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Heinemann Senior Science 2 Chapter 5 answers Chapter 5 Space science 5.1 Space is not ‘empty’ Questions 1 To supply the air we breathe, regulate the global temperature, and filter out dangerous levels of radiation. 2 The ozone layer and greenhouse gases such as carbon dioxide, water vapour and methane, have an important effect on the distribution of temperature in the lower atmospheres, as they absorb ultraviolet radiation from the sun. They allow the visible shorter wavelength and infrared radiation to pass through to the Earth’s surface and heat it. The Earth emits some infrared radiation back into space but much of it is absorbed by the greenhouse gases before reaching space. Hence, at 15 km the temperature is lower than at 50 km. Here the largest amounts of ultraviolet radiation are present and the distribution of ozone is mostly affected by meteorological conditions. At an altitude of 85 km concentrations of ozone and water vapour become negligible and so the temperature cools off faster than it heats up. 3 carbon dioxide (0.03% of the atmosphere) 4 Space consists of areas where there is a dense concentration of matter, such as stars and planets, and areas called the interstellar medium—thinly dispersed layers of gases and dust particles. While the distances between these particles may seem large compared with particle distances in, say, the gases of a planetary atmosphere, their presence means that space is not really empty. 5 During the lunar day there is no atmosphere to protect the Moon’s surface from the Sun’s rays, so it gets extremely hot. During the lunar night, since there are no atmospheric gases to retain the heat, it gets extremely cold. 6 Individual student response or class discussion. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 1 Heinemann Senior Science 2 Chapter 5 answers Further questions 1 Atmospheric layers are characterised by differences in chemical composition, and this produces variations in temperature. 2 The universe is composed of objects ranging in size from the subatomic to supergiant stars. The volume of these particles is very much smaller than the volume taken up by the universe. Most of the volume taken up by the universe is empty space. Objects in space move rapidly in fixed orbits about central entities. Gas and dust particles can collide with each other, forming new entities such as stars. The gravitational forces between objects such as stars and planets are weak but additive. So the larger the body, the greater the attraction it can exert. The forces act over very long distances. Weak nuclear forces govern the properties of particles such as electrons. Strong nuclear forces bind together protons, neutrons and other heavy particles, and this is the force that provides the energy that fuels the stars and makes them shine. Collisions between objects in space are not elastic. Energy is still conserved but changed to other forms such as heat and light. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 2 Heinemann Senior Science 2 3 Chapter 5 answers Gases in space are not confined to a ‘container’ as such. (While the known universe can be regarded as a container if it is a ‘closed’ universe, these boundaries have not yet been reached. Recent evidence suggests an ‘open’ universe.) So distances between gas particles are great and become greater as the universe continues to expand. Collisions between particles will become less frequent resulting in the birth of fewer new stars, eventually leading to the demise of the universe. 4 Earth’s atmospheric conditions—wind, rain, heat, and so on—have removed traces of meteor impact. Most of the rocks that enter our atmosphere burn up before reaching the surface of the Earth. Mercury and our Moon have no atmosphere to prevent this. 5 a Light from the star travels through the vacuum of space in a straight line. When it enters the Earth’s atmosphere it travels through layers of air that are at different temperatures. As it passes from one layer to the next, the light is refracted and appears to twinkle to the observer. b Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 3 Heinemann Senior Science 2 Chapter 5 answers 5.2 Gravity in space Questions 1 Satellites don’t fall into the Earth because of their tremendous speed. Although they are pulled towards the Earth by gravity, their speed enables them to keep falling ‘over the horizon’. Thus if they are travelling with exactly the correct speed they never actually get any closer to the Earth’s surface. The diagram shows four paths of satellites which have moved too slowly and fallen back to Earth. The circular paths around the Earth are successful satellite orbits. 2 Laika, a dog, was the first living thing in space. This was significant as it showed that it might be possible to send humans safely into space. 3 When the cable breaks, both the lift and myself are in free-fall. I feel weightless— there is no force under my feet because my acceleration equals the acceleration of gravity. 4 a friction b inertia Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 4 Heinemann Senior Science 2 Chapter 5 answers Further questions 1 The mass of the neutron star is hundreds of thousands of times greater than the mass of the Earth, while its radius is much smaller. This huge increase in mass and decrease in radius would make the force of gravity millions of times greater on the neutron star, compared to on Earth. 2 Your weight reading on the scales would increase (lift going up) and decrease (lift going down). If the scales read zero, the lift would have broken and you would be in freefall. 3 The gravitational pull at the Earth’s equator is less than in Hobart because the Earth’s slightly squashed-sphere shape means the chocolate is further from the centre of mass. Therefore, the chocolate would weigh less and you would get more mass to the gram if using a spring balance. (In reality there would be a negligible difference.) 4 Students can extrapolate from their graph to find the answer. The Moon has this time of orbit (24 hours). 5.3 Humans in space Questions 1 Changes to the muscular, nervous and skeletal systems. 2 Bodies have adapted to live under Earth gravity, not microgravity conditions. 3 Shuttle food can be freeze-dried, dehydrated or thermostabilised. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 5 Heinemann Senior Science 2 4 Chapter 5 answers Sealed plastic packaging with straws, trays with adhesive straps, plastic containers similar to those used in the home with airtight lids. 5 Playing ball, looking out the window, reading and exercising. 6 Muscles are no longer adapted to Earth conditions, so the increased gravity causes problems with movement and cardiac function. Further questions 1 Individual student response. 2 The doctor could ask: Did you at any time experience nausea (due to changes to the inner ear), heart palpitations, optical illusions (inner ear), loss of sense of touch (spine stretches causing back pain and nerve blocks), or puffiness and swelling of the face? The doctor could also give tests for muscle strength and flexibility. 3 Individual student response. 4 a Similar problems to astronauts returning to Earth from long space stays, only worse. For example, standing would be impossible, any movement would be tiring, heart muscle would not be strong enough to pump blood upwards against the force of gravity, sense of balance would not work properly. b Build up muscle, bone and fluid absorption rates and calcium development; inner ear adjustment. This would involve stringent exercise routines, and medical intervention to assist with inner ear adjustment (possibly a mechanical implant). 5 Individual or group response. 5.4 Constructing for space flight Questions 1 The shuttle is re-usable, so is more cost-effective. 2 Solid fuel consisting of powdered aluminium with oxygen provided by ammonium perchlorate. 3 A step-rocket discards empty rocket casings as their fuel is exhausted, thus decreasing the mass. Less inertia means more speed. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 6 Heinemann Senior Science 2 Chapter 5 answers 4 5 The shuttle uses Earth gravity to bring it back to the ground on re-entry. 6 The shuttle is not protected from the Sun’s heat, which is normally filtered out by the Earth’s atmosphere. Further questions 1 The skateboard is an example of where Newton’s Third Law applies. The person’s foot pushes backward, which causes an opposite reaction and the skateboard’s wheels move forward. 2 Thrust means to push forward with force. Thrust occurs in a firing gun, a person skateboarding, a propeller, and a balloon expelling air. 3 Advantages of space shuttle: cheaper than manufacturing a new craft for each trip; reusability; more passenger room. Disadvantage: not enough rocket fuel to travel long distances (rocket boosters fall off after leaving Earth). 4 Individual student response. 5 Individual student response. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 7 Heinemann Senior Science 2 Chapter 5 answers 5.5 Exploring the universe Questions 1 A refracting telescope uses lenses that bend the light to form an image, whereas a reflecting telescope uses mirrors to reflect the light to form an image. 2 pollution, lights, tall objects such as mountains or buildings 3 The atmosphere causes interference in Earth-based telescopes. There is less interference with a telescope in orbit above the atmosphere, such as the Hubble Space Telescope. 4 The purpose of Mir was to maintain long-term human presence in space and to observe the long-term effects of space habitation on the human body. 5 Mir was used to house astronauts and equipment. Hardware equipment originally intended for Mir was used in the construction of the ISS. 6 The purposes of the ISS are research in medicine, materials and fundamental science. Further questions 1 The Pioneer space probes carry plaques to greet aliens. They are engraved with a sketch of a human, various mathematical symbols and a map of the location of Earth. The main language is mathematics. 2 Defects in the curved mirror of a telescope would cause images to be distorted. 3 Larger telescopes can collect more light rays, which gives sharper images. 4 In binoculars, light rays enter through the lenses and are bent to form larger images. 5 19 February 1986: Mir Core launched to altitude of 235 km (later 330 km) 30 July 1987: Kvant (astrophysics module) launched and docked 26 November 1990: Kvant 2 (scientific and airlock module) launched and docked 10 June 1990: Kristall (biological and materials processing module) arrives at Mir 19–25 July 1991: Sophora antenna constructed January 1994–March 1995: Valeri Polyakov undertakes the longest duration in space 26 April 1996: Priroda remote sensing module arrives, completing the Mir Space Station (used to measure aerosol and ozone concentrations in atmosphere) Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 8 Heinemann Senior Science 2 Chapter 5 answers 25 June 1997: Mir collides with a resupply ship and is damaged June 2000: Last crew leaves Mir 20 February 2001: Mir completes its fifteenth year in orbit 22 March 2001: Mir is deorbited and returns to Earth in a fiery blaze, coming to rest in the Pacific Ocean 6 Individual student response. 5.6 Impacts of space technology Questions 1 Astronauts should be trained in survival procedures, such as hunting and gathering food, hiding from possible enemies, and how to prepare survival equipment from the local environment. 2 A spacesuit protects against heat, cold, meteorites and space junk. It is made from many layers of flexible, airtight materials such as nylon and Teflon and is inflated to the correct atmospheric pressure for astronaut survival. It provides counterpressure and anti-exposure functions in case the crew has to parachute from the orbiter in an emergency. 3 Andrew Thomas 4 mission specialists 5 thermal gear to protect against the cold Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 9 Heinemann Senior Science 2 Chapter 5 answers Further questions 1 A timeline of piloted space flight Program Launch Date Crew Notable events Vostok (USSR) 12 Apr 1961 Gagarin First human in space; orbital flight Mercury (USA) 5 May 1961 Shepard First American in space; suborbital flight Mercury (USA) 21 Jul 1961 Grissom Capsule sank on landing Vostok (USSR) 6 Aug 1961 Titov First human in space for over 24 hours Mercury (USA) 20 Feb 1962 Glenn First American in Earth orbit Mercury (USA) 24 May 1962 Carpenter First meal eaten in space; missed landing site by 400 km Vostok 3 (USSR) 11 Aug 1962 Nikolayev First joint mission (Vostok 4) Vostok 4 (USSR) 12 Aug 1962 Popovich Came within 6.4 km of Vostok 3 Mercury (USA) 3 Oct 1962 Schirra First splashdown in Pacific Ocean Mercury (USA) 15 May 1963 Cooper First US flight to exceed 24 hours 2 Individual student response. 3 Individual student response. 4 Individual student response. 5 Mechanical engineers to take care of mechanical systems; computer engineers to take care of computing systems; electrical engineers to take care of electrical systems; medical personnel to monitor astronauts’ health; communications experts to support all communication systems. 6 Individual student response. 7 Astronauts work in unusual, confined and possibly dangerous spaces for long periods of time. Full cooperation between astronauts and acceptance of the team leader’s decisions are important. Each astronaut’s life depends on a successful working relationship with the other astronauts. Exam-style questions 1 a nitrogen and oxygen b Refer to Figure 5.4 of text (p. 239). Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 10 Heinemann Senior Science 2 c Chapter 5 answers The mass of the Earth produces a gravitational force towards the centre of the planet. All matter close to the Earth is attracted to this centre. The gases of the atmosphere achieve a balance between escaping into space (for example, the lighter gases such as hydrogen and helium are found in the upper atmosphere) and being attracted by the Earth’s mass (heavier gases such as oxygen are found in the lower atmosphere). 2 a Space is not considered ‘empty’ because it contains particles such as gas and dust separated by long distances, as well as light particles and dark matter. b The particles in space make up the interstellar medium—composed of 99% gas and 1% dust. Ninety per cent of the gas is hydrogen and the remaining 10% is composed of other elements, mostly helium. Carbon and silicate grains make up the dust component. c 3 a Both the Moon and Earth have mass, and hence exert a gravitational pull on each other—that is, an attraction. As the Earth has greater mass, its influence on the Moon is far greater. Thus the Moon is kept in orbit around the Earth as it continuously falls towards the Earth, travelling at a constant speed. b The term ‘weightlessness’ implies that the force of gravity is not acting at all. However, all objects display a gravitational pull on each other so it is not possible to fully escape the force of gravity. ‘Microgravity’ is the correct term for the reduced gravity experienced by astronauts in space. The astronauts appear to be weightless because they are in freefall around the Earth. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 11 Heinemann Senior Science 2 c Chapter 5 answers Microgravity can be simulated on earth in a falling elevator or a jet craft in a parabolic flight pattern. The effects experienced include weightlessness and possibly nausea. d A spacecraft in orbit around the Earth is actually experiencing ‘freefall’—that is, it is falling freely around the Earth under the influence of gravity. All the objects (including the crew) inside the craft are also falling freely and appear to have no weight. Refer to Figure 5.13 of text (p. 247). 4 F = mg, g = F/m = 540/120 = 4.5 m/s2, less than half that on Earth. 5 If the brick was quite heavy, the throw would provide a forward thrust to the brick. Newton's Third Law would send you into recoil and you would fall off he edge of the cliff. 6 a Individual student response. Dehydrated foods would be rehydrated by adding hot or cold water. Thermostabilised foods (heat-sterilised) would be eaten directly from the can or plastic pouch with a spoon or fork. b The circadian rhythm is the 24-hour period of human activity where a person rests for 8 hours and is awake for 16 hours. In space there is no day or night to help regulate the body clock, so astronauts must train their bodies to a regimented 24-hour cycle. c Body systems affected by living in space for long periods of time are the musculoskeletal system, the nervous system and the cardiovascular system. Major effects on body functions include wasting of muscles and heart, constipation, anaemia, loss of bone mass, kidney stones nausea, radiation sickness, reduced immune system and psychological stress. While in space, astronauts can exercise regularly to keep muscles from deteriorating. They can wear eye shades to help in regular sleep by providing artificial darkness. They can play board games with each other to break the monotony. 7 Individual student response. 8 a During lift-off, the effects of the Earth’s gravity pulling the rocket downwards need to be counteracted. Gravity is used to assist re-entry into the Earth’s atmosphere. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 12 Heinemann Senior Science 2 b Chapter 5 answers Orbiter: main body of the space shuttle, made of metal alloys, aluminium plates and graphite epoxy. These substances sustain lift-off and re-entry conditions such as extreme heat and cold. They must be durable and easily replaceable or repairable. Solid rocket boosters: provide thrust for first stage of lift-off. External tank: contains propellants used by main engines. c Staging removes fuel sections as they are depleted, so there is less mass to push upwards. 9 a Less than one hundredth of normal for 15–25 seconds. Less than one thousandth of normal for 5–15 seconds. b 7 km c 2.5 g d 10 km 10 The shuttle was called the ‘space plane’ because of its shape and because it would re-enter the Earth’s atmosphere and land in a similar way to a plane. ‘Shuttle’ is also an appropriate name because it implies that the vehicle can be re-used and it can carry passengers to and from space. 11 Optical telescopes (refractive and reflective) pick up light rays coming from an object and bend the light rays to meet inside the tube to form an image of the object (such as a star or galaxy). They give better resolution when in space, where there is no interference from Earth’s atmosphere. Radio telescopes pick up radio waves, which are not affected by the Earth’s atmosphere and so can be observed from the Earth’s surface 24 hours a day in all weather. Infrared telescopes pick up heat rays. These telescopes are located on satellites above the atmosphere. 12 a SETI stands for Search for Extra-Terrestrial Intelligence. OSETI stands for Optical Search for Extra-Terrestrial Intelligence. SETI uses microwave radio astronomy to search for other life in space. OSETI uses pulsed lasers to attempt interstellar communication. b The Voyager Interstellar Mission (VIM), consisting of the twin Voyager spacecraft, was sent to explore the giant outer planets in our solar system. Voyager 1 and 2 were launched in 1977. They both visited Jupiter and Saturn, and then Voyager 2 continued its journey to Uranus and Neptune. In 1990, Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 13 Heinemann Senior Science 2 Chapter 5 answers Voyager 2 transmitted images looking back across the span of the entire solar system. Both Voyagers continue to explore interstellar space. The mission has the potential for obtaining useful data on interplanetary, and possibly interstellar, fields, particles, and waves (FEW) until around 2020. It has returned more new knowledge about the outer planets than had existed in all of the preceding history of astronomy and planetary science 13 a Space particles, which may damage or penetrate a space vehicle or spacesuit, exposing the astronauts to space; and radiation, which can cause radiation sickness, cancer or death. b Spacesuits and vehicles are both made of appropriate materials that withstand the extremes of space such as damage from radiation and micrometeoroids. 14 a Advances in medical research—for example, prolonging life and increasing comfort. Advances in technology—for example, personal computers. b 15 a b Individual student response. Temperature, air pressure and oxygen levels similar to conditions on Earth. A space station must provide an environment suitable for long stays in space. It must have features that the human body is accustomed to on Earth—oxygen for breathing, suitable gravity, heat and cold protection, and food storage. c A spacesuit keeps an astronaut alive for six to eight hours outside the space vehicle. It provides protection from micrometeoroids and radiation, and insulation from the temperature extremes of space (–160ºC to 120ºC). It is designed from flexible, airtight materials. Copyright © Pearson Australia (a division of Pearson Australia Group Pty Ltd) 14