Monday, Sept 20, 2010

Elected student council rep by secret ballot.

Quiz on phases of the moon.

Showed cartoon of Hi and Lois about the Autumn Equinox
The Autumn or Fall Equinox is Wed, Sept 22, 2010

Equi-nox means equal night. At the equinox (first day of fall) we get equal hours of night and day.

At the summer solstice (first day of summer), the sun is highest in the sky. "sol-stice" comes from sun and stationary. As we approach the summer solstice, the sun gets higher and higher in the sky at noon, reaching its most overhead position at the summer solstice (around June 21). After that the Sun goes lower in sky reaching its lowest position at noon in the sky on the winter solstice (first day of winter - about Dec 21).

Went over the order of the seasons showing the position of the Earth at the start of each season - Summer, Fall, Winter, Spring

Discussed causes of the seasons. Seasons are NOT due to how close or far away the Earth is from the Sun. If it were, we would have the same seasons in both the northern and southern hemispheres. On Earth, the seasons are reversed for the two hemispheres. When it is winter in the northern hemisphere, it is summer in the southern hemisphere, etc.

Instead, the seasons are due to the tilt of the Earth's axis. It is tilted about 23.5 degrees from the perpendicular to its orbital plane. Without this tilt, we would not have seasons. Showed how we get 24 hours of sunlight at summer solstice at the north pole and get 24 hours of darkness at the same time at the south pole.

Uranus has the greatest tilt, about 90 degrees, so it has the most extreme seasons.

Did measuring exercise of length and width of table. Students need to measure in centimeters (100 to the meter) to the nearest 0.1 centimeter.

Had students draw similar triangles and measure the ratios of height to base for the two triangles. Did not get a chance to discuss the significance of the ratios. Had students calculate the ratios for homework.