear to move less 
• Examining how bright a star is tells distance
• Problems : atmosphere absorbs some before it reaches us, light pollution
• Hubble Space Telescope in space = no problems

Stars & Galaxies

• Radiation from the Sun that reaches us leaves 8 minutes before we actually see it
• So, we see the Sun as it was 8 minutes ago
• Sun = 4.2 light years away, light takes 4.2 years to get to us so we see it as it was 4.2 years ago
• We see the North Star as it was 430 years ago

Red Shift

• Red shift = galaxy moving away, wavelength of light changes & looks red
• Seeing how much light has been red-shifted = how quickly it's moving away
• Greater the red shift = faster it's moving away
• More distant the galaxy = faster it moves away
• This provides evidence that the Universe is expanding

Big Bang Theory

• All matter & energy must have been compressed & exploded to make it expand
• Still expanding today
• 14 thousand million years ago
• Difficult to know how much the expansion has slowed down
• The more mass there is = the greater the slowing down of the Universe's expansion
• Big Crunch = enough mass compared to how fast galaxies are moving = contraction
• Not enough mass in universe to stop expansion = expanding forever 

Rocks on Earth

• Fossils provide evidence that Earth is constantly changing
• Age of Earth can be estimated from rocks
• Sedimentary rocks = eroded rocks settle as sediment in sea & get crushed together
• Can be pushed onto surface or into Earth & then can be changed due to heating
• When pushed to Earth = cycle starts again

Observations of Wegener & Land Bridges

• Wegener = supercontinent 300 million years ago
• Land Bridges = land sunk or covered by sea as Earth cooled
• Factors that supported W = fossils, interlinking coastlines, matching layers of rock
• Scientists thought it was impossible land could moved by tidal forces & Earth's rotation
• Wegener wasn't a geologist

Real Reason

• Investigated Mid-Atlantic ridge in 1950s which is whole length of Atlantic
• Magma rises through sea bed, solidifies & forms underwater mountains = evidence shows sea floor is spreading
• Continents moving because of magnetic orientation to align themselves with Earth's magnetic field - as it cools they set in position
• Every half million years Earth's magnetic field swaps direction & the rocks on either side of ridge have different bands showing how old they are & the movement of land

Crust, Mantle & Core

• Crust = what we live on, very thin, continental crust = forming land, oceanic crust = underwater
• Mantle = all properties of a solid but can flow slowly by heat from core & radioactive decay in mantle which causes mantle to flow in convection currents
• Core = centre of the Earth made of iron & nickel

Tectonic Plates

• Crust & upper part of mantle cracked into tectonic plates
• Convection currents causes them to move
• Movements in mantle cause sea floor spreading
• Move at a few cm per year
• Earthquake = plates move suddenly, often near edges of plates
• Volcanoes = magma produced where plates meet, magma rises to form volcano
• Mounatins = plates crash into each other
• These processes contribute to rock cycle - plates collide, rock gets pushed underneath

Earthquakes

• When shock waves travel on the surface & inside Earth (recorded using seismographs)
• Seismologists measure time taken for shock waves to reach each seismograph & which places on Earth don't get any shock waves

Seismic Waves

• P-Wave = travels through solids & liquids, faster than S-Waves, longitudinal
• S-Wave = travels through soilds, slower than P-Waves, transverse
• Some can be reflected when reached a boundary between layers of the Earth
• Change speed as properties of mantle & core change so they change direction (refraction)
• Usually changes speed gradually = curved path, quick change = kinked path
• Half way through Earth, P-Waves change direction = sudden change in properties as you go from mantle to core
• No S-Waves in core's shadow = outer core is a liquid
• P-Waves travel faster through middle of core = solid inner core
• S-Waves travel through mantle = mantle is a solid but melts to form magma in 'hot spots'

Amplitude, Wavelength, Frequency & Speed

• Waves = disturbances caused by a vibrating source that carry/transfer energy 
• Amplitude = distance from rest position to the crest or trough, bigger amplitude = more energy
• Wavelength = length of a full cycle of a wave - crest to crest
• Frequency = number of waves produced by a source each second or number of complete waves passing a certain point per second
• Distance wave has travelled (m) = speed (m/s) x time (s)

Transverse or Longitudinal

• Transverse = most waves are, vibrations are 90degrees to the direction of travel of wave
• Longitudinal = sound etc, vibrations along the same direction as the wave is travelling

Wave Speed

• Wave speed (m/s) = frequency (Hz) x wavelength (m)
• Speed of sound waves in air is constant, lower frequencies = longer length, higher = shorter