Snow and Sky: From Earth to Earth

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April 18, 2005

From Earth to Earth

Here it is, the inaugural installment of Science Corner!

All right, enough with the fanfare. Let's get down to business. I'll start with the write-ins.

My father asked three questions, perfectly valid and intellectually intriguing I might add, but since it's my blog I'll respond in the order that I choose :) The first question is really quite amusing...

Why do outhouses have a half-moon on their door?

According to The Straight Dope, a very thorough and reliable online source for information about those funny questions we've always had, the moon on an outhouse door actually has nothing really to do with the highschool definition of "mooning". It actually appears as though the concept of moons on outhouse doors is limited to our imagination, as Cecil rightly points out that it is tough to recall ever actually seeing a real outhouse with a moon on its door. Nevertheless, he has traced the origins of this phenomenon through a few ancient and definitive tomes, and his conclusion is that both the moon and the sun were used in illiterate times to delineate between women and men, respectively. It is also likely that not only is it more difficult to carve a sun out of an outhouse door than a moon, but that women's outhouses were generally better maintained than the men's, and so popular conception has passed the moon as the universal sign of relief when Nature calls.

What is the maximum power output of the human body through muscles?

It's an interesting question, and spans a lot of thought space - everywhere from projects in micro power generation in third world countries to The Matrix (yeah, that's right, Coppertop!) Real numbers are hard to come by, though. Part of the problem is in that definition of maximum. I would guess that very few experiments have actually been done to determine the true maximum - because that would likely kill a person, if not destroy their muscles! Another related point is that the power output depends strongly on the load - i.e. the system is nonlinear. Everybody could agree that to walk across a very shallow incline seems to take much less effort than traveling the same height completely vertically, even if ultimately the potential energy gained is equivalent (Science-speak: potential energy is a state function -- translation: it doesn't matter how you get there, the result is still the same.) What this all means is that you might get different numbers for max power output depending on how hard the person is working (or how hard you're making them work!) Oh yeah, one last point too. You asked about the maximum human power output using muscles, but it's a physical impossibility to have every muscle in our body contributing simultaneously to this hypothetical power measurement, since many muscles pull against each other! So most tests of this kind only really measure leg output since that's where the most powerful muscles in the body are.

A really crummy Figure 1 shows several power curves for "healthy men", "first-class athletes" and estimated maximum. Taking one somewhat clear data point from that graph, Eddy Merckx was able to sustain 440W for one hour, or about 0.6 HP. This is a measure of power, power being energy over time. You asked for this in ergs, ergs being a unit of energy, so the energy expended by Mr. Merckx was 440 watts * 60 minutes in ergs which Google Calculator can easily handle. 1.54 x 10¹³ ergs is the simple, ballpark answer.

This seems like a lot of ergs, but an erg isn't very much energy. An erg per second is about a tenth of a microwatt. Compared to a lawn mower? Which lawn mower? A push lawnmower has about 4 HP. A riding lawnmower can have up to 12 HP. Energy to energy, this amount of energy would run a 4 HP lawnmower for almost 9 minutes or a 12 HP lawnmower for almost 3 minutes. Of course there are reel-type lawn mowers which a normal human can push for more than 9 minutes so clearly 4 HP is pretty inefficient.

What happens to an onion when it is cooked?

What a tasty question! Onions are such a versatile ingredient, and every food changes chemically when it is cooked, so this is a very important thing to understand. I should point out that the definitive reference for these questions is a book titled On Food and Cooking by Harold McGee. Unfortunately I don't have a copy of this book (hint, hint) so I will have to make do with Internet sources and what I can glean by Amazon's "Search inside the book" (what a useful feature!)

Onions are a member of the genus Allium, which also includes such esteemed members as garlic and chives. The most distinctive thing about the alliums is that they contain compounds which are normally sequestered inside vacuoles (cellular compartments). When these plants are cut or crushed, these compounds combine to form the lachrymators, chemicals which make you teary! Different plants have different levels of these lachrymators, but they are the common compound which give onions through leeks their 'bite'. When cooked, these compounds mostly break down and somewhat react with each other in certain ways depending on the heat and what they are cooked in. This breakdown tends to remove a lot of the sharpness of the onion flavor. Hot fats likely have their strongest effect because they even the heat out significantly and can reach temperatures higher than boiling. One thing not to be taken too lightly is the effect of heat on the sugars that onions contain. We don't often think of onions as sweet (except perhaps the sweet onions like Vidalia) but it turns out that most onions have roughly the same sugar content - the sweet ones simply have less of the lachrymatory chemicals! (This means also that soaking yellow onions in several changes of cool water will tend to remove their sharp flavor and make them taste sweeter.) Those sugars can break down and combine with each other during caramelization, producing a mild, sweet flavor.

Next time, if all goes well, I'll make some mention about the current state of the art in smell chemistry and what makes such a lovely smell or a horrid stink! See you soon!

Posted by kgutwin at April 18, 2005 04:13 PM