ADM-201 dump PMP dumps pdf SSCP exam materials CBAP exam sample questions

大海捞针:寻找宜居星球 – 译学馆
未登录,请登录后再发表信息
最新评论 (0)
播放视频

大海捞针:寻找宜居星球

A needle in countless haystacks: Finding habitable worlds - Ariel Anbar

宇宙大约包含一千亿个星系
The universe contains about 100 billion galaxies.
每一个星系大概包含一千亿个恒星
Each of those galaxies contains about 100 billion stars.
许多恒星都有环绕着的卫星
Many of those stars have planets orbiting them.
在浩瀚的宇宙中,我们该怎样找寻生命?
So how do we look for life in all that immensity?
这就像是大海捞针
It’s like searching for a needle in trillions of haystacks.
我们或许想集中探索这些支持生命存在的星球
We might want to focus our search on planets that we know can support life as we know it —
或者说,适宜生命居住的星球
what we call habitable worlds.
那么这些星球是怎样的呢?
What do such planets look like?
如果要回答这个问题,我们不必非要见到这些星球
To answer that question, we don’t look out there.
我们可以看看我们的地球
Instead, we look at ourselves. At Earth.
因为地球是目前为止发现的唯一适合居住的星球
Because this is the one planet in the universe that we know for certain is habitable.
从外太空来看,地球是一个蓝色的,布满水的世界
When we look at Earth from space, we see a blue, watery world.
不巧的是,地球表面四分之三都被海洋覆盖着
It’s no coincidence that three quarters of the surface is covered by oceans.
由于这个独特的化学和物理特性
Because of its unique chemical and physical properties,
水对所有生命都是极其重要的
water is absolutely essential for all life as we know it.
对那些水资源丰富的星球,
And so we get especially excited about other worlds on which water is abundant.
幸运的是,水在宇宙中很常见
Fortunately, water is very common in the universe.
但是生命需要的是液态水,而不是固态水或是气态水
But life needs water in the form of liquid, not ice, and not vapor,
那么这就不常见了
and that’s a little bit less common.
在星球表面想要存在液态水,有三件事是很重要的
For a planet to have liquid water at its surface, three things are important.
首先,这个星球要有足够的重力
First, the planet needs to be large enough that the force of gravity
这样就可以捕获从太空飞过来的水分子
keeps the water molecules from flying off into space.
比方说,火星比地球小,所以他的重力也比地球小
For example, Mars is smaller than Earth, and so has less gravity,
这是火星只有很薄的大气层的一个重要原因
and that’s one important reason that Mars has a very thin atmosphere,
也是其表面没海洋的一个原因
and no oceans at its surface.
其次,星球需要有一个大气层。为什么需要?
Second, the planet needs to have an atmosphere. Why?
因为没有大气层的话,这颗星球就处于真空之中
Because without an atmosphere, the planet is in a vacuum,
而液态水不能在真空之中存在
and liquid water isn’t stable in a vacuum.
月球就没有大气层,所以如果你倒一些水到月球上
For example, our moon has no atmosphere, and so if you spill some water on the moon,
不是蒸发成水蒸气,就是冻结成冰
it will either boil away as vapor, or freeze solid to make ice.
没有大气层提供的压力,液态水就不会存在
Without the pressure of an atmosphere, liquid water can’t survive.
最后,这种星球要离恒星有合适的距离
Third, the planet needs to be at the right distance from its star.
太近的话,表面温度会超过水的沸点,
Too close, and the surface temperature will exceed the boiling point of water,
海洋就会变成水蒸气;
and oceans will turn to vapor.
太远的话,表面温度又会低于水的冰点,
Too far, and the surface temperature will fall below the freezing point of water,
导致海洋冻结成冰洋。
causing the oceans to turn to ice.
火海或冰山,都不能满足条件
Fire or ice. For life as we know it, neither will suffice.
假设恒星周边存在液态水,并且它们像带子一样环绕着这颗恒星
You can imagine that the perfect zone where water stays liquid looks kind of like a belt around a star.
我们称这片带状区域为“可居住带”
We call that belt the habitable zone.
所以当我们寻找另一个适宜居住的世界之时,我们一定要寻找恒星周边的“可居住带”
So when we search for habitable worlds, we definitely want to look for planets in the habitable zones around their stars.
这些区域内最有可能找到类地行星
Those regions are the best bets to find planets like Earth.
但是即使“可居住带”是我们找寻带生命的星球的不错地带
But while habitable zones are a pretty good place to begin the search for planets with life,
仍然有一些复杂的问题需要解决
there are a couple of complications.
首先,不能因为行星处于可居住带就说它一定适宜居住
First, a planet isn’t necessarily habitable just because it’s in the habitable zone.
可以参考一下太阳系的金星
Consider the planet Venus in our solar system.
如果你是一个外星宇航员,你八成觉得金星会存在生命
If you were an alien astronomer, you’d think Venus is a pretty good bet for life.
因为他有合适的尺寸,存在大气层,位于太阳系的可居住带
It’s the right size, it has an atmosphere, and it’s in the habitable zone of our sun.
你或许会把它当成地球的孪生兄弟
An alien astronomer might see it as Earth’s twin.
但是金星可不适宜居住,至少表面是这样
But Venus is not habitable, at least not at its surface.
金星太热了,不适合生命存在
Not by life as we know it. It’s too hot.
因为金星的大气层满是二氧化碳,一种温室气体
That’s because Venus’ atmosphere is full of carbon dioxide, an important greenhouse gas.
实际上,金星大气层几乎全是二氧化碳
In fact, its atmosphere is almost entirely carbon dioxide,
而且比地球的稀薄近一百倍
and is almost 100 times thicker than our own.
由此,金星的温度足够使铅熔化
As a result, the temperature on Venus is hot enough to melt lead,
金星也干燥得跟骨头一样
and the planet is dry as a bone.
所以找到一颗合适大小的星球,并且离恒星合适的距离还只是个开端
So finding planets of the right size and distance from their stars is only a beginning.
我们也要了解它们大气层的组成成分
We also want to know about the makeup of their atmospheres.
第二个复杂的问题当我们朝地球深处望去之时就出现了
The second complication emerges when we look a little more deeply at planet Earth.
过去三十年,我们发现了所有极端环境下的微生物
In the last 30 years, we’ve discovered microbes living in all sorts of extreme environments.
在我们脚底下几英里远的裂隙岩体中,
We find them in fissures of rock miles beneath our feet,
在大洋底的沸水之中,
in boiling waters of the ocean floor,
在温泉的酸性水中
in acidic waters of thermal springs,
在我们头顶几英里远的云层之中。
and in cloud droplets miles above our heads.
这些所谓的极端环境并不罕见
These so-called extremophiles aren’t rare.
一些科学家预测,一些微生物生存在深层地底之中
Some scientists estimate that the mass of microbes living deep underground
像地球表面的生物一样聚集而居
equals the mass of all the life at Earth’s surface.
这些深藏的微生物不需要海洋或是阳光
These subterranean microbes don’t need oceans or sunshine.
这些发现证明类地行星只是天体物理学的冰山一角
These discoveries suggest that Earth-like planets may be only the tip of the astrobiological iceberg.
火星的表面以下含水层存在生命是可能的
It’s possible that life might persist in aquifers beneath the surface of Mars.
木星的木卫二上也许生存着微生物
Microbes may thrive on Jupiter’s moon Europa,
因为木卫二的液态水可能存在于其冰层之下
where liquid water ocean probably lies beneath the icy crust.
另一个在土卫二下面的海洋是喷向太空的间歇泉的源头
Another ocean beneath the surface of Saturn’s moon Enceladus is the source of geysers erupting into space.
这些间歇泉可能存在微生物吗》?
Could these geysers be raining microbes?
我们飞过时可以发现它们吗?
Could we fly through them to find out?
那么关于其他的使用液体而不是水的那些生命,那些我们暂时没发现的生命呢?
And what about life as we don’t know it, using a liquid other than water?
或许我们是一群生活在不同寻常的极端环境中的生物。
Maybe we are the crazy creatures living in an unusual and extreme environment.
或许真正的可居住区有很大
Maybe the real habitable zone is so large
毕竟浩瀚无垠的宇宙(==)
that there are billions of needles in those trillions of haystacks.
从大场景来说,地球或许只是许多不同的可居住星球中的一种。唯一的方法是去到太空并探索太空
Maybe in the big scheme of things, Earth is only one of many different kinds of habitable worlds.The only way to find out is to go out and explore.

发表评论

译制信息
视频概述
听录译者

收集自网络

翻译译者

收集自网络

审核员

自动通过审核

视频来源

https://www.youtube.com/watch?v=qY1R0UBBZk0

相关推荐