Celebrity spotted using decimal time

Grammy winner John Mayer tweeted about decimal time, and specifically about the DeciTime iPhone app.  Here is what he said last night, in chronological order:

Trying to switch to decimal time. 10 dours, 100 dinutes, 100 deconds. Check out the DeciTime app.
Posted 55282.109

This is what time it is now in decimal time. http://twitpic.com/1b7fmf
Posted 55282.273


It's 2:60. I really should go to bed. Maybe I'll get 3 dours of decimal sleep. On stage tomorrow night at 8:75.
Posted 55282.555

MJD 55282.967

Star Trek: The Exhibition

Today we went to Star Trek: The Exhibition at the Tech Museum in San Jose.   My captain is more interested in the later series, especially Voyager, while her first officer prefers the earlier shows.  We sat in the captain's chair and stood on the transporter pad while watching ourselves dissolve on the monitor.  I saw several different PADDs there, from various centuries, and noted their resemblance to the new iPad, and the smaller ones resembled the iPhone I carried with me.  The communicators reminded me of flip phones, although in function they are more like satellite phones.  And scattered around the exhibit were LARS displays, including an entire corridor, but no matter how much I tapped the screens, I got no response from the ship's computer.  Nor did the jelly beans on the TOS bridge do anything.  Oh, well.  There was also a large display of a timeline, with separate sections for each series and movie, starting the 20th century, and mentioning the return to the moon during the 21st century by the Constellation Program.  Oops!  I guess this was an alternate universe where Obama did not cancel Constellation.  I only noticed year numbers, no stardates, although I did not pay that much attention, since I'm already familiar with Star Trek chronology, and I was more interested in examining props than reading a bunch of stuff that I can get online.  I did try jumping through the Guardian of Forever to past centuries, but found only this one on the other side, and no Joan Collins.

Stardate 55275.0

Go ask Alice

Yesterday I saw the movie Alice in Wonderland and I noticed the price tag on the Mad Hatter's hat said "10/6".  I recognized that it was a price in old English currency of ten shillings and six pence.  Since there were twenty shillings in a pound and twelve pence in a shilling, 10s 6d would today be equivalent to 52½p or £0.525, although halfpennies stop being minted in 1984.

That got me thinking of duodecimal measures.  The words "inch" and "ounce" both come from the Latin uncia, meaning a twelfth part, and there are twelve inches in a foot, and twelve troy ounces in a troy pound, although other types of ounces no longer represent a twelfth of anything.

Years are divided into twelve months.  Originally sun dials divided the period of daylight into twelve hours, which varied in length depending on location and time of year, but eventually mechanical clocks came to represent periods between midday (noon) and midnight, and these clocks are divided into twelve hours of equal length.  An additional hand likewise divides each hour into twelve parts; adding marks between the numerals multiplies this division by five, giving 60 minutes, but have you ever noticed that the time is almost always rounded to the nearest multiple of five minutes, so we're still dividing hours by twelve?

A dozenal system of units would be fine, and in some ways better than decimal, but traditionally there have been only a handful of dozenal units.  A shilling were divided into twelve pence, but a penny was divided into two ha'pennies or four farthings, a pound into twenty shillings, etc.  Since Decimal Day, 1971 February 15 (MJD 40997), a pound is divided into 100p, period.

MJD 55269.198

Calendrier

I posted before about the French Republican Calendar iPhone app called Calendrier.  It seems that it has been updated.  Originally it used a calculation that skipped a leap year every 128 years, so that all Republican years between 128 and 256 (1919 and 2047 CE) start on September 23.  Version 1.2, released 2010 March 4 (MJD 55259/14 Ventôse an CCXVIII) has all years starting on the autumnal equinox in Paris, as during the French Revolution, with an option to display the current date according to Romme's Gregorian-style proposal to skip leap days on most century years.  (Romme went to the guillotine before it could be adopted.)  Under Romme's plan, all years between 200 and 300 (1991 and 2091 CE) start on September 22.  Under the original rule, all years between 141 and 300 (1932 and 2091 CE) start on either September 22 or 23.

The app also now converts Gregorian dates between 1792 and 2195 CE (1 and 404 ER) to Republican dates, although apparently only by the equinoctial rule.  (Not sure why the Gregorian months appear to be in Spanish.)  Now I'm actually tempted to pay $1.99 for it!

MJD 55266.380

Primidi 21 Ventôse an CCXVIII à 3^hd 86^md t.m.P.

What is a planet?

This week's episode of Nova on PBS, "The Pluto Files", reminded me of a story.  It was around the beginning of a new century, and an astronomer was predicting that a planet existed which had yet to be discovered, and he organized a search for that planet.  An object was observed and declared to be a new planet.  However, the new planet was quite small, and other objects were later found to orbit in roughly the same part of the solar system, so after half a century or so, a large number of astronomers stopped calling it a planet.  Then, in 2006, a proposal was made to the International Astronomical Union that would have included it as a planet, but this was rejected because it shared its region of space with other objects, so it became reclassified as a "dwarf planet".

Legacy of the French Revolution

Decimal time was the law of the land for only a brief time.  In 1793, during the French Revolution, decimal time was declared mandatory for public acts, starting on 1794 September 22, or 1 Vendémiaire, year III, in the new calendar.  However, the law establishing the metric system on 18 Germinal, year III, (1795 April 7) suspended mandatory use just six months after it started.  This did not entirely kill decimal time, though.  It still continued to be used in some parts of France, such as Toulouse, for a number of years in official records, perhaps until Napoleon abolished the new calendar at the end of 1805, or maybe when ten-day weeks were dropped in 1802.

But even then, decimal time did not disappear completely.  The great French astronomer and mathematician, Pierre-Simon Laplace, was enthusiastic about decimal time and had a decimal watch made.  He also used decimal time in his work, Traité de Mécanique Céleste, in 1799.  He represented the time of day as a decimal fraction, such as 0^j,60566.  He also added the fraction to the Gregorian calendar date, such as:

...l'instant du passage au périhélie, sept.29^j,10239, temps moyen compté de minuit à Paris. 

In English, that's "...the instant of perihelion passage, Sept. 29^d.10239, mean time counted from midnight at Paris."  This became common practice by astronomers, with French astronomers using mean time in Paris and British astronomers using Greenwich mean time.  After the British astronomer John Herschel proposed Julian days, astronomers added decimal fractions to Julian days, creating Julian Dates, which are still in wide use in astronomy, along with variants such as Modified Julian Dates.  Calendar dates with times given as decimals of a day in Universal Time have been used in astronomical circulars for the past century.  Others, such as computer programmers, also use decimal fractions of a day to represent time.

So these modern applications of decimal time can be linked, through Laplace, to the decimal time established back in the 18th century during the French Revolution, and possibly inspired the stardates that are projected in future centuries.

MJD 55253.234

Octidi 8 Ventôse an CCXVIII à 2^hd 41^md t.m.P.

New pages

I have posted several pages on this site which were on the old site, links to which may be found at the top of this blog.  They are still a work in progress, and I have to fix all the internal and external links and make other updates.

I also made changes to the decimal times in the sidebar.  For the local decimal time, I now use the Excel (for PC) serial date, which includes local time as a fractional day, the same as the calendar date in the title bar.  I also moved the French republican date (Calendrier Républicain) into the same gadget and made it update with decimal seconds.

So the decimal time is represented in up to five different time zones:

• Excel for local time
• NASA/NORAD Two-Line Element for Universal Time = GMT
• Julian Date for astronomical time = GMT + 12h
• Swatch for Biel Mean Time (actually Central European Winter Time or British Summer Time) = GMT + 1h
• Republican calendar for Paris mean time (temps moyen de Paris) = GMT + 9m21s

MJD 55248.125

Site design

As you can see, I've made some changes to the site.  In order to match the original logo, I've changed the background from black to white.  The image does not fit well at the top, so I've put it on top of the sidebar. Perhaps I'll create one that fits the new site better later.  I also restored the favorites icon (favicon) which is based on the same image, replacing the Blogger icon.  [And added an Apple Touch icon, so I can add it to my iPhone.]  I am also working on adding back some of the other pages from the old site, such as the one on calendars.  Unfortunately, the URL has to be slightly different, so any incoming links will still be broken. :(

MJD 55239.050

Pads

I have heard people making fun of the iPad because of the similarity to a feminine hygiene product, never mind that "pad" is a generic term that has many other uses. For one thing, it's sounds the same as very similar devices on Star Trek! Only according to Memory Alpha, the Star Trek wiki, it's spelled PADD, which stands for Personal Access Display Device.  Most likely, this is really a backronym, just as another Apple product, the Lisa, supposedly stood for Local Integrated Software Architecture, even though Steve Jobs's daughter also happened to be named Lisa.

The name iPad may have been chosen so that all three devices have the same first two letters, iPod, iPhone and iPad.  I think that from now on I'll just call them collectively iP.

MJD 55236.476

Lunar Holidays

"The Holidays" are considered to be at the end of the (solar) year, but around the beginning of the year there are a series of holidays which are based upon the phases of the moon.  These are determined according to various lunar calendars, which are sometimes called luni-solar calendars, because they are periodically adjusted by adding months to keep them somewhat synchronized with the solar seasons.