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More than 1.5 billion people use the internet every day, and they search for all kinds of stuff.
每天都有超过十五亿人使用互联网 搜索各种各样的网络信息
And good for them! We're all about curiosity here at SciShow.
这是件好事 好奇心是这档科学秀栏目的核心
That's why we've worked with Google and YouTube to answer ten of the most popular questions searched on the internet.
正因如此 我们和谷歌以及Youtube进行合作 回答网络搜索中十个最热门的问题
This is The World's Most Asked Questions. And today's question is: How old is Earth?
这就是 全球最热搜问题 今天的问题是：地球多大了？
Our best estimate is that the planet is 4.54 billion years old give or take fifty million years.
我们最新估测的地球年龄是45.4亿年 上下误差五千万年
It's taken scientists hundreds of years to narrow it down to that range.
一代代的科学家用了几百年的时间才把范围缩小到如今的水平
So the better question really is, "HOW do we know how old Earth is?"
但我们更想问：“地球的年龄是怎么测出来的？”
Well, for a long time, scientists just looked for the oldest parts of the planet's surface
在很长一段时间内 科学家仅仅在地球表面寻找最古老的区域
and then determined the age of the rocks there.
之后测定那里岩石的年龄
The thing is, Earth is always churning around the plates that make up its surface,
然而事实上 地球表层的板块在不停地变化
forming new crust and recycling older crust into the planet's interior.
不断形成新的地壳 而原来的地壳便循环利用 再次进入地球内部
So, most rocks on the surface today are an average of 100 million years old.
因此现在地表大部分的岩石平均年龄只有一亿岁
But geologists have found older rocks, mostly those that were once in the deepest layers of the crust,
但地质学家找到了年代更加久远的岩石 它们大部分曾经存在于地壳的最深层
but then got thrust upward before they could be recycled.
但却在进入循环之前就被推出了地表
The oldest of these are the Acasta Gneisses in northwestern Canada.
其中最古老的岩石是加拿大西北部发现的阿加斯塔片麻岩
By measuring the amounts of radioactive isotopes of elements in the rock,
通过测量岩石中放射性同位素的含量
scientists were estimate their age at 4.04 billion years old.
科学家们推测 这些岩石的年龄大约是40.4亿年
But to find the oldest material of ANY kind on Earth, you have to go to Western Australia,
但是 要想寻找地球上最古老的物质 就不得不提澳大利亚西部地区
where geologists have discovered crystals of zircon in sedimentary rocks.
在那里 科学家从沉积岩中发现了锆石晶体
Zircon contains uranium, which decays at a fixed, predictable rate,
锆石中含有铀 铀会以固定、可预测的速率发生衰变
so geologists were able to use that to determine that the crystals are 4.3 billion years old.
因此地质学家得以确定这些晶体的年龄是43亿年
So, evidence like this tells us that Earth must be at least four billion years old.
诸如此类的证据表明 地球的年龄至少有40亿年
But we've found even more clues to Earth's age … in space.
但在太空中 我们找到了更多的线索
The moon isn't geologically active like Earth is, so material from its surface can be dated pretty reliably.
月球的地质变化远不如地球活跃 因此我们能将月球表面物质的年龄 推测得相当精确可靠
And the moon rocks brought back from the Apollo missions have been found to be 4.4 to 4.5 billion years old.
阿波罗计划中 研究人员推测从月球带回的岩石 大约为44到45亿岁
Since the moon formed about the same time as Earth, that helps narrow down Earth's age even further.
因为月球和地球大致在同一时期内形成 这帮助我们进一步 缩小了范围
Then there are meteorites which come from lots of different sources in space,
此外 有许多不同来源的陨石造访地球
but many are leftover debris from the formation of the solar system.
其中许多陨石都是太阳系形成之初剩余的碎片
And sure enough, more than 70 meteorites have been dated to the same exact range as the moon rocks,
能够确定的是 有超过70颗陨石和月球上岩石的年龄相符
4.4 to 4.5 billion years ago.
均为44到45亿年
So you put all this evidence together, and, our little Earth is pretty old. So thanks for googling that,
所以当我们整合所有信息后就会发现 地球确实很古老 那么 很感谢各位的谷歌搜索
and let us know in the comments what the oldest thing you've ever interacted with is... besides the Earth.
也欢迎在评论里分享你打过交道的最古老的东西是什么 ……除了地球
According to our unscientific research via our SciShow survey,
根据科学秀不科学的调查显示
viewers who follow us on Facebook are more likely than others to own something that's over 300 years old.
相比其他观众 脸书用户更有可能拥有300年以上历史的物品
And those of you who own older things are less likely to get frequent hiccups.
而那些拥有古董的人有更小的几率罹患经常性的呃逆［打嗝］
Let us know what other questions you'd like us to answer by using the hashtag #WMAQ,
如果你想让我们回答更多其他问题 使用标签#WMAQ
for World's Most Asked Questions, and we'll compile the most asked questions into a video at the end of the month.
即全球最热搜问题 在月底我们会把所有这些问题 整合到一个视频中
Thank you for watching this episode of SciShow.
感谢收看本期科学秀
If you have any more planetary questions, don't forget to check us out at youtube.com/scishowspace.
如果你还有更多关于行星的问题 别忘了通过youtube.com/scishowsapce 联系我们
