It assures that the astronomical cycles have been in existence for billions of years.
这使人们确信天文周期已经存在了数十亿年。
We are the products of evolution, and not just evolution that occurred billions of years ago.
我们是进化的产物，并且不仅仅是发生在数十亿年前的进化。
Over billions of years, the gas was compressed by gravity into galaxies, stars, plants and eventually, even humans.
在数十亿年的时间里，这些气体被引力压缩成星系、恒星、植物，最终甚至变成了人类。
Biological systems have been doing this for billions of years.
生物系统亿万年来都在这样做。
Astrogeologists suspect that these scarps having formed billions of years ago as the planet's surface cooled and shrank.
太空地质学家猜测这些陡坡是在几十亿年前当行星表面冷却收缩时开始形成的。
Red dwarfs, meanwhile, burn for hundreds of billions of years.
而红矮星，可以燃烧成百上千亿年。
Building up the elements needed for life this way takes billions of years.
构成这些生命所必需的元素需要几十亿年的时间。
Stars that form planetary nebulae typically live for billions of years.
具有代表性的是，构成行星状星云的恒星已经存活了十亿年。
Different theories predict how this metallicity gradient changes over billions of years.
已有几种不同的理论对金属丰度梯度在亿万年间如何变化作了推测。
Scientists have analysed meteorites that formed billions of years ago before falling to Earth.
科学家们是在分析检验了在数十亿年之前坠落到地球上的陨石之后得出这一发现的。
Expansion has apparently continued, but much more slowly, over the ensuing billions of years.
膨胀很显然在继续着，但是在之后的百亿年里变得更为缓慢。
'if life can evolve, it's going to have billions and billions of years to adapt to the surface.
如果Gliese 581g上的生命也能进化，它肯定是花费了数亿年的时间来适应行星表面。
For billions of years, the environment and how it affected organisms' genes was the key to evolution.
数十亿年以来，环境以及对基因的影响一直是生物体进化的关键。
These may be primitive bacteria whose close relations are known to have thrived billions of years ago.
这些可能是原始的细菌，其近亲物种曾经在亿万年前繁荣过。
The hot, remnant stellar core of NGC 2818 will eventually cool off for billions of years as a White Dwarf.
炽热的恒星内核会在几十亿年里逐渐冷却，内核在这段时间里叫做白矮星。
The finding comes from simulations to show how orbits of planets might evolve billions of years into the future.
这一发现源自显示未来数十亿年中行星轨道会如何演变的模拟计算。
Drawn out over billions of years, the encounters will likely result in their merger into a single galaxy of stars.
数十亿年过去，会合最终可能导致它们合并成一个星系。
Fossil stromatolites are regarded by some people as evidence of the same thing having gone on billions of years ago.
而层叠岩石的化石被一些人认为是几十亿年前发生着同样过程的证据。
It's possible the star was originally part of the Milky Way when it collided with the other galaxy billions of years ago.
这颗恒星很可能是银河系几十亿前年与其他星系碰撞时最原始的一部分。
We on Earth have protection in the form of a magnetic shield. But that shield is dead on Mars, gone for billions of years.
我们在地球上受磁场的保护，而火星上的磁场早就在亿万年就消失了。
Even though some of these elements take billions of years to decay (on average), the Earth has been around for billions of years!
虽然它们中有些元素发生衰变(平均)要历经数十亿年，地球的存在也只有数十亿年历史！
Billions of years ago, free-living bacteria are thought to have become incorporated into living cells as energy-providing mitochondria.
据测在数十亿年前，一些自由生活的细菌进入到活细胞内部，变为负责提供能量的线粒体。
Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago.
矮星系之间的如此遭遇通常发生在几十亿光年之外，也就是几十亿年之前。
Look for an alien artifact here on Earth: Earth has been around for billions of years-who says that aliens haven't been here before?
在地球上搜寻外星人工物品：地球已经存在了几十亿年，谁能说外星人过去未曾来过呢？
Eventually—over tens or even hundreds of billions of years—a white dwarf cools until it becomes a black dwarf, which emits no energy.
在几百亿年甚至几千亿年之后，白矮星最终冷却形成黑矮星，后者不再散发任何能量。
For billions of years, certain bacteria and fungi have produced chemical substances to protect them from attack from other microorganisms.
数十亿年以来，某些细菌和真菌通过产生化学物质来保护自己，抵御来自其它微生物的攻击。
Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished.
对于这个星系起源有几种假设，其中包括数十亿年前的一次星系撞击以及重力对中间消失地带的影响。
If their speed had been constant, they would all have been on top of one another billions of years ago. Was this how the universe began?
若它们的速度恒久不变，那它们在上一个几十亿年前就存在了。那宇宙是怎么出现的？
If their speed had been constant, they would all have been on top of one another billions of years ago. Was this how the universe began?
若它们的速度恒久不变，那它们在上一个几十亿年前就存在了。那宇宙是怎么出现的？
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