Download One Km Walk - measurementmagic

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!