q: why is the sky blue? q: describe the key features that distinguish the earth from other planets...
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Q: Why is the sky blue?
Q: Describe the key features that distinguish the Earth from other planets in the Solar System.
Q: State the major causes of light pollution.
Q: Describe the benefits of the Earth’s atmosphere to humankind.
Q: State the shape and diameter of the Earth.
Q: Describe the evidence that the Earth is approximately spherical.
Q: State the rotation period of the Earth and the time to rotate through 1 degree.
Q: Define the terms: equator, tropic
A: Its atmosphere of mainly oxygen and nitrogen, liquid water (covering about 70% of its surface), life in all its diverse forms.
A: Because of the selective scattering (‘Rayleigh scattering’) of the shorter, bluer wavelengths of sunlight by gas molecules in the atmosphere.
A: It absorbs harmful solar UV, X-ray and gamma radiation; it regulates the temperature so we rarely experience ‘extremes’; it provides us with oxygen to breathe; it partially protects us from meteoroids.
A: Commercial and sports floodlights, urban streetlights and motorway lights, domestic and industrial security lamps, lights above car parks and shopping centres.
A: Ships disappear over the horizon, satellites orbit the Earth, the curvature of the Earth’s shadow during a partial lunar eclipse, aircraft fly in arcs rather than straight lines, images of Earth from space.
A: Average diameter of 13 000 km, slightly flattened (by 42 km) at the poles, making it an oblate spheroid.
A: Equator = the circle around the Earth an equal distance from either pole. Tropic of Cancer = line of latitude of 23.5oN; Tropic of Capricorn = line of latitude of 23.5oS.
A: Rotation period 23 h 56 min (and 4.1 s), time to rotate through 1 degree 4 min.
Q: Define the terms: latitude, longitude.
Q: Define the terms: pole, horizon.
Q: Define the terms: meridian, zenith.
Q: What are the drawbacks to astronomers of the Earth’s atmosphere?
Q: What is the difference between a refracting and reflecting telescope?
Q: What are the advantages of large telescopes over smaller ones?
Q: Why are most large telescopes reflectors, not refractors?
Q: What are some disadvantages to space telescopes?
A:Poles = the northern and southern points of the axis on which the planet rotates. Horizon = the outer ring of the Earth’s surface, at 90o to the zenith line.
A: Latitude = the angle above or below the equator. Longitude = the angle East or West of the Greenwich Meridian.
A: Refraction of light through the turbulent atmosphere causes stars to scintillate and restricts resolution; Rayleigh scattering prevents daytime observation; most EM wavelengths absorbed.
A: Meridian = imaginary lines drawn from pole to pole through a place of interest, e.g. the Prime Meridian through Greenwich. Zenith = the point in the sky directly above the observer.
A: They can collect more light in proportion to area, and they have better resolution in proportion to diameter.
A: Refractor = a glass convex lens collects the light and brings it to a focus. Reflector = a curved mirror (or one made from several segments) collects the light.
A: Reduced lifetime, difficult or impossible maintenance / repairs /upgrades, more expensive to build and launch into orbit.
A: Large mirrors can be manufactured and engineered to a much higher precision than lenses (that are heavy and difficult to support).
Q: Which wavelengths of light is the Earth’s atmosphere transparent to?
Q: Where are radio, infrared, UV and X-ray telescopes located?
Q: What are the Van Allen belts?
Q: How were the Van Allen belts discovered?
Q: State the lunar features you are required to know for the GCSE Astronomy specification.
Q: What is the Moon’s diameter and approximate distance from the Earth?
Q: What are the Moon’s rotational and orbital periods?
Q: Why is the far side of the Moon not visible from Earth?
A: Radio telescopes can be at sea level. Infrared telescopes need to located atop high mountains. UV and X-ray telescopes need to be located in space.
A: Visible light, microwaves and some radio waves.
A: Inner belt (January 1958), using a Geiger counter aboard the US satellite Explorer 1. Outer belt (December 1958) using similar instruments aboard the US lunar probe Pioneer 3.
A: Two doughnut-shaped rings of spiralling high-energy particles held in place high above the Earth’s equatorial region by the Earth’s magnetic field.
A: Diameter of 3,500 km, approximate distance of 380,000 km.
A: Sea of Tranquillity, Ocean of Storms, Sea of Crises, the Apennine mountain range, the craters Tycho, Copernicus and Kepler.
A: Because the Moon’s rotational period is the same as its orbital period (both 27.3 days).
A: They are both 27.3 days.
Q: How do we know what the far side of the Moon looks like?
Q: How is the far side of the Moon different from the near side?
Q: What is the difference between maria and terrae?
Q: What does the relative number of craters in the maria and terrae imply about their relative ages?
Q: What are rilles? Q: What are wrinkle ridges?
Q: Why is there no significant atmosphere on the Moon?
Q: What is the difference between recessive and dominant?
A: The far side is almost devoid of seas (The Eastern Sea, Mare Orientale being the only notable exception) and is almost entirely mountainous and heavily-cratered.
A: First observed by the unmanned Soviet probe Lunik 3 (October 1959). The first humans to observe it were the Apollo 8 astronauts (December 1968).
A: The relatively small number of craters in the maria suggest that they are much younger in age.
A: Maria = Large, dark-grey, relatively smooth lunar seas made of iron-rich basaltic rock. Terrae = lighter-grey, mountainous, high-cratered highlands composed of anorthosite, a course-grained igneous rock.
A: Thought to have been caused by the buckling of the lunar surface as a result of compressive forces within the cooling, contracting lava, forming ridges up to hundreds of kilometres long.
A: Narrow channel-like depressions in the lunar seas that can either be straight, smoothly-curved or sinuous; believed to be caused by lava flows.
A: If a dominant allele is present, the characteristic it codes for will always be displayed. For a recessive characteristic to be displayed the organism must possess 2 copies of the recessive allele.
A: Owing to its relatively small mass , the strength of the Moon’s gravity is only about 1/6 of that on the Earth.
Q: What were the objectives of the Apollo space missions?
Q: Describe the experiments carried out by ALSEP.
Q: What are the four competing theories for the formation of the Moon?
Q: What is the evidence for the Giant Impact Hypothesis?
Q: How can we safely observe the Sun?
Q: State the Sun’s diameter and distance from the Earth.
Q: What is the temperature of the Sun’s photosphere?
Q: Describe the solar atmosphere and state the approximate temperature of the corona.
A: Measure, analyse and monitor: structure of the Moon’s interior; composition and pressure of the lunar atmosphere; intensity and direction of the solar wind; minute changes in lunar gravity; lunar dust; presence of micrometeorites and secondary particles ejected by meteorite impacts; thermal and electrical properties of the lunar sub-surface.
A: Landing a man on the Moon and returning them safely to Earth, collection of lunar soil and rock for analysis, deployment of ALSEP, winning the ‘race’ to the Moon against the Soviet Union.
A: Relative abundance of isotopes of oxygen in moon rocks, lack of water and other volatile compounds in the lunar rocks, discovery of KREEP-rich rocks on the Ocean of Storms and Sea of Showers
A: Condensation or Co-Formation Hypothesis; Capture Hypothesis; Fission Hypothesis; Giant Impact Hypothesis.
A: Diameter = 1.4 million km. Distance from the Earth = 150 million km.
A: Indirect projection method in which a telescope / pinhole camera focuses an enlarged image of the Sun on a screen
A: Above the photosphere is the relatively thin chromosphere (~2000 km) and extensive corona. Both are only observed during a solar eclipse. The corona is a glowing region of ionised gas with a temperature of 2 million K, which is hot enough to emit X-rays.
A: 5800 K.
Q: What is a sunspot?Q: What are the two constituents of a sunspot?
Q: State what the Sun’s rotation period is, and how it can be determined.
Q: What is a Butterfly Diagram?
Q: What is the solar cycle?Q: What was the Maunder Minimum?
Q: What process powers the Sun’s energy output?
Q: Describe the process of nuclear fusion at the centre of the Sun.
A: Umbra = central darker region, about 2000 K cooler than the photosphere. Penumbra = a lighter (less dark) surrounding area, with a temperature about 200 K cooler than the photosphere.
A: A cooler area of the photosphere that corresponds to a strong localised magnetic field. These inhibit the upward motion of convecting solar material and prevent it reaching the top of the photosphere, resulting in lower temperature.
A: The traditional way to study the positions of sunspots by plotting their latitude against time on a chart.
A: The rotation period varies from 25 days at the equator to 36 days at the poles. It can be determined by tracking the apparent movement of sunspots across the Sun’s surface.
A: Between the years 1645 and 1715, the Sun was relatively inactive and very few sunspots were observed; this period corresponds with a period of extremely cold winters in Europe.
A: Although individual or groups of sunspots can last for a few days to several weeks, the relative number of sunspots follows a well-known 11-year pattern called the solar cycle during which the number of sunspots increases to a maximum before falling again.
A: The Sun’s core is around 15 million K, which allows hydrogen nuclei (not atoms!) to fuse to form helium nuclei in a series of reactions called the proton-proton chain.
A: Nuclear fusion.
Q: What is the significance of the equation E = mc2?
Q: What solar features can you observe using an H-alpha filter that you can’t otherwise?
Q: What is the solar wind?Q: Why is it that we can experience solar eclipses?
Q: What is the period of a lunar phase cycle?
Q: Why is the lunar phase longer (by 2.2 days) longer than the orbit period of the Moon?
Q: What are Bailey’s Beads?Q: Why do solar eclipses not occur every new moon?
A: Solar prominences (huge clouds of cooler gas in the Sun’s atmosphere), filaments (the same but appearing as dark silhouettes against the brighter photosphere), solar flares (sudden releases of energy), sunspots and the chromosphere.
A: During the proton-proton chain, at each stage in these reactions, matter (m) is ‘lost’ and converted into an equivalent amount of energy (E). c is the speed of light (3 x 108 m/s).
A: Because (by coincidence) although the Sun is about 400 times further away from the Earth than the Moon, it is also 400 times larger in diameter.
A: A flow of charged particles streaming out from the Sun.
A: During the complete orbit of the Earth by the Moon, the Earth itself has moved significantly in its orbit of the Sun – the extra time is needed to bring the Moon, Earth and Sun in alignment once more.
A: 29.5 days.
A: Because the plane of the Moon’s orbit around the earth is tilted slightly (by about 5o) to the plane of the Earth’s orbit around the Sun
A: Small bright spots of sunlight caused by the Sun’s rays shining through valleys on the Moon at the beginning and end of totality. When just one bead is visible, this is known as the Diamond Ring effect.
Q: What is a solar day? Q: What is a sidereal day?
Q: Why is a solar day 4 minutes longer than a sidereal day?
Q: What is apparent solar time?
Q: What is the mean Sun?Q: What is the Equation of Time?
Q: What is an aurora?Q: Where on Earth are aurorae likely to be observed?
A: A sidereal day is the time it takes for the Earth to spin from East to West (in an anticlockwise sense if viewed from directly above the North Pole); the time taken for successive crossings of a given star across an observer’s meridian.
A: A solar day is exactly 24 hours. This is the time taken for successive crossings of the Sun (any given part of it) across the observer’s meridian.
A: Apparent solar time is the time that is shown on sundials.
A: The extra 4 minutes are needed because during one complete Earth-rotation, our planet has moved slightly in its orbit around the Sun, and it must rotate for an extra 4 min to allow the Sun to return to the same position in the sky
A: EOT = apparent solar time – mean solar time (GMT)
A: An imaginary body travelling eastward along the celestial equator, at a rate of motion equal to the average rate of the real Sun along the ecliptic.
A: Generally only visible from high latitudes, but can be observed from lower latitudes such as those in the UK when solar activity is very high.
A: Aurorae are caused by electrons from the solar wind that have been accelerated to high speeds in the Earth’s magnetic field, exciting atoms and molecules of oxygen and nitrogen in the upper atmosphere. As the atoms or molecules de-excite, they emit light at certain wavelengths that are characteristic of the element concerned.