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2. The Four Seasons Is the changing seasons caused by the change in the distance between the Sun and the Earth?
No. If it is, then
The northern and southern hemisphere should have the same season, not opposite season like we have.
We should experience real seasonal changes in Hawaii also.
3. The Four Seasons: The Effect of the Tilt of Earths Rotation Axis
4. Factors Affecting Earths Temperature
5. Solstices and Equinoxes Equinox: An equinox is one of two opposite points on the celestial sphere where the celestial equator and ecliptic intersect.
Solstice: A solstice is either of the two times of the year when the sun is at its greatest distance from the equator.
Spring Equinox ~ March 21
Summer Solstice ~ June 21
Fall Equinox ~ September 22
Winter Solstice ~ December 21
The dates of the equinoxes and solstices are only approximate dates.
The actual length of a year is about 365 days (365 days, 5 hours, 49 minutes), not exactly 365 days. We have to add an extra day to a year every four years to keep the seasons synchronized with the seasons (leap year). Over a longer period of time, we need to skip a leap year to compensate the extra minutes we add in every leap year to keep the calendar in sync.
6. The Reasons for the Seasons on Earth The seasons on Earth are caused by the 23.5 tilt of its rotation axis, and its revolution around the Sun.
Although the distance of the Earth to the Sun changes slightly as it orbits around the Sun, its effect is not big enough to cause the four seasons.
The seasons for other planets may be due to the changing distance to the Sun, not the tilt of their rotation axisFor example, the orbit of Pluto has a very large eccentricity.
7. The Effects of Precession
8. The Moon The moon revolves around the earth with a period of about 29 days ~ one month!
9. Motions of the Sun-Moon-Earth System
10. The changing phase of the Moon
The un-changing face of the Moon
11. The Face and Phases of the Moon The phase (how much and which side of the Moon is illuminated) of the Moon changes with about one month period
The face (the features on the surface of the Moon) does not change at all
12. The Phase of the Moon
13. Phases of the Moon You can use this tool from the Phases of the Moon tutorial to present the idea behind phases in another way. As usual, please encourage your students to try the tutorial for themselves.
You can use this tool from the Phases of the Moon tutorial to present the idea behind phases in another way. As usual, please encourage your students to try the tutorial for themselves.
14. Moon Rise/Set by Phase
15. Why do we Always See the Same Side of the Moon?
16. The changing phase of the Moon
The un-changing face of the Moon
17. Solar and Lunar Eclipses Eclipse:
The total or partial obscuring of one celestial body by another
The obscuration can be either
One celestial body blocking the view to the other:
Solar eclipse---Moon blocking Earths view to the Sun
One celestial body is in the shadow of another:
Lunar eclipse---Moon is in the shadow of the Earth
18. Solar Eclipses
The solar corona is revealed during a total solar eclipse
The corona is about one millionth times fainter than the disk of the Sun.
Similar to observing stars next to the Sun, the light from the disk must be blocked (by the moon, or by special occulter in the telescope) before we can see the solar corona.
19. What Causes Eclipse?
20. Lunar eclipses Lunar eclipses happens when the Moon passes through the shadow of the Earth
Everybody on the night side of Earth can see the lunar eclipse.
Lunar eclipses can be partial, penumbral, or total.
Lunar eclipses can occur only at full moon. Use the interactive figure to show the conditions for the 3 types of lunar eclipse. Use the interactive figure to show the conditions for the 3 types of lunar eclipse.
21. Solar eclipses Solar eclipses occur when the shadow of the Moon falls on the surface of Earth
Only people in the shadow can see the eclipse.
Solar eclipses can be partial, annular, or total.
Solar eclipses can occur only at new moon. Use the interactive figure to show the conditions for the 3 types of solar eclipse. Use the interactive figure to show the conditions for the 3 types of solar eclipse.
22. Eclipse Path When total or ring solar eclipse happens
The diameter of the umbra of lunar shadow is no more than 270 kmyou can see the total eclipse only if you are in a very narrow and long eclipse path.
In the 1990 total eclipse that passed through the big island of Hawaii, people on Maui and Oahu cannot see the total eclipse!
The diameter of the penumbra of the lunar shadow is about 7000 km (Earths diameter is about 13,000 km). So, the region that partial eclipse can be seen is quite largeand people on Maui and Oahu could see partial eclipse!
? Eclipse Prediction
23. Total Solar Eclipse Whats the difference between a total and ring eclipse?
The distance between the Earth and the Sun.
24. Ring Eclipse Ring eclipse happens when the Moon does not completely block the Sun, like partial eclipses
25. Distance Between the Moon and Earth Like the Earths orbit around the Sun, the orbit of the Moon around the Earth is not a perfect circle.
Eccentricity of Earths orbit is ~ 0.016
The distance between the Moon and Earth change. This is why we have total and ring eclipses
Eccentricity of Lunar orbit is ~ 0.05
26. Solar Eclipses: A Coincidence? What if the Moon is closer (say twice as close) to the Earth?
What if the Moon is farther (say twice as far) away from the Earth?
What if the Moon is two-time bigger?
What if the Moon is two-time smaller?
27. How Often Does Eclipse Occur? Do we have one solar and one lunar eclipse every month, since we have a full and a new Moon every month?
28. How Often Does Eclipse Occur? Do we have one solar and one lunar eclipse every six month, when the nodes line-up with the Earth-Moon line?
NO! Because of the precession of the lunar orbit!
29. The Precession of Lunar Orbit The orbital motion of the Moon around Earth slowly precesses with an 18.6 year cycle as the Earth orbit the Sun
30. How Often Does Eclipse Occur? The combination of these motions of the Moon
29 day orbital motion around Earth,
5 tilt of the orbit w.r.t. the ecliptic, and
Precession of the lunar orbit w.r.t. the ecliptic,
Eclipse occurs with a period of about 18 years and 11-1/3 days ? Soras cycle
But these eclipses dont happen at exactly the same location over the Soras cycle
31. Solar Eclipse Forecast
32. Eclipses: Summary The parties involved: Sun, Moon, and Earth
Motion of the Moon around Earth:
29 day revolution of the Moon around the Sun
Tilt (~5) of the lunar orbit (around the Earth) w.r.t. the Ecliptic plane (Earths orbital plane around the Sun)
The precession of the lunar orbit w.r.t. Earth-Sun direction
Solar eclipse happens when the Moon is between the Earth and the Sun.
The size and distance of the Moon need to be just right for us to see total eclipse.
The changing distance between the Earth and the Moon explains the occurrences of the total and ring solar eclipses.
The changing distance between the Earth and the Sun, and the Earth and the Moon explains the difference in the duration of the solar eclipses.
Lunar eclipse happens when Earth is between the Moon and the Sun.