Download 5.1 Space is not `empty`

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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.
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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.
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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
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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
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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.
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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.
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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.
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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)
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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
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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).
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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.
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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.
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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,
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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.
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