Q: From a Richmond, Va., reader: "Why is it that September, October, November and December are the 9th, 10th, 11th and 12th months of the year when their etymological roots suggest they should be the 7th, 8th, 9th and 10th?
A: In fact they were 7th, 8th, 9th and 10th for the ancient Romans, whose 10-month calendar began with Martius, then Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, December, says ScienceWorld at wolfram.com. The last six obviously contain the Latin roots for the numerals.
But the 10 months accounted for only 304 days, with an unnamed period afterward in winter. Later, January and February were introduced at the top, rounding out what eventually became the 12- month Gregorian calendar but throwing off monthly nomenclature.
Actually, many different calendars have been used, some 40 of them still employed around the world, particularly for determining religious events, says Webexhibits.
org. Ours is based on the apparent motion of the sun around the Earth, while the Islamic calendar looks to the motion of the Moon and the Jewish calendar links to both. "Most modern countries use the Gregorian calendar for their official activities."
Q: Why are identical twins not so identical after all?
A: Identicality is a common misconception about single-egg twins, says University of Cambridge clinical anatomist David Bainbridge in "Making Babies: The Science of Pregnancy." But it is essential to realize that they are never perfect replicas, because not only are their in-utero environments different but their genes are as well.
First, the two may implant at different points in the uterus -- if double-placenta twins -- or at different regions of the same placenta.
"Because of this, they may have different degrees of access not only to food but also to poisons and infections in their mother's bloodstream."
Then the dramatic birthing process can treat the two differently, heading them along their separate ways.
To the genes: As the cells multiply, errors in replication occur, either subtle or large enough for only one of the twins to have a genetic disease -- such as Beckwith Weidemann syndrome, causing "gigantism."
Imprinting is another factor, where genes are switched on or off depending on the contributing parent, a patchy (random) process.
Finally, for girls "X inactivation" switches off certain genes in every cell, apparently randomly. Thus two single-cell girl twins can be very different depending on which bits of their bodies use which genes. In one case, X inactivation led to one sister being wheelchair- bound with muscular dystrophy while the other was a gifted athlete.
So it goes way beyond parents of twins dressing them differently, etc., to build separate characters.
"The simple biological fact is that they are always different."
Send STRANGE questions to brothers Bill and Rich at firstname.lastname@example.org.
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