Mpemba Effect

The Mpemba effect is named after Erasto Mpemba, a student in Tanzania who, in 1963, observed that sometimes hot liquid would freeze more quickly than cold liquid. This effect was noted by many scientists throughout history, at least as far back as Aristotle.

The idea that something hot can freeze more quickly than something that is cold sounds counterintuitive. How could it happen?

The problem is that the conditions where this phenomenon might be observed are not well known. How do you compare the two liquids in the first place? Do you measure out equal amounts before heating? Or do you measure the heated liquid to have the same volume as the cold? For that matter, how do you even know when one of the liquids has frozen?

There could be all sorts of reasons why this might happen. If you measured out equal amounts of liquid, and then heated one of the containers, that liquid would expand. That makes its surface area – which determines how quickly heat is lost – greater. So possibly that extra surface area lets the liquid cool more quickly. The objection to this could be that at some point the surface areas of the water in both containers will be equal; so why would one container continue to cool more quickly?

Another possibility is similar, but first you heat the liquid, then measure out the same volume as in the other container. Here, the mass of the hod liquid would be less, because the liquid had expanded. Lower mass might mean the liquid would cool more quickly.

Possibly this effect happens when the containers are both left open to the air. In this case, the heated liquid might lose more heat through evaporation, causing it to cool more quickly.

Ultimately, even though this phenomenon was described as early as Aristotle, we still don’t really know what’s happening.

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The EM Drive

In about 2001 or so, reports began to surface about a new kind of thruster for a spacecraft. This thruster was said to produce a slight push in a way that violated the law of Conservation of Momentum. Despite this difficulty, there were experiments which seemed to support the possibility that the thruster worked.

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The Dogon Tribe

There is a tribe in Western Africa known as the Dogon people. They have a tradition of having been visited by beings who taught them various skills. The Dogons explain that these beings come from the sky, from a star we know as Sirius. The Dogons explain that this star is actually two stars, one of which cannot be seen. One star circles the other.

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Cooper Family Falling Body

This refers to a photograph purportedly taken by the father of a family. The story is that when the father developed the image, he was horrified to see that a hanging body appeared. They state that the hanging body wasn’t present at the time the photo was taken.

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Faster Than Light Neutrinos

In 2011, researchers at CERN reported that some neutrinos appeared to travel faster than the speed of light.

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Tools and Rules

These are some basic principles I use to help sort through the various topics and suggested explanations. Using them can simplify discussions.

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The Fermi Paradox

The Fermi paradox is the observation that, although there are billions upon billions of stars, we have not discovered any evidence of intelligent life. The question is, “Why not?”

Enrico Fermi

Enrico Fermi

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The Dunning-Kruger Effect

Briefly, the Dunning-Kruger (DK) effect is the erroneous self-assessment of skill, knowledge, or other qualities in a field that is not the person’s area of expertise. This can be laymen grappling with an unfamiliar discipline, or experts who have strayed from their own fields into others. The DK effect is partly due to the person not knowing enough to understand the difficulties and complexities of the unfamiliar field.

From xkcd.com

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Conspiracy Theories

Bielefeld

Conspiracy theories strike me as an attempt to hold on to a cherished idea when there is insufficient evidence to support it. Rather than consider that the idea is wrong, a person clings to it and invents reasons to explain the lack of evidence.

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Cottingley Fairies

Before There Was Photoshop

In 1917, two girls borrowed their father’s camera and took some photos in their back yard. When the photos were developed, they showed several fairies dancing and playing in the yard as the girls looked on. For the first time there was photographic evidence that fairies exist.

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