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雨滴不是水滴形!

Raindrops Don't Look like Raindrops!

This Scishow video describes the closest thing in nature
本期《科学秀》讲的是大自然中
to a perfect sphere as far as we know.
我们所知的最接近完美球体的东西
To find the area of a sphere, you need π,
计算球体的表面积需要用到π
3.14 etc.
约等于3.14
And that’s only one of the many reasons we need π.
而π的用途远不止如此
So, to show our appreciation for this incredible numerical value,
所以 为了感谢这个了不起的数值
we are launching a very exciting new π themed calendar.
我们推出了一款超棒的全新π主题日历
You can get it for a limited time at ComplexlyCalendars.com
你可以在限期内登录ComplexyCalendars.com购买

《科学秀》
On a rainy day,
在一个雨天
when you’re lounging inside with a cup of hot cocoa,
当你懒洋洋地躺在家里喝着热可可时
you’ll see raindrops with all sorts of shapes hitting your window,
你会看见各种形状的雨滴落在窗户上
long streaks, big round blobs, tiny smears,
有长条状的 大圆点状的 小点状的
your window pane turns into an abstract painting pretty fast.
窗户很快便成为了一幅“抽象画”
But what you won’t see falling outside
但窗外飘落的雨滴
is the well-known pointy tipped raindrop shape you see in drawings,
并非是图示中众所周知的尖头水滴状
or even what you see dripping out of your faucet.
或从水龙头滴出来的那种形状
Because that’s not what raindrops look like as they’re falling.
因为雨滴下落时并不是那个样子的
The real cast of characters is way more interesting
真正的雨滴其形状要有趣得多
with wobbling blobs droplets that look like jellyfish and dinosaurs and more.
晃动的小雨滴看起来像水母 恐龙等等
Welcome to the hidden world of raindrops.
欢迎来到雨滴的神秘世界
Some of the first experiments that rigorously studied
第一批严谨地研究
the shapes raindrops form as they fall
雨滴下落形状的实验是
were done at UCLA in the 1960s.
20世纪60年代在加州大学洛杉矶分校完成的
And this wasn’t just like a bunch of scientists sitting around,
这并不是一群科学家围坐在一起
being curious and bored.
充满好奇又觉得无聊
They figured that understanding what shapes raindrops make and why
他们认为了解雨滴形成的形状及原因
would also help with weather forecasting.
还能帮助预测天气
And they were right for the record.
请注意 他们是对的
Their results did end up in forming weather models.
实验结果最终形成了天气模型
In any case, though, they used a wind tunnel in their experiments
不管怎么说 他们在实验中使用风洞
to suspend droplets of water mid-fall
通过向降落中的水滴吹风
by blowing air up at them.
使它们悬浮在空中
They basically created one of those indoor skydiving experiences just for raindrops.
他们给雨滴创造了一次室内跳伞的体验
And that allowed them to take detailed in-flight photos of them.
也让他们能够拍摄到雨滴飞行中的详细照片
Their main finding was that raindrops looked pretty spherical.
他们主要发现雨滴看起来近乎球体
There were no pointy tops.
没有尖头
This is actually about what they expected to see
事实上 基于之前的研究以及表面张力形成的原因
based on previous research and the reason why was surface tension.
科学家们也是这样预测的
Water is a surprisingly clingy molecule.
水分子的凝聚力极强
The pull of water molecules toward each other
水分子之间的吸引力
is often stronger than the pull of gravity dragging them down.
通常强于重力作用于水分子的向下拉力
This allows droplets of water to cling together,
这使得水滴能凝聚在一起
to walls, or to your skin.
能附着在墙上或人的皮肤上
This is also why raindrops don’t look like they do in cartoons.
这也是雨滴看起来跟卡通片里不一样的原因
As surface tension pulls the water molecules together,
由于表面张力把水分子凝聚在一起
any pointiness in the raindrop gets smoothed out.
雨滴中凸出的部分会变得平滑
But this team in the 60s also found that
而60年代的这组科学家同样发现
when different forces get involved,
当受到多个不同的力时
the droplets don’t stop its spheres.
雨滴依然能保持球状
Like although smaller raindrops tended to stay spherical,
尽管较小的雨滴倾向于保持球形
when droplets got to around four millimeters across,
但当雨滴直径达到4毫米左右时
they had more flattened out bottoms, like hamburger buns.
其底部就会变得平坦 像汉堡面包那样
This shape forms because as the droplet falls,
究其原因 是因为雨滴在下落时
it pushes against the air below it.
它会受到下面空气的阻力
And because bigger droplets get buffeted by the air more,
并且因为偏大的雨滴受到空气的阻力更大
they get flattened more.
所以底部就变得更平了
And the factors that affect droplet shape and size don’t stop there.
其实影响雨滴形状及大小的因素不止这些
Electric charge and even aerosols like soot from cars can also impact things,
电荷 甚至像汽车尾气形成的气溶胶也会产生影响
meaning human activity can also affect droplet shapes.
也就是说人类的活动也会影响雨滴的形状
In fact, so much goes into this process
事实上 这个过程受到众多因素的影响
that different storms will generally have different looking raindrops,
以致不同的暴风雨中雨滴的形状是不一样的
depending on the conditions.
这都取决于天气状况
Like heavier rainstorms tend to have bigger raindrops
比如暴风雨更猛烈时雨滴会更大
because there’s just more water around.
因为空气中有更多的水汽
But when those raindrops get too big,
但是当雨滴变得太大时
they can often inflate and burst like the world’s tiniest water balloons
在空气的挤压下 会像世间最小的水球那样
as they get buffeted by the air.
膨胀并破碎
Plus, if the air is moving in an especially erratic way during heavy rain,
此外 如果下大雨时风刮的异常狂乱
that can cause turbulence,
就会引起湍流
which can push around the droplets in unpredictable ways
会以不可预测的方式吹打着雨滴
and make them wobble.
使它们摇来晃去
And the next thing you know,
接下来的事可想而知
those droplets are twisting and turning
那些雨滴会被风吹得四处飘窜
and moving through all kinds of distorted shapes.
以各种扭曲的形状移动
For instance, if you’ve ever seen rain at night backlit by a street lamp,
举个例子 如果你见过路灯背光下的夜雨
you might have noticed a streaking effect,
你可能注意过一种拖尾效应
that’s caused by the raindrops wobbling.
那就是由雨滴晃动引起的
But burger buns, streaks, that’s pretty tame,
但跟雨滴碰撞 融合 破碎后形成的形状相比
compared to what happens when raindrops collide, combine and break up.
汉堡面包形 线形雨滴显得尤为平淡
That’s where the real fun starts.
那才是真正的乐趣所在
In the 1970s, researchers from the University of Toronto
在20世纪70年代 多伦多大学的研究人员
set up an experiment to photograph droplets colliding,
开展了一个实验 拍下了雨滴碰撞的过程
and things got weird.
奇怪的事情发生了
They found that the shapes they noticed during collisions fell into four categories,
他们发现雨滴碰撞后形成四种形状
which they called “sheet”, “neck”, “disc” and “bag”.
分别定义为“丝状” “条状” “盘状”以及“包状”
The “sheet” is the most common type of collision,
“丝状”是雨滴碰撞后最常见的形状
and it’s when the smaller droplet tears a chunk off the larger one,
是由小雨滴冲破大雨滴形成的
leaving it looking like an upside down jellyfish.
看起来像是一只倒立的水母
Meanwhile, the “neck” shape, also known as a filament,
第二种是“条状” 也叫线状
is when the smaller droplet just glances off the larger one.
是当小雨滴擦过大雨滴时
Instead of savagely ripping a piece off,
没把大雨滴冲破
it just drags a stream of water along with it as the drops separate.
而是在雨滴分离时拽出了一条水流线
It kind of looks like a long neck dinosaur.
看起来有点像长脖子恐龙
Next up, the “disc” shape is
下一种是“盘状”
when the smaller drop hits near the center of the larger one
当小雨滴以清脆的啪嗒声
in a nice satisfying splat,
撞到大雨滴中心附近
the collision makes the droplets coalesce for a bit before moving apart.
碰撞使雨滴在分开前短暂地融合 形成盘状
And lastly, there’s the elusive “bag” shape.
最后一种是难得一见的“包状”
If you’re playing raindrop bingo,
如果玩雨滴宾果游戏
this is going to be an especially hard box to check,
这会是很难填对的一格
because it’s a rare variant of the “disc”
因为”包状”是一种罕见的“盘状”变形
caused by a dead-on collision.
是由雨滴正面碰撞产生的
It results in a big lump,
最终变成一大团
followed by a larger shower of droplets when everything breaks up.
破碎散开后形成更大的雨滴
Although these researchers in the 70s stopped at four categories,
虽然70年代的研究人员只分了四个类别
later teams expanded the list
后来的研究组通过描述其见过的其它形状
by describing other shapes they saw.
扩充了这一列表
For instance, they identified another variant of “disc” called “crown”,
例如 他们定义了另一种“盘状”的变形 “王冠状”
which was caused by slower collision speeds like,
由较慢的碰撞速度造成
like you might guess, it looks like a crown.
如你所想 它看起来像一顶王冠
They also found the aftermath of the collision is different in each case too,
他们还发现每次碰撞结果都不同
resulting in different numbers, sizes
以致雨滴分离后会形成
and even more shapes of droplets after the droplets separate.
不同的数量 大小甚至更多的形状
But whatever the scenario, there’s not a pointy topped raindrop in sight.
但不管什么情况 都没有见过尖头状的
So the next time you’re staring wistfully out the window on a rainy day,
所以下一次雨天 你若有所思地盯着窗外时
know that what you see passing you
你要知道眼前飘过的雨滴
doesn’t look like the tear-shaped form in cartoons,
并不是卡通片里的泪珠形状
but the truth is way more interesting.
真正的雨滴形状要比那有趣得多
It turns out there’s lots to learn when studying the shape of water.
事实证明 关于水的形状还有很多有待研究
So raindrops are way cooler than that teardrop shape.
因此雨滴远比泪珠的形状酷得多
They go through so many dynamic stages
雨滴在降落中经历的动态变化太多
that it doesn’t even begin to capture.
以至于我们来不及捕捉
And to learn about their qualities in the tiny spherical stage, we need π.
要想知道这个微小球体的质量 我们需要用到π
In fact, we need π for so many reasons.
事实上 我们需要用π的原因很多
We need it to make sense of this universe.
我们需要用它来探索宇宙
And because it’s so important to us,
因为π对我们来说太重要了
we’ve designed a calendar in homage to π.
所以我们设计了一本日历来表达对它的敬意
Each month represents one digit of π,
每一个月代表了π的一个数字
starting with the three hearts in an octopus.
封面是章鱼的三颗心
And if you didn’t know that an octopus has three hearts,
如果你不知道章鱼有三颗心
there’s a very Scishow you blurb in each month to tell you more about it.
每个月都会有一期《科学秀》给你介绍更多
The calendar has all sorts of amazing holidays, highlighted in it,
日历中有各种有趣的节日 都特别标注出来了
like February 11th, which is International Day of Women and Girls in Science,
例如2月11日是妇女和女童参与科学国际日
and November 18th, which is LGBTQ+STEM day.
11月18日是STEM领域LGBTQ+人士国际日
To get yours before they run out,
在日历卖完之前
you can head over to ComplexlyCalendars.com,
你可以前往ComplexyCalendars.com
or click the link in the description.
或者是点击说明里的链接购买
Thanks for watching this video,
感谢观看
and thanks for supporting Scishow.
感谢支持《科学秀》

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译制信息
视频概述

你见过卡通片里的尖头雨滴吗?你见过路灯下纷飞的雨滴吗?你还见过暴雨中狂乱飞舞的雨滴吗?小小的雨滴,却暗藏大大的秘密。你真的认识雨滴吗?快来看看雨滴的真实面貌吧!

听录译者

Kris

翻译译者

Grace

审核员

审核员ART

视频来源

https://www.youtube.com/watch?v=X046d7bLQ3s

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