I’m back to teaching science again! This term’s topic is Earth and Space. I am going to be doing activities with kids in grade 4 and 1. I am reviewing some more advanced topics with the year 4 kids, because I taught them last year when the topics were forces and heat. For the first lesson we talked about what happens when the earth rotates on its axis (day/night) and revolves around the sun (seasons).

Seasons

Season Demonstration

The Earth has seasons because it is tilted on its axis. This happened when a large object from space hit young Earth. Parts of Earth that were broken off from this collision formed our moon, and the impact tilted the Earth.

I used a knitting needle in a ball of yarn to demonstrate the tilt of the earth as it goes around the sun. When the Northern Hemisphere is pointed towards the sun, the Southern Hemisphere is pointed away from it. When a Hemisphere is pointed towards the sun it receives more energy and is warmer. It is summer there. At this time it is winter in the opposite hemisphere. We reviewed what happens to the molecules on hearth when they are exposed to the energy from the sun. The molecules move in various ways and this results in the Earth warming.

Days

Day and Night Demonstration

When the Earth rotates on it’s axis, one side faces the sun and it is the daytime. The other half faces away from the sun and it is nighttime. I put a pin on the ball of yarn so the kids could see how a point on the Earth experiences sunlight as the Earth rotates. Then, I had the kids hold up one hand in front of their head. I asked them to turn their head to their left and imagine that their nose was our city. Then I had them slowly turn their head to the right so they could see the sun (their hand) was in their peripheral vision, then in front of their face, and then in their peripheral vision again.  I discussed that it looks like the sun moves across the sky, but we are the ones that are moving. This situation is similar to when you ride on a train and it looks like the trees are rushing past you. You are siting down and not moving, and the trees aren’t really moving, but the train is moving. Earth is like that train, and the sun is like the trees.

The Stars During the Day

I had some dim electric tea lights turned on in a sunny room. Then I turned off the lights (or you can bring them into a dark area). I told the kids that the lights were like the stars. The stars are always shining in the sky, but when we are facing the sun, the light from the sun is so bright that we can’t see them.

Making a Sundial

As the Earth turns, the sun appears to move in the sky. As the day goes on, the angle of the sun changes and it causes shadows change their location and be shortest at noon. Shadows are also shorter in the summer compared to the winter.

In ancient times, people used this change in shadows to mark the time with a sundial. You can make your own sundial with a stick, a compass,  and something to mark the hours. If you are in the Southern Hemisphere, you must point the stick to the south and in the Northern Hemisphere you must point the stick to the north. This is a good opportunity to teach the kids how to use a compass. If any of the students know how to use one, they can demonstrate it for the other kids. The shadows move in opposite directions in the Northern and Southern Hemisphere. I had the kids pair up and have one kid move their hand in a circle like they were stirring a pot. Then I had the other child look above and below this to see that it looked clockwise from one side and counter clockwise from the other side. In the Northern Hemisphere the shadows on a sundial move in the clockwise direction, and in the Southern Hemisphere they move in the counterclockwise direction. I didn’t tell the kids which direction the shadows would move. I wanted them to find out by marking the shadows every hour. We had different pairs of them go out each hour and plant the markers in the ground so they could see which way the shadows moved. The first mechanical clocks were made in Europe so they go in the same direction as the shadows in sundials in the Northern Hemisphere.

Southern Hemisphere Sundial