Wikipedia:Reference desk/Archives/Science/2018 January 25

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January 25

Super blue blood moons

There's to be a "super blue blood moon" on 31 January, due to a triple coincidence of a super moon, a blue moon, and a total lunar eclipse. I read that the last time this happened was "150 years ago". What was the exact date, and does this come around in any sort of regular pattern? When were the earlier incidences? -- Jack of Oz ^{[pleasantries]} 10:30, 25 January 2018 (UTC)

The article you linked says that "super moon" has no precise definition, so it is not possible to list earlier occurrences. --70.29.13.251 (talk) 10:53, 25 January 2018 (UTC)

Ok, so what was the event that occurred "150 years ago"? -- Jack of Oz ^{[pleasantries]} 11:08, 25 January 2018 (UTC)

Unfortunately, the c. 1868 incidents at List of 19th-century lunar eclipses don't have articles, and Category:2nd-millennium lunar eclipses has no articles about individual eclipses between 1573 and the 20th century. Nyttend (talk) 12:54, 25 January 2018 (UTC)

A "supermoon" is a full moon which is unusually close to Earth (i.e. near perigee). There is a full moon roughly every 29 1/2 days, the "anomalistic month" is 27d 13h, and the full moon "gains" on the perigee about 2 days per month. Thus supermoons happen about every fourteen months. "Blue moon" is a fluid term but the writer's attention appears to have been attracted by the fact that this year January and March have two full moons apiece and February has none. In the last 150 years at Greenwich this has happened in 1866, 1885, 1915, 1934, 1961 and 1999. It is theoretically possible for this to happen in a leap year - anyone interested might want to check the records and let us know when the last time was.

For the moon to be eclipsed it must be at or very near a "node". The full moon "gains" on the node about 2 1/3 days per month. It is to be noted that the above mentioned "blue" moons often recur at intervals of nineteen years. The nodes line up with the full moon every 18.6 years and about 70% of the time an eclipse will be repeated nineteen years later (because the moon has moved round to the opposite node). The "blue moons" in the above sense were eclipsed in January 1915, January 1934, March 1961 and January 1999. 86.169.56.163 (talk) 13:15, 25 January 2018 (UTC)

... and, of course, Jack and 86.169.56.163 are referring to an American blue moon, as in J. H. Pruett's 1946 misunderstanding of the 1937 Maine Farmers' Almanac. The last spectacular British blue moon was in 1950. Dbfirs 15:16, 25 January 2018 (UTC)

On that point, we say: The March 1946 issue of Sky & Telescope misinterpreted the traditional definition, which led to the modern colloquial misunderstanding that a blue moon is a second full moon in a single solar calendar month with no seasonal link (my highlight).

I would argue that that "misunderstanding" has become "the common understanding" of the term. The article is very informative and instructive, but I have to say I have only ever known the term to mean the second full moon in a calendar month. Words and expressions mean what they are now generally taken to mean, not what we are told they once meant. -- Jack of Oz ^{[pleasantries]} 20:37, 25 January 2018 (UTC)

The American usage must have spread to your continent long before it spread to northern England, because I've only recently become aware of the American meaning. The literal British meaning has been around since 1702 according to the OED, though I admit that I haven't personally known of it for quite that long. Dbfirs 22:32, 25 January 2018 (UTC)

Consecutive Full Moons obviously cannot be blue. The 1st moon of the 2nd month would have to be only a few days after the 2nd moon of the 1st month. But if a month is shorter than a moonth it might be Full Moon-free allowing blue moons 2 moonths apart (similar to how twin primes are 2 numbers apart because it's not possible for consecutive numbers to be prime) This is only possible in February (moonths are 29d 6h to 29d 20h long) so twin blue moons only happen in January and March. I searched this database of blue moons less than a year apart, a database of lunar eclipses and a database of supermoons and found the last blood double blue supermoon (Gregorian) was January 30 or 31, 1646 in all time zones. That total lunar eclipse was farther than this month's. Even so, the January 31, 2018 moon isn't a supermoon by strict definitions so I searched till 481.5 AD and couldn't find a double blue blood supermoon closer than 2018's (unless I missed something). Obviously (to astronomers) both blue moons can't be lunar eclipses since lunar eclipses cannot occur 2 moonths apart. Sagittarian Milky Way (talk) 03:28, 26 January 2018 (UTC)

Nobody ever said consecutive full moons are blue. If two consecutive full moons both fall in the same calendar month, the second one - not both of them - the second one is a blue moon. In January 2018, there was a full moon on 2 January, and another will come on 31 January. The one on 31 January is blue, the one on 2 January wasn't. -- Jack of Oz ^{[pleasantries]} 04:20, 26 January 2018 (UTC)

The point about the original meaning of "blue moon" is that it's the fourth in a season. The moons are named, three to a season, so when a fourth one comes along it doesn't have a name. 92.19.172.194 (talk) 15:50, 26 January 2018 (UTC)

I've seen different versions of moon names: based on the equinox/solstice months and based on January, February etc. Some of these are Native American, some Old World. Also the harvest and hunter's moons have been squished into "September and October by definition" or "Libra and Scorpio" or "after equinox and the one after" but that wouldn't jive with what Wikipedia defines them as being "closest to equinox and the one after". Interestingly, non-literal blue moon definitions are both solutions for what to do the one time in ~30 a simple naming system's ambiguous. If anyone names blue moons by meteorological season or one of the other two ways to cut at Gregorian months like quartering the year (business quarters) then that's the only way a moon can be blue (season) and blue (calendar month) at the same time. Sagittarian Milky Way (talk) 17:45, 26 January 2018 (UTC)

It seems we're palavering around the topic but not really focussing on what I want to know. Sure, there's a definitional issue, but can we just accept that the term "blue moon" is widely understood to mean the second full moon in a calendar month? That's how I am using it here. All I want to know is when, exactly, was the last time that a total lunar eclipse coincided with a blue moon and also with a "super moon". The internet is full of assertions that this last occurred "150 years ago". That's fine, I'm not surprised it's rare - but I want the exact date. -- Jack of Oz ^{[pleasantries]} 18:10, 26 January 2018 (UTC)

How Rare Is The All-In-One Supermoon, Blue Moon, And Lunar Eclipse, Really? says: "the last combination of blue Moon, Supermoon, and lunar eclipse wasn't so long ago: it happened on December 30, 1982", but you couldn't see it in North America or Australia. The same article gives a date of 1866 for one that Americans could see.

Incredibly Rare 'Super Blue Blood Moon' Is About to Appear For The First Time in 150 Years says: "According to the Canon of Lunar Eclipses, the last time humans saw a total eclipse of a blue moon was 31 March 1866". Alansplodge (talk) 13:08, 27 January 2018 (UTC)

See also Supermoon Eclipse Will Be the First Since 1982. Alansplodge (talk) 13:13, 27 January 2018 (UTC)

(edit conflict)"Blue moon" is a fluid term but the writer's attention appears to have been attracted by the fact that this year January and March have two full moons apiece and February has none. In the last 150 years at Greenwich this has happened in 1866, 1885, 1915, 1934, 1961 and 1999}}.

There is a later reference to eclipses in January 1915, January 1934, March 1961 and January 1999. The actual dates are 31 January 1915, 30 January 1934, 2 March 1961 and 31 January 1999. None of these eclipses was total. The reference to 2 March 1961 suggests that the second of the two full moons in March, the "blue moon" by your definition, might not have been investigated. The writer says there were blue moons in 1866 and 1885. Now checking your March blue moons we find that the one on 31 March 1866 was totally eclipsed. We could go further back but we then run into the problem that countries changed from the Old Style to the New Style at different times. There are either two or three total lunar eclipses per decade, i.e. about 5% of full moons are totally eclipsed and blue moons happen roughly every 2 3/4 years. This means we're looking at a totally eclipsed blue moon (on average) every 55 years, but the numbers are augmented by the fact that sometimes there is a double helping of blue moons in the months from December to May. In this century we have had blue moons on 30 November 2001, 31 July 2004, 30 June 2007, 31 December 2009, 31 August 2012 and 31 July 2015. None of these was totally eclipsed. Turning to the twentieth century, the "blue moon" of 30 December 1982 was totally eclipsed. In the nineteenth century there is nothing after the 1866 event mentioned above. If you can clarify how far from perigee a full moon can be and still qualify as a "supermoon" we can answer the second part of your question. 92.19.172.194 (talk) 14:35, 27 January 2018 (UTC)

Yo banned user, this is not an edit conflict as the timestamps clearly show. And there are not either 2 or 3 total lunar eclipses per decade, we just had a tetrad with 4 TLE's in <17.5 months of the mid-2010s. Sagittarian Milky Way (talk) 18:27, 28 January 2018 (UTC)

That's not true, the December 1982 lunar eclipse was visible in all of Australia and North America except the Heard and McDonald Islands, Cocos (Keeling) Islands and southeast Caribbean islands. The total phase ended December 30, 1982 at 10:58:44 pm Sydney and Melbourne time plus or minus a few seconds. However, the previous Full Moon was December 1, 1982 00:21 UTC so the eclipse was not blue in America. Thus the last blue, blood supermoon according to Americans ended March 30, 1866 11:19.6 pm proleptic Central Standard Time which as the time suggests was also visible in North America except peripheral Arctic areas. The January 2018 lunar eclipse will in fact be less super and less visible in America than that one. (though still visible to many Americans (at the super inconvenient time of 6:52 in the morning Central/4:52 Pacific till twilight hiding it)) The 1866 one was much more convenient for Americans, mideclipse occurring at 8-12 and high in the sky. Also, the Full Moon's Feb 1, 2018 in Australia (in Eastern Daylight Time at least) you miss the blueness by 26 minutes and 44 seconds. Sagittarian Milky Way (talk) 03:28, 28 January 2018 (UTC)

Paradoxically, missing the blueness still leaves one rather blue. -- Jack of Oz ^{[pleasantries]} 03:39, 28 January 2018 (UTC)

In the article the eclipses are listed in groups of eight, of which two or three can be total. There are about eighty total eclipses per century, which means about 15% of full moons are totally eclipsed. This gives an average of one totally eclipsed blue moon every 18 years, augmented because of the "twin primes effect" you noted above. 82.43.223.32 (talk) 18:51, 28 January 2018 (UTC)

Stop spouting nonsense banned user, the percent of full moons that are totally eclipsed is 5 or 6% (5000 year average). There are an average of 7 total lunar eclipses a decade, the average time between blue total lunar eclipses is 43 or 44 years. Sagittarian Milky Way (talk) 20:22, 28 January 2018 (UTC)

There were 63 total lunar eclipses in the 19th century. That's about 20%. Can you link to your source? 82.43.223.32 (talk) 20:32, 28 January 2018 (UTC)

There were 62 [1]. Divide 0.62 by 12. Sagittarian Milky Way (talk) 20:38, 28 January 2018 (UTC)

When the century begins is a discussion in itself. The editor who originally did the calculation gave the 5% figure (post 14:35 yesterday). Does your 43/44 year average allow for the "twin primes effect"? 82.43.223.98 (talk) 21:00, 28 January 2018 (UTC)

Except there were no TLEs in 1800 or 1900 so it's still 62. Sagittarian Milky Way (talk) 22:08, 28 January 2018 (UTC)

OK, let's spell it out -

1801(2), 1805(2), 1808(2), 1812(2), 1815(2), 1816, 1819(2), 1823(2), 1826(2), 1830(2), 1833, 1834, 1837(2), 1841(2), 1844(2), 1845, 1848(2), 1852(2), 1855(2), 1856, 1859(2), 1862(2), 1863, 1866(2), 1870(2), 1873(2), 1874, 1877(2), 1880(2), 1881, 1884(2), 1888(2), 1891(2), 1892, 1895(2), 1898, 1899, for a total of 63.

Having checked your source, I confirm it gives 62, which corresponds with an annexed catalogue of lunar eclipses during the century. The total eclipses are classified as either "T+" or "T-". What do the operators signify? There is a discrepancy in 1856 for the eclipse of 13 October. The details are:

Wikipedia                                  Your source 
Gamma               0.481                  0.4809                                                
Magnitude Penumbra  1.98                   1.9545
Magnitude Umbra     1.002                  0.9960 
Partial (minutes)   186                    186.2 (penumbral phase 302.7)
Total (minutes)       6                    0
Start time          21:21
Start of totality   22:51
End of totality     22:57
End time             0.27

You can't say Wikipedia is wrong and you are right for the simple reason that whether an eclipse is partial or total is to some extent dependent on parallax. There is a video at [2]. Your source describes this as a partial eclipse with a "QSE" of "a-". What does that mean? 82.43.223.98 (talk) 13:56, 29 January 2018 (UTC)

Hits center, over or under. Quincena Solar Eclipse Parameter. Sagittarian Milky Way (talk) 18:00, 29 January 2018 (UTC)

Detecting an aortic aneurysm

From A study in scarlet:

"Then put your hand here," he said, with a smile, motioning with his manacled wrists towards his chest. I did so; and became at once conscious of an extraordinary throbbing and commotion which was going on inside. The walls of his chest seemed to thrill and quiver as a frail building would do inside when some powerful engine was at work. In the silence of the room I could hear a dull humming and buzzing noise which proceeded from the same source. "Why," I cried, "you have an aortic aneurism!" "That's what they call it," he said, placidly. "I went to a Doctor last week about it, and he told me that it is bound to burst before many days passed."

Can an aneurysm be so advanced that a human could notice it without any equipment? I see from Aortic aneurysm#Abdominal aortic aneurysm that "A bruit may be heard from the turbulent flow in the aneurysm", but Bruit only mentions hearing it via a stethoscope, and anyway if it's in the chest it's not an abdominal aneurysm. I'm guessing that it's just a fictionalized device (Jefferson Hope needs to be strong and mostly healthy to do the murder, but he needs to be near death to have a reason to tell his story), but as the aortic aneurysm article says Most intact aortic aneurysms do not produce symptoms without saying anything really about bruits in thoracic aneurysms, I was curious. Nyttend (talk) 12:51, 25 January 2018 (UTC)

I'd say it was a case of WP:FILMSCI, but then again, Conan Doyle was a doctor. Gråbergs Gråa Sång (talk) 15:25, 25 January 2018 (UTC)

It is possible to feel an advanced aortic aneurysm. It feels like a throbbing in the abdomen. One that is likely to burst soon would likely be advanced. 209.149.113.5 (talk) 17:26, 25 January 2018 (UTC)

Anecdotally, my mother noticed throbbing or “thumping” from hers and the doctor confirmed it. It was repaired successfully. Edison (talk) 19:55, 25 January 2018 (UTC)

A palpable vibration over an aneurysm is an aneurysmal thrill. Klbrain (talk) 23:46, 25 January 2018 (UTC)

Funnily enough, this Tuesday I watched the second episode of Nurse Jackie, in which this very question is a minor plot point. —Tamfang (talk) 03:57, 28 January 2018 (UTC)

Gametes of decreased size occurring in evolution of sexual reproduction

Medium sized gametes would have been favored to increase in size (eventually leading to the appearance of female gametes) due to better nutrient storage, but soon after this size had begun to increase, a size decrease would begin among other medium sized gametes (eventually leading to the appearance of male gametes). Why did this occur in the evolution of sexual reproduction? MisterH2005 (talk) 21:53, 25 January 2018 (UTC)

Egg and sperm developed simultaneously (but sperm probably developed slightly sooner). Yellow Sunstreaker (talk) 07:08, 30 January 2018 (UTC)

Our writings on this: Evolution of sexual reproduction#Origin of sexual reproduction, and read other sections in this article too. Graeme Bartlett (talk) 23:07, 25 January 2018 (UTC)

The idea of disruptive selection driving the evolution of anisogamy from isogamy is presented in our Anisogamy article. Jmchutchinson (talk) 19:10, 26 January 2018 (UTC)