TED科普：为何番茄酱很难倒出来？

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我们都知道炸薯条很好吃，再配上番茄酱简直就是人间美味。但问题是挤出适量的番茄酱实在是太难了。为什么番茄酱的设计这么不解人意？来看看今天的内容。

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French fries are delicious. French fries with ketchup are a little slice of heaven.

我们都知道炸薯条很好吃，再配上番茄酱简直就是人间美味。

The problem is it's basically impossible to pour exactly the right amount.

但问题是挤出适量的番茄酱实在是太难了。

We're so used to pouring ketchup that we don't realize how weird its behavior is.

我们平时经常挤番茄酱，但是从来没注意到过它有多么的奇怪。

Imagine a ketchup bottle filled with a straight up solid like steel.

想像你的番茄酱瓶里装的是固体，比如不锈钢。

No amount of shaking would ever get the steel out.

不管你怎么摇晃，不锈钢都不会出来。

Now imagine that same bottle full of a liquid like water.

现在再想像一下番茄酱瓶子装水。

That would pour like a dream.

把水倒出来简直易如反掌。

Ketchup, though, can't seem to make up its mind.

但是番茄酱呢，好像很纠结。

Is it is a solid? Or a liquid?

它到底是固体？还是液体？

The answer is, it depends.

答案是，看情况。

The world's most common fluids like water, oils and alcohols respond to force linearly.

这世界上最常见的液体，比如水、油还有酒精，会对力的作用产生线性反应。

If you push on them twice as hard, they move twice as fast.

如果你用两倍的力去挤它们，它们就会以两倍的速度流出来。

Sir Isaac Newton, of apple fame, first proposed this relationship, and so those fluids are called Newtonian fluids.

因为苹果而出名的艾萨克·牛顿先生，首次提出了上述现象，所以它们被称为牛顿流体。

Ketchup, though, is part of a merry band of linear rule breakers called Non-Newtonian fluids.

番茄酱呢，却是线性规则破坏者小团体中的一员，称为非牛顿流体。

Mayonnaise, toothpaste, blood, paint, peanut butter and lots of other fluids respond to force non-linearly.

蛋黄酱，牙膏，血液，颜料，花生酱还有其他很多流体，都不会对力的作用产生线性反应。

That is, their apparent thickness changes depending on how hard you push, or how long, or how fast.

也就是说，它们的浓度会根据你的用力大小，时间和速度改变。

And ketchup is actually Non-Newtonian in two different ways.

事实上，番茄酱会表现出两种非牛顿流体现象。

Way number one: the harder you push, the thinner ketchup seems to get.

现象一：你越用力挤，番茄酱越稀。

Below a certain pushing force, ketchup basically behaves like a solid.

但是如果力道小到特定程度，番茄酱看起来就像固体一样了。

But once you pass that breaking point, it switches gears and becomes a thousand times thinner than it was before.

但是一旦超过了那个临界点，它就摇身一变，变得比刚才稀很多。

Sound familiar right?

听起来很耳熟吧？

Way number two: if you push with a force below the threshold force eventually, the ketchup will start to flow.

现象二：如果你的力道没有达到临界点，番茄酱最后还是会流出来的

In this case, time, not force, is the key to releasing ketchup from its glassy prison.

这种情况下，时间是挤出番茄酱的关键，而不是力。

Alright, so, why does ketchup act all weird?

好吧，那番茄酱到底为什么这么与众不同呢？

Well, it's made from tomatoes, pulverized, smashed, thrashed, utterly destroyed tomatoes.

嗯，首先，它是番茄做的。番茄经过各种切碎，挤压，搅拌之后变得面目全非。

See these tiny particles?

看到这些小颗粒了吗？

This is what remains of tomatoes cells after they go through the ketchup treatment.

它们是在番茄被各种处理后残留下来的番茄细胞。

And the liquid around those particles?

那么这些小颗粒周围的液体呢？

That's mostly water and some vinegar, sugar, and spices.

大部分都是水，还有一些醋，糖，以及香料。

When ketchup is just sitting around, the tomato particles are evenly and randomly distributed.

当番茄酱静止的时候，番茄颗粒都很均匀的分布其中。

Now, let's say you apply a weak force very quickly.

现在，假如你突然用很小的力挤番茄酱。

The particles bump into each other, but can't get out of each other's way, so the ketchup doesn't flow.

这些小颗粒就会冲到一起，谁都不让谁，当然就不会流动啦。

Now, let's say you apply a strong force very quickly.

那如果你突然用很大力去挤番茄酱呢？

That extra force is enough to squish the tomato particles, so maybe instead of little spheres, they get smushed into little ellipses, and boom!

力度大到可以把颗粒压扁，它们不再是球型而是变成了椭圆体然后挤爆！

Now you have enough space for one group of particles to get passed others and the ketchup flows.

现在有空间让一部分小颗粒穿过去，番茄酱就开始流动了。

Now let's say you apply a very weak force but for a very long time.

再假如你用很小的力挤番茄酱，持续一段时间后。

Turns out, we're not exactly sure what happens in this scenario.

但是，嗯，我们也不是很清楚会怎样。

One possibility is that the tomato particles near the walls of the container slowly get bumped towards the middle, leaving the soup they were dissolved in, which remember is basically water, near the edges.

有一种可能是，靠近瓶壁的番茄颗粒会慢慢移到瓶子中间去，剩下溶解的液体，基本上就是水留在边缘。

That water serves as a lubricant betwen the glass bottle and the center plug of ketchup, and so the ketchup flows.

于是水就会变成瓶壁和番茄酱之间的润滑剂，番茄酱就出来了。

Another possibility is that the particles slowly rearrange themselves into lots of small groups, which then flow past each other.

另一种可能就是小颗粒重新组合形成一个个小团儿，然后再慢慢移动。

Scientists who study fluid flows are still actively researching how ketchup and its merry friends work.

研究流体运动的科学家们还在探索到底番茄酱之类的东西是怎么回事呢。

Ketchup basically gets thinner the harder you push, but other substances, like oobleck or some natural peanut butters, actually get thicker the harder you push.

番茄酱是你越用力，它们就会变得越稀，但是其他物体呢，比如欧波力客或者花生酱，你越用力它们反倒变得越稠。

Others can climb up rotating rods, or continue to pour themselves out of a beaker, once you get them started.

有一些能顺着转动的棍棒向上流动的，还有一些，一旦你开始倾倒，它们就能一直不停的倾泻。

From a physics perspective, though, ketchup is one of the more complicated mixtures out there.

从物理学的角度来讲，番茄酱是世界上少数几个最复杂的混合物之一。

And as if that weren't enough, the balance of ingredients and the presence of natural thickeners like xanthan gum, which is also found in many fruit drinks and milkshakes, can mean that two different ketchups can behave completely differently.

如果这还不够的话，它的平衡成分以及在水果饮料和奶昔等天然增稠剂黄原胶中的表现，能够证明两种不同的番茄酱会有截然不同的表现。

But most will show two telltale properties: sudden thinning at a threshold force, and more gradual thinning after a small force is applied for a long time.

但是一般会出现两种迹象，在临界强度压力下突然变稀，或者在持续的轻缓挤压下慢慢变得稀薄。

And that means you could get ketchup out of the bottle in two ways: either give it a series of long, slow languid shakes making sure you don't ever stop applying force, or you could hit the bottle once very, very hard.

也就是说你有两种方法可以把番茄酱挤出来，要么就是缓缓的慢慢的摇晃，注意不要停止用力，或者你可以对着瓶底猛地一击。

What the real pros do is keep the lid on, give the bottle a few short, sharp shakes to wake up all those tomato particles, and then take the lid off and do a nice controlled pour onto their heavenly fries.

一般内行会先不打开瓶盖快速的晃动几下瓶子，把里面的小番茄颗粒摇醒，然后拧开瓶盖，就可以将番茄酱自如的挤到美味的薯条上啦。

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