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Now it is time for the walk – have you got everything including permission, water, a hat, pencil and paper? Go outside. If possible you need to start at a spot where you can walk for one kilometre in a line. If you need to you can go around corners. If you really have to you can go up and back making each leg as long as possible (talk to your teacher about this) Take the sun and the planets with you. Make sure they are named so you can locate them when you need to. Find a spot from which you can walk a thousand metres in something like a straight line. This may not be easy. Straightness of the course is good if you can but not essential; nor do you have to be able to see one end of it from the other. You may have to "fold" it back on itself. It should be a unit that will make a good story afterwards like "All the way from the flagpole to the supermarket!" You may use the road / street outside the school. (get permission first) Put the Sun ball down, and walk away as follows. 10 paces / metres from your ‘sun’. Call out "Mercury, where are you?" and have the Mercury-bearer put down their card and pinhead, weighting them with a pebble if necessary. Another 8 paces / metres. Put down the Venus peppercorn. Another 7 paces / metres. Earth Have a look back at the sun. Mercury is supposed to be so close to the Sun that it is merely a scorched rock, and we never see it except in the Sun's glare at dawn or dusk-yet here it is, utterly lost in space! As for the Earth, who can believe that the Sun could warm us if we are that far from it? Think about how large the sun appears when you look at it in the sky. Don’t stare at it but get a feel for how wide it appears – maybe hold you fingers apart to show its size. Now look back at your [pretend’ sun – does it look about the same size – in scale of course. [After the first few planets, you might want to appoint someone else to do the actual pacing-call this person the "Spacecraft" or "Pacecraft"- so that you are free to talk.] Another 13 paces / metres. Mars Now come the gasps, at the first substantially larger leap: Another 92 paces / metres to Jupiter Here is the "giant planet"- but it is a table tennis ball, and so far away from its nearest neighbour in space! Now watch the distances grow Another 108 paces / metres. Saturn Another 240 paces / metres. Uranus Another 271 paces / metres. Neptune Another 234 paces / metres. Pluto You have walked about one kilometre! (The distance in the model adds up to 1,019 paces.) Look back toward the Sun ball, which is no longer visible even with binoculars, and look down at the pinhead Pluto. This gives you some idea of the size of the solar system and will start you wondering about space. Prediction time – You have another ‘sun’ to represent the nearest star (Proxima Centauri) to our sun (which is of course just one of billions of stars). How far away do you think you would have to walk before you dropped it. Write down your prediction. You might have to pick a place that you know – maybe an atlas might help. Now turn around and retrace your steps. As you pick up your objects make a note of which planet it is and approximately where on your journey it is eg. a tree or someone’s letterbox. If you have put your ‘planets’ on cards then write the position on each card. Then, back in the classroom, put the ‘planets’ on a shelf, as a reminder of the walk. Or they may be hung on strings from a rafter. The nine planets do not stay in a straight line. They stay about the same distances from the Sun, but circle around it (counterclockwise as seen from the north). They go around at various speeds. The inner planets not only have smaller circles to travel but move faster. Thus, Mercury goes around in about 3 months; the Earth, in a year; and Pluto in about 250 years. The circling movements mean that the planets spend most of their time much farther apart even than they appear in out straight-line model. The distance between two planets can be up to the sum of their distances from the sun, instead of the difference. Jupiter and Saturn, for instance, can be as close as 95 paces as in the model, or up to 382 paces apart at times when they are on opposite sides of their orbits. This is the case in the years around 1970,1990, and 2010. (Jupiter overtakes Saturn about every 20th year.) Think of the spacecraft Pioneer 11, which actually covered this immense distance. Launched from Earth in April of 1973, it looped around Jupiter in December 1974, and arched back all the way over the solar system, on its way to visit Saturn also. This journey is so long - the distance back from Jupiter plus the even greater distance out to Saturn - that the spacecraft did not reach Saturn till September 1979. Think about the One K walk and reflect on how the spacecraft had to be aimed, from our tiny Earth around the south pole of Jupiter in just such a way that it might five years later drop between Saturn (the acorn) and its rings!