Erasto mpemba biography of martin

Like most great moments in the history of science, Mpemba did not follow the usual procedure, which generally required him to wait for the hot milk to cool before placing the ice cream in the freezer to solidify. Instead, he decided to do the opposite placing his hot ice cream into the freezer and to his shock it froze much quicker than those of his classmates who waited for the ice cream to cool before putting in the freezer.

Mpemba then informed his teacher of the marvelous discovery but the teacher dismissed it. However, the little student did not relent. Mpemba's findings was intriguing. Graph: By Ben Tier Through his later years in school, Mpemba kept experimenting the phenomenon, and he always got the same result: hot water froze quicker than cold water.

It depends on random vibrations and wafts of air so you get different effects on different occasions. But after tracking down Professor Osborne in Britain, the task became straightforward as they had remained in touch with each other. This is where the big annual sale of Tanzanian ivory used to be held before marketing the tusks was banned.

Ivory is still stored there from elephants that are damaging crops and have to be killed. The leader dominating the herd was tuskless. They were ruining peoples crops. He had to go. He went down. He stood up again and charged. I shot him again at 50 yards. I shot him for a third time, a fourth time. A fifth time. He was over my head. As he finally fell, his body grazed my leg.

Simple experiments in which cadavers, sand, and grain were isolated and observed demonstrate that these beliefs were wrong. The vendors would probably have used freezers without a dehumidifier. In the course of a day, a freezer is opened and shut many times, each time allowing an amount of hot, humid air in. Because cold air can contain less humidity than warm air, surplus humidity settles in the form of ice crystals inside the freezer and forms a layer of frost.

Air is a good thermal insulator, and if a cup of water is put inside a freezer, most cooling will occur through the bottom of the freezer that the cup is standing on. However, if the cup is standing on a layer of frost, the cooling will be slower. This is because the frost is porous and contains a lot of air. The layer of frost effectively acts like a wool sweater between the cup and the cold surface.

But now imagine that a hot cup of water is put on a thin layer of frost. It is then possible that the layer of frost is melted away and that the cup will ultimately make full contact with the bottom of the freezer. The subsequent cooling will then be faster, and it is possible that a cup that started at a colder temperature will be caught up with and overtaken on the race to freezing.

The claim that warm water freezes faster than cold water is too general to be considered scientific. Lake Michigan will not freeze over during one freezing night while a small container with hot water placed on the edge of Lake Michigan will readily freeze from top to bottom. So, scale is a factor. The material of the contact surface also plays a role.

Water in a metal container will freeze faster than water in a wooden container of the same size and shape.

Erasto mpemba biography of martin

This is because metal is a better heat conductor than wood. The shape of the container is also significant. Because of the larger contact surface, water on a flat tray will freeze faster than the same amount of water in a spherical container. Scientific articles that give experimental results generally have a Materials and Methods section in which detailed descriptions are given of procedures and the equipment used.

A good Materials and Methods section guarantees the reproducibility of the reported results. The one-liners of Aristotle and Francis Bacon are such that there is no way to ever find out again how the underlying observation of the Mpemba Effect came about. In the first few decades after the article by Mpemba and Osborne, much experimental work was done on the Mpemba Effect.

Sometimes the effect was observed and sometimes it was not. Different researchers used different setups and only rarely did someone try to exactly reproduce the results of someone else. The large number of variables involved in the freezing of water, the lack of appropriate detail in the reporting, and the lack of a proper emphasis on reproducibility ultimately led to the Mpemba Effect myth lasting much longer than it should have.

The way in which the Mpemba Effect is written about has changed in the decade following the publication of the Brownridge article. Articles in which exotic mechanisms are postulated to explain the Mpemba Effect no longer abound. In , the British Royal Society of Chemistry organized a contest with a thousand English pounds in prize money for the best explanation of the Mpemba Effect.

Unlike, his physics teachers, the visiting scholar treated him as a scientist by asking: "Is it true, have you done it? After acknowledging he did not know why, the visitor promised to try the experiment when he gets back to Dar es Salaam. So began a collaborative effort that resulted in the publication of this seminal article: Mpemba, Erasto B.

It took a lot of guts for Mpemba to weather the ridicule from some of his fellow students who said he did not understand his chapter on Newton's law of cooling. His courage finally paid off. For those who are still wondering what does the "Mpemba Effect" actually mean even after reading his own version of the story as retold herein, be as curious as him.

It simply means that, contrary to what is generally perceived to be the case, at a certain level of temperature, hot water actually cools off quicker — and thus freezes faster — than cold water. This is indeed a puzzling phenomenon.