Earth Clock Earth Clock

WARNING This is not a toy. It is an educational kit and must be used under adult supervision. This product is not suitable for children under 3 years. It contains sharp or small parts that could be dangerous Ca!re for young children. Needed EEaartrthh Manufactured and Supplied by Mindsets Copyright © Mindsets (UK) Limited, 2011 The Earth Clock is one of a number of innovative educational products designed at CCloclockk Middlesex University to interest young people in science and technology. Please ask your supplier for more details. Earth clock What to do next Welcome to the fascinating world of timekeeping. You have just Soil is an ideal material for your earth clock, but it must be wet. You bought a high-tech electronic clock that gets all of its power could run the clock from a pot plant but the pairs of metal strips from ordinary earth! You will never need expensive batteries – must be at least 5cm apart. If the soil gets too dry, the clock stops and you will be able to run your clock using other unlikely working and tells you that the plant must be watered. materials. Any other material that is slightly acidic can be made into a battery Avoiding the use of batteries is environmentally friendly. All the for your clock. Newspapers and cheap books use paper that has a energy and materials that go into the battery are saved, and high acid content. That is why they go brown over time. The acid there is nothing to dispose of when the battery is used attacks the paper. If you tear and mash up some old newspaper in up. water, you can run you clock from that instead of earth. Make sure the newspaper is well mixed up – like mashed potato. About timekeeping You can try out all kinds of other materials and liquids to see if they give you a voltage. If you push the pairs of metal strips into fruits From the earliest days, people have used the such as lemons or oranges, the acidic juice will work. Lemon juice position of the sun to tell the time. We still use squeezed into two small pots will work well. If you are using earth sundials today; a thin piece of metal casts a and it doesn’t work very well, then you can make it more acidic by shadow on to a scale, so that we can read off adding a small amount of fruit juice or vinegar. Most fizzy drinks are the hours. slightly acidic, but will not work as well when ‘flat’. NOTE: After some time, the metal strips will be ‘eaten’ by the In the Greek and Roman world, other things chemical action. If the clock stops working, clean the strips with were also used for timekeeping. These included abrasive paper or wire wool. burning candles with hourly markings down the side and water clocks. Water clocks consist of a container with a small hole at the bottom. The falling level measures passing time as water slowly leaks out. Mechanical clocks were invented during the Middle Ages. These used weights and (later) springs to turn hands on a dial. The important part of a mechanical clock is the escapement that produces the ‘tick tock’ sound. This releases the energy stored in the falling weight or unwinding spring in tiny regular amounts. Over hundreds of years, mechanical clocks and watches became far more accurate – and we still use them today. Setting the clock In the last century, electronic clocks and watches were developed. These use an 1. Press the centre button on the rear of the clock twice and the clock electronic circuit instead of a mechanism, and will enter the setting mode – the display will flash between time and they show time with either moving hands date. (analogue display) or numbers on a screen (digital display). They are much more accurate 2. Press the centre button again and the month will be displayed. This than most mechanical clocks and watches. can be changed by pressing either of the outer buttons. Your clock has a digital display and is accurate to around two 3. Press the centre button again and the day will be displayed, change seconds per week. It requires only a small electrical current to as before. work. 4. Press the centre button again and the hour and AM or PM will be displayed, change as before ensuring that AM or PM is correct. Getting electricity from earth 5. Press the centre button for minute setting. Over two hundred years ago, a scientist called Volta discovered a way of producing electricity using two different metals and weak 6. Press the centre button again and clock will be in run mode, acid. In the world’s first battery (called a voltaic pile after Volta), he indicated by flashing dots. placed silver and zinc disks either side of paper soaked in weak acid (eg vinegar). This produced electricity. To produce greater voltage, The pressing of either outer buttons will show the date. he connected several pairs of metal disks together in series. Your earth battery uses pairs of two different metals: copper and zinc. If you dip them into acid they will produce electricity – about 0.5 volts. We now understand that a special chemical reaction takes place between the metals and the acid. Your clock needs about 1 volt, so if you connect two pairs of metals in series (like Volta did with his disks) and dip them in vinegar you would get 0.5 volt + 0.5 volt = 1 volt. So, why use earth? Most soil is either slightly acidic or slightly alkaline (alkaline is the opposite of acidic). In fact, you will find that most wet soils work very well. How to assemble the earth clock 4. Cut the plastic covering off the ends of the wires from the black clock and screw them into the wire connecting blocks. Make sure the wires are connected the red right way around as shown. wire 1. If you would like your clock to display a graphic you may design your own insert. The size of the insert should be 35 x 55mm. Slide the graphic into the top of the clock. 5. Put some damp mud into the containers provided. Carefully 2. Screw the metal strips into the connecting press the metal strips into the blocks as shown. mud, taking care that the strips copper strip copper strip do not touch each other. zinc zinc (silver) (silver) strip strip The clock should now start to work. 3. Screw the loose metal wire into the connecting blocks as shown. Make sure it connects a zinc strip to a copper strip. Note: If the mud dries out, the clock will stop working – keep the mud moist by adding an occasional drop of water. If the clock stops working, remove the metal strips and clean them with an abrasive cleaner. This will remove the layer of oxide that has built up..

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