VI Astronomy and Space Science (25 hours)
Overview
Astronomy is the earliest science to emerge in history. The methods of measurement and the ways of thinking developed by early astronomers laid the foundation of scientific methods which influenced the development of science for centuries. The quest for a perfect model of the universe in the Renaissance eventually led to the discovery of Newton’s law of universal gravitation and the laws of motion. This had a profound influence on the subsequent rapid development in physics. Using physical laws in mathematical form to predict natural phenomena, and verifying these predictions with careful observation and experimentation, as Newton and other scientists did some three hundred years ago, has become the paradigm of modern physics research. Physics has become the cornerstone of modern astronomy, revolutionising our concepts of the universe and the existence of humankind. Modern developments in space science, such as the launch of spacecraft and artificial satellites, still rely on Newtonian physics. In this topic, students have an opportunity to learn principles and scientific methods underpinning physics, and to appreciate the interplay between physics and astronomy in history, through studying various phenomena in astronomy and knowledge in space science.
Students are first given a brief introduction to the phenomena of the universe as seen in different scales of space. They are also encouraged to perform simple astronomical observations and measurements. Through these processes, they can acquire experimental skills, and become more familiar with the concept of tolerance in measurement. A brief historic review of geocentric model and heliocentric model of the universe serves to stimulate students to think critically about how scientific hypotheses were built on the basis of observation.
Kepler’s third law and Newton’s law of gravitation are introduced with examples of astronomy. Kepler’s third law for circular orbits is derived from the law of gravitation and concepts of uniform circular motion, including centripetal acceleration. Besides the motion of planets, moons and satellites, latest astronomical discoveries can also serve as examples to illustrate the applications of these laws.
The concepts of mass and weight are applied. Feeling weightlessness in a spacecraft orbiting the Earth is explained in terms of the fact that acceleration under gravity is independent of mass.
The expression for gravitational potential energy can be obtained from the law of gravitation and work-energy theorem. Motions of artificial satellites are explained by the conservation of mechanical energy in their orbits. The meaning of escape velocity, together with its implications for the launching of a rocket, are introduced.
In the last part of this topic, students are exposed to astronomical discoveries, including the basic properties and classification of stars and the expansion of the universe. As only a simple, heuristic and qualitative understanding of these topics is expected, students are encouraged to learn actively by reading popular science articles and astronomical news – which promotes self-directed learning. Also, oral or written presentation of what they have learned may serve to improve their communication skills.
Students should learn: Students should be able to:
a. The universe as seen in different scales
structure of the universe use the “Powers of Ten” approach to describe the basic features and hierarchy of celestial bodies such as satellite, planet, star, star cluster, nebula, galaxy and cluster of galaxies, as seen in different spatial scales
define the basic terminologies such as light year and astronomical unit for describing the spatial scale
b. Astronomy through history
models of planetary motion
compare the heliocentric model with the geocentric model in explaining the motion of planets on the celestial sphere
Students should learn: Students should be able to:
c. Orbital motions under gravity
Newton’s law of gravitation
apply Newton’s law of gravitation 2 r
F GMm to explain the
motion of celestial bodies in circular orbits
derive Kepler’s third law T2 r3 for circular orbits from Newton’s law of gravitation
state Kepler’s third law for elliptical orbits
GM T a
3 2 2 4
apply Kepler’s third law to solve problems involving circular and elliptical orbits
weightlessness explain apparent weightlessness in an orbiting spacecraft as a result of acceleration due to gravity being independent of mass
conservation of energy interpret the meaning of gravitational potential energy and its expression
r UGMm
apply conservation of mechanical energy to solve problems involving the motion of celestial bodies or spacecraft
determine the escape velocity on a celestial body
d. Stars and the universe
stellar luminosity and classification
determine the distance of a celestial body using the method of parallax
use parsec (pc) as a unit of distance
realise magnitude as a measure of brightness of celestial bodies
distinguish between apparent magnitude and absolute magnitude
describe the effect of surface temperature on the colour and luminosity of a star using blackbody radiation curves
realise the existence of spectral lines in the spectra of stars
state major spectral classes: O B A F G K M and relate them to the surface temperature of stars
Students should learn: Students should be able to:
state Stefan’s law and apply it to derive the luminosity L=4R2T4 for a spherical blackbody
represent information of classification for stars on the Hertzsprung-Russell (H-R) diagram according to their luminosities and surface temperatures
use H-R diagram and Stefan’s law to estimate the relative sizes of stars
Doppler effect realise the Doppler effect and apply
c vr
o
to determine the
radial velocity of celestial bodies
use the radial velocity curve to determine the orbital radius, speed, and period of a small celestial body in circular orbital motion around a massive body as seen along the orbital plane
relate the rotation curve of stars around galaxies to the existence of dark matter
relate the red shift to the expansion of the universe
Suggested Learning and Teaching Activities
Students should develop basic skills in astronomical observation. Observation can capture students’ imagination and enhance their interest in understanding the mystery of the universe.
It also serves to develop their practical and scientific investigation skills. Students may use the naked eye to observe the apparent motion of celestial bodies in the sky, and use telescopes/binoculars to study the surface features of the Moon, planets and deep sky objects.
Simple application of imaging devices such as a digital camera, webcam or charge-coupled device (CCD) is useful. Project-based investigation may also enhance students’
involvement and interest. Space museums, universities and many local organisations have equipment and expertise on amateur astronomical observation, and welcome school visits and provide training for enthusiastic teachers.
analysis. Animation may be used to complement this and to strengthen their understanding of the analytical content, and train their data- acquisition and handling skills. Standard animation tools, and a huge source of photos and videos are available in the NASA website.
Software such as Motion Video Analysis may help students to use these resources to perform useful analysis. Connection of the analysed results with curriculum content and modern astronomical discoveries should be emphasised. This will help students to appreciate the importance of the physics principles they learn, and to realise that physics is an ever-growing subject with modern discoveries often emerging from the solid foundation laid previously.
Apart from the acquisition of practical and analytical skills, students may take the learning of advanced topics and new astronomical discoveries as a valuable opportunity to broaden their perspectives on modern science. They should not aim at a comprehensive understanding of these topics, but rather try to gain a simple, heuristic and qualitative glimpse of the wonders of the universe, as well as to appreciate the effort that scientists have made in these important discoveries. A huge number of astronomy education resources/articles is available on the Web. Students may develop the ability to learn independently through studying these materials, and polish their communication skills in sharing what they have learned with their classmates.
Possible learning activities that students may engage in are suggested below for reference:
Observation of astronomical phenomena
Observing stars with the naked eye, and recognising the constellations and the apparent motion of celestial bodies in the sky
Observing meteor showers with the naked eye
Observing the surface of the Moon with a small telescope
Observing a lunar eclipse with a small telescope
Observing the features of major planets with a small telescope, like the belts and satellites of Jupiter, the phases of Venus, the polar caps of Mars, and the ring of Saturn
Observing special astronomical events such as the opposition of Mars, and the transit of Venus over the Sun with a small telescope
Observing bright comets with a small telescope
Observing binary stars and variable stars with a small telescope
Observing deep sky objects with a small telescope
Observing features of the Sun (e.g. sunspots and granules) and solar eclipse by projection
Recording the position and/or features of the above objects with a digital camera, a webcam or an astronomical CCD
Possible learning activities
Constructing a sundial to make time measurement
Using a transparent plastic bowl to trace the path of daily motion of the Sun on the celestial sphere. Students can examine the paths in different seasons to understand how the altitudes of the Sun and the duration of sunshine vary throughout the year.
(Reference: http://www.ied.edu.hk/apfslt/issue_2/si/article4/a4_1.htm)
Recording the position of Galilean satellites of Jupiter. Students may use the size of Jupiter as the reference length to estimate the period and orbital radius of the satellites.
To avoid technical difficulties in observation, students may use the Solar System Simulator provided by NASA (http://space.jpl.nasa.gov/) and Motion Video Analysis Software (http://www.hk_phy.org/mvas) to perform a virtual analysis of the motion of satellites. They can also verify Kepler’s third law in this case. (Reference:
http://www.hk-phy.org/astro/tcs.zip)
Recording the position of planets/asteroids in the sky by using a digital camera over a few months. Students may use a star map to estimate the coordinates of the planets/
asteroids and use standard astronomical software to analyse the orbit of the planet.
Mapping of sunspots. Students may observe the projected image of the Sun and map the sunspots in a period of time. From this they can understand the rotation of the Sun and the evolution of sunspots. Recording the relative sunspot number over a period of time may also reveal the change in solar activity.
Studying the physics of Shenzhou manned spacecraft. The historic journey of Shenzhou involves many interesting physics phenomena that secondary school students can understand – for example, the thrust and acceleration of the rocket during its launch, the orbital motion around the Earth, the weightless condition in the spacecraft, the deceleration and return of the returning capsule, the effect of air resistance on the returning capsule, and communication problems when returning to the atmosphere. Analysis of spacecraft data provides a lively illustration of physics principles. Motion video analysis may also be useful in studying the launching motion.
Studying orbital data of artificial satellites provides an interesting illustration of Newtonian mechanics. Students may check the satellite pass-over time to actually observe the satellite in the evening sky.
Using a spectrometer and suitable filter to observe the spectrum of the Sun. Some prominent spectral absorption lines can be observed without much difficulty.
Studying radial velocity curves in celestial systems like stars with extrasolar planets, black holes in binaries, exposes students to the latest advances in astronomy. Based on the information extracted from the curves, students can use Kepler’s third law to deduce the mass and orbital radius of the unknown companion in binary systems, and
written presentation in class is encouraged.
Visiting the Hong Kong Space Museum. Students may be divided into groups, with each group being responsible for gathering information on a particular astronomy topic in the exhibition hall of the museum. Each group can give a short presentation in class to share their learning experience.
Contacting local organisations, observatories and museums
Hong Kong Space Museum (http://hk.space.museum)
Ho Koon NEAC (http://www.hokoon.edu.hk)
TNL Centre, The Chinese University of Hong Kong (http://www.cuhk.edu.hk/ccc/tnlcenter)
Sky Observers’ Association (Hong Kong) (http://www.skyobserver.org)
Hong Kong Astronomical Society (http://www.hkas.org.hk/links/index.php)
Space Observers Hong Kong (http://www.sohk.org.hk)
Using educational websites that provide useful resources for activities
Astronomy picture of the day (http://antwrp.gsfc.nasa.gov/apod/astropix.html)
NASA homepage (http://www.nasa.gov/home)
The Hubble Space News Center (http://hubblesite.org/newscenter)
Chandra X-ray Observatory (http://www.nasa.gov/centers/marshall/news/chandra)
Jet Propulsion Laboratory (http://www.jpl.nasa.gov/index.cfm)
NASA Earth Observatory (http://earthobservatory.nasa.gov)
China National Space Administration (http://www.cnsa.gov.cn)
National Astronomical Observatories, Chinese Academy of Sciences (http://www.bao.ac.cn)
Values and Attitudes
Students should develop positive values and attitudes through studying this topic. Some particular examples are:
to appreciate the wonders of deep space and understand the position of humankind in the universe
to appreciate astronomy as a science which is concerned with vast space and time, and the ultimate quest for the beginning of the universe and life
to appreciate how careful observation, experimentation and analysis often lead to major discoveries in science that revolutionise our concepts of nature
to appreciate physics as an ever growing subject in which new discoveries are often made on the solid foundation that was laid previously
to appreciate the ability of famous scientists in history and their profound contribution towards our understanding of the universe and the existence of humankind
to accept uncertainty in the description and explanation of physical phenomena
to accept the uncertainty in measurement and observation but still be able to draw meaningful conclusions from available data and information
to be able to get a simple and heuristic glimpse of modern advances in science, even though a comprehensive understanding of these advanced topics is beyond the ability of ordinary people
to recognise the importance of lifelong learning in our rapidly changing knowledge-based society and be committed to self-directed learning
to appreciate the roles of science and technology in the exploration of space and to appreciate the efforts of humankind in the quest for understanding nature
to become aware of daily phenomena and their scientific explanations
STSE connections
Students are encouraged to develop an awareness and understanding of issues associated with the interconnections among science, technology, society and the environment. Some examples of such issues related to this topic are:
studies in astronomy which have stimulated the development of modern science and eventually changed our ways of living
the interplay between technological development, the advance of modern science and our lives
the effects of astronomical phenomena on our lives (e.g. solar activity maximum affects communication and power supply on Earth)
the effects of light pollution on astronomical observations, the environment and the lifestyle
disasters that may come from outer space and our reactions to them (e.g. a big meteor impact causing massive destruction to life on Earth)
the applications of modern technologies in space science, including artificial satellites and spacecraft
the need to rethink some of Earth’s environmental problems as a result of exploration of planets (e.g. the runaway greenhouse effect of Venus may be compared with global warming on Earth)
the implications of the advances in space technology and their impact on society (e.g.
Shenzhou manned spacecraft)
VII Atomic World (25 hours)
Overview
The nature of the smallest particles making up all matter has been a topic of vigorous debate among scientists, from ancient times through the exciting years in the first few decades of the 20th century to the present. Classical physics deals mainly with particles and waves, as two distinct entities. Substances are made of very tiny particles. Waves, such as those encountered in visible light, sound and heat radiations, behave very differently from particles.
At the end of the 19th century, particles and waves were thought to be very different and could not be associated with each other.
When scientists looked more closely at the nature of substances, contradictory phenomena that confused scientists began to appear. Classical concepts in Mechanics and Electromagnetism cannot explain the phenomena observed in atoms, or even the very existence of atoms. Studies on the structure of an atom and the nature of light and electrons revealed that light, the wave nature of which is well known, shows particle properties, and electrons, the particle nature of which is well known, show wave properties.
In this elective topic, students learn about the development of the atomic model, the Bohr’s atomic model of hydrogen, energy levels of atoms, the characteristics of line spectra, the photo-electric effect, the particle behaviour of light and the wave nature of electrons, i.e. the wave-particle duality. Through the learning of these physical concepts and phenomena, students are introduced to the quantum view of our microscopic world and become aware of the difference between classical and modern views of our physical world. Students are also expected to appreciate the evidence-based, developmental and falsifiable nature of science.
Advances in modern physics have led to many applications and rapid development in materials science in recent years. This elective includes a brief introduction to nanotechnology, with a discussion on the advantages and use of transmission electron microscopes (TEM) and scanning tunnelling microscopes (STM), as well as some potential applications of nano structures.
Nanotechnologies have been around for hundreds of years, although the underlying physics was not known until the 20th century. For example, nano-sized particles of gold and silver
suntan lotions and cosmetics, to absorb and reflect ultra-violet rays. Tiny particles of titanium dioxide, for example, can be layered onto glass to make self-cleaning windows.
As in any newly developed area, very little is known, for example, about the potential effects of free nano particles and nano tubes on the environment. They may cause hazards to our health and might lead to health concerns. Students are, therefore, expected to be aware of the potential hazards, and issues of risk and safety to our life and society in using nanotechnologies.
In studying this elective topic, students are expected to have basic knowledge about force, motion, and waves. Some basic concepts of covalent bonds of electrons would be helpful in understanding the structures and special properties of nano materials. Knowledge of electromagnetic forces, electromagnetic induction and electromagnetic spectrum is also required.
Students should learn: Students should be able to:
a. Rutherford’s atomic model
the structure of atom describe Rutherford’s construction of an atomic model consisting of a nucleus and electrons
state the limitations of Rutherford’s atomic model in accounting for the motion of electrons around the nucleus and line spectra
realise the importance of scattering experiments in the discovery of the structure of atoms and the impact on the searching for new particles
b. Photoelectric effect
evidence for light quanta describe photoelectric effect experiment and its results
state the limitations of the wave model of light in explaining the photoelectric effect
Students should learn: Students should be able to:
Einstein’s interpretation of photoelectric effect and photoelectric equation
state photon energy E = hf
describe how the intensity of the incident light of a given frequency is related to the number of photons
explain photoelectric effect using Einstein’s photoelectric
equation max2
2 1mv hf e
realise the photoelectric effect as the evidence of particle nature of light
apply E = hf and Einstein’s photoelectric equation to solve problems
c. Bohr’s atomic model of hydrogen
line spectra describe the special features of line spectra of hydrogen atoms and other monatomic gases
explain spectral lines in terms of difference in energies
realise that the energy of a hydrogen atom can only take on certain values
realise line spectra as evidence of energy levels of atoms
Bohr’s model of hydrogen atom
state the postulates that define Bohr’s model of hydrogen atom
distinguish between the “quantum” and “classical” aspects in the postulates of Bohr’s atomic model of hydrogen
realise the postulate
2 vr nh
me as the quantization of
angular momentum of an electron around a hydrogen nucleus where n=1,2,3… is the quantum number labelling the nth Bohr orbit of the electron
realise the equation for the energy of an electron in a hydrogen atom asEtot (
2 2
4
2 8
1
o e
h e m
n )
2
6 . 13
n
eV