(The British Felix Baumgartner)
英国版的菲利克斯•鲍姆加特纳
How does stirring compare to microwaving?
那么搅拌和微波炉加热比起来有什么区别呢？
Based on figures from industrial mixer engineering reports, I estimate that vigorously stirring a cup of tea adds heat at a rate of about a ten-millionth of a watt. That 8217;s completely negligible.
从工业混合机工程手册上的数字来看，我估计剧烈搅拌一杯茶增加热能的速率约为十万分之一瓦。这完全可以忽略不计。
The physical effect of stirring is actually a little complicated.5 Most of the heat is carried away from teacups by the air convecting over them, and so they cool from the top down. Stirring brings fresh hot water from the depths, so it can help this process. But there are other things going on-stirring disturbs the air, and it heats the walls of the mug. It 8217;s hard to be sure what 8217;s really going on without data.
而搅拌所产生的物理效果则要复杂一些。5茶杯里绝大多数的热量都被茶杯上方对流的空气带走了，也就是说空气使得茶从上至下冷却。搅拌使得茶杯底部的热水被带到表层，因而加快了散热的速度。但同时还发生了其他事情——搅拌也扰乱了空气流动，使得茶杯壁温度升高，但没有数据，这种讨论没有太大意义。
Fortunately, we have the Internet. Stack Exchange user drhodes measured the rate of teacup cooling from stirring vs. not stirring vs. repeatedly dipping a spoon into the cup vs. lifting it. Helpfully, drhodes posted both high-resolution graphs and the raw data itself, which is more than you can say for a lot of journal articles.
但别忘了我们有互联网！StackExchange用户drhodes恰好测量了搅拌、不搅拌、不停把勺子浸入和拿出对茶冷却速率的影响。而且drhodes不仅上传了高分辨率的图像，还上传了原始数据，这可比许多论文提供的信息有用多了。
The conclusion: It doesn 8217;t really matter whether you stir, dip, or do nothing; the tea cools at about the same rate (although dipping the spoon in and out of the tea cooled it slightly faster).
结论：不管你是不停搅拌，拿勺子放进去或者干脆啥事都不做，茶冷却的速度都差不多。（虽然拿勺子不停放进放出能让茶冷却得略微快一些。）
Which brings us back to the original question: Could you boil tea if you just stirred it hard enough?
于是我们又回到了最初的那个问题：我们能够靠拼命搅拌把茶烧开吗？
No.
不能。
The first problem is power. The amount of power in question, 700 watts, is about a horsepower, so if you want to boil tea in two minutes, you 8217;ll need at least one horse to stir it hard enough.
首先是因为功率。700瓦差不多是1马力，所以要是你想在2分钟内把茶烧开，那么你至少需要一匹马帮你来拼命搅拌。
You can reduce the power requirement by heating the tea over a longer period of time, but if you reduce it too far the tea will be cooling as fast as you 8217;re heating it.
当然了你可以通过延长做功时间来降低对功率的要求。只是如果时间太长的话，茶冷却的速度就要和你加热的速度一样快了。
Even if you could churn the spoon hard enough-tens of thousands of stirs per second-fluid dynamics would get in the way. At those high speeds, the tea would cavitate; a vacuum would form along the path of the spoon and stirring would become ineffective.6
即使你能以极高的速度搅拌——比如每秒成千上万转——流体力学会让你失望的。在这种高转速下，茶会发生空化；蒸汽泡会沿着勺子的路径生成，此时搅拌的效率会大大下降。6
And if you stir hard enough that your tea cavitates, its surface area will increase very rapidly, and it will cool to room temperature in seconds.
而如果你真的拼命搅拌到茶发生了空化，那么它的表面温度会急速增加，然后它会在几秒钟内冷却到室温：
No matter how hard you stir your tea, it 8217;s not going to get any warmer.
不管你搅拌得多么拼命，茶都不会变暖。
1 Hydrogen and helium have a higher heat capacity by mass, but they 8217;re diffuse gasses. The only other common substance with a higher heat capacity by mass is ammonia. All three of these lose to water when measured by volume.
1． 按质量来算氢气和氦气有更大的比热容，但是它们是扩散性气体。剩下唯一一种按质量算有更大比热容的常见物质是氨。但如果按体积算的话，这三者都比不过水。
2 Note: Pushing almost-boiling water to boiling takes a large burst of extra energy on top of what 8217;s required to heat it to the boiling point 8211; this is called the enthalpy of vaporization.
2． 注意：把即将沸腾的水加热到煮沸状态比把水从室温加热到接近煮沸的状态需要更多的能量——这些能量叫作蒸发能。
3 If they didn 8217;t, we 8217;d just blame “inefficiency” or “vortices.”
3． 如果水不够热，我们就会归咎于“效率太低”或者“涡流影响”。