P1 Summary
- Created by: icanteven
- Created on: 02-01-15 13:01
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- P1 Summary
- Scientific Explanations
- Scientists use journals and conferences to inform about their experiments and explanations.
- A scientists' judgement about an explanation may be affected by their personal background.
- An explanation is only accepted when it can account for all the data.
- Scientists repeat experiments done by others to check their data.
- The Solar System
- The solar system was formed from gas and dust in space about 5000 million years ago.
- The distance from a star can be estimated from its brightness and parallax.
- The source of the Suns energy is fusion of hydrogen nuclei, making it hot enough to emit light, which moves through space at 300 000 km/s
- The star at the centre of the solar system is called the sun.
- Earth is one of eight planets which orbit around the sun.
- Comets, asteroids and dwarf planets orbit the sun.
- Galaxies
- The sun is one of thousands of millions of stars in the Milky Way Galaxy.
- The universe is made up of thousands of millions of galaxies.
- Redshift and distance data suggest that the Universe expanded from a single point about 14 000 million years ago.
- The redshift of light from galaxies can be used to measure how fast they appear to be moving away.
- The expansion of space means that the greater the distance to a galaxy, the faster it appears to be moving away.
- The Changing Earth
- The oldest rocks on Earth are about 4000 million years old.
- Mountain building, earthquakes, seafloor spreading and volcanoes happen at the edges of tectonic plates.
- The Earth's solid crust floats on a soft mantle and is continually worn down by erosion.
- Convection currents in the mantle split the crust into tectonic plates and move them.
- The theory of tectonic plates explains Wegner's idea of continental drift.
- Seismic Waves
- Distance moved by a wave = wave speed x time of travel
- Wave Speed = frequency x wave length
- Waves have an amplitude, wavelength, frequency and speed.
- Earthquakes produce waves which carry enough energy as they travel through the Earth.
- P-waves are longitudinal waves which can move through the liquid core.
- S-waves are transverse waves which can only move through the solid mantle and crust.
- Scientific Explanations
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