It’s started again. They’re abandoned in the jungle and confronted with slimy, irritating, nauseating creatures on a daily basis. Yes if they’d drop Ant and Dec then ‘I’m a Celebrity…’ would be infinitely more watchable. In fact, talking of habitats, why not turn the whole thing upside down and see the effects of exposing ten of nature’s jungle-dwellers to four weeks in a shopping mall in Manchester. “I’m a Pink Tongue Skink …Get Me Outa Here!”

The line-up this week:

1. A Spot of Agri-Culture
2. Scicast Tip of the Week
3. Return of Making a Mint
4. Stump the Scientist: ouch my foot!
5. Activity of the Week: Wave machine
6. Mouses at the Ready: Letts GCSE practice papers
7. Noticeboard: FYI
8. Recommended website of the week
9. The Winners’ Enclosure
10. Joke of the Week

This week Guy Smith gets into ploughing and maths. Odd to think that so long after horses were commonplace, horsepower is still used when talking about a machine's power. So, is a Shetland pony half a horsepower?
			December on the farm is a quiet time of year. The days are at their shortest and fieldwork tends to be a diurnal job. For the arable farmer the main concern is to complete the winter ploughing. Ploughing as a technique is as old as farming itself. Basically it amounts to inverting the soil so that the trash from the previous crop is buried and a friable, loose seed-bed is created ready for the spring. This latter role is partly done by the farmer and partly done by the frost. The frost acts to break up the clods created by the plough so they form a fine tilth by the spring. Hence the farmer is keen to complete his ploughing in December before the hardest frosts arrive. One hundred years ago ploughing was done by horses pulling single furrow ploughs. It was the accepted lore that one man and two horses could plough an acre a day. Today farmers use tractors instead of horses. Most tractors used for ploughing are rated at around 200 horsepower pulling five or six furrow ploughs. Logically you might think such a team could achieve a hundred times more than two horses – that being ploughing one hundred acres. In fact a good ploughman in a 200 horsepower tractor will plough 50 acres a day. What this does mean is that what one tractor and one man can achieve today it would have taken fifty men and 200 horses to achieve a hundred years ago. Some lament the passing of the age when the power of the farm was provided by horses and human muscle. It is true that the pleasure of working with horses and the camaraderie of working on farms which employed scores of men is now largely gone. What should be remembered though is that guiding a plough pulled by horses in winter weather for seven hours a day was hard and dull work. It could also be dangerous as it was not unknown for horses to trample on farm workers. Working in the warmth and comfort of a tractor cab is far more civilised and safer. The fuel for horses was grown on the farm in the form of hay and oats. It is interesting that in the future farmers may grow fuel for tractors. Crops such as oilseed rape can be crushed and turned into bio-diesel. As mineral oil prices go up it becomes more financially attractive for farmers to grow their own diesel rather than buy it from oil companies.
Thanks for that Guy. Can you guess how many square metres of oilseed rape it would need to run a tractor for a day? Send us your guess and you could win a packet of seeds from Garden Organic, the leading charity dedicated to researching and promoting organic gardening, farming and food. Simply email us with your answer and your name and address, and the words GONE 2 SEED in the subject line, to planet-science.news@nesta.org.uk. The nearest guesser will be picked on Wednesday 21st November at 5pm.

This week Jackie Rea asks

Ronald George replies

Adam Southwell agrees

Thanks also to Chris Dew, Janet Dowle, Dr Alan P Glaze and Dan Hannard for their comments.

So, thankfully, on this occasion the scientist was NOT stumped!

If you can help or have a burning question of your own then send us an email with STUMP THE SCIENTIST in the subject line to planet-science.news@nesta.org.uk

Wave Machine

You will need:

• A roll of gaffer or duct tape. Duck or Elephant brands are the best.
• Lots of wooden kebab skewers.
• More jelly babies than seems reasonable.
• Two tables or chairs of the same height. These will have tape stuck to them, so don't use good ones.
• A ruler, or a number of fingers that are approximately the same width as a ruler.

For every metre of wave machine you will need about 20 skewers and at least 40 jelly babies.

What to do:

1. Stretch the gaffer tape between the furniture. It's probably best to try this with a 2 metre span the first time. You need to stretch the tape taut, which means sticking it down firmly - go right round the table or chair if you can but be careful of the varnish!
2. Starting from one end, stick kebab skewers across the tape so they stick out evenly on either side. This is why you need good-quality tape: you'll need strong adhesive to hold the skewer. A damp day will ruin the adhesive, too. If your skewers fall off, this could be why.
3. Space the skewers about a ruler's-width apart, about 5cm. The exact spacing isn't critical, so long as they're fairly evenly spread. Keep adding skewers until you've reached the end of the tape.
4. Now put a jelly baby on each end of each skewer. You might think you'd only need twice as many sweets as skewers, but mysteriously they tend to disappear.
5. Be careful when pushing the sweets onto the skewers. Be careful in case you accidentally poke your finger, but also be careful because you want the skewer to stay balanced - it should rest horizontally. You may need to push things around a bit to make sure your wave machine stays balanced all along its length.
6. Once that's done, your wave machine is ready. Hold one of the skewers at one end, swiftly pulse it up and down, then let go. You should see the pulse travel the length of your tape, reflect off the far end, and return to the start. If you drive the end continuously, you can set up a standing transverse wave, too.

What’s going on?

The tape acts as a torsion spring. A torsion spring is one that works by twisting: the more it is twisted the greater the force it exerts to try and return to its original shape. The tape in this experiment has a very low spring constant - you actually don't need very much force at all to twist it - and because of this a disturbance in one skewer will easily create a disturbance in the next. This is how the wave moves - or propagates - down the line. There is also very low damping: instead of the spring returning back to its original position immediately it will continue to twist back and forth for some time after the original disturbance has passed.

The jelly babies and kebab skewers provide a high angular momentum. They are reasonably heavy and so will not move particularly quickly up and down under the wave disturbance. The result is a wave that travels down the tape at a surprisingly slow speed, as the tape struggles to return to its central position.

With a little practice, you can demonstrate not just standing waves, but things like wavepacket dispersion too.

Special Safety advice

Be careful of fingers when stabbing the jelly babies onto the skewers.

This activity can be viewed at Planet-SciCast.

Keep checking back for new films and, whilst you’re about it - how about submitting one of your own?

Other than kudos, admiration, fun, science and showing off your skill, there are financial incentives for sending a film now – oh yes, win in a category and get your team £250 worth of Amazon Vouchers, Win the SciCast d’Or overall best film and get another £250’s worth on top. Send us a film before the end of November and win five free cinema tickets to see a movie of your choice near you.

This week we have a pack of OCR GCSE Gateway Science Higher Practice Papers from Letts to give away. The pack contains 2 complete sets plus instructions, answers and a Mark Scheme Booklet.

If you’d like to win it then email us with your name and address, and the words ‘PRACTICE MAKES PERFECT’ in the subject line, to planet-science.news@nesta.org.uk.

The draw will take place at 5pm on Wednesday 21st November.

This week we’re looking at the Science Postcards website. Science exploration through stories. The resources are freely downloadable. Each Postcard comes with free Teaching Activities (experiments and lesson plans) and Pupil Notes that lead you through the experiments. The copiable worksheets/ masters lead you into exploring literacy ideas through picture books across all ages. Like ‘The Duck in the Truck’ for instance, which looks at friction. What a great idea! The resource is from New Zealand so you may find that the curriculum links etc. need a bit of a tweak for your purposes - but what the hey!