Calendar Trivia, Part I

I love time zones and calendars.  I'm reading up on calendars today to re-familiarize myself with the different kinds of calendars different populations use.  Mostly for now I'm interested in:

• How Julian Dates work--they're used in astronomy and I used to understand them, but the details have grown hazy
• How a lunar calendar works, because I have no idea, and I have a friend born in Korea who explained that she has two birthdays to sync up with both that calendar and the Western Gregorian calendar, and I was curious to understand this better
  

I'm reading through Dershowitz and Reingold's Calendrical Calculations and some related papers and websites for this.  I'm learning that there are numerous calendaring systems, and I'm not going to read up on all of them.  They all have different epochs (Day 1s) and different ways to measure years, days, and months.  Some calendars start the day at midnight, some at noon, some at sunrise or sunset.

Julian Date is not the same thing as the Julian Calendar.  It's a pretty simple arithmetic system used by astronomers to get rid of confusion about different calendars.  Every day is Julian Day (JD) [some number], and it increases by one every day.  Today (July 9, 2009) is JD 2455022, which started at noon UT (8am EDT).  Days change at noon because astronomers work at night, right?  Tomorrow will be JD 2455023, and so on.  The Julian Period is 7980 years, after which it starts back at zero.  This will happen on January 1, 3268.  Mark your (Gregorian) calendars.

Julian Day 1 was November 24, 4713 BC.  Background on this in Reese, Everett, and Craun, American Journal of Physics 49, p 658-661, 1981.  (The Wikipedia article on Julian Day is also good and cites its sources. Yay!)  I read a bit of this and it refers to several other sources, so I didn't get the complete picture.  Essentialy, the guy who created the system, Joseph Justus Scalinger (in 1583) used a combination of solar, lunar, and Roman tax collection cycles to arrive at 7980. 

Anyway, astronomers like Julian Dates because it's simple to determine when something is happening relative to some other event.  Astronomers sometimes start with January 1, 1980, which was JD 2444240 and add or subtract from there, (mostly, I think, because their software does), as a benchmark.  So, you can say that something that happened on JD 2443240 happened 1000 days ago.  A lot of what happens in astronomy has no relationship to the length of an Earth year, month, or day, so why get bogged down by it?

Unrelated bits of trivia I thought were neat:

• There are two major kinds of calendars: arithmetical and astronomical.  Arithmetical calendars start from some epoch and proceed by a mathematical formula, plus or minus adjustments.  Astronomical calendars are controlled by "irregular astronomical events", with some additional algebraic razzmatazz.
• The Western world uses the Gregorian calendar, named after Pope Gregory XIII, adapted from the Julian Calendar.  It was pretty much the same, but the Gregorian calendar has more complicated leap year rules.  Any year divisible by four gets a leap day, except for century years (years divisible by 100), unless they're also divisible by 400.  2000 was a leap year, 2100 won't be.
• The Ides of a month comes from the Julian Calendar.  I didn't know it was not always in the 15th.  Actually it's usually the 13th.  If it's March, May, July, or October, then it's the 15th.  It also has the Kalends (the 1st of the month), and the Nones (the 5th, except in March-May-July-October, when it's the 7th).  I have no idea what's special about those four months.

I'll get to the Korean calendar later on.

Posted at 11:39AM Jul 09, 2009 by WILSON, JOSHUA in Thought experiments  | 

Science! is back sort of, maybe, depending

Before I hit the one-year without updating point, I'll proactively post some updates to previous entries.  Will I resume updating Science!?  I dunno.

In this entry, I was talking about my National Geographic Wall Clock.  What you should know is, it was not all it was cracked up to be.  The original clock I got failed to update itself when Daylight Savings Time began last year, to my great disappointment.  I presumed this was due to its location in my house, buried on an interior wall fairly near the television, when the instructions said specifically it should be near a window facing the appropriate direction and not near electrical devices.  So I tried a few other things, like leaving it near a window, or even outside overnight, in the hopes that it would get word from the mother station that time had advanced without it.  No such luck.  Note, there is NO WAY to change the clock by hand.  Because it is advanced technology that will never break so you will never need to manually fix it, like Microsoft Windows. 

Then, a few weeks later, I get an e-mail from the clock manufacturer stating that my clock was recalled because it was faulty.  Apparently something about the new DST rules messed it up, and they were sending me a new one.  So, now I have two clocks: one which recognizes DST, one which denies its existence.  The latter must simply serve as wall decoration and will likely have to be banished upstairs until fall.

In this entry, I listed ingredients I found in a package of vending machine donuts.  Most of them turned out to be advanced emulsifiers, whose purpose is to maintain the integrity of a floury cake product for shipping, stacking, storing, and weeks of downtime until purchase and (regrettable) consumption.  I'm looking to read Twinkie Deconstructed at some point to learn more about industrially processed foods with the hope that I will inspire myself to avoid them forever.  I also want to note that one of the ingredients, xanthan gum, was also found in many lotions.

Posted at 05:10PM Mar 13, 2008 by WILSON, JOSHUA in Thought experiments  | 

Whoa

This is fascinating.  Over on Cognitive Daily, they posted the results of a quick experiment in which readers were asked to select a number, any random number they wanted, between one and twenty.  Here were the results:



For whatever reason, an extremely high percentage of the 347 respondents picked 17 (dark blue bars).  By comparison, 347 numbers randomly generated by a computer (light blue bars) were much more evenly distributed.  Significant analysis follows, and several objections to the conditions of the experiment are posted in the comments. 

Mostly I think it shows that humans and computers have different ideas about what "random" really means.  Many readers probably felt like 17 was the least common number in daily life (although if you're a cribbage player, you'd argue that it's 19) so therefore it seemed the most random.  Whereas you can see that 5, 10, 15,  and 20 all got a low response.  A machine wouldn't differentiate the same way.

So speaking of random number generation, every year I participate in a college bowl game-picking pool organized by a friend of mine.  Essentially, it's just a contest between about twenty people to try to pick the most bowl games correctly.  I only vaguely follow college football so I'm out of my depth to begin with, although the pool is comprised of a range of people, from those obsessed with college football, down to people who are completely ignorant.  I'd guess I'm in the 20th percentile or so of participants.  Meaning I have more base subject knowledge (on college football) than about 1 in 5 others.  But I think anyone who's participated in a NCAA tournament pool knows that knowledge can be a dangerous thing, and the person who has followed the game closest throughout the season not only doesn't have an advantage, they probably, in fact, have a disadvantage. 

The point is, I make all of my picks via random number generation.  I've tried different methods in the four years I've played, all lacking scientific validity.  Here's a summary of my methodology:

Year 1: Random number generation by MS Excel
Year 2: Combination of Excel and polling my roommate (whom I perceived as lucky) for random numbers
Year 3: Asking friends to gather numbers from random.org, which I compiled and gleaned results
Year 4: Random number generation by Google spreadsheet

This last year I finished in 2nd place in the pool.  Second place!  Picking entirely randomly, going only by meaningless numbers generated by Google spreadsheet software, I out-picked nearly the entire field.  Year 1, the other year with no human intervention, was similarly successful--in the top three I think.  The worst year was Year 3, which required the most human participation.  Even though the numbers were random, I asked people to gather them.  I finished last, easily.  Year 2 was somewhere in the middle.

What I'm saying is, if you're in an NCAA tournament pool with me this year, beware Google spreadsheet!

Posted at 09:56AM Feb 09, 2007 by WILSON, JOSHUA in Thought experiments  | 

Little chocolate donuts

My next exercise as chemistry reference librarian:  look up all the dubious compounds contained in the donuts I just ate.  (Ironically and idealistically known as Mrs. Freshley's Chocolate Mini-Donuts, purchased out of a vending machine.  The good news is that they had an expiration date.)  My short-term goal is to use library resources to understand the purpose of each of the mystery ingredients.  My long-term goal is to scare myself into never being tempted to eat these things again:

sodium acid pyrophosphate
sodium aluminum phosphate
monocalcium phosphate
dextrins
guar gum
karaya gum
monoglycerides
sodium stearoyl lactylate
xanthan gum
bees wax
cellulose
enzyme [this is frighteningly vague--I'm not quite sure this counts as full disclosure of ingredients, to be honest]
sodium propionate
potassium sorbate (to preserve freshness)

Posted at 04:18PM Oct 30, 2006 by WILSON, JOSHUA in Thought experiments  | 

In praise of argon

Harlow Shapley's Beyond the Observatory provides a fun thought exercise with argon.

Most of the "other" is actually argon, an inert gas.  Find some basic information about argon here.  But let's face it, argon in and of itself is pretty boring.  It's a noble gas*, meaning it thinks it's too good to react with anything else.  In fact, argon is so inert, its name comes from the Greek word meaning inactive.  So it's just been meandering around Earth's atmosphere since the Earth had an atmosphere--about five billion years, give or take.  The total amount increases slowly but steadily: it's a biproduct of the radioactive decay of a potassium isotope in some rocks.

Despite it making up only 1% of the atmosphere, with each breath, Shapley calculates that we inhale and exhale around 3x10^19 (30,000,000,000,000,000,000) argon atoms.  These atoms get diffused throughout the atmosphere in the subsequent minutes, days, and months.  He further supposes that the breath you take a year from now includes at least 15 of the exact same atoms.  Since these atoms don't react with you, or anyone else, we see an interesting implication.  You're sharing your breath with everyone else.

Shapley theorizes that with each breath, you take in 400,000 argon atoms that Gandhi breathed during his life.  You also share the same argon used by Shakespeare, Hitler, and dinosaurs (although there's a lot of new argon since then, too).  He writes:

We have argon from the sighs and pledges of ancients lovers, from the battle cries at Waterloo, even from last year's argonic output by the writer of these lines, who personally has had already more than 300 million breathing experiences.

Harlow Shapley is generally credited with the first understanding of the shape and scale of the Milky Way, and recognizing our solar system's location in it.  His obituary, as it appeared in Nature in 1972, is reprinted here.


The image above, and more information about Earth's atmosphere, is located at http://liftoff.msfc.nasa.gov/academy/space/atmosphere.html.
*From Hawley's Condensed Chemical Dictionary, "In chemical terminology, this term describes an element that either is completely unreactive or reacts only to a limited extent with other elements." 

Posted at 09:48AM May 17, 2006 by WILSON, JOSHUA in Thought experiments  |  Comments[2]