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Astronomy gcse

What are the key features that distinguish Earth from other planets? - Atmosphere of mainly nitrogen and oxygen. - Liquid water (70% of surface). - Life in many forms.
What is the Earths diameter? 13000km.
What is Earth's shape? Oblate spheroid.
How do we know that the Earth is flat? - Ships disappear over the horizon. - Satellites orbit the Earth. - Curved shadow in partial lunar eclipse. - Aircrafts fly in arcs (shortest distance). - Images of Earth from space.
What is latitude? The Latitude of a place gives the position of it north or south of the equator (0 degrees). The North Pole is 90 degrees north and the South Pole 90 degrees south. Latitude is measured in degrees and the lines of latitude dissect the earth horizontally.
What is longitude? The Longitude of a place gives the position of it from east to west; the lines of longitude are also referred to as Meridians (which pass through the points on the North Pole and South Pole).
What is the Prime Meridian? The ‘prime Meridian’ is 0 degrees and points west of it are measured in degrees west and points east of it are measured in degrees east. The prime Meridian runs through the Greenwich Observatory in London.
What is an observer's Zenith? An imaginary point dircetly above them on the celestial sphere.
At what angle is the Earth tilted to the ecliptic? 66.5 degrees.
What is the ecliptic? The plane of orbit around the sun.
What is an observer's Horizon? It is the imaginary line along which the sky meets the land/sea. It can also be viewed as a plane that meets the observer at a tangent to the Earth's surface.
What is he latitude of the Tropics of Cancer? 23.5 degrees north.
What is the latitude of the Tropics of Capricorn? 23.5 degrees south.
What are the equinoxes? The only two dates a year that the sun lies directly above the equator. he day is exactly 12 hours long and the night exactly 12 hours as well
When is the spring equinox? The 21st of March.
When is the autumnal equinox? The 22nd/23rd of September.
What are the issues with light pollution? It gives the night sky an orange background haze (skyglow) which stops observers from being able to see faint stars, nebulae or the Milky Way.
What are the main causes of light pollution? Floodlights, streetlamps, motorway lights, domestic/industrial secutiry lights, lights above car parks and shopping centres.
Who was Eratosthenes and what did he discover? Hwe was a Greek geographer and mathematician in the 3rd century BC. He discovered the first accurate(ish) circumference of the Earth.
How did Eratosthenes discover this? He knew that on the 21st of June the sun lay directly overhead in Syene in the tropic of cancer. On that date he used a column in Alexandria, there was a 7° shadow (1/50th of a circle). Since Syene was 790 km away he did: 790km x 50 = 39500km.
What percentage of the Earth's atmosphere is nitrogen? 78%.
What percentage of the Earth's atmosphere is oxygen? 21%.
What percentage of the Earth's atmosphere is argon? 1%.
What percentage of the Earth's atmosphere is water vapour? On average 1%.
What percentage of the Earth's atmosphere is carbon dioxide? 0.04%.
What are the benefits of the Earth's atmosphere? (5) Absorbs harmful solar ultraviolet radiation that causes quicker skin aging/cancer. Absorbs harmful energetic X-rays/gamma-rays. Regulates temperature=little extremes+liquid water. Oxygen-needed to breath. Protects us from meteoroids (burn in atmospher
What are the drawbacks of our atmosphere for astronomers? The refraction of light as enters atmosphere restricts sharpness, clarity and detail of image. Selective scattering of shorter (blue) wavelengths make sky blue so we cant make observations in the day. Absorption/reflection of electromagnetic radiation.
What is the issue of the absorption and reflection to most of the electromagnetic radiation caused by our atmosphere? It stops a majority of wavelengths from reaching sea-level. Due to this most observatories for: ultra-violet,X-ray and gamma-ray to be on a satellite in Earth orbit.
What is the effect that the atmosphere has on radio waves? The longest are reflected back into space by electrons in the ionosphere. Some pass through onto land/sea-level.
What is the effect that the atmosphete has on microwaves? Microwaves are absorbed by water vapour (h20) and oxygen (o2).
What is the effect that the atmosphere has on infra-red radiation? Except a few small windows, most is absorbed by water vapour (h20), carbon dioxide (co2) and methane(ch4).
What is the effect that the atmosphere has on ultra-violet radiation? It is absorbed by ozone (03) and at shorter wavelengths (o2).
What is the effect that the atmosphere has on X-rays? They are absorbed by the oxygen and nitrogen in the atmosphere. They ionise atoms/molecules but the radiation loses energy and does not go in any further than the upper layer.
What is the effect that the atmosphere has on gamma-rays? They are absorbed by the oxygen and nitrogen in the atmosphere. They excite atoms'/particles' nuclei however they don't go far into the atmosphere as the radiation loses energy.
What is the order of the electromagnetic spectrum? Gamma-rays, X-ray, Ultra-violet (UV), Optical/visible, Infra-red (IR), Microwave, Radio.
What is the use of telescopes? It collects as much light as possible to produce a focussed image with as much detail and clarity as possible.
What are the two types of telescopes? Refractor telescopes and reflector telescopes.
How does a refractor telescope work? A glass convex lens collects the light and brings it to focus.
How does a reflector telescope work? A curved mirror collects the light.
What are the advantages of large telescopes? They collect more light as this is proportional to the area. They have a better resolution (sharpness/detail) as this is proportional to the diameter.
If a telescope collects 25 times more light than a 2 metre one, how many metres is it? 10 metres as 25 is 5 squared, therefore it has 5 times the metres.
Wat do you have to consider for ideal observing sites? Cloud cover Sky brightness Water vapour content of the air Light pollution Ground stability Access Availability of utilities.
What are the advantages of using space telescopes? No atmosphere to blur images. No light pollution. No weather problems. Long observing periods (not waiting for the night). Can detect other wavelengths (not absorbed by Earth's atmosphere).
What are the drawbacks of using space telescopes? Shorter lifespan. It is hard or impossible to maintain/repair/upgrade. Much more expensive.
What are the Van Allen Belts? Two doughnut-shaped rings of spiralling high-energy particles that are held in place by the Earth's magnetic field.
Of what does the inner belt consist? Mainly high energy protons which were formed by the collisions between cosmic rays and atoms in the atmosphere.
Approximately what is its altitude in Earth-radii and in kilometres? Between 0.1 and 1.5 Earth-radii. Between 600 and 10,000 Kilometres.
Of what does the outer belt consist? Mainly of electrons and other carged particles emitted by te sun due to the increased solar activity.
Approximately what is its altitude in Earth-radii and in kilometres? Between 3 and 10 Earth-radii. Between 15,000 and 65,000 Kilometres.
What is the Moon's diameter? Just under 3,500 km - 1/4 of the Earth's diameter.
What is the Moon's it's approximate distance of orbit from Earth? 380,000 Km - 60 Earth radii.
What is the strength of the Moon's gravity? 1.6 N/KG - 1/6th of the Earth's gravity.
What is the effect that the Moon's gravity has on it's atmosphere? Although the Moon never really had an atmosphere if it was given one it could not keep it as it's gravity would not be string enough to hold it.
What is the Moon's rotational period? 27.3 days.
What is the Moon's orbital period? 27.3 days.
What is the consequence of the Moon's rotational and orbital period being the same? The same side of the Moon is always facing the Earth.
How do astronomers know the appearance of the Moon's far side that does not face us? Man made probes. The first images were captured by the Soviet probe Luna 3 in 1959.
How does the Moon's far side differ from it's near side? It is much more mountainous and cratered with fewer maria, this is likely to be because the crust is thicker making it harder for the molten rock to flow to the surface to form the maria.
What are maria on the Moon? Dark greay, smooth lunar seas - so called as were though to be water. Now know that it is iron rich basaltic rock.
What are terrae on the Moon? Light grey mountainous, highly cratered highlands made of anorthosite (igneous rock).
How are craters on the Moon formed? They are formed when the Moon is struck with meteoroids from the Solar system.
What are Rilles, where are they found and how are the formed? They are narrow channels found in the lunar seas formed from lava flow. They can be straoght, smoothly curved or winding.
What are wrinkle ridges, where are they found and how are they formed? They are ridges up to hundreds of kilometres long on the Moon. They are formed by the buckling of the lunar surface from compressive forces within cool, contracting lava <- not a clue what that means.
Why did John F. Kennedy want to have a man on the moon? - To collect lunar soil/rocks for Earth analysis. - To deploy scientific experiments on the m,oon's surface. - To win the space race against the Soviet Union. - Because its awesome.
Which lunar mission reached John F. Kennedy's goal? Apollo 11 - 1969.
Who were the first two men on the moon? Neil Armstrong and Edwin 'Buzz' Aldrin.
How many astronauts in total have been on the moon? Twelve.
What kind of experiments have been deployed on the moon? Generally ALSEP (Apollo Lunar Surface Experiments Packages). On Apollo 11 they deployed EASEP (Early Apollo Surface Experiments Packages).
What can the instruments in ALSEP measure? Moon's interior structure. Atmosphere's composition/pressure. Intensity/direction of solar wind. Minute changes in gravity. Detect micrometeorites/secondary particles ejected by meteorite impacts. Lunar dust. Thermal/electric properties lunar sub-su
What is a LRRR? A Laser Ranging Retroreflector, deployed on the moon to reflect a laser back to earth. This allowed us to work out the distance between the Moon and the Earth accurately.
What is the Condensation or Co-formation hypothesis? The hypothesis that the Moon formed at the same time and place as the Earth from material in the solar nebula.
What is the Capture hypothesis? The Moon was formed separately and far away from the Earth. In a chance meeting it was captured by the Earth's gravitational pull. It has since then remained in orbit around us.
What is the Fission hypothesis? A rapidly spinning Earth caused a large blob of material to spin-off. This form the Moon.
What hypothesis is now generally regarded as being correct for the Moon's formation? The Giant Impact Hypothesis (the Big Whack)!
What is the Giant Impact Hypothesis? The young Earth was struck by a Mars-sized object (Theia). Theia and the Earth's outer layer then merged
Created by: grabm
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