A speech please on Solar and Lunar Eclipse?

Answer 1

ECLIPSE
An eclipse (Greek verb: ekleipô, "to vanish", though it derives from the prefix 'ex-', "away from", and Greek 'leipein', "to leave") is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Earth-Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its parent planet, or a moon passing into the shadow of another moon. An eclipse is a type of syzygy, as are transits and occultations. Eclipses are impossible on Mercury and Venus, which have no moons.



SOLAR ECLIPSE
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring Earth's view of the Sun. This configuration can only occur during a new moon, when the Sun and Moon are in conjunction as seen from the Earth.

In ancient times, and in some cultures today, solar eclipses are attributed to mythical properties. Total solar eclipses can be frightening events for people unaware of their astronomical nature, as the Sun suddenly disappears in the middle of the day and the sky darkens in a matter of minutes. However, the spiritual attribution of solar eclipses is now largely disregarded.

Total solar eclipses are very rare events for any given place on Earth because totality is only seen where the Moon's umbra touches the Earth's surface. A total solar eclipse is a spectacular natural phenomenon and many people consider travel to remote locations in order to observe one. The 1999 total eclipse in Europe, said by some to be the most-watched eclipse in human history, helped to increase public awareness of the phenomenon. This was illustrated by the number of people willing to make the trip to witness the 2005 annular eclipse and the 2006 total eclipse. The next solar eclipse takes place on March 19, 2007, while the next total solar eclipse will occur on August 1, 2008.


Types

Annular eclipse.There are four types of solar eclipses:

A total eclipse occurs when the Sun is completely obscured by the Moon. The intensely bright disk of the Sun is replaced by the dark outline of the Moon, and the much fainter corona is visible (see image above). During any one eclipse, totality is visible only from at most a narrow track on the surface of the Earth.
An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the outline of the Moon.
A hybrid eclipse is intermediate between a total and annular eclipse. At some points on the surface of the Earth it is visible as a total eclipse, whereas at others it is annular. Hybrid eclipses are rather rare.
A partial eclipse occurs when the Sun and Moon are not exactly in line, and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can only be seen as a partial eclipse, because the umbra never intersects the Earth's surface.
The Earth's distance from the Sun is about 400 times the Moon's distance from the Earth. The Sun's diameter is about 400 times the diameter of the Moon. Because these ratios are approximately the same, the sizes of the Sun and the Moon as seen from Earth appear to be approximately the same: about 0.5 degree of arc in angular measure.

Because the Moon's orbit around the Earth is an ellipse, as is the Earth's orbit around the Sun, the apparent sizes of the Sun and Moon vary.[1][2] The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse when the Moon is near its closest distance from the Earth (i.e., near its perigee) can be a total eclipse because the Moon will appear to be large enough to cover completely the Sun's bright disk, or photosphere; a total eclipse has a magnitude greater than 1. Conversely, an eclipse when the Moon is near its farthest distance from the Earth (i.e., near its apogee) can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Slightly more solar eclipses are annular than total because, on average, the Moon lies too far from Earth to cover the Sun completely. A hybrid eclipse occurs when the magnitude of an eclipse is very close to 1: the eclipse will appear to be total at some locations on Earth and annular at other locations.[3]

The Earth's orbit around the Sun is also elliptical, so the Earth's distance from the Sun varies throughout the year. This also affects the apparent sizes of the Sun and Moon, but not so much as the Moon's varying distance from the Earth. When the Earth approaches its farthest distance from the Sun (the aphelion) in July, this tends to favor a total eclipse. As the Earth approaches its closest distance from the Sun (the perihelion) in January, this tends to favor an annular eclipse.

LUNAR ECLIPSE

A lunar eclipse occurs whenever the Moon passes through some portion of the Earth's shadow. This can occur only when the Moon is full, and when the Sun, Earth and Moon are exactly on a line, or very closely so. The type and length of a lunar eclipse depends upon the Moon's location relative to its orbital nodes. The next total lunar eclipse will take place at on March 3, 2007 and will be visible over the eastern Americas, Europe, Africa, and western Asia.[1]


Schematic diagram of the shadow cast by a spherical object. Within the central umbra, an object is totally shielded from direct illumination. In contrast, within the penumbra, only a portion of the illumunation is blocked.A lunar eclipse occurs whenever some portion of the Earth's shadow falls upon the Moon. In order for this to occur, two general conditions need to be met. First, the Moon must be full; that is, from the perspective of the Sun, the Moon must be directly behind the Earth. However, since the orbital plane of the Moon is inclined by about 5° with respect to the orbital plane of the Earth (the ecliptic), most full moon's will occur when the Moon is either north or south of Earth's shadow. Thus, a second condition for an eclipse to occur is that the Moon must be near one of the two intersection points it makes with the ecliptic, which are referred to as the Moon's ascending and descending nodes.[citation needed]

The shadow of the Earth can be divided into two distinctive parts: the umbra and penumbra. Within the umbra, there is no direct solar radiation. However, as a result of the Sun's large angular size, solar illumination is only partially blocked in the outer portion of the Earth's shadow, which is given the name penumbra.


Descending node lunar eclipse pathsA penumbral eclipse occurs when the Moon passes through the Earth's penumbra. The penumbra does not cause any noticeable darkening of the Moon's surface, though some may argue it turns a little yellow. A special type of penumbral eclipse is a total penumbral eclipse, during which the Moon lies exclusively within the Earth's penumbra. Total penumbral eclipses are rare, and when these occur, that portion of the Moon which is closest to the umbra can appear somewhat darker than the rest of the Moon.

A partial lunar eclipse occurs when only a portion of the Moon enters the umbra. When the Moon travels completely into the Earth's umbra, one observes a total lunar eclipse. The Moon's speed through the shadow is about one kilometer per second (2300 mph), and totality may last up to nearly 107 minutes. Nevertheless, the total time between the Moon's first and last contact with the shadow is much longer, and could last up to more than 6 hours.[citation needed] The longest total lunar eclipse between 1000 BC and 3000 AD had a duration of 1h47m14s, and took place on May 31, 318.[citation needed] The relative distance of the Moon from the Earth at the time of an eclipse can affect the eclipse's duration. In particular, when the Moon is near its apogee (that is, the farthest point from the Earth in its orbit) its orbital speed is the slowest. The diameter of the umbra does not decrease much with distance. Thus, a totally-eclipsed Moon occurring near apogee will lengthen the duration of totality.


[edit] Appearance

Lunar eclipses in 2003. Two total lunar eclipses occurred in 2003. The eclipse on May 15 grazed the northern edge of the earth's shadow, and the eclipse on November 8 grazed the southern edge. These images show the eclipse in November was much brighter as the bottom rim of the Moon did not darken as much after completely entering the umbra. The color and brightness of the Moon during an eclipse varies according to the amount of light refracted by the Earth's atmosphere.The Moon does not completely disappear as it passes through the umbra because of the refraction of sunlight by the Earth's atmosphere into the shadow cone. The amount of refracted light depends on the amount of clouds or dust in the atmosphere, and this light causes the Moon to glow with a coppery-red hue that varies from one eclipse to the next.

The following scale (the Danjon scale) was devised by André Danjon for rating the overall darkness of lunar eclipses:[2]

L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow has a bluish, very bright rim.

Answer 2

given if the earth moon and sun were in a straight line, they would happen twice a month,
one lunar (earth between moon and sun) at full moon, and one 2 weeks later at new moon
(solar eclipse). But they are not as the Sun and earth have their own orbit tilt, and the
moon and earth have their own orbit tilt. So you are looking at three different planes of
orbit. Now there is a time when these orbits cross each other and that point is called a
node. So when the earth moon and sun hit at a node, an eclipse happens. The Earth shadow
is expanse due to size and distance from the sun. Consequently, the moon enters the earths
shadow (lunar eclipse) a lot more frequent than the moon shadow hitting the earth
(solar eclipse) but is usually partial and not a total eclipse. More info and diagrams
available by email.

Answer 3

Eclipses
Eclipses occur due to the alignment of the Earth, Moon, and Sun.



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Solar Eclipses
A solar eclipse occurs when the Moon blocks the light from the Sun and causes a shadow to be cast on a small area of the Earth. There are three types of solar eclipses: total, partial, and annular. Due to the relative sizes of the Moon and the Sun and their distances from us, at times they appear to be the same size in the sky. If a solar eclipse occurs during this time, the Moon exactly covers the Sun and a total eclipse occurs. These are of interest because during total eclipses, outer layers of the Sun which are not usually visible can be seen. The alignment of the Earth, Moon, and Sun have to be exact for a total eclipse to occur. Even when the alignment is exact, not everyone will see a total eclipse. This is because, if the alignment is correct for the northern hemisphere, it is slightly off in the southern hemisphere (and vice versa). During total eclipses, astronomers specify zones where the alignment is exact (the umbra) and where it is slightly off (penumbra). For more information on the umbra and penumbra (and to see a simulation of the moon crossing in front of the sun, click here
If the alignment is not exact, a partial eclipse may occur. This is when the Moon only partially overlaps the Sun and blocks only part of the Sun from our view.

An annular eclipse occurs when the apparent size of the Moon is smaller than that of the Sun, and the Moon does not fully block the Sun from our view. This occurs because the Moon's orbit is elliptical, and so the Moon's distance from the Earth varies. When the Moon is farther away from the Earth, it appears to be smaller. Therefore, there are times when the Moon appears to be smaller than the Sun. If an eclipse occurs at this time, an annular eclipse results. Annular eclipses lok like a "bull's eye".

To see a picture of an actual total solar eclipse and to learn more about eclipses, click here



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Lunar Eclipses
A lunar eclipse occurs when the Moon passes through the Earth's shadow. Because the Earth is much larger than the Moon, usually the entire Moon is eclipsed. Because the full phase can be seen from anywhere on the night side of the Earth, a lunar eclipse can be seen by more people than a solar eclipse. Since the Moon is moving through the Earth's shadow, and the size of the Earth is much greater than the size of the Moon, a lunar eclipse last for about 3.5 hours (as opposed to a solar eclipse which last on the order of about 7.5 minutes).
To learn more about lunar eclipses, see pictures of actual eclipses, and find out when the next lunar eclipse will occur, click here.



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Tilt of the Moon's Orbit
While the Moon is always in a new phase during a solar eclipse, a solar eclipse does not occur every time the moon is in the new phase. This is because the orbit of the Moon is tilted relative to the Earth's orbit around the Sun. This tilt is only 5 degrees, but it is enough that the alignment of the Earth, Moon, and Sun only occurs about once every six months. This holds true for lunar eclipses as well. In fact, lunar and solar eclipses generally occur together; that is, if the alignment is correct for a lunar eclipse during the full phase of the Moon, it will also be correct for a solar eclipse during the next new phase of the Moon.

Answer 4

Lunar Eclipse!

Answer 5

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