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The oldest glue in the world is over 8,000 years old and comes from a cave near the Dead Sea.
世界上最古老的胶水在超过八千年以前出现于死海附近的一个山洞中。
Ancient people used this glue, made from a mixture of animal bone and plant materials,
这种古人使用的胶水是由动物骨头和植物材料混合而成，
to waterproof baskets and construct utensils.
用于篮子的防水以及器皿的制作。
And for thousands of years after, plants and animals were the glue that held human civilization together.
几千年之后，植物和动物仍是将人类文明连接起来的“胶”。
Today, we have enough types of tape and glue to build and repair almost anything.
现今，我们有各种胶带和胶水，几乎足以建造和修复任何东西。
But what gives glue and tape their stickiness? And is one stronger than the other?
但胶水和胶带为什么会有粘性？胶水和胶带何者比较强？
Adhesives can be made from synthetic molecules or natural proteins and carbohydrates like the vegetable starch dextrin,
粘着剂的成分可以是合成分子或是天然蛋白质及碳水化合物，像是植物淀粉糊精、
the milk protein casein, and the terpenes in tree resin.
牛奶酪蛋白以及树脂中的烯。
In order to work, glue and tape need both adhesive bonds and cohesive bonds.
胶水和胶带要能有作用，需要“附着键”以及“聚合键”。
Adhesive bonds occur between an adhesive's molecules and the molecules of whatever it's sticking to.
附着键位于粘着剂的分子和被粘着物品的分子之间。
Cohesive bonds happen between a glue or tape's own molecules, holding it together.
聚合键则是在胶水或胶带自己本身的分子之间，将它维持不分开。
Most glues consist of adhesive polymers dissolved in a solvent that prevents them from sticking to the inside of the bottle.
大部分的胶水含有会在溶剂中溶解的粘着性聚合物，这种聚合物能避免胶水粘在瓶子里。
The strong smell of many glues comes from the solvent, which evaporates when exposed to air.
许多胶水有很重的味道，就是溶剂因为接触空气而蒸发时所产生的味道。
Some glues use water as a solvent, but others use chemicals that can be harmful to inhale.
有些胶水的溶剂是水，但其他胶水用化学物质来当溶剂，吸入可能会造成伤害。
Glues with two or more components that chemically react instead of just drying can create stronger bonds.
有些胶水用两种以上的成分产生化学反应，而不是用干燥的方式，这样的键结力会更强。
Both the adhesive and cohesive bonds of glue are strong, but the drying process makes them irreversible.
胶水的附着键结和聚合键结都很强，但干燥的过程会让它们变成不可逆。
This is why, if a glued surface is broken after it dries, it can't be reattached without new glue.
这就是为什么如果用胶水粘着的表面在胶水干掉之后被打破了，若不再用新的胶水，就无法重新粘回。
By contrast, when tape is applied to a surface, it forms weaker, reversible bonds,
相对的，当把胶带粘在表面上时，它会形成较弱、可逆的键结，
so you can peel a piece of tape off a surface and use it again.
所以当你把一条胶带从物品表面撕下来后，还能再次使用它。
These weak bonds, called Van der Waals forces, can occur between any two materials,
这些弱键结被称为范德华力，任何两种材料间都可能产生，
but only if they're extremely close together, closer than the naked eye can see.
但前提是它们要非常靠近，比肉眼能看见的还要更近。
Tape usually consists of a backing coated with a combination of a rubber or rubber-like "stretchy" component,
胶带通常含有衬背，衬背上覆盖着橡胶或是类似橡胶的弹性元素，
and a compound called a tackifier. That's the "sticky" component.
再加上一种叫做增粘剂的元素。那就是“粘着”的成分。
A tape's stickiness is determined by the proportion of elastic component and tackifier,
胶带的粘度取决于弹性成分和增粘剂的比例、
the thickness of adhesive spread onto the backing, and the type of backing material.
衬背上涂布的粘着剂的厚度，以及衬背的材质。
No chemical reaction occurs when tape is pressed onto a surface.
当把胶带粘贴到物品表面上时，并不会发生化学反应。
Instead, the soft adhesive flows into the cracks and grooves of the surface.
相反，这种软的粘着剂会流入到表面的裂缝和沟槽中。
This ability to slide into cracks and then stay in place is called viscoelasticity.
这种流入裂缝中并留在那里的能力，叫做“粘弹性”。
Once the viscoelastic adhesive fills these microscopic crevices, it is close enough to form Van der Waals forces.
一旦粘弹粘着剂填满了这些微小的裂隙，就近到足以产生范德华力。
So what's the world's strongest adhesive? Well, there's no one answer.
所以，世界上最强的粘着剂是什么？并没有唯一的答案。
In terms of absolute strength of adhesive bonds, glue is stronger than tape,
就聚合键的绝对力量强度来说，胶水胜于胶带，
but no single adhesive works well in all circumstances.
但并没有单一种粘着剂能在所有情况下都非常有用。
Of the glues, cyanoacrylates, or super glues, may form the strongest bonds,
胶水中，氰基丙烯酸酯（强力胶）可能可以形成最强的键结，
but two-component epoxy glues have much higher resistance to heat and shearing, and are compatible with a wider range of surfaces.
但两种成分的环氧树脂胶对于高温和修剪的耐受度会比较高，且适用于更广泛的表面上。
So, if you wanted to dangle an anvil in the air, super glue might be your best bet.
所以，如果你想要把铁砧悬挂在空气中，强力胶可能是最佳选择。
But if you're doing so over an active volcano, you'd want an epoxy instead.
但如果你想要在活火山的上方做这件事，用环氧树脂胶会比较适当。
And in order to work at all, glues need enough real estate where surfaces touch.
胶水要能够有效，需要有足够的接触表面积。
If for some reason you wanted to make a chain of bowling balls, duct tape would be better.
如果出于某种理由，你想要把保龄球粘成一串，防水布胶带会比较适合。
Engineers weigh similar, if less absurd, factors all the time.
工程师也总是在考虑类似的因子，但可能没那么荒谬就是了。
Choosing the right glue to withstand the heat inside an engine is a matter of life and death.
选用正确的胶水，能够承受引擎中的高温，是攸关生死之事。
And though the strength of duct tape's adhesive bonds can't compete with those of epoxy glues,
虽然强力胶带的聚合键没有环氧树脂胶那么强，
tape does have the advantage of instantaneous stickiness in an emergency.
但是它还是有个优点，就是在紧急时刻可以马上粘着。
Glue may be necessary to get a rocket to space,
胶水可能是把火箭送入太空所必需的，
but when it comes to extraterrestrial repairs, stick to duct tape: liquid glues don't work in zero gravity.
但若要在地球以外的地方维修，就用强力胶带吧：在无重力下，液态胶水是没有用的。
