(单词翻译:单击)
Hey there! Squeaks and I are learning about things that lived in the past.
你们好啊！吱吱和我正在学习生活在过去的事物。
Squeaks made this pretend time machine, so we can imagine what it’s like to go back in time and see things that lived long ago!
吱吱制作了这台假想的时光机，所以我们可以想象回到过去看到很久以前的东西是什么感觉！
Our pretend time machine is fun to use.
我们的假想时光机使用起来很有趣。
But we can also look at the way things are right now to understand what life was like in the past!
但是我们也可以通过观察现在的事物来了解过去的生活是什么样的!
Did you know that even though many old forms of life aren’t around any more, they have relatives that we can see today?
你知道吗?尽管许多古老的生命形式已经不复存在，但它们还有我们今天还能看到的亲戚。
Yep! Like dinosaurs.
是啊！就像恐龙一样。
Even though dinosaurswent extinct a long time ago, meaning there are none alive on Earth right now…
即使恐龙很久以前就灭绝了，也就是说现在地球上没有活着的恐龙了…
They are related to animals that are still alive today!
它们与今天仍然活着的动物有亲缘关系！
Can you guess what they are?
你能猜出它们是什么吗？
They’re birds!
它们是鸟！
Birds are actually relatives of dinosaurs!
鸟类实际上是恐龙的近亲！
You’re right!
你说得对!
It is pretty cool. But it’s not the only example!
这相当酷。但这并不是唯一的例子！
How would you like to see a very early relative of some of Earth’s bugs？
你想不想看看地球上一些虫子的早期亲戚?
This is a fossil of an animal called a trilobite.
这是一种叫做三叶虫的动物的化石。
Fossils are clues left by animals and plants a long time ago.
化石是很久以前动植物留下的线索。
And they can help us understand what life was like way back then.
它们可以帮助我们了解很久以前的生活是什么样子。
From those clues, we know that trilobites lived on Earth millions and millions of years ago, even before dinosaurs lived!
根据这些线索，我们知道三叶虫在几百万年前就生活在地球上，甚至比恐龙还早！
That’s a long time!
那可是很长的一段时间啊！
You’re right, Squeaks.
你说得对，吱吱。
It’s hard to thinkabout all the time that’s passed between when trilobites lived, and today.
很难想象从三叶虫生存到今天，经过了多长时间。
But I have an idea!
但我有个主意！
Let’s use our time machine!
让我们用我们的假想时光机吧！
And you can pretend, too!
你们也可以假装！
Even though we can’t really travel through time, we can use our imaginations.
即使我们不能真的穿越时间，我们也可以发挥我们的想象力。
Scientists use their imaginations all the time to help them solve problems.
科学家无时无刻不在用他们的想象力来帮助他们解决问题。
Okay, Squeaks, are you ready？
好了，吱吱，你准备好了吗?
Then let’s go!
我们出发吧！
We’ll pretend to travel backto the time when most trilobites lived, and imagine what it was like to live on Earth then!
我们将假装回到大多数三叶虫生活的时代，想象一下那时生活在地球上是什么样子！
Here we go!
我们开始吧！
Ok, Squeaks, I think we’re there!
好了，吱吱，我想我们到了！
Scientists think that Earth was warmer back then than it is now.
科学家们认为当时的地球比现在更暖和。
And almost all life at that time lived in the ocean.
那时几乎所有的生物都生活在海洋中。
In fact, scientists think that most of the Earth at the time was covered in ocean.
事实上，科学家们认为当时地球的大部分地区都被海洋所覆盖。
So I hope you brought your snorkel!
所以我希望你带了你的呼吸管！
Yes! The ocean certainly looked a lot different when the trilobites lived.
是!三叶虫生活的时候，海洋看起来确实有很大的不同。
A lot of land that’s dry now… including where the Fort is... was under water.
现在很多土地都是干燥的，包括福特堡所在的地方....是在水里。
But the Fort’s not under water any more, thank goodness.
不过，谢天谢地，福特堡已经不在水里了。
The Fort is on land now because the Earth is always changing.
福特堡现在在陆地上，因为地球总是在变化。
The kind of change I’m talking about isn’t like what happens when wind blows up a dust cloud…
我所说的这种改变不像风吹起尘雾时所发生的那样……
or water washes away some mud from a creek bank.
或者用水冲走小溪岸边的泥土那样。
This change happens over a long period of time… and happens really slowly.
这种变化会在很长一段时间内发生…而且发生得很慢。
We couldn’t see this kind of change if we tried!
如果我们试过了，我们也看不到这种变化！
But those changes are why the Earth’s oceans look a lot different today than they did when trilobites lived.
但这些变化就是为什么今天的地球海洋看起来与三叶虫生存时大不相同。
Good question, Squeaks!
问得好，吱吱！
Squeaks wants to know how we know all of this!
吱吱想知道我们是怎么知道这一切的！
One reason we know trilobites existed at all is because of fossils like this one.
我们知道三叶虫存在的一个原因是因为像这样的化石。
We can look at both the fossils themselves, and the things we find near them, to understand the clues.
我们既可以看化石本身，也可以看我们在它们附近发现的东西，以了解线索。
We’ve found fossils of other animals that lived in the ocean in the rocks around the trilobites.
我们在三叶虫周围的岩石中发现了生活在海洋中的其他动物的化石。
So we know that trilobites lived in the ocean too.
所以我们知道三叶虫也生活在海洋里。
Let’s take a look and see what we can learn from the actual trilobite fossil!
让我们看一看，看看我们能从真正的三叶虫化石中学到什么！
We can see how big it is.
我们可以看到它有多大。
This one is about as big as my hand.
这个和我的手差不多大。
But we’ve found all different sizes of trilobite fossils.
但我们发现了各种大小不一的三叶虫化石。
Some are about the size of a penny.
有些只有一便士大小。
But others are much bigger: just a little shorter than the size of two bowling pins laid end to end!
但其他的要大得多：只比首尾相连的两个保龄球的大小略短一点！
And we also see what it looked like.
我们也看到了它长什么样。
It has lots of body structures called segments.
它有很多叫做节的身体结构。
See these little sections, here. That means the trilobite’s body was divided into many parts that all worked together.
观察这些小小的节。这意味着三叶虫的身体被分成许多部分，所有这些部分都在一起工作。
Notice anything else about the trilobite,Squeaks？
吱吱，注意到关于三叶虫的其他事情了吗?
Yes, the segments look pretty tough, don’t they Kind of like they have a shell？
是的，这些节看起来很硬，是不是有点像有壳？
Soft body parts don’t usually make fossils that look like this one.
柔软的身体部位通常不会形成这样的化石。
So we think trilobites had tough shells to protect them.
所以我们认为三叶虫有坚硬的外壳来保护它们。
Scientists put together clues like these to figure out what kind of animals trilobites are, and if they are related to animals we see today.
科学家们将这样的线索组合在一起，以找出三叶虫是哪种动物，以及它们是否与我们今天看到的动物有亲缘关系。
They look for patterns by trying to find out how things are the sameand how they’re different.
他们通过试图找出事物的相同之处和不同之处来探寻规律。
Some animals, like this roly poly, have segments, and they have a hard outer shell.
有些动物，比如西瓜虫，有节，有一层坚硬的外壳。
These are reasons why we think that trilobites are relatives of animals like insects and roly polys.
这就是为什么我们认为三叶虫是昆虫西瓜虫等动物的亲戚。
In fact, we think they are part of a group called arthropods.
事实上，我们认为它们属于一个叫做节肢动物的类群。
Those are animals with segments and tough shells, like insects, spiders, roly polys, and crabs.
这些都是有节和坚硬外壳的动物，如昆虫、蜘蛛、西瓜虫和螃蟹。
There are other patterns we can see, too.
我们还可以发现其他的规律。
Like, arthropods have many legs.
比如，节肢动物有很多腿。
It’s hard to see from this fossil, but we think trilobites had many legs too.
从这块化石上很难看出，但我们认为三叶虫也有很多腿。
So that’s another pattern.
这是另一种规律。
Oh, fun idea!
哦，好主意！
We’re going to go outside to see if we can spot any arthropods to compare to our trilobite fossil!
我们要去外面看看能不能找到什么节肢动物来和三叶虫化石比较!
Thanks for joining me here at the Fort.
感谢收看我们在福特堡的节目！
If you want to keep learning and having fun with Squeaks, me, and all our other friends,
如果你想继续与吱吱，我和其他的朋友一起学习和玩耍，
be sure to hit the subscribe button, and we'll see you next time on SciShow Kids!
一定要点击订阅按钮，我们下次继续相遇在《少儿科学秀》节目！
