P1

P1

1. Planets orbit in Elipses and reflect sunlight.

   • Stars and planets differ
     • Solar system = 5000 million yrs old. big clouds of dust and hydrogen which was compressed, until gravity took over, causing the cloud to collapse in on itself. The particles at the centre formed a protostar, and when temperatures were high enough, fusion occurred, so the hydrogen nuclei fused to form helium nuclei. This was the way the Sun was created and other planetary heavier elements were formed by more fusion. The clouds and the heavier elements began to clump together, creating planets. The graity of the sun then took hold, causing them to orbit around the sun, thus creating the known solar system
     • Asteroids and comets
       • Asteroids = Lumps of rock and rubble
       • Comets = balls of rock dust and ice which orbit the sun in very elongated orbits. As it approaches the sun, it melts, leaving a trail of gas and debris

2. Universe = 14,000 million yrs old. Big bang

   • Big Bang. All galaxies are moving away, so if we were to reverse time, all galaxies would converge at a single point. All matter and energy were compressed into a singularity, which exploded and expanded, the age of the universe was calculated on these expansion rates.

3. Electromagnetic radiation can be detected and used to identify galaxies and stars, as they emit them.

   • Brightness can be used to measure distance, but has problems: Close to earth but not bright or a long away but very bright.
   • Atmospheric pollution causes problems: atmosphere absorbs some radiation and light pollution.
   • Distant galaxies are moving away from us; the more distant the galaxy the faster it moves away. This is called Red Shift, as the light gradually changes in wavelength to the red spectrum of light as it moves away. This provides evidence that the universe it expanding.

4. The earth has been changing for thousands of millions of years. Rocks can be used to measure this: through erosion and the formation of new rock by lava and fossil formations, as the rock has built up around them. The age of the earth can be estimated from rocks.

   • Rocks are recycled in the rock cycle. Sediment is eroded from existing rock, and are washed into the sea and settle as sediment. The sediement gets crushed into sedimentary rocks. These can descend into the heat and pressure of the earth. The structure can then be changed completely as it is heated and crushed. The rock can melt and form new rock as lava from a volcano. These new rocks then feed the start of the process. The cycle requires some very powerful forces.

5. Very similar plants and animals had been found in Africa and South America, so some argued that there was a land bridge which had sunk or been eroded.

   • Wegener proposed that Africa and South America had once been part of the same continent or 'supercontinent' called Pangea, which had split into seperate continents.
     • To reinforce this he found similar structures in the rock strata, as well as similar fossils
       • At first, Wegner's theory was not accepted due to: the big change which caused other scientists to be hostile, the inability to explain how the continents drifted as it was not detectable and the fact that he was not a geologist
         • Eventually, the discovering of seafloor spreading proved it, as the magma from constructive plate boundaries rises to the suraface, cools and solidifies, causing the seafloor to spread by a few cm per year. Also, the flipping magnetic orientation in the rock was used to show how it has been going on for a long time, as the flip in the magnetic orientation occurs every half million years. This proved that continents were moving apart.

6. The Earth's structure: crust(solid oceanic + continental), mantle(solid but can flow due to convection currents created by heat and radioactive decay), outer core(liquid), inner core(solid iron and nickel)