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托福TPO-26 Lecture 4(上)

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Listen to part of a lecture in an astronomy class.

听一段天文学课程。

OK. We've been looking at some of the smaller members of our solar system, comets.

我们已经讲过太阳系中体型较小的成员——彗星。

You already know about the structure of comets.

你们已经知道彗星的结构了。

Let's continue our discussion now by talking about orbits, especially those of the so-called periodic-orbit comets.

我们继续讲讲轨道,特别是那些所谓的“周期轨道彗星”。

哈雷彗星1.jpg

These are the comets that circle around the Sun pretty regularly.

这些彗星绕太阳规律性旋转。

They return again and again, predictably, after a certain period of time.

可以预测的是,它们在一定时间段后会一次又一次地回归。

That's why we say their orbits are periodic.

这就是为什么我们说(彗星的)轨道是周期性的。

Probably the most famous and brightest of these is Halley's comet.

也许在彗星中,最著名最明亮的就是哈雷彗星了。

Halley's comet comes from far out in the solar system, goes in close to the Sun, and then out again.

哈雷彗星从远处进入太阳系,接着靠近太阳,然后再离开太阳系。

At its closest approach to the Sun, Halley's comet is about twice as close to the Sun as Earth is.

在最接近太阳时,哈雷彗星与太阳的距离是地日距离的一半。

And at its farthest, it's about thirty-five time farther from the Sun than we are, which puts it out beyond Neptune.

在离太阳最远时,哈雷彗星与太阳的距离是地日距离的三十五倍,比海王星还远。

Basically, the idea here is that a periodic comet, with its very elongated orbit, just keeps coming back around again and again.

基本上,这种观点就是,一个沿着延长轨道运转的周期性彗星,会一次又一次回到原处。

With Halley's comet, well, it returns every 75 years, roughly.

对哈雷彗星来说,差不多每七十五年回归一次。

But where is Halley's comet during most of this time?

但这大部分时间里哈雷彗星都在哪儿呢?

Well, like all orbiting bodies, a comet moves faster when it's closer to the Sun, so it only spends about a year or two in our neighborhood, inside the orbit of Jupiter.

和其它绕轨道运行的星体一样,彗星在接近太阳时运转较快,所以哈雷彗星只会在我们附近即在木星轨道范围内待一两年左右,。

Most of its time is spent way out beyond Jupiter's orbit, poking along near the farther reaches of it own orbit.

大部分时间里,哈雷彗星都在木星轨道外,在自己轨道的远端流连。

Because of this, we can only see Halley's for a few months every 75 years, first on its way in toward the sun, and then on its way out again.

正因如此,每七十五年,我们也只能在几个月内看见哈雷彗星,先是它靠近太阳的时候,接着是它离开。

Now, you remember from our previous discussion that comet's nucleus, its core, is made up of ice and dust, like frozen snowball.

你们还记得我们先前的讨论说过,彗星的核由冰和尘土组成,就像一个冰冻的雪球一样。

And as it approaches the sun, it starts to heat up.

在它靠近太阳的时候,它开始升温。

And some of the ice vaporize into gas and spreads out from the nucleus.

一部分冰会蒸发成气体,从核部散发出去。

The gases that vaporize from the comet, the comet never collects them back again, so on every orbit, the comet leaves part of itself behind.

从彗星蒸发出去的气体,是无法被彗星回收的,所以每次绕轨运行,彗星都会留下自己的一部分。

OK, how old is this solar system? Four and a half billion years, remember?

太阳系有多少岁了?四十五亿年,你们还记得吗?

And Halley's is going around the sun once every 75 years and losing stuff each time.

哈雷彗星每七十五年就要绕太阳旋转一次,每次都会失去些东西。

重点单词   查看全部解释    
certain ['sə:tn]

想一想再看

adj. 确定的,必然的,特定的
pron.

 
comet ['kɔmit]

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n. 慧星

 
predictably

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adv. 可预言地

 
approach [ə'prəutʃ]

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n. 接近; 途径,方法
v. 靠近,接近,动

联想记忆
periodic [.piəri'ɔdik]

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adj. 周期的,定期的,间歇的,完句的

 
astronomy [əst'rɔnəmi]

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n. 天文学

联想记忆
nucleus ['nju:kliəs]

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n. 核,核心,细胞核,原子核

 
core [kɔ:]

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n. 果心,核心,要点
vt. 挖去果核

 
circle ['sə:kl]

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n. 圈子,圆周,循环
v. 环绕,盘旋,包围

 
previous ['pri:vjəs]

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adj. 在 ... 之前,先,前,以前的

联想记忆

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