Julie Cave and David Wonnacott show how teaching astronomy can involve time travel as well as elementary physics.
It is the start of the autumn term. You have before you a new class of 13 and 14-year-olds. With great enthusiasm you announce that the first topic is astronomy. You pretend not to hear the groans from the back row and continue, promising exciting lessons exploring the wonders of the Universe.
You notice that one quiet child has whipped out a popular book on astronomy and is gazing with barely concealed excitement; it won't be long before you're facing questions on warp drives, black holes and inter-universe travel.
Meanwhile, someone starts to relate last night's episode of Star Trek or The X-Files. If you're really unlucky one member of the class is fixated on UFOs. Love it or hate it, astronomy is part of the curriculum, and this term, with its shortening daylight hours, is a popular one for tackling "The Earth's place in the Universe".
Surely a subject based on exotic objects, incredible distances and facts, full of amazing pictures and tales of exploration should be a joy to teach? We have generally found it fascinates students. But it took us a while to appreciate the mild terror this topic instils in many teachers.
When, after a career in research astronomy, Julie entered teacher training, her enthusiasm for the subject was met with a mixture of disbelief and just-wait-till-she-tries-this-in-the-lab looks from experienced staff.
Doubts grew when we discovered - as a husband and wife team offering in-service - that concepts we had learned at university were now being taught in schools. How could you satisfactorily explain the origin of the Universe when university students require quite complicated physics to grasp the arguments? Unless you've taken an astronomy degree you're unlikely to have studied this subject in depth, even as a physics specialist.
In fact, this is a topic capable of undermining usually confident teachers who may be bombarded with all sorts of awkward questions (see box below). It also has a non-practical nature, which can cause classroom management difficulties with pupils who expect lots of activity in science lessons.
It doesn't have to be this way. Teaching astronomy in schools can be immensely rewarding. It is a popular hobby among children, as demonstrated by the number of space-related books and magazines on the market. It is very visual and full of high technology which readily captures young imaginations. On top of the incredible facts, astronomy gives us our scientific understanding of where our planet and even our atoms came from, and of our ultimate fate.
It's perfectly valid to fend off some questions by saying, "It's a highly specialised area only understood fully by a few scientists." To teach it confidently, however, background reading is needed both to boost confidence and to provide the amusing stories of trial and error which bring the subject to life. Time and access to professionals is limited.
Introduce the topic with enthusiasm and you may well find that members of the class who you'd previously suspected of being present only in body suddenly perk up and participate.
The sequence of discoveries which led to the current Big Bang theory is a rich ground for debate, and shows that our understanding of the Universe is constantly being refined. Owing to its descriptive nature at this level (be warned: at higher levels it becomes fiendishly mathematical), astronomy provides the opportunity for the less numerate to shine.
Use the chance to set less formal work such as essays on what life would be like without gravity, or planning missions to explore other planets.
Be flexible with discussion sections so that you can go off on a tangent if the pupils are interested in space travel, aliens, science fiction - all of which can be used to illustrate scientific points. Look out for newspaper articles about recent discoveries, missions, and events such as eclipses or meteor showers, and keep a notice board going during the term.
The London Planetarium runs excellent programmes targeting the Key Stages and using effects such as the planets by season in 3-D, which is nigh-on impossible in the lab. Consider starting up an astronomy club or entering teams in competitions (such as the one run by the Planetarium) to encourage extra-curricular activity. Several organisations now offer entertaining talks by astronomers in schools.
Given a bit of imagination in the structuring of lessons, Space can be a highly motivating and enjoyable part of the syllabus. There are few teachers who don't feel pleasure when pupils unexpectedly start bringing in articles, staying after class to continue discussions and start asking for details about telescopes and Internet sites for NASA images. All this and more can happen when you bring Space into your lab.
Dr David Wonnacott is a research astronomer at Mullard Space Science Laboratory, Surrey. Dr Cave and Dr Wonnacott offer in-service training courses, resources and talks for physics teachers and can be contacted on 0181 339 0520
Partial eclipse: five Questions about astronomy which may make teachers see stars.
Is there life on Mars?
Almost certainly not - its atmosphere is too cold and thin for liquid water, which is necessary for all known life. Signs of very primitive life (resembling nano-bacteria) in a meteorite thought to come from Mars implies that life started to evolve in an ancient and wetter Martian environment. All of the cited features could, however, have formed inorganically - the scientific jury is currently out on this one.
* How do we know the temperature of stars?
By looking at the amount of radiation they emit at different wavelengths - the shorter the wavelength of the peak emission, the hotter the star. Temperatures for the centre of stars are calculated from computer models (based on hydrostatic equilibrium and the perfect gas law).
* How are distances measured?
Several techniques are used. Parallax (nearby objects apparently move faster across the sky than ones further away) is used for objects closer than a few tens of light years. Another relies on knowing how bright a star is, seeing how it appears and using the "inverse square law" for radiation (the rate at which brightness recedes as you move away). Computer models also exist.
* What was there before the Big Bang?
It sounds strange but, because both space and time were created in the Big Bang, there was no "time" in existence before the Big Bang and so no "before".
* Can we travel to other universes?
Only in theory. Other universes could also have formed in other Big Bangs, although this is unlikely. Black holes are thought to form tunnels (or wormholes) between different places, times or even universes. But holding such a tunnel open for long enough to journey down it is not easy (even assuming we would be able to get to one in the first place).