Wikipedia:Reference desk/Archives/Science/2015 December 15

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December 15

finding the work according to the blood pressure and the heart rate

I found on Facebook (later I found the same question -with the same typo- that looks like a source on Google) a very nice question and I decided to take advantage and to try to understand it. But before I'm going to do that, I would like to know if the answer (I found it also there) is correct or not. Afterward, I would like to understand where did the number 1300 come from to the solution. This is the question and the answer:

The pumping action takes place in less than 1/3 cardiac cycle while the heart muscle rests for over than 2/3 of the cycle .
Ex: - A patient of heart rate of (120/min) his pressure is 150/90 mmHg. Calculate the work done by the left ventricle for 2 seconds.
Sol:- W= p x ∆V
P= (150+90)/2 = 120 mmHg.
=120 x 1330 = 1.6 x 10⁵ dyne/cm²
∆V = 120/60 sec x 80 ml =160 ml/sec.
W=120 x 1330 x 160 =2.6 x 10⁷erg/sec
W/2sec = (120 x 1330 x 160) x 2=5.2 x 10⁷ erg/sec.
— Preceding unsigned comment added by 92.249.70.153 (talk) 00:01, 15 December 2015 (UTC)

Regarding the 1330 used in the solution (I assume that is the 1300 you are asking about), see millimeter of mercury (and Torr, which is essentially the same thing). 1 mmHg ≈ 133.3 Pa (where Pa is the unit of pressure Pascal). But your example problem appears to work with CGS derived units, where 1 barye (symbol: Ba) = 1 dyne per square centimeter = 0.1 Pa. So 1 mmHg ≈ 1333 Ba. Presumably the students were told to use the approximation 1 mmHg ≈ 1330 dyne/cm². -- ToE 03:46, 15 December 2015 (UTC) (I added linebreaks to the original question and repaired the exponential notation for readability.)

Regarding the problem itself, an unstated assumption is that the volume pumped each beat is 80 ml.

Also assumed is that the pressure increase imparted by the left ventricle is equal to the average of the systolic and diastolic pressures. This doesn't seem to account for the inlet pressure coming from left atrium, but perhaps that is insignificant.

Given those assumptions, calculating pumping power is easy, but their solution is sloppy with its units and confusion of work and power.

The work done on the fluid by a single stroke of a reciprocating pump is W = ∆p x ∆V (change in pressure times the volume displaced) and the average power of the pump is P = ∆p x Q (change in pressure times the volume flow rate).

So if your pressure increase really is equal to the average of the systolic and diastolic pressures, then yes, ∆p = 120 mmHg (133 Pa / mmHg) ≈ 1.6x10⁴ Pa (or 1.6x10⁵ Ba).

∆V = 80 ml, so the work done each beat is 1.6x10⁴ Pa x 8.0x10^-5 m³ = 1.3 J (or 1.3x10⁷ erg).

At 120 bpm, there are four beats in two seconds, so the total work done during that time is 4 x 1.3 J = 5.2 J (or 5.2x10⁷ erg).

Or, doing it their way, the average flow rate Q (not ∆V) is indeed 160 ml/sec. And the average power P (not W) is indeed 1.6x10⁴ Pa x 1.6x10^-4 m³/s = 2.6 J/s (or 2.6x10⁷ erg/s).

Thus the work done over two seconds is P x 2 s = 2.6 J/s x 2 s = 5.2 J (or 5.2x10⁷ erg).

Working CGS and getting your answer in erg saves you having to convert 1 ml = 1x10^-6 m³, but at the scale of this problem Joules seem more appropriate than erg. (You should pick up from context what units are expected in the particular field, though this may change over time.)

So their solution was particularly sloppy, and while their final numerical answer was correct, the units of that answer should have been erg (units of work) and not erg/s (units of power). If you make $10/hr, how much money have you earned after working 4 hours? $40, right, not $40/hr. -- ToE 15:37, 15 December 2015 (UTC)

Wow! this is very nice answer with complete explanation! I enjoy it (and I believe I can guess, too) Thank you very much! 15:23, 17 December 2015 (UTC) — Preceding unsigned comment added by 92.249.70.153 (talk)

A medium-size object

If the biggest thing is the universe and the smallest thing is a quark (or something like that), then how big is an object that is half way between? Does this question make any sense? Anna Frodesiak (talk) 00:07, 15 December 2015 (UTC)

We have an article, Orders of magnitude (length). The way you have phrased your question is a little bit difficult to answer - the question is valid English syntax, but it's not really the way physicists describe or compare sizes. You are not entirely correct in asserting that a quark is the smallest object we know about; nor in the implication that the universe is a single object. These details entirely depend on how you define "object," and subsequently how you choose to measure or define the size of an object. Universes and quarks are different types of entities, so it's strange to compare them; but we can use characteristic length scales to compare different types of objects. Finally, it's not clear how you want to measure "half way between" different length scales - we could use the arithmetic mean or the geometric mean; or we could look at some kind of logarithmic scale; and so on.

Nimur (talk) 00:18, 15 December 2015 (UTC)

Okay, I'm reading Orders of magnitude (length) and it sort of clears stuff up. I guess it is hard to ask such a question.

Anyhow, I'm pretty sure that if the observable universe sat down in a restaurant with a neutrino, the known universe would order a lot and the neutrino would probably have the small salad. Anna Frodesiak (talk) 00:31, 15 December 2015 (UTC)

But the universe would have to cover the check, because the neutrino has no charge. *groan* --71.119.131.184 (talk) 01:50, 15 December 2015 (UTC)

I suspect that joke was invented within a day or two of the neutrino's discovery. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:23, 16 December 2015 (UTC)

See the "Visualization" section under Planck length; you could sort of make the argument from that that it's a period. Wnt (talk) 03:35, 15 December 2015 (UTC)

Very nice, Wnt! Now that is something I can grasp. Many thanks. :) Anna Frodesiak (talk) 05:44, 15 December 2015 (UTC)

Anna Frodesiak, I have a clear memory of being stunned by the short documentary film Powers of Ten (film) (1968) when I first saw it as a college student in the 1970s. It makes the case that the realm of things that humans see and deal with every day is at the halfway point on the scale. Highly recommended. Cullen³²⁸ Let's discuss it 07:17, 15 December 2015 (UTC)

Thank you, Cullen328! I just watched it. I found it in my archives and actually remember watching it years ago. It is very good. Many thanks. :) Anna Frodesiak (talk) 08:04, 15 December 2015 (UTC)

The concept of "half way between" is not clearly defined. The arithmetic mean would be an object about half the size of the universe (if we could define such an object). The orders of magnitude approach leads to the Geometric mean, but there are other possibilities. Dbfirs 10:32, 15 December 2015 (UTC)

Does the universe really qualify as an "object"? However, if X represents the number of objects within that universe, then halfway would be approximately X / 2. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:38, 15 December 2015 (UTC)

You mean the size of the middle object when all objects are arranged in order of size? That would be the median which, I guess would be much smaller than the geometric mean ... probably around the size of a proton a neutrino since there are at least a million neutrinos for every proton. Dbfirs 17:24, 15 December 2015 (UTC)

No, I mean the size of half the total matter + energy in the universe. As to what the OP means, that's not altogether certain. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:34, 16 December 2015 (UTC)

I agree that half the total matter would be half the size. Usually, counting objects leads to the median, but we don't know what "objects" we are supposed to be counting here. Dbfirs 08:23, 16 December 2015 (UTC)

• Miss Frodesiak^* is clearly asking about the geometrical mean, as Dbfirs has pointed out, and the movie and later book editions of Powers of 10, which Cullen mentions, demonstrate graphically that everyday objects lie around that mean. See YouTube μηδείς (talk) 17:13, 15 December 2015 (UTC) ^*Of no relation to the Passyunk Avenue Frodesiaks

This stands or falls on the definition of an "object". It's arguable that the universe isn't "an" object - but rather a collection of objects. Sadly, the same could be said of a rock or an atom or even of a proton. If you allow a "collection" to be an object - then should we consider the collection of all of the people named "Steve" to be "an object"? If not, then calling the universe "an object" seems wrong...but if you do include collections, then should we consider "The set of all people named 'Steve' who were born under a full moon" to be a different object than the larger set of all people named "Steve"? If the answer to that is "Yes" then we can count "Everything in the universe made of hydrogen" to be "an object" - which is nearly as big as the entire universe.

Worse still, it's perfectly possible that the universe is infinite - in which case, the thing that's halfway between its' size and that of a quark is still infinite.

So you need a stronger definition. You can ask "What is the tallest mountain?" and we stand a good chance of getting you an answer - but "object" is just too vague. SteveBaker (talk) 21:21, 15 December 2015 (UTC)

If you look at time however the human lifetime is quite large, and the total time of life is a large fraction of the age of the universe so far. Graeme Bartlett (talk) 21:14, 15 December 2015 (UTC)

I am referring to the geometrical mean. And when referring to the universe as an "object", just pretend it is a big ball the size of the universe. Anyhow, "everyday object"? Wow. Isn't that like standing on an ink dot and saying that the entire universe is inside? That seems odd to me. From my person-size viewpoint, big seems bigger than small seems small. Anna Frodesiak (talk) 00:51, 16 December 2015 (UTC)

You're criticizing the responders, but you have yet to define what you mean by "object". Is the earth an "object"? Is the sun an "object"? Is a galaxy an "object"? Is a given cluster of galaxies an "object"? Also, geometric mean of what? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:39, 16 December 2015 (UTC)

Criticizing? Good heaven, no. I'm enormously grateful and just asking. I should have phrased it better. You see, this is why I always salt and pepper my posts with lots of smileys. :) It is so hard to judge tone. When I say "...Anyhow, "everyday object"? Wow. Isn't that...", I mean, really, wow. It is so cool that an everyday object is the "mean". And when I say "mean", as others have said above, I mean "mean" as in the middle or average sort of thing. I'm not even sure if that can be a thing considering it kind of means that half the objects are bigger and half smaller. I'm not too good at maths. :) With sincerity, plenty of smiles, gratefulness, humility, and deference to be sure, I would never criticize responses here. I am not qualified to do so. Best, Anna Frodesiak (talk) 08:41, 16 December 2015 (UTC)

Anna Frodesiak, perhaps you can't imagine just how small the elementary particles really are? We can't see the millions of bacteria on our skin, but these are enormous on an atomic scale. Dbfirs 08:29, 16 December 2015 (UTC)

Absolutely right! I just can't get my head around the very small. I can feel the magnitude when I think of the universe, but with the very small, I just can't imagine it. I think, for me, this is all about perception. For me, a universe inside a dot of ink is inconceivable. :) Anna Frodesiak (talk) 08:41, 16 December 2015 (UTC)

All is well, except you did not answer my question. For example, is the earth an "object"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:00, 16 December 2015 (UTC)

An object is some physical object like a tangerine or planet or bunch of grapes or sure, a galaxy -- anything that is or can represent a particular size. :) I'm really looking for that cubic volume that is between the things with the biggest and smallest cubic volumes. Anna Frodesiak (talk) 11:56, 16 December 2015 (UTC)

So the earth itself is an object, and the solar system is an object (which contains the earth) and the Milky Way galaxy is an object (which contains the earth), and the cluster of nearby galaxies is an object (which contains the earth), and the universe itself is an object (which contains the earth). So the earth is being counted multiple times. What does that do to the mean calculation? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:17, 16 December 2015 (UTC)

This might be a better example. Consider the state of Florida and pretend it's the universe. Consider one specific orange growing somewhere in Florida, and pretend it's the smallest object in that "universe". So there are multiple oranges on the tree, multiple trees in the grove, and multiple groves in Florida. What would be the mean, under your scenario? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:23, 16 December 2015 (UTC)

Good question. I don't know. Maybe a mountain? How about an ant as the smallest animal and an elephant as the biggest. I'd say a cat would be the mean. Anna Frodesiak (talk) 13:22, 16 December 2015 (UTC)

I should further add that in my hypothesis, Florida contains nothing except oranges, growing on orange trees. There will be a finite number of those kind of objects. So what would the mean be? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:34, 16 December 2015 (UTC)

But Elephants, ants and cats are "well-defined objects" - which makes it relatively easy...but atoms, solar systems and universes aren't...which makes it impossible.

Also, we have literally no idea how big the universe is. We only know how much of it we can possibly see (due to the limited age of universe and the finite speed of light) - it's almost certainly bigger than that - possibly very much bigger - and it's quite possible that the universe is infinitely big. Halfway between "tiny" and "infinite" is still "infinite" under any sane definition you can come up with. If it comforts you to take the "human-scale" answer - then by all means take it - but it's bullshit.

So, we can't (or at least "shouldn't") give you an answer...we just can't. This is the science ref desk and anything other than "There is no answer to this question" is scientifically untenable. SteveBaker (talk) 15:51, 16 December 2015 (UTC)

That's why "infinite" in the mathematical sense doesn't work. But for the sake of the example, let's suppose there is only one galaxy in the universe. What would the mean be? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:37, 16 December 2015 (UTC)

But there are constraints we can set based on reasonable definitions (which we've agreed to constrain ourselves by, for the purpose of providing an answer). For obvious reasons, it isn't always helpful to throw up our hands and say "it can't be defined ever so don't bother". It's OK to say "there are no absolutes, so we can't give an absolute answer", but we should always be able to follow that up with "we can still come up with a workable answer so long as we all understand and agree upon the approximations or assumptions we are making." So, for example, while "The universe" is not a well defined set of dimensions, the Observable universe is, and it is a sphere 8.8×10²⁶ meters across. That's a reasonable upper bound to set (as long as we all know that it isn't the real upper bound, and we're OK with that). Likewise, there is a similar level of "lack of knowledge" regarding things at the small end. Most elementary particles are assumed to be point particles, which have a size of literally zero, but this is a convenient assumption, just as the state of the universe beyond the observable universe is unknowable (and thus assumed to be infinite because there's no difference between infinite and unknowable here), the dimensions of elementary particles like quarks and electrons and neutrinos are unknowable (though in this case assumed to be zero, because there is no difference between zero and unknowable here). If we take the smallest composite particle for which we have a measurable size, that would likely be the meson, of which there are many varieties and which have a size on the order of the femtometer (10^-15 meters) Assuming we're dealing in the average orders of magnitude here, the midpoint between 8.8×10²⁶ and 10^-15 is about 10⁶ meters, or 1000 kilometers, or about the size of the planet Pluto. So if we put reasonable constraints on the sizes we're dealing with, the "object" which comes "midway" (in a logarithmic sense) between the smallest "thing" we can measure (a meson) and the largest "thing" we can measure (the observable universe) is on the scale of small planet or large moon. --Jayron32 16:31, 16 December 2015 (UTC)

You guys are too smart for me and this question I asked got out of my depth. I am sorry. I should have said "average", but even then, no. You must understand that I think of things so simply, like in terms of elephants and ants. I just figured there ought to be some sort of middle size. I agree that the question cannot be answered. If I ask what length is half way between the width of the smallest object and the width of the known universe, then it doesn't make sense either. I've go to learn to ask questions where I would have a reasonable chance of understanding the answer. I'm also asking unanswerable questions. Best wishes and a thousand thanks to all. Again, I am sorry. :) Anna Frodesiak (talk) 23:39, 16 December 2015 (UTC)

I don't think you need to apologize - it's a perfectly reasonable thing to ask - it just doesn't happen to have a clear answer. But you didn't know that when you asked - and in asking it, you provoked some very interesting replies - and lots of people learned stuff. We get these kinds of question all the time - and some of them are deeply fascinating. Take the classic: "How long is the coastline of England?" - the answer is (annoyingly) that there isn't an answer...but the reason that there isn't an answer is fascinating and takes us all for a stroll down some of the darker alleyways of mathematics.

So by all means, if you have a question - go ahead and ask it. SteveBaker (talk) 03:53, 17 December 2015 (UTC)

Fitting 7 coins around a single coin in another universe

(Splitting this off into a new question SteveBaker (talk) 15:19, 18 December 2015 (UTC))

Thank you Steve. . And I remember that coastline question in a documentary about fractals. Very interesting. As for future questions, you don't want to know. I still wonder if there could be a universe where 7 coins fit around 1 instead 6. :) Anna Frodesiak (talk) 23:32, 17 December 2015 (UTC)

Take a coin, place six identical ones around the perimeter - place another coin on top of it - all you need is a universe with three or more spatial dimensions - hmmmm....I wonder where we could find one of those?  :-) SteveBaker (talk) 02:58, 18 December 2015 (UTC)

I don't know but here's an infinite honeycomb where 12 coins should fit around a coin instead of 6. [1] Sagittarian Milky Way (talk) 03:24, 18 December 2015 (UTC)

Yeah - but unless we're in a non-euclidean space, those "coins" are all of different sizes and shapes - which (I think) is cheating! Perhaps we might find a sufficiently non-euclidean space in a universe where space-time is horribly distorted by enormous gravitational forces or something?

SteveBaker (talk) 15:19, 18 December 2015 (UTC)

high blood pressure/donating blood

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

The reference desk will not answer, and will remove, requests for medical advice. Nimur (talk) 00:49, 15 December 2015 (UTC)

We cannot diagnose the OP, but it does no harm to point out that cannabis is a drug, and effects of cannabis include some cardiovascular side effects. A judge may have called it "safer than aspirin", but that's not actually saying much. See also [2]. Wnt (talk) 03:50, 15 December 2015 (UTC)

Don't forget paranoia. Now, if someone would just ask if donating blood has an immediate effect on blood pressure... 209.149.113.52 (talk) 19:43, 15 December 2015 (UTC)

Orangutan humor?

You may be familiar with that video of a young orangutan "laughing" when being shown a (pretty poor) "magic trick". I tried to find an analysis of what was going on a bit more serious (scientifically speaking) than what you usually get. All I could find was this. Have you seen anything by a bona fide ape specialist? It certainly didn't come up in my top Google results. Contact Basemetal here 12:05, 15 December 2015 (UTC) PS: I am aware that, unfortunately, Dan Zaleski (the American tourist who posted that video) showed the orangutan the trick "a few times" and then decided to post only "his best reaction" (rather than post the whole sequence) which might make it difficult for anyone to understand what's really going on: what if what we see was the tenth time he showed him the trick and the orangutan was laughing at him)? Contact Basemetal here 12:05, 15 December 2015 (UTC)

Wikipedia has a short article titled Laughter in animals and this article presents an overview of recent research in this area, with links to actual studies and other articles on the general question of humor in non-human animals. --Jayron32 12:39, 15 December 2015 (UTC)

Thank you for these useful links. Has anyone seen anything relating specifically to this case though? Contact Basemetal here 17:01, 15 December 2015 (UTC)

What does the exact moment of sunrise and sunset signify?

I read the articles (sunrise and sunset), but I am still not exactly clear. So I ask my question here. The news will report sunrise and sunset as an exact time. Let's say that sunset is reported as 5:00 PM as a hypothetical example. So, what exactly is different from 4:59 PM and 5:00 PM? What exactly has happened at 5:00 PM that did not occur at 4:59 PM? Thanks. 2602:252:D13:6D70:14DE:69F5:F4C:EAE3 (talk) 20:21, 15 December 2015 (UTC)

See Sunrise equation for the calculation of sunrise (and sunset). 209.149.113.52 (talk) 20:29, 15 December 2015 (UTC)

Unless you are looking out to sea, or on a perfectly flat plain, your local sunrise and sunset are unlikely to be at the published times for your area. In theory, what happens at a 5 p.m. sunset is that at 4:59 p.m. you can just see a tiny part of the top edge of the sun, but at 5:01 p.m. all of the sun is below the horizon. Sagittarian Milky Way explains below why even in an ideal situation, the exact minute is unlikely to be observed. Dbfirs 21:17, 15 December 2015 (UTC)

(edit conflict) At sunrise the first point of Sun circle would appear if the Earth was free of obstructions (like buildings, mountains, and waves) and the same elevation everywhere. I believe that height is mean sea level but I'm not sure if anyone ever does it with the location's height (which would make more sense for Denver for example). The result is slightly wrong if the air isn't whatever temperature and humidity they use or doesn't have the same air density to altitude graph (coldness and to a small extent lower water vapor % makes astronomical objects appear higher in the sky). The Sun generally rises and sets slower the higher latitude you are (it takes many, many hours to at the poles) and temperature inversions happen when it's cold enough so high latitude sunrise predictions can be very wrong. If they don't calculate this every year (because of leap days and stuff) or use good enough formulas (because near perfect formula is very long) then that introduces some error. At midlatitudes everything happens about 5 seconds earlier for each mile east of the newspaper's spot. They might calculate for sea level eye height and if they do then even if they calculate for your point of beach exactly and that spot's mean sea level and the sea is glass smooth and the Sun is setting over it and the sunset tide is mean sea level and everything else I wrote till now is perfect it'll still be around a quarter minute too soon at midlatitude just because you're standing and 6 feet tall instead of swimming. If you moved your eyeballs to 9 inches above the glass sea then the prediction would be 5 seconds too soon. If you're up to you're nostrils in water and your eye is 2 inches above sea level that 2 inches still makes the sun set 2.5 seconds later. If you hold your breath and put your pupils 1 inch above sea level (this is some calm sea!) then the sun sets about 1.667 seconds later because of that inch. (Reference: [3], the horizon is what hides the sun so that's the important part and 1 minute of arc is 4 seconds of right ascension but the sun sets in a slanting path at midlatitudes so add a little time for that)). Also, even if eyeball is in the place of prediction and everything else is perfect if it's only to the minute then it'll be at least 30 seconds wrong some days just for that, which is important if you're wondering about what's so special about 5:00 am. Make it 60 seconds wrong if they truncate. Sagittarian Milky Way (talk) 21:38, 15 December 2015 (UTC)

More important is that the published times for your area are actually times for a specific location in your area (e.g. the town hall). So you have to consider how far you are from the town hall. 89.240.30.128 (talk) 09:25, 16 December 2015 (UTC)

I mentioned that when I said it's about 5 seconds earlier for every mile east (and west would have to be later obviously). Sagittarian Milky Way (talk) 16:58, 16 December 2015 (UTC)

These days the times are recalculated every year but that wasn't always the case. During the Second World War Whitaker's Almanac started printing sunrise and sunset times for a variety of locations across the UK. After four years they just recycled the data for four years before. This continued for most of the second half of the twentieth century. When the almanac went over to computer typesetting they started using the accurate times provided by the Royal Greenwich Observatory. 89.240.30.22 (talk) 09:36, 16 December 2015 (UTC)

As Dbfirs is introducing some inaccuracies in his reply at "Length of Day" below, just to clarify:

• Dbfirs lives in the UK, so his responses purport to reflect the position as it is here.
• Leap seconds are not officially used in the UK. Published times are in GMT (or possibly BST in the summer, neither of which uses leap seconds).
• The only way that the general population will come into contact with leap seconds is if they listen to the "Greenwich Time Signal" broadcast periodically on BBC Radio 4.
• Very few people listen to the BBC, and even fewer listen to BBC Radio 4. 89.240.30.73 (talk) 09:59, 16 December 2015 (UTC)

I don't know about your other points (though "Leap seconds are not officially used in the UK" seems implausible), but "Very few people listen to the BBC, and even fewer listen to BBC Radio 4" is simply untrue. From 2013 data: "we saw a record 11m tuning in to the station each week". More recently, the report linked from here for April-June 2015 shows "average weekly reach" for BBC radio as 35m, with 10.6m for Radio 4. (And that doesn't include the World Service, with an estimated audience of 210m.)

The UK doesn't use the leap second? - that seems incorrect too "At the last meeting in Norway in September, 20 countries voted in favor of dropping the leap second... but the U.K., Russia, and six other countries opposed the proposal, which was enough to quash it".[4] Richerman (talk) 17:18, 16 December 2015 (UTC)

It has to, otherwise it would be 13:00 in the UK and 12:59 or 12:58 in the rest of the world. We can't have that. The non-leap second time (I think GMT) is probably still used for almanacs, especially more technical almanacs so you don't have to screw with leap seconds when navigating with a sextant or calculating astronomy. Almanacs for farmers instead of astronomers and sailors probably mention leap second-less time little at most. Sagittarian Milky Way (talk) 17:31, 16 December 2015 (UTC)

89.240.30.73 seems to be making comments deliberately intended to provoke, in the same style as a known banned user from the same city. Is my suspicion justified? See our article Greenwich Time Signal for accurate facts, and note that millions of clocks in the UK are synchronised with the atomic clocks at the National Physical Laboratory through Time from NPL broadcast on a 60 kHz carrier from Anthorn Radio Station, and others use a Radio Data System for their time. All three systems broadcast Coordinated Universal Time, complete with leap seconds. Dbfirs 20:05, 16 December 2015 (UTC)

Thanks, all. 2602:252:D13:6D70:258E:2FDC:D3C8:55C9 (talk) 15:41, 17 December 2015 (UTC)