Wikipedia:Reference desk/Archives/Miscellaneous/2024 February 14

= February 14 =

Operation of small-craft marine toilet
The page for "Marine Toilet" redirects to a page with nothing about the operation of a manual pump toilet as found on small and medium-sized watercraft. The excellent article "Toilet" covers just about all other types, but not that one. Please provide something about how these devices work. I think it would be pretty interesting. IrlSmith (talk) 14:12, 14 February 2024 (UTC)


 * Hello, IrlSmith. A request like yours translates to "Would one of the busy volunteers work on this idea of mine please?" It is possible that somebody will see it and be moved to do so, but not very likely.
 * Three possibilities suggest themselves. One is to post on one of the talk pages, either Talk:Toilet or Talk:Head (watercraft) - they will at least probably be seen by people with some interest. Another is to post at WT:WikiProject Ships, for the same reason. A third possibility is to try to write it yourself. Since it would probably be an extension to one of those articles, rather than a stand-alone article, this is not quite so challenging as creating an article from scratch; but you would still need to base whatever you wrote on reliable published sources, rather than on your own knowledge. ColinFine (talk) 15:21, 15 February 2024 (UTC)


 * actually, the third alinea of the Design section mentions the (hand operated) pump and valve system. In my experience with the vacuum type toilet, it is usually a membrane pump with a rubber flap valve on one side and a trileaflet valve on the other side, but different ones probably exist. Rmvandijk (talk) 14:11, 22 February 2024 (UTC)

Coincidence of Ash Wednesday and Valentine's Day
Today is both Ash Wednesday and Valentine's Day. This coincidence last occurred in 2018 and will next occur in 2029. Those two years (2018 and 2029) along with the current year 2024 are the only three coincidences in the 21st century.

In the following nine centuries of the third millennium, this coincidence will occur in the following years:


 * 22nd century: 2170, 2176, 2181
 * 23rd century: 2238, 2244, 2249
 * 24th century: 2306, 2312, 2317, 2396
 * 25th century: 2401, 2480, 2485
 * 26th century: 2548, 2553
 * 27th century: 2610, 2616, 2621, 2700
 * 28th century: 2762, 2768, 2773
 * 29th century: 2852, 2857, 2863
 * 30th century: 2920, 2925

In general, for this coincidence to occur, Easter must be on April 1 in a common year (possibly a century year, as it will be the case in 2700, for example) or March 31 in a leap year.

As one could see, this coincidence could occur two, three, or four times in a single century. Is it also possible for this coincidence to occur just once or five or more times in a single century (assuming 01 to 00 as usual)?

GeoffreyT2000 (talk) 16:27, 14 February 2024 (UTC)


 * If the calendar is never modified, seven coincidences are even possible : 
 * 129th century: 12801, 12812, 12863, 12874, 12880, 12885, 12896
 * 2109th century: 210801, 210812, 210863, 210874, 210880, 210885, 210896
 * 2945th century: 294401, 294412, 294463, 294474, 294480, 294485, 294496
 * 4385th century: 438401, 438412, 438463, 438474, 438480, 438485, 438496
 * 5221st century: 522001, 522012, 522063, 522074, 522080, 522085, 522096
 * 6365th century: 636401, 636412, 636463, 636474, 636480, 636485, 636496
 * 7201st century: 720001, 720012, 720063, 720074, 720080, 720085, 720096
 * 8641st century: 864001, 864012, 864063, 864074, 864080, 864085, 864096
 * 9477th century: 947601, 947612, 947663, 947674, 947680, 947685, 947696
 * --Lambiam 18:36, 14 February 2024 (UTC)
 * The year wrongifies by 13 days every ~43,200 years, if they don't fix by then then G*d damn. Sagittarian Milky Way (talk) 00:57, 15 February 2024 (UTC)
 * 9 days every 29,000 years is a better approximation of the deviation of the mean Gregorian year with the current mean tropical year. However, the latter is not constant. 43,200 years into the future the deviation will be closer to 1 day every 1800 years. --Lambiam 13:57, 15 February 2024 (UTC)
 * Unless man ends leap seconds forever. Sagittarian Milky Way (talk) 18:12, 15 February 2024 (UTC)
 * Alternatively, we can develop the technology to speed up the rotation of the Earth by about 0.000085% to match the length of the tropical year to the calendar year. The speeding up can be spread over many centuries. Or we can move the Earth to a slightly higher orbit, increasing the major axis by about 85 km. Or use a combination of the two. --Lambiam 14:11, 15 February 2024 (UTC)
 * The percent and kilometers increases over time because days per year declines as friction mostly tidal slows the rotation. I learned the length of the year and Gregorian error from books as the 1900.0 sum 365.242199 and 26 seconds short they copied Newcomb's Tables of the Sun or something long after 1900.0 was replaced by 1950.0 or 2000.0 it's now 365.24218-something. Sagittarian Milky Way (talk) 15:02, 18 February 2024 (UTC)
 * The years ending in 12 or 96 in your list do not actually work, as they are leap years with Easter on April 1 (like 2040, 2108, 2192, etc.), so Ash Wednesday would be on February 15 (not February 14), and the centuries in your list would actually only have five coincidences of Ash Wednesday with Valentine's Day. But in fact, there are already examples of such centuries in the fifth and sixth millennia. Namely, the first century to have five such coincidences will be the 46th century, with coincidences in 4503, 4514, 4576, 4587, and 4598; while after that, another five coincidences will occur in the 58th century, in 5703, 5714, 5725, 5787, and 5798. GeoffreyT2000 (talk) 01:28, 17 February 2024 (UTC)
 * There was a bug in my program. After fixing it, the maximum number of coincidences in any century reported is 5. The first three are:
 * 46th century: 4503, 4514, 4576, 4587, 4598
 * 52th century: 5100, 5106, 5168, 5179, 5190
 * 58th century: 5703, 5714, 5725, 5787, 5798
 * 110th century: 10903, 10914, 10976, 10987, 10998
 * --Lambiam 21:29, 18 February 2024 (UTC) [edited 16:59, 19 February 2024 (UTC)]
 * The above answers the case where there are at least five coincidences within a single century. However, the "just once" case has not been answered yet. Is there also a century that has just one Ash Wednesday/Valentine's Day coincidence, or no such coincidences at all? GeoffreyT2000 (talk) 03:48, 20 February 2024 (UTC)
 * My program (now hopefully bug-free) does not find any outside the range of 2 to 5. --Lambiam 10:45, 20 February 2024 (UTC)
 * I think the pattern repeats every 57000 centuries. Easter in year 5700000 + $Y$ is on the same day as Easter in the year $Y$, so Easter 5702024 is again on March 31st. --Lambiam 19:24, 14 February 2024 (UTC)