By the way, if you have a suggestion for a different name for the Day-Night Globe, don't be shy, e-mail it to the address shown at the bottom of this page and, if we like it, we may use it.
The simplest and easiest way to set up a DNG is to use an ordinary globe. As usual when using maps, the larger the scale, the better is the outcome. In other words, using a larger globe is easier and will produce more obvious results.
However, the success
of the DNG also depends on the material from which the globe itself is
constructed. Most modern globes are constructed from cardboard or plastic.
Old globe may be constructed from metal. in general, the better heat-conducting
material, the better the DNG. For example, plastic is better than cardboard
and metal is better than plastic.
One sunny day;
One compass, the kind that points to the north (not the a circle-drawing tool), or some other means to tell where the geographic north is;
A stand for your DNG.
If not, you need a
makeshift stand. You can improvise one, using a cereal bowl, a small cooking
pot or a vase. Whatever you use, it should be round and you should be able
to rest your globe on its rim without the globe falling inside.
Do you know where you are?
Place your globe on its stand in direct sunlight.
(It is not ncessary to have a level place or to level the stand of the globe. Can you figure out why this is not necessary?)
Find your location on the globe.
Now orient your globe on its stand such that where you are is at its topmost point.
If your globe has a built-in stand and you can use it, wonderful. If not, improvise a stand as suggested above.
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The built-in stand of our globe lets us only spin the globe on its axis. Therefore, we removed the base of the stand and the globe was placed on top of a glass vase. If the base were not removed, its weight would have interfered with the proper balancing of the globe on the vase. (Also visible is the electric cord for illuminating this globe from its inside.)
Not to worry. Most home and school globes are too small for making this sort of an error significant enough to spoil your DNG experience.
If you don't have a compass but you know the general direction of the north this may be good enough.
See, working with a small-scale globe may be beneficial after all. It is more tolerant to errors.
If you really want to know where is the true geographic north and be a little more accurate, you just need a little planning work. On a clear night, prior to making your DNG, go outdoors and find the North Star. This is the direction to the geographic north.
Now take some measures to remember this direction when you need it. How to do this you are on your own. It shouldn't be too difficult. For instance, check the position of the North Star on your magnietic compass. On a clear-skies night in the San Francisco Bay Area you would find the North Star at 16 degrees. In other words, the geographic north is 16 degrees east of the magnetic north.
Also, do not change location. I mean, if you live in San Francisco and find the North Star there then do not try to impress your friends by making a DNG for New York, using your San Francisco measurements. It will not work. You must take all the necessary measurements at each location.
Point the North Pole on your globe toward the geographic north.
This is it. You are
now the proud engineer and owner of a Day-Night Globe.
Watch it for a while.
What time is it where you are?
Where is the dawn line on the globe?
This is the line where the shade meets the sunlight, marking the transition from night to day.
Where is the dusk line on the globe?
This is the line where the sunlight meets the shade, marking the transition from day to night.
What is the relationship between the dawn line and the dask line?
You can spin the globe about its axis (not the finger you used when you set it up) and simulate the passage of a day in just a few seconds.
What about the Earth's poles?
After the DNG stands in the sun for a while touch its surface in different places.
(Now is the time to figure out why the material from which the globe is fabricated makes a difference.)
What can you learn if you leave the globe in the same location and in the same orientation for many days?
Reuven Anati, Chief Exhibit Developer in the Clore Garden of Science at the Weizmann