P1 - The Earth in the Universe

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Cambridge IGCSE Physics Flashcards on P1 - The Earth in the Universe, created by franimal on 10/12/2013.
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These cards are for the OCR 21st Century Science Course and are complete. :-) ... They're neither easy nor impossible and you're very welcome to use them.
What is the Universe? The universe is everything observed, directly or indirectly.
Name our galaxy. The milky way.
Name the four layers of earth, in order, with their state (eg liquid). Crust - solid. Mantle - solid. Outer Core - liquid. Inner Core - solid.
What are comets? Large balls of ice and dust. Comets plunge inwards towards the sun and then far off into outer space on their orbits.
What is the process that creates light in the sun and how does it work? At millions of degrees, nuclear fusion takes place. The nuclei join together, releasing huge amounts of energy.
How fast is the speed of light? 300 000 km/s
What is a light year? The distance light travels in one year. A unit of measurement.
Describe the parallax method. As the earth moves from one side of the sun to the other, stars appear to shift position in the sky. The nearer the star the more it moves.
Describe the brightness method. IF two stars are the same heat and type the one that appears fainter will be further away.
How do we know the universe is expanding? When galaxies move away they appear red - 'redshift'. The further away they are, the more redshift, so the faster they're going.
Explain (briefly) the big bang? The universe was once hot, tiny and dense. Then it went boom, and is still 'booming' aka expanding today.
In 1965, two radio engineers found an annoying hiss in their equipment. What was this hiss? The afterglow of the big bang, filling the Universe with microwaves.
Is the expansion of the Universe slowing down, staying the same or speeding up? Speeding up - we think.
What is the rock cycle? Continuing changes in rock material, caused by processes such as erosion, sedimentation, compression, and heating.
What is deep time? The millions of years over which the earth has changed.
What was Wegener's theory, and what was the two pieces of evidence for it? Continental drift, supported by matching plant and reptile fossils in different continents and the jigsaw-like fit between South America and Africa.
What's an oceanic ridge? A chain of mountains under the ocean, caused by seafloor spreading.
Why are there stripe patterns either side of an oceanic ridge? As magma rises the rock cools in the direction of the magnetic field at the time. When the field switches, the new magma cools in the new direction.
What are tectonic plates and what do they cause? Giant slabs of rock that form the crust. Where they collide and shove past each other they cause earthquakes and volcanoes. Where they pull apart magma rises up to form new land.
What are P-waves? Primary waves arrive first, are longitudinal, tend to cause less damage and go through solids and liquids
What are S-waves? Secondary waves arrive second, are transverse, tend to cause more damage and can only pass through solids.
What are transverse and longitudinal waves? Longitudinal: series of compressions. Transverse: side to side movement.
What is amplitude and wavelength? Amplitude: height of the wave crest above the undisturbed level. Wavelength: distance from one crest to the next.
What is frequency in a wave? The number of waves that pass any given point each second, measured in hertz (Hz). Equal to the amount of vibrations from the source.
What is wave speed? The speed at which a wave crest moves, measured in metres per second (m/s). Dependant on the material the wave is travelling through.
How do you calculate wave speed? frequency X wavelength
How do P-waves and S-waves prove that the outer core is liquid? P-waves can be detected around the world, but S-waves, which can only travel through solids, are blocked by the core.
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