Wikipedia:Reference desk/Archives/Science/2016 May 16

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May 16

.1 (leading 0 is implicit)

Is .1 (leading 0 is implicit) always the same as 0.1? And even if mathematically they are the same, could a manual of style advise editors not to use the one or the other?--Llaanngg (talk) 01:37, 16 May 2016 (UTC)

yes and yes, seems obvious..is there a specific context for asking this?68.48.241.158 (talk) 01:44, 16 May 2016 (UTC)

It may not be the same if the "." in .1 is actually a blemish on the paper. Note that there could be infinite leading zeros, as there is no unit, no ten, no hundred etc.... Our style guide should have something to say on the matter. Graeme Bartlett (talk) 01:46, 16 May 2016 (UTC)

The style manual says to use the leading 0:Wikipedia:Manual of Style/Dates and numbers#Decimals. Graeme Bartlett (talk) 01:59, 16 May 2016 (UTC)

Indeed the mathematics and interpretation of .1 is the same as 0.1 - and style determines which to use. The leading '0' is a huge aid to readability - especially when you consider that there are parts of the world where the role of '.' and ',' are interchanged in their meaning within numbers. SteveBaker (talk) 02:17, 16 May 2016 (UTC)

I think Steve should have stopped before "especially". In areas where "," is the decimal point and "." is the thousands separator, neither ".123" nor "0.123" is a possible number; instead we would be talking about ",123" and "0,123", neither of which is a possible number where we live. --69.159.60.83 (talk) 05:51, 16 May 2016 (UTC)

The problem comes in when it is used cross-culturally. For example, if we wrote "Color was blue,and the quantity measured,123", that might be taken to mean 0.123 in a place where a decimal comma is used. Adding a space after each comma helps reduce this type of error. StuRat (talk) 16:30, 16 May 2016 (UTC)

Why is this question on the Science Desk? Joseph A. Spadaro (talk) 04:21, 16 May 2016 (UTC)

Perhaps because such questions of notation often arise in reporting on science. —Tamfang (talk) 00:57, 2 July 2016 (UTC)

Species of deer fly

A deer fly with a centimeter scale

Can anyone identify the species of this deer fly (from near the Atlantic coast of Georgia)? Bubba73 ^{You talkin' to me?} 03:25, 16 May 2016 (UTC)

Not a very clear image - but it could be Chrysops vittatus (full description here - http://animaldiversity.org/accounts/Chrysops_vittatus/ ) 81.132.106.10 (talk) 20:44, 16 May 2016 (UTC)

Thanks. It is hard to take a photo of things that small. Here is another one. Bubba73 ^{You talkin' to me?} 02:54, 17 May 2016 (UTC)

Another view

Follow-up question

Why do the eyes change from one photo to the other? (It is the same deer fly.) Bubba73 ^{You talkin' to me?} 03:36, 18 May 2016 (UTC)

It's a still dead no eyed deer fly. Vespine (talk) 06:28, 16 May 2016 (UTC)

Not sure if it's the same as for fish, but their eyes cloud up after death, so you want clear eyes to get fresh fish. StuRat (talk) 15:06, 18 May 2016 (UTC)

That is probably it. The first photo was taken shortly after death - the other was several hours later. Bubba73 ^{You talkin' to me?} 22:31, 18 May 2016 (UTC)

User:Bubba73 That might be part of it, but it's not the only factor, nor even necessarily the dominant factor. When you take a photo of an insect's compound eye, it's sort of like taking a photo of a sphere composed of cylindrical straws - so very slight changes in angle can change the apparent darkness of one tiny lens. Look at the photo of Arthropod_eyes, and you'll see lots of refractive shimmering colors, like an oil slick. So even if the two photos were taken within seconds, you'd expect rather different-looking eyes. In this case, there may be some effects of dessication, but flies are rather robust to water loss. 65.111.115.16 (talk) 15:19, 19 May 2016 (UTC)

Can a pregnant woman become pregnant again while still pregnant?

Can a pregnant woman become pregnant again while still pregnant? Just curious about that odd situation. If this were the case, the woman might give birth to a baby. And then, say, 4 months later, give birth to a second baby. Is this possible? Has this ever happened? Does this have a name? Thanks. Joseph A. Spadaro (talk) 04:23, 16 May 2016 (UTC)

Superfetation which has happened with human children conceived two months apart. This was very easy to find with google. μηδείς (talk) 04:59, 16 May 2016 (UTC)

It's possible, as noted, but very rare and abnormal in humans. Normally in humans, ovulation is suppressed during pregnancy by high levels of progesterone. Most hormonal contraceptives work the same way, by containing a progestin that has the same effects. --71.110.8.102 (talk) 06:30, 16 May 2016 (UTC)

It is worth noting that although there are a few recorded cases of a second conception (though only during the early stage of the first pregnancy - two months seems to be the longest recorded gap) the births in each case have been simultaneous. It seems extremely improbable that the first conceived child could be delivered, while the second one then continued to develop in the womb for a significant period. 81.132.106.10 (talk) 08:21, 16 May 2016 (UTC)

However, there are cases where twins are born some months apart because of danger to one of the babies. Do a Google search on "twins born some months apart" for examples. --TammyMoet (talk) 10:06, 16 May 2016 (UTC)

I believe these two cases can be reconciled by stating that it normally requires medical intervention to deliver only one of the babies without the other(s) being born soon after. A C-section, presumably, is the normal medical intervention. Not sure if this would be possible with identical twins, which share the same amniotic sac (could it be cauterized/sutured ?). StuRat (talk) 16:18, 16 May 2016 (UTC)

No, StuRat; monoamniotic twins are extremely rare. DMacks (talk) 16:37, 16 May 2016 (UTC)

Not that rare, "about 1% of twin pregnancies", according to our article. StuRat (talk) 17:17, 16 May 2016 (UTC)

No Stu. 0.00285714285714% to 0.0016666666666667% of pregnancies is extremely rare!--TMCk (talk) 17:41, 16 May 2016 (UTC)

I don't think it is. We wouldn't call a disease that was that common "extremely rare", as then up to 200,000 people worldwide would have it. But, again, you are taking the percentage of the entire population, while I was only talking about identical twins. StuRat (talk) 17:47, 16 May 2016 (UTC)

Sure. That's why you removed the inconvenient part of your post. Full of it as always.--TMCk (talk) 17:55, 16 May 2016 (UTC)

I didn't notice that they had stated the odds directly in the article the first time, and removed my math and replaced it with a direct quote as soon as I did. And keep the attitude off the Ref Desk, please. StuRat (talk) 22:52, 16 May 2016 (UTC)

While it isn't a "disease", the accepted medical definition of "rare" is covered at Rare disease, with definitions ranging from 1/1000 of 1/200,000 as being "rare". .002% is 1 out of 50,000 pregnancies. --Jayron32 17:57, 16 May 2016 (UTC)

Do they define "Extremely rare" ? StuRat (talk) 22:52, 16 May 2016 (UTC)

That would be rarer than rare. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:19, 19 May 2016 (UTC)

I actually believed something similar. But I also did what TammyMoet recommended. From there I read sources like [1] which suggest this can occur without apparent significant medical intervention medical intervention. In fact [2] suggests medical intervention in the opposite direction i.e. ensuring the second twin was delivered at the same time used to be more common.

Note also that the original discussion was about pregnancies with conception happening at different times. Monoamniotic twins are already rare enough. Monoamniotic non identical twins with conception happening at different times is probably as close to impossible as we get in biology.

Perhaps of more relevance to the original question is that in rare cases a women with double uterus have had successful pregnancies in both uterus simultaneously. StraighDope mention a few, another slightly more recent one is here [3]. Possibly conception happening at different times is more likely in these cases than in a more "normal" case although since there are so few of them, conceptions happening at different times would be more likely in more "normal" cases. (To be clear, I'm not saying conception at different times is likely if a woman has a double uterus, but rather the probability of it happening, low that it is, may be higher.)

Nil Einne (talk) 18:23, 16 May 2016 (UTC)

Would that be "double uteri" ? StuRat (talk) 22:56, 16 May 2016 (UTC)

Thanks. Let me follow up with a question of semantics. Let's look at two possible scenarios. Scenario "A": Two babies are conceived at different times, but both are born at the same time. For example, the first conceived is delivered normally today, but the second conceived is delivered early (prematurely), also today. Scenario "B": Both babies are conceived at the same time. One is delivered today, and the other is delivered some time down the road, maybe a month later (for whatever medical reasons). Are the babies in Scenario "A" properly called "twins"? And how about Scenario "B"? Thanks. Joseph A. Spadaro (talk) 03:56, 17 May 2016 (UTC)

(sorry, just an opinion, but I can't help myself): I think that if a woman spends a day with two babies (well, fetuses or embryos) inside her, she is carrying twins. And once a twin, always a twin. So I'd say A and B. Requiring the same moment for conception or parturition doesn't make sense because babies are rarely conceived nor born at precisely the same moment. (Well, identical twins are conceived at once, or fertilization might truly simultaneous, and maybe they can be "born" the same moment by Caesarian, but that's kind of stretching it) A consequence of this logic is that in theory baby 1 can be a twin of baby 2, and baby 2 of baby 3, but not baby 1 of baby 3. If someday that happens, I can live with that semantics. Oh, also I see the source used above actually uses "twins" to refer to staggered pregnancies two months apart in two uteri. Wnt (talk) 09:50, 17 May 2016 (UTC)