首页>英语角 > 听力 > 美音 > 课 程 > 科学 > 大三>What Is An Eclipse?
What Is An Eclipse?
Question
Lunar Eclipses last longer than solar eclipses because
提交
The Moon goes around the Earth every 28 days and as it does we see the different phases of the Moon.Occasionally the Moon, when it is between us and the Sun in the new Moon stage is perfectly in line with the Sun as seen from Earth and for a short period it covers and blanks out the Sun causing a Solar Eclipse.As luck would have it the Moon and the Sun appear as almost exactly the same size as each other in the sky. It is because of this small scale that the shadow which the Moon casts onto the Earth is very small indeed and only people standing on this narrow band get to see a Total Eclipse.Anybody standing outside of this band would get to see only part of the Sun obscured by the Moon; this is known as a partial eclipse. On occasions the Moon appears slightly smaller than the Sun leaving a ring of the Sun still showing all around the Moon, this type of eclipse is known as an annular eclipse.During an eclipse as the Moon creeps across the Sun's disc it gradually gets darker and darker on Earth. Animals and birds react as though it is night fall and return to roost. The temperature drops dramatically and the stars appear.The Moon's shadow can be seen racing across the face of the Earth from the West to the East.You must never look directly at the Sun as this can cause damage to your eyes; instead use a telescope or binoculars to cast an image of the sun onto white paper held behind, but never look through the telescope or binoculars at the Sun.As totality nears, less and less of the Sun can be seen until just a tiny part of the Sun can be seen peeping from behind the Moon giving, what Astronomers call the Diamond ring effect, basically because it looks like a diamond ring!Then for a few short minutes the Sun is completely blacked out by the Moon and the Sun's atmosphere or Corona can be seen glowing all around the Eclipsed Sun.Slowly the Moon then moves away from the Sun and narrow shafts of sunlight can be seen shining through the mountains and valleys at the edge of the Moon, these beads of light are known as Bailey's beads.An Eclipse of the Moon can also occur. Lunar eclipses happen at full Moon when the Moon is on the opposite side of the Earth to the Sun and it passes through the Earth's shadow.Unlike Solar Eclipses, anybody who is on the night time side of Earth and are able to see the Moon will be able to see a Lunar eclipse. Lunar eclipses are quite safe to look at too.During a Lunar eclipse, the Moon doesn't completely disappear but instead goes very deep red in colour. This is due to some of the Sun's light refracting through our atmosphere and shining a red light onto the Moon.As the Earth's shadow creeps across the Moon the curve of the Earth can quite clearly be seen.Because the Earth is bigger than the Moon, we cast a larger shadow than the Moon does and so Lunar Eclipses last longer than solar eclipses. Also, the entire Moon is covered by our shadow not just a narrow band as in Solar eclipses.So why don't we have an eclipse at every new Moon and every full Moon? Well we would if it wasn't for the Moon being on a slight tilt in its orbit and for the fact that it usually passes either above or below the Sun and above or below the Earth's shadow.In ancient times eclipses were treated with dread and fear, people thought that a giant dragon was eating up the Sun and they would bang drums and make lots of noise to chase the dragon away, which of course always worked!For more intriguing information about our solar system, check out our other films on the VideoJug website.
视频文本已隐藏,本文本来自网络或网友仅供参考
显示视频文本

Discuss

0 comments
characters remainingSubmit
反馈