- Review questions on the sun and seasons - Begin to study magnets and learn how to map magnetic fields - Investigate the magnetic field of the earth TODAY’S OUTCOMES: SUN AND MOON MAGNETISM

> The earth is tilted at 23.5°. Is the sun ever directly overhead in Lexington? Why or why not? Explain where on the earth the sun sometimes passes directly overhead, and what conditions are necessary for this to happen. The diagram to the right shows the earth on the summer solstice - where will the sun appear directly overhead at noon here? In between the latitude lines, 23.5°N and 23.5°S, in a belt around the equator, there is a zone where the sun is directly overhead at (local) noon at certain times of the year. sunlight gnomon pointing straight up, parallel to sun rays makes no shadow! 23.5° N 23.5° S This happens twice per year at any location in this zone; it happens exactly at the equinoxes at the equator. North or south of this zone, the sun is never directly overhead to an observer on earth.

> In the extreme north, there are places where the sun doesn’t set at all in the middle of the summer. How does this happen? The diagram again shows the earth on the summer solstice - indicate the region of the earth that will receive no nightfall. Above a certain latitude line, no points rotate into the dark half of the earth at all, when the earth’s northern hemisphere is tilted toward the sun. On the summer solstice (the longest day of the year), this line is the Arctic Circle. Exactly at (and only exactly at) the North Pole, the sun doesn’t set at all for the 6 months around the summer solstice. sunlight No night above this latitude on summer solstice

If we did a sun plot at the North Pole on a summer day, what would it look like? sunlight

If we did a sun plot at the North Pole on a summer day, what would it look like? sunlight The gnomon location doesn’t move at all! Shadow stays in place, earth traces a circle as it rotates A gnomon placed on the North Pole would not move at all when the earth rotated, so the shadow would stay in one place. As the earth rotated, it would trace a circle through the shadow. The plot would just be a circle!

- How the axial tilt causes seasons - Why and how the days and nights change length during seasons - Why and how the direction toward the sun changes during seasons WHAT YOU ARE EXPECTED TO KNOW:

TOPICS: MAGNETISM Magnetic fields Magnetic forces Relationship between electricity and magnetism

- Review questions on the sun and seasons ✓ - Begin to study magnets and learn how to map magnetic fields - Investigate the magnetic field of the earth TODAY’S OUTCOMES: SUN AND MOON MAGNETISM