GCSE Astronomy Specification Flashcards

Question	Answer
1.1a - Describe features of the Earth that distinguish it from other planets.	Within the habitable zone of our Sun meaning it has liquid water. It also has a nitrogen and oxygen rich atmosphere that allows us to breathe. It sustains life.
1.1b - Relate the blue sky to the preferential scattering of light in its atmosphere.	Shorter wavelengths of light are absorbed by gas molecules in the atmosphere. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Most of the longer wavelengths pass through the atmosphere (red etc.)
1.1c - Demonstrate an understanding of the benefits of the Earth’s atmosphere to humankind.	-It absorbs harmful UV radiation that causes accelerated skin aging + skin cancer. -It absorbs harmful energetic x - rays and gamma rays. -It regulates the temperature meaning we rarely experience 'extremes' and allows water to exist in liquid form. - Provides us with oxygen to breathe.
1.1d - Describe some of the major causes of light pollution and demonstrate an understanding of why it is undesirable to astronomers.	Observations of the night sky are hindered by skyglow - a cause of light pollution. The main sources of light pollution are: - Floodlights/streetlights. -Sports stadiums. -Shopping centre lights/motorway lights. -The Moon. -Aurorae.
1.1e - Describe how Eratosthenes made the first accurate calculation of the circumference of the Earth.	Erastosthenes found out that on the summer solstice there was no shadow visible in a well in Syene, on the Tropic of Cancer. Measurements in Alexandria on the same date at noon showed it was slightly over 7 degrees from zenith. He found out that Syene was roughly 790 km further south than Alexandria meaning that 7 degrees = 790 km. 360/7 = 51.42... He multiplied this by 790 to get the Earth's approximate circumference - 40628 was his value. The actual value is 40,075 km. Flaws in Erastosthene's calculations include the fact Syene was not exactly on the Tropic of Cancer, the uncertainty in the distance between Alexandria and Syene, and the conversion between the unit Erastosthenes used and km.
1.1f - Recall the shape and diameter of the Earth.	Earth is an oblate spheroid (flattened sphere) and has an approximate diameter of 13,000 km.
1.1g - Describe the evidence that the Earth is approximately spherical.	-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.
1.1h - Recall the rotation period of Earth and the time to rotate 1 degree.	-It takes the Earth 23 hours and 56 minutes to complete one rotation on it's axis. -The time taken for Earth to rotate 1 degree on it's axis is 4 minutes.
1.1i - Demonstrate an understanding of the terms: equator, tropics, latitude, longitude, pole, horizon, meridian and zenith.	Equator - a circle around the middle of the Earth at equal distances from each pole. Tropics - imaginary circles 23.5 degrees north and south of the equator, the Tropic of Cancer and Capricorn respectively. Latitude - the angle of a location North or South of the equator. Longitude - the angle East or West of the prime meridian. Poles - the point that the axis of rotation of the Earth passes through. Horizon - an imaginary line where land meets the sky. Meridian - an imaginary circle that passes through both the poles; the prime meridian passes through Greenwich. Zenith - the point directly above you in the sky.
1.1j - Demonstrate an understanding of the drawbacks to astronomers of the Earth’s atmosphere and relate these to the need for optical and infra-red observatories to be sited on high mountains or in space.	The atmosphere creates many variables that can hinder observations including cloud cover, air turbulence, the twinkling effect on stars, blurred images with reduced resolution. Moreover, the atmosphere absorbs many times of wavelengths that astronomers may want to detect such as gamma rays and x - rays. By placing telescopes in space, there are no atmospheric drawbacks to using telescopes and wavelengths are more easily detected as they are not being absorbed by the atmosphere. By placing telescopes on high mountains the light pollution is reduced and the atmosphere may be thinner higher up, meaning better resolution images but not better than those taken with space telescopes.
1.1k - Describe the features of reflecting and reflecting telescopes (detailed ray diagrams not needed)	Refractor: a glass convex lens collects the light and brings it to focus. Reflector: a curved mirror collects the light. The lens or mirror is called the objective and 'size' of a telescope refers to it's diameter.
1.1l - Demonstrate an understanding of why the world’s largest telescopes are reflectors rather than refractors.	Larger telescopes have advantages over smaller ones as they collect more light and have a higher resolution in proportion to diameter. Reflecting telescopes are seen as better as they are easier and cheaper to be produced on a larger scale.
1.1m - Demonstrate an understanding that the Earth’s atmosphere is transparent to visible light, microwaves and some radio waves.	Visible light and some microwaves and radio waves are able to reach Earth. X-ray and gamma-rays are absorbed by oxygen and nitrogen. Most infrared radiation is absorbed by water, carbon dioxide and methane. UV radiation is absorbed by ozone and at shorter wavelengths oxygen. The longest radio waves are reflected back into space by electrons in the ionosphere.
1.1n - Interpret data on the effect of the Earth’s atmosphere on infra-red, ultra-violet and X-rays.	X-ray and gamma-rays are absorbed by oxygen and nitrogen. Most infrared radiation is absorbed by water, carbon dioxide and methane. UV radiation is absorbed by ozone and at shorter wavelengths oxygen. The longest radio waves are reflected back into space by electrons in the ionosphere.
1.1o - Describe where infra-red, ultra-violet and X-ray observatories are sited and explain the reasons why.	Many infrared, UV and X-ray telescopes are in space because they are often unable to penetrate Earth's atmosphere. In space they will be easier to detect.
1.1p - Describe the nature and discovery of the Van Allen Belts.	The Van Allen Belts were discovered by James Van Allen. The inner belt was discovered first in January 1958 by a Geiger counter on board Explorer 1. It's existence was confirmed by Explorer 3 and Sputnik 3. The outer belt was discovered in December of 1958 by Pioneer 3 with similar instruments. The compact inner belt consists mainly of high energy protons whereas the outer belt is more dynamic and consists mainly of electrons and charged particles emitted by the Sun and other solar activity.
1.2a - Identify the Moon’s principal features, including the Sea of Tranquility, Ocean of Storms, Sea of Crises, the craters Tycho, Copernicus and Kepler, and the Apennine mountain range . (Answers shown on reverse + Appenine mountains)	Image: moon_flashcards (image/jpg)
1.2b - Recall the Moon's diameter and it's approximate distance from Earth.	Diameter - 3500 km. Distance from Earth - 380 000 km.
1.2c - Recall the Moon's rotational and orbital period.	Both are 27.3 days.
1.2d - Demonstrate an understanding of why the far side of the Moon is not visible from Earth.	The Moon's orbital and rotational periods are the same - once the Moon has rotated 90 degrees on it's axis, it has also orbited 90 degrees. This means that only one side of the Moon is visible from Earth (the near side).
1.2e - Describe how astronomers know the appearance of the Moon’s far side and how it differs from the near side.	The Moon's far side almost completely lacks maria and consists mainly of terrae - it is also very mountainous and rich in craters. The near side contains a lot more maria.
1.2f - Distinguish between the lunar seas (maria) and lunar highlands (terrae).	Maria are dark grey, relatively smooth lunar seas made of iron rich basaltic rock that contain less craters than terrae. Terrae are very mountainous, light grey coloured and highly cratered highlands composed of anorthosite, a course grained igneous rock.
1.2g - Demonstrate an understanding of the origin of the lunar seas and craters. ORIGIN OF LUNAR MARIA NEEDS TO BE CONFIRMED.	The lunar craters are believed to have been caused by impacts from solid bodies such as meteoroids and the larger craters such as Tycho and Copernicus may have been caused by asteroid impacts.
1.2h - Demonstrate an understanding that the relative numbers of craters in the seas and highlands implies different ages of these features.	Lunar maria contain much fewer craters than lunar terrae. This suggests that lunar maria are younger as they have been struck by fewer bodies than the highlands.
1.2i - Describe the nature of rilles and wrinkle ridges.	Rilles are narrow channel like depressions in the lunar seas that can be straight, curved or sinuous. The majority are believed to have been caused by lava flows. Wrinkle ridges are believed to have been caused by the buckling of lunar surface under compressive forces of cooling and contracting lava forming ridges up to hundreds of kilometres long.
1.2j - Relate the lack of atmosphere to the Moon's low gravity.	The strength of the Moon's gravity is only approximately 1/6th of Earth's due to it's small mass and this is the most likely reason for the lack of significant atmosphere. This is likely because due to the Moon's low gravity it is unable to hold gases in place and therefore have an atmosphere.
1.2k - Describe the nature and purposes of the Apollo space programme and its experimental packages (ALSEPs).	The primary purpose of NASA's Apollo missions was to send humans to the Moon and return them safely to Earth. Some ALSEPs included to analyse, monitor and measure: -The structure of the Moon's interior. -Minute changes in lunar gravity. -The composition and pressure of the lunar atmosphere. -The intensity and direction of solar wind.
1.1l - Describe the likely origin of the Moon.	The likely origin of the Moon is the giant impact hypothesis. This suggests that a relatively young Earth was struck by a Mars sized object called Theia, Earth absorbed Theia and the debris remaining from the collision cooled and condensed to form the Moon. It was close enough to the Earth to remain in orbit.
1.2m - Describe the evidence that allowed astronomers to develop the giant impact hypothesis.	Evidence includes: - The Moon lacks a substantial iron core suggesting the Earth and Moon were not formed together. - The relative abundances of the isotopes in oxygen in moon rocks were almost identical to those on Earth. - Lack of water and other volatile compounds in lunar rock supports the idea of a collision involving so much energy that these were vaporised. - The discovery of KREEP rich rocks.
1.3a - Demonstrate an understanding of how the Sun can be observed safely by amateur astronomers.	The safest way for amateur astronomers to observe the sun is by using indirect projection method in which a pinhole camera, pair of binoculars or a telescope focuses an enlarged image of the Sun onto a screen, reducing the brightness to a safe level.
1.3b - Recall the Sun's diameter and it's distance to Earth.	Diameter - 1.4 million km. Distance to Earth - 150 million km (1 AU).
1.3c - Recall the temperature of the Sun's photosphere.	5800k.
1.3d - describe the solar atmosphere and recall the approximate temperature of the corona.	The solar atmosphere consists of the chromosphere above the photosphere, the visible 'surface' of the Sun. Above this is the extensive corona, the 'crown', a glowing region of ionised gas about 2 million K, hot enough to emit x-rays.
1.1e - Describe the appearance and explain the nature of sunspots.	Sunspots are cooler, darker areas of the photosphere that correspond to strong localised magnetic fields. They have a darker central umbra about 2000K cooler than the photosphere and a lighter outer penumbra about 200K cooler than the photosphere.
1.1f - Recall that the Sun's rotation period varies at it's equator and poles.	The Sun's rotation period varies from 25 days at the equator to 36 at the poles.
1.1g - Demonstrate an understanding of how astronomers use observations of sunspots to determine the Sun’s rotation period.	Astronomers can follow the movement of sunspots across the Sun's disc to determine the rotation period of that specific part of the Sun as the rotation period varies at different latitudes. Astronomers can monitor how long it takes for a sunspot to return to the same place they began monitoring it at, this value is the rotation period for this point on the Sun.
1.1h - Interpret data (for example a Butterfly Diagram) in order to describe the long-term latitude drift of sunspots, determine the length of the solar cycle and predict the year of the next solar maximum.	Image: sunspots (image/jpg)
1.1i - Demonstrate an understanding on how the Sun's energy is generated.	The Sun's energy is generated by nuclei fusion it it's core - the hydrogen nuclei fuse together to make helium nuclei. This process is known as the proton-proton chain.
1.1j - Describe how astronomers observe the Sun at different wavelengths.	Telescopes fitted with H-alpha filters allow narrow ranges of wavelengths either side of 656 nm to pass through and blocks the remaining light. The increased contrast creates prominences, filaments, solar flares, sun spots and the chromopshere to be observed more clearly.
1.3k - Demonstrate an understanding of the appearance of the Sun at different wavelengths of the electromagnetic spectrum, including visible, H-alpha, X-ray. SEE 1.3J.	Telescopes fitted with H-alpha filters allow narrow ranges of wavelengths either side of 656 nm to pass through and blocks the remaining light. The increased contrast creates prominences, filaments, solar flares, sun spots and the chromopshere to be observed more clearly. Exceptionally hot areas of the Sun emit x-rays. The bright regions at the edge of the solar disc reveal the Sun's extremely hot corona, and the bright areas on the solar disc are associated with active region (magnetic) loops where ionised hydrogen flows along curved magnetic field lines.
1.3l - Describe the structure and nature of solar wind.	Solar wind is a steady stream of charged particles (mainly protons and electrons but with traces of ions of helium and other elements) flowing outwards in all directions from the Sun's corona often at speeds of 400 km/s.

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GCSE Astronomy Specification Flashcards

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