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11/10/2005 Science / Measurement / Time. Reader Comments.

I really enjoy teaching examples like this, thanks.

"... you discuss the inability of people to grasp time periods such as millions and billions of years. This is a favorite topic of mine - I like to look for analogies to help people understand the enormity .... Here is a new one I'm playing with: Think of the average lifespan in terms of days, e.g. 80 years x 365 days a year = 29,200. ... How long is a million days in terms of years? About 2,740. So a few million days is about the length of recorded history. A billion days? That would be about 2,740,000 years. So a million or a billion years is quite a lot, when you think about it in terms of days.

Another fun one is with smaller units like a second. We can all grasp a second. How long does it take for a million seconds to pass by? About eleven and a half days. How about a billion? Most people would not guess anywhere near the number of 32 years. And a trillion seconds is about 32,000 years. [ By comparison, our species has been around for 300,000-500,000 years according to this review. - ed]

This is handy when thinking about small quantities too. If you are talking about one part per million, it is like one second out of eleven days. Twenty parts per billion would be like 20 seconds out of 32,000 years." - Dr. B.

If you moved one inch per second, in 1 year you'd have traveled about 498 miles. If could walk on water, at one inch per second you'd circle the globe at the equator ( 24,901.55 miles) in 50 years.

Try this odd idea: The Mayan Calendar's connection to the Solar System.

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4/1/2004 Science / Measurement. Find out how much you weigh on other planets.

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10/23/03: Science / Measurement. Units of Measurement: Daltons.

A water molecule, consisting of two hydrogen atoms and one oxygen atom has a mass of 18 daltons. What in the heck is a dalton? We say that a molecule of water weighs 18 daltons, but weight and mass are two different things. What? Right, your weight and your mass are not the same. Weight measures the force of gravity between two objects, for example, yourself and the Earth. Weight changes if you go, for example, to the moon. Mass, however, is the amount of something and this does not change. Your mass in grams would be the same on the moon as on the Earth. Your weight in pounds, however, would be less on the Moon because there is less gravity on the Moon. To recap, a dalton measures mass. It doesn't measure size, it doesn't really measure weight.

When we say, for example, that one hydrogen atom weighs approximately 1 dalton, we mean that it has a mass of 1 dalton. A dalton is also called the atomic mass unit (amu) and is the mass of a hydrogen atom or 1/16th the mass of an oxygen atom. Avogadro's number is 602,214,199,000,000,000,000,000 of a thing. Avogadro's number of atoms is called a mole. One mole of oxygen atoms, for example, means 602,214,199,000,000,000,000,000 oxygen atoms. Since we saw above that one hydrogen atom weighs about 1 dalton, 602,214,199,000,000,000,000,000 hydrogen atoms weigh (have a mass of) 1 gram. A dalton is the number of grams per mole. Said another way, a dalton is the mass of avogadro's number of atoms. If this is still confusing, simplify. Pretend Avogadro's number is only 6. A mole of rasins is now six rasins. Six rasins will have a certain mass. Six oranges will have a much larger mass. The rasins "weigh" 1 dalton in our simple model, and the oranges "weigh" 6 daltons.

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10/23/03: Science / Measurement. Notes on Size.

Above, we saw the mass of a water molecule, but we didn't talk about the size. A water molecule is only about 2 angstroms in size. A hydrogen atom is about 1 angstrom in size. One human hair is about a million (1,000,000) angstroms wide. One nanometer is 10 angstroms. 100 nanometers is about one ten-millionth of an inch. 1,000 nanometers is 1 micron. For comparison a human hair is about 0.1 millimeters, or 100 microns, or 100,000 nanometers or 1,000,000 angstroms wide. You could fit 500,000 water molecules across the width of a human hair. Another useful comparison: A dime is approximately one (1) millimeter or 1,000 microns thick, or 10 human hairs thick.

 

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