Print Friendly, PDF & Email

Orbit of the Earth around a room

Beginners Notes
Happy Birthday Theremin

Most Classrooms have a Globe. These usually have the planet correctly inclined (to show its tilt of spin in relation to the plane of our orbit around the Sun), as well as a small plate on top, at the North pole, marked off in hours.

For children to visualize where their planet is in a year, in relation to the Sun, it is useful to work with a model. A shared experience makes the learning easier. This could be perhaps a weekly class focus…where is the planet today in its orbit around the Sun? To model this is relatively easy.

Pretend the Sun is in the middle of the room. The globe can be moved around the perimeter of the classroom, anti-clockwise, in a rough circle.

Either select the front of the Classroom as North, or, more preferably, determine true North where you are. Our planet is spinning at a tilt of 23.44 degrees (from the perpendicular to its orbital plane), and the North pole of our planet is constantly pointing toward Polaris, the North Star.

If the front of the Classroom is “North”, then that is the position where the planet will be when it is our Winter Solstice, December 21 (usually). Place the globe so that it is in the middle of the front wall (or true North, depending how you are modeling) tilted directly away from the pretend Sun. (If you are modeling with true North, the North pole of the globe itself will be pointing towards Polaris.)

Our Earth is moving around the Sun in an anti-clockwise direction. As it does so, it spins. (Conveniently to remember, it also spins in an anti-clockwise motion.)

The spinning brings us day and night at our specific locations on the spinning Earth. The progression around the Sun, because of our tilted rotation, brings us the changing Seasons.

All of this is a smooth motion, with our sightings of the Sun during the time we are turned in its direction called “day”; and the times when we are turned away and looking out into Space, shadowed by our Earth from the sun’s direct glare, able to now make out the light from the numerous stars that are part of the Milky Way Galaxy in which the Sun twirls, and broadcasting heat (lower energy light) out into Space ourselves.

These seasonal changes are a direct result of differences in solar energy received by different parts of the planet during different parts of the yearly orbit. Simplistically, as more, or less, solar energy strikes a surface during a day, so the temperature rises or falls.

Remember that, as the globe is moved around the outside of the class (circling the pretend Sun in the middle of the class), it is always tilted in the same direction, towards the front wall of the class (or, if you have selected, true North).

At the back of the class would be “South”. Summer Time!! for us in the Northern hemisphere. At that point in our annual orbit our Earth appears tilted towards the Sun. Australia, on the other hand, experiences its least light in June.

Our planet is always maintaining the same spinning tilt in the same polar direction, always steadily spinning with no change in direction of its tilt…it is only by virtue of where Earth is in it’s orbit whether the North pole of this spinning globe appears to be pointing away from or towards the Sun. Again – the tilt of the Earth does not change with the Seasons – where we are in our orbit around the Sun does. The tilt is always in the same direction, throughout the year.

At the mid-sides of the class would be the Equinoxes, when in Spring and Fall (usually March 21 and September 21) the whole planet receives equal sunlight during the daily spin.

The reason it gets colder too, in the winter, can be seen by how the light from the Sun, coming in approximately parallel lines towards the Earth, gets spread over the curve of the globe. And how much more time, in the longer nights, heat has to escape the surface into outer Space.

If an effort is made to mark off the room roughly into twelve parts of a circle, the children can track where the Sun is during our calendar year by moving the globe to its new location slowly, as the days advance.

If the front of the Classroom was selected as “North”, as the solstice point, then, moving counter-clockwise around the room, it will take three months to reach the right side of the classroom (viewed from the front), taking us to March 21. Where is January? Where is mid-January? The beginning of February?

By modelling, and then working with the model, children will see that where in the Earth’s orbit we are determines the amount of solar energy we receive at our location at any time of year.

If you have a large lamp, and can darken the room, so much the better – one can then model (only approximately – the lamp’s light is near, and the rays not parallel) the amount of sunlight falling on the different parts of our rotating planet each day. The light from a slide or film projector would serve this purpose.

[Note that at the Summer Solstice, the Tropic of Cancer (at 23.44 degrees north of the equator) is perpendicular to the Sun, and during the Winter solstice the sun’s light strikes most directly the Tropic of Capricorn (which is 23.44 degrees south of the equator). During the Equinoxes, which part of the globe receives sunlight most directly?]
As well, as the hours of any day advance, the children can turn the globe just the right amount by noting the dial at the top of the globe. For example, if the class starts at 9 and ends at 12, which part of the planet was experiencing “noon” when the class began? At 12, the part of the planet the class is on should be facing towards the imaginary Sun in the center of the room.

By referring to the correctly positioned globe in this way, at various times through-out the year, the children will form a picture of how the planet moves as it goes around the Sun, and how the days and years go by. There is nothing linear about our existence – it’s spinning while orbiting, all the way!

Beginners Notes
Happy Birthday Theremin