For water to freeze, it must reach 32 degrees Fahrenheit. For water to boil, it must reach 212 degrees Fahrenheit. The question: Which freezes faster: Room temperature water (say, 75 degrees Fahrenheit) or boiling water (212 degrees Fahrenheit)?
The common sense answer would be room temperature water would freeze faster because it is only 43 degrees away from freezing, while the boiling water is 180 degrees away from freezing. That answer is often wrong. Boiling water can freeze faster than lukewarm water due to something known as the Mpemba effect. When the eponymous modern discoverer of this property asked his teacher why boiling water froze faster, based on his own observations, he was mocked.
The Mpemba Effect is one of the best examples of counterintuitive truths. Boiling water can freeze faster than room temperature water under certain conditions. It makes no sense and shouldn’t happen but it does. It’s a powerful mental model that reminds us not to extrapolate conclusions based on past observed truths.
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If you want to think better, train yourself to consider all proposals, even those that appear absurd. Look at the evidence. Some situations involve Mpemba effects.
For example, we’ve discussed many times that evidence illustrates if you want less teen pregnancy and sexually transmitted diseases, the worst possible thing you can do is teach abstinence only. That seems absurd. It shouldn’t be the case. It makes no sense. But that is what the data shows. It’s counterintuitive.
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The Mpemba Effect teaches us that you need to be guided by demonstrable facts and evidence, not what you expect to happen; not what you think should be the truth. Consider all possibilities and then let the outcomes of your experiments and research lead you to truth, even if that means you don’t like the implications or don’t fully understand the reasons.
Reader Comments (7)
Comments are presented chronologically, with replies indented beneath the comments to which they respond.
Anon
December 21, 2012
"If you want less drug addicts, then stop treating it as a crime." "If you want less teen pregnancy and sexually transmitted diseases, then do not teach abstinence."
Do these studies take into account that, for example, when something is decriminalized or not looked down upon, chances are more people will consider partaking in the previously criminalized or looked down upon activity? So, for example, instead of 10 out of 100 people doing drugs with a success rate of 50%, you now have 20 out of 100 people doing drugs with a success rate of 50%, which means 5 more people have ruined lives now? I don't know how exactly a study could factor this effect in.
Joshua Kennon
December 21, 2012
Replying to Anon
Yes. Almost every study I've ever seen looks at per capita data since that is what matters, which would be captured in your question. On the case of teen pregnancy rates, the University of Georgia had just such a release five days ago, which you can read here. The evidence is, in their own words, "overwhelming".
AJ
December 21, 2012
True, reminds me of this video I watched yesterday where these guys threw a pot of freshly boiled water over a balcony in Siberia (it was -41C). The water froze almost immediately, I don't think the same thing would have happened with say room temperature water? Anyways, if it gets that cold where I am perhaps I will try it out myself.
As this theory relates to behaviours surrounding drugs & other "wreckless" practices, I've always thought this to be true, I just never looked into it enough to find data to back it up.
TheLonelyHumanist
December 21, 2012
Replying to AJ
I heard about that at work.
Martel
December 21, 2012
Portugal has greatly relaxed its drug laws starting in 2001, largely decriminalizing illicit drugs. Overall drug use has gone down, drug-related crimes down, teen drug use down which has resulted in freeing up public resources, most notably law enforcement.
I'm not sure if it would work in the United States, but it harkens back to the same concept as Prohibition: There is a demand for certain substances, and people will get them whether it's legal or illegal. If it's illegal, people cannot utilize the laws and safeguards put in place by society and government, hence criminal organizations step in to fill that role.
Patrick Jones
June 29, 2014
Replying to Martel
Why would it not work in the USA. Are Americans of a different species than the Portuguese ?
Guest
December 29, 2012
The Mpemba Effect reminds me of people. I'm always cautious of people who are too happy because I know that this energy could be shifted to extreme anger or sadness. Same for fanatics. They're a fanatic Catholic one minute, a fanatic Buddhist the next. The energy doesn't disappear. It just changes direction. Maybe it's the same for the water.