Eclipse

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ECLIPSE
‡ Eclipse is caused by the shadow of the earth or the moon when they re in a straight line. The shadow is divided into 2 regions: ‡ The main shadow (the Umbra) ‡ The umbra forms a cone-shaped region of shadow from the earth or the moon. The moon s umbra has length ± 370,000 km; meanwhile the earth s umbra has length ± 1,376,000 km. ‡ The outer shadow (the Penumbra) ‡ The end of the umbra (the antumbra) ‡ Antumbra is a region where a planet or moon will be seen transiting across the star but not completely covering it.

Lunar Eclipse
‡ A lunar eclipse occurs when the moon enters the shadow of the earth. The earth is positioned between the sun and the moon. As the consequence, the sunlight is blocked by the earth, but the moon isn t completely dark, so we still can see it in a faint illumination. ‡ Types of lunar eclipse: ‡ A partial lunar eclipse occurs when the moon partially crosses the earth s umbra. ‡ A total lunar eclipse occurs when the moon passes through the earth s umbra. ‡ A penumbral lunar eclipse occurs when the moon enters the earth s penumbra. ‡ A lunar eclipse takes about 6 hours to complete, while a total lunar eclipse takes only 1 hour and 40 minutes.

Lunar Eclipse

Solar Eclipse
‡ A solar eclipse occurs when the moon s shadow crosses the earth surface. The moon is located between the earth and the sun. ‡ Types of solar eclipse: ‡ A total solar eclipse occurs when the moon s umbra crosses an area on the earth s surface (about 6 minutes, in daytime). ‡ A partial solar eclipse occurs when the moon s penumbra crosses an area on the earth s surface which is partially blocked the sunlight on that area. ‡ An annular eclipse occurs when the length of the umbra cone doesn t reach the earth s surface, but only the extension of the cone. The area on the earth s surface which is crossed by the shadow experiences an annular eclipse.

OCEAN TIDE
‡ The earth s is affected by the gravitational force of the moon, and the water is more affected by the moon s gravity than the land. As a result, the areas which are in a straight line with the moon s gravity undergo a high tide and the areas which are perpendicular to the moon s gravity undergo an ebb tide. ‡ The high tide is the rise of the sea water level, while the ebb tide is the reduction of the sea water level. ‡ Due to earth s rotation, the ocean tide in an area is altered in every 6 hour. Thus, a place will experience a spring tide and a neap tide twice a day.

2 types of ocean tide:
‡ The spring tide occurs around the full moon and new moon, when the sun, the earth and the moon are in a straight line. Because the sun s gravity and the moon s gravity work in an opposite direction, then it result an ocean tide. When the sun s gravity and the moons gravity attract the earth in one direction, there will be a maximum tide range. ‡ The neap tide is the minimum tide range which occurs in the first/third quarter of the moon, when the sun s gravity and the moon s gravity are perpendicular.

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