CHAPTER 2: EARTH

EARTH AND SPACE SYSTEMS

Did you know?

Earth’s surface is 66% water and 34% land. From space, Earth appears as a blue and white sphere hanging in the darkness. It seems so fragile. Originally, Earth was the only planet in the solar system known to have liquid water on its surface; however, recently remains of water have been found on Mars. It is also the only planet known to have life. Earth is unique among the 8 planets , and possible unique in the entire milky way galaxy.

Activity 1: Day and Night

1. Turn off the room lights and illuminate the globe from one bright light source, such as a spotlight

2. Place a small piece of clay on the globe close to where you live. Make sure to stick up about 1 cm high so it leaves an obvious shadow

Activity 1: Day and Night

3. Pretend the modeling clay represents you standing on the ground. Turn the globe to each of the following positions in relation to you standing on the Earth

12:00 noon 12:00 midnight Sunrise Sunset

4. Turn the glob again until it is sunrise at your location. Think about this carefully: The sun should be in the east. Now, turn the globe in the correct direction to make one full day from sunrise to sunrise. In which direction did you turn the globe?

Recording and Reflecting

1. Where do you live? Were you able to find your location on the globe?

2. What is it called when the globe is turned one complete rotation?

3. Describe how you positioned the globe for each of the following: noon, midnight, sunrise, sunset.

4. Which was does the earth turn when viewed from above the North Pole, clockwise or counterclockwise?

Activity 2: The reason for the seasons Use the diagram below to help you

make a simulation to demonstrate why we have seasons.

Activity 2: The reason for the seasons Place the rope in a circle on the floor and

the lamp in the centre. Be careful of the electric cord and the hot, bare bulb. Put a piece of modeling clay on the globe, as you did in activity 1. Step 2: turn off the overhead room lights.

Arrange the signs in the correct sequence and place the globe on the sign marked summer. Make sure the northern hemisphere is angled towards the sun.

Activity 2: The reason for the seasons From this point, move the globe

around the sun. Stop at each sign and measure the length of the shadow cast by the modeling clay. Continue until you complete one full year

Recording and reflecting

1. Draw four diagrams that shoe Earth in relation to the sun during each season. Label your diagrams as Spring, Summer, Fall, and Winter.

2. When viewed from above, which direction does Earth travel around the Sun, clockwise or counterclockwise?

3. Compare the length of the shadow cast by the modeling clay for each of the 4 seasons

4. Earth is tilted, just like your globe on its stand. What would our seasons be like if the earth was tilted?

5. We are a country that is close to the equator. How does this effect our seasons?

Notes

The Earth, the third planet from the sun, averages a 150 million km away from the sun. Earth spins on its axis (rotates) one ration every 24 hours. This is called one day. This gives us the cycle of daytime and nighttime.

Notes

Earth orbits (revolves) around the sun once every 365 and ¼ days, or one earth year.

The Earth’s axis is an imaginary line that runs through the north and south poles. The Earth rotates around this axis just like a wheel rotates around its axel. The Earth’s axis is not perpendicular to the sun, it is tilted at a 23.5 degree angle. We experience seasons because of this tilt.

Notes

The sun’s rays hit each part of the earth at a different angle each season. When it is summer in the northern hemisphere it is winter in the southern, and visa versa. Many people mistakenly think we have seasons because Earth travels near and father to the sun. Although Earth’s orbit is an ellipse (a slightly elongated circle), this has no effect on the seasons.

Notes

Our summer occurs when the northern hemisphere is titled towards the sun. the northern hemisphere has its longest day and shortest night at the summer solstice, June 21. places north of the arctic circle have continuous daylight. During summer, daylight shines directly on the ground at a 90 degrees angle at noon, warming it up. The sun appears high in the sky for most of the day. Daytime lasts longer than nighttime.

Notes

Our winter occurs when the northern hemisphere is tilted away from the sun. We have our shortest day and longest night at the winter solstice, December 21. Places north of the arctic circle have continuous night. During winter, the sunlight is at a shallower angle, its energy does not warm up the ground as much. In winter, the sun appears lower in the sky and nighttime lasts much longer than daytime.

Notes

The vernal equinox is the first day of Spring, March 21st. The sun is directly above the equator. Neither the northern nor southern hemisphere is titled towards the sun. 6 months later is autumnal equinox, the first day of fall. Again, the sun is situated directly above the equator.