5 Things That Don't Make Sense in the World

The Mpemba effect is a phenomenon in which it's quicker to cool water to a given temperature when the initial temperature is higher.

It was named after Tanzanian Erasto Bartholomeo Mpemba, who, as a teenager, noticed warm ice cream mix would freeze faster than cold ice cream mix. Curious, Mpemba conducted experiments in his own house using water. He found that, like the ice cream, boiling hot water containers seemed to take less time to freeze than cold water.

Mpemba approached Dr. Denis Osborne, a physicist from the University College in Dar es Salaam who was visiting his high school. When the teenager asked why this phenomenon happened, he was laughed at by his teachers and schoolmates.

But Dr. Osborne agreed to help him and carried out numerous tests in his laboratory back at the university. He confirmed Mpemba's original observations, and the duo published a paper together in 1969.

The assertion that hot liquids freeze faster than cold ones seems counter-intuitive. Yet, records of the effect go back to the writings of Aristotle, who wrote in his journals that [QUOTE]: "Water that has previously been warmed contributes to its freezing quickly."

Scientists from various fields say they have observed the effect. For many decades it was a formally accepted scientific phenomenon. In 2012, there was a spike in interest among researchers and the public when the Royal Society of Chemistry launched a public competition, challenging participants to explain its origin and cause.

There is no official cause for this mysterious and contradictory phenomenon. Some theorize that the evaporation of hot water reduces the mass to be frozen. Others believe that colder water forms a layer of frost at the top that reduces heat loss, increasing the freezing time.

And some others argue it must be due to an unseen interaction between temperature and gases or solutes in the water.

The Mpemba effect is quite controversial, and many scientists are reluctant to abandon their research on the effect just yet.