Science desk
< April 27	<< Mar \| April \| May >>	April 29 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

April 28[edit]

Girls having more moles on arms[edit]

This is a question I'm wandering about. Do you think on average girls have more moles on their arms than on guy's arms, focussing on teens and twenties? When wearing short sleeve shirts with arms exposed, I know girls tend to show more moles on their arms because girls tend to wear shorter sleeves than that of guys' as well as wearing sleeveless shirts more frequently. Asking a side question: do you think girls have greater average number of moles on their right arm than on the left; I can judge that based on the internet pictures I've seen. Planet Star 02:18, 28 April 2017 (UTC)[reply]

@PlanetStar: Do you perhaps mean freckles, rather than moles? I ask this because your question suggests to me a relatively large number. Moles (nevus or melanocytic nevus) are normally small in number, as far as I'm aware. Due to the potential for malignancy, a large number of moles would likely be of significant medical concern. As for numbers relative to gender, age, demographics, etc — I don't know. Murph9000 (talk) 02:47, 28 April 2017 (UTC)[reply]

No I mean moles. Moles are usually benign and are not usually of medical concern. But if moles suddenly appearing and are rapidly changing would be a concern. Moles are part of development. See a picture of moles on teenage girl's arm here. Planet Star 04:43, 28 April 2017 (UTC)[reply]

FWIW (not much), I'm a guy, and I have a similar density of moles on my arms/body. I think any casual personal observations are likely to be subject to confirmation bias, so we really need scientific sources to confirm or deny the hypothesis. This 1985 paper found in their survey (in New Zealand) no sexual differentiation in overall numbers, but that women have more on the arms, face and neck, while men have more on the back. From glances at other sources, there seems to be some correlation between mole development and sun exposure (though some moles are congenital) so this might reflect clothing and lifestyle habits in New Zealand (which might not apply elsewhere). {The poster formerly known as 87.81.230.195} 90.217.249.244 (talk) 05:15, 28 April 2017 (UTC)[reply]

remember also in New Zealand in the period before 1985, so it might not even apply in NZ any more. Nil Einne (talk) 06:51, 28 April 2017 (UTC)[reply]

Wind rose[edit]

Just for fun, I decided to look up the Wind rose for Portland, OR. But I got wildly different result from different[1] sites[2]. Which one is more correct? ECS LIVA Z (talk) 10:08, 28 April 2017 (UTC)[reply]

Are you sure they are in the same location in Portland? --Jayron 32 10:38, 28 April 2017 (UTC)[reply]

Here's current data for KPDX (Portland International Airport): KPDX. At the top of that page is a link to "past weather..." including Frequency of Wind DIRECTION, based on Time of Day. These data are compiled by the National Weather Service, and all the raw records are available at no cost.

A lot of internet websites will try to commercially package and re-sell these free government services, but you can always go directly to www.weather.gov or www.noaa.gov to browse for what you seek, directly from its source.

If you put that data into a wind rose (for example, using your favorite spreadsheet charting and plotting tool), you can see that there are many options for plotting the result - do you want to average all winds or only winds during specific hours (e.g. only during daytime)? Do you want to consider all months, or produce a wind rose for a specific month? ... and so on. So, you can imagine that a few variations on the final chart may occur, depending on the kind of analysis you care to conduct.

Looking at prevailing wind is not only fun, it's useful: for example, here's Planning and Design of Airports, which has a whole chapter on wind speed and direction as they apply to the ... planning and design of airports.

Nimur (talk) 19:24, 28 April 2017 (UTC)[reply]

The first site listed by the OP says that it uses observations, while the second site listed by the OP uses fairly coarse-resolution (30 km) model output (look at "General information" near the bottom of the page). Model output will always differ from observations. Shock Brigade Harvester Boris (talk) 00:41, 29 April 2017 (UTC)[reply]

Is "queen ant" or "queen bee" accurate or anthropomorphizing bees and ants?[edit]

The term "queen" sounds like a lofty title. Why not just call these queens "baby producers"? 50.4.236.254 (talk) 11:59, 28 April 2017 (UTC)[reply]

Because we use the word "queen". Language is neither logical nor precise, nor is the language use of millions of people subject to the momentary whims of someone such as yourself. The word has been "queen" has been used in this context for a long time, in English since 1807. You aren't going to change it because you don't like it. --Jayron 32 12:13, 28 April 2017 (UTC)[reply]

Doesn't every bee or ant in the respective colonies serve the queen bee or ant? If so, the term "queen" seems totally logical. "Baby producers" seems inadequate. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:24, 28 April 2017 (UTC)[reply]

That's assuming a one-way function. You can also assume the reverse: that the "queen" is serving the workers and replenishing the population, but not directly telling them what to do. 50.4.236.254 (talk) 12:32, 28 April 2017 (UTC)[reply]

That's true of proper royalty too. I mean, they theoretically serve a purpose that benefits the citizens of their domain. ApLundell (talk) 14:14, 28 April 2017 (UTC)[reply]

User:Baseball Bugs. It's complicated. Bumblebees are basically beaten into submission by the queen, and if she stops beating them for whatever reason, the strongest daughter will become fertile, start laying eggs, and start beating her sisters. Sometimes, in transition, there are multiple proto-queens, all fighting amongst themselves. Unlike human queendoms, ant colonies of many species have multiple fertile queens. Sometimes colonies established by multiple fertile queens. See Ant_colony#Organizational_terminology for some of the different ways they do it. Finally, though there are no true solitary ants, there are many solitary bees who "serve" no queen. SemanticMantis (talk) 19:13, 28 April 2017 (UTC)[reply]

The not-quite-aptness of the terminology is discussed in the article Queen ant.

On the other hand, they do form the center of their community, and they have servants that wait on them hand and foot. (Mandible and antenna?) So it's not entirely spurious.

In some species the queen has at least some small decision-making capabilities. In Honey Bees she has some control over the swarming behavior. (Although, surprisingly enough, the new hive construction site is chosen democratically. Swarming_(honey_bee)#Nest_site_selection)

ApLundell (talk) 14:14, 28 April 2017 (UTC)[reply]

The term "queen" better matches the modern role of the Queen of England. That is, she is well taken care of, but doesn't have much real power. StuRat (talk) 15:06, 28 April 2017 (UTC)[reply]

Don't use the term if you don't like it. "Queen ant" is technically informal, but plenty of myrmecologists use the term, even formal in scholarly writing e.g. (here [3]).

If you want to avoid anthropomorphic language, use gyne; that is the formal term for a queen ant, bee, or termite. See e.g. here [4] for usage in the scholarly literature.

There are also terms gynergate and ergatogyne that describe various intermediate forms between workers (erg) and queens (gyne). We also have gamergate and ergatoid. SemanticMantis (talk) 19:21, 28 April 2017 (UTC)[reply]

That's no solution at all, the Attic Greek γυνη "gyne" is the exact cognate of English queen, Welsh Gwen, and Russian жена "zhena", all meaning "wife, woman, queen", from the PIE root *gwena- μηδείς (talk) 16:08, 29 April 2017 (UTC)[reply]

The term "Queen" is also use for the vertebrate naked mole-rat and the Damaraland mole-rat. Interestingly, these are the only two eusocial mammals we know of, so they have a lifestyle and reproductive system similar to some of the ants and bees discussed above. DrChrissy ^(talk) 19:33, 28 April 2017 (UTC)[reply]

Hey @DrChrissy:. Not all authors consider those mole rates to be eusocial. Our NMR article gives this ref [5] which says they are "arguably" eusocial. As you may know, there are (still) competing definitions, even in this decade. Here [6] is an article that clearly considers them NOT to be eusocial, but instead semisocial, and also gives further refs on that. I'm wondering if this merits a more careful treatment in our article? SemanticMantis (talk) 20:23, 28 April 2017 (UTC)[reply]

@SemanticMantis: thanks for this. A while ago, I was heavily re-writing Tool use by animals. Every time I found one definition, another one popped up. It became apparent to me that authors were tweaking definitions or sets of criteria so that their observations or arguments were considered as "tool use". After looking at several articles on eusociality, I get a similar feeling. Having said that, you are perfectly correct that we should be informing the readers that there are multiple definitions/sets of criteria for eusociality. DrChrissy ^(talk) 20:41, 29 April 2017 (UTC)[reply]

So, humans aren't eusocial, because they do not divide individuals into reproductive and non-reproductive categories? What kind of social organization do humans have then? Homosexual humans do not reproduce. Do they make humans eusocial? 50.4.236.254 (talk) 19:53, 28 April 2017 (UTC)[reply]

No. It's when a species has most individuals non-reproductive that it becomes eusocial, as then the non-reproductive members have no purpose of their own, and only act like cells for the larger super-organism. I don't believe gay, infertile, or otherwise childless people in our society would say they have no purpose in life other than to serve the collective. StuRat (talk) 20:03, 28 April 2017 (UTC)[reply]

Eusocial has a definition. Some people might argue that some human societies may have counted as such, but in general we don't have obligate non-reproductive adults. Even gay people often reproduce, they're not sterile. Here's a nice article on evolution of sterility [7] in honey bees. The generally accepted reason that eusociality is so rare outside of Hymenoptera is because they have haplodiploid sex determination, and this messes with the evolutionary pressures, relative to diploids like us. Male bees don't have fathers and can't have sons, and sister bees are more related to each other than they are to their parents or potential offspring! This is the short version of why we think sterility evolved in those clades. See Haplodiploidy#Relatedness_ratios_in_haplodiploidy for more info. SemanticMantis (talk) 20:10, 28 April 2017 (UTC

Quite an attachment?[edit]

The idea came to me while using the Dremel.

If a tool resembling the one in the picture along exists, it would be a very capable way of making a neat hole in wood or plastic etc. Is an attachment like this there? Jon Ascton (talk) 15:13, 28 April 2017 (UTC)[reply]

You're looking for a Hole saw. They exist for dremels[8]. Notice that unlike the one you drew, they often(but not always) have a pilot bit in the center to guide them in. Otherwise they would skitter all over your work piece. ApLundell (talk) 15:18, 28 April 2017 (UTC)[reply]

Also notice the slots in the side of the saw pictured above. Some, but not all hole saws have these. The purpose is to allow you to insert a screwdriver or other tool to pry out the plug of wood, which often gets stuck in the saw after completing the hole. CodeTalker (talk) 17:07, 28 April 2017 (UTC)[reply]

The OP's image drill looks suitable for sawing large holes in soft material such as wood but the tools for the Dremel are for grinding small holes (3 to 12mm) in hard material. This is a single conical step drill for my cordless drill that gives a choice of hole sizes, works in most non-brittle materials and leaves suitable holes for countersunk wood screws. It's even occasionally useful as a crude reamer. Blooteuth (talk) 18:39, 28 April 2017 (UTC)[reply]

"Dremel"-tools dont have enough power for these kind of drills. Worse even you best use a bench drill because slightest changes in the drill angle will cause these drills to jam. --Kharon (talk) 17:03, 29 April 2017 (UTC)[reply]

That depends a lot on what you're trying to cut through. And you can certainly get a drill-press kit for a Dremel. (I was about to say that they're quite nice and very useful for people who need a drill-press that size, however I notice the reviews for the current version are terrible, they seem to have replaced some important steel components with plastic ones. It's always the way.) ApLundell (talk) 18:17, 30 April 2017 (UTC)[reply]

Alien fungus?[edit]

A friend of mine showed me this link purporting that alien fungus is growing on space stations. It sounds bogus, but I'm curious how that fungus grew on those places in the first place. Would terrestrial fungus somehow hitch a ride on a ship and then grow in space? ScienceApe (talk) 18:27, 28 April 2017 (UTC)[reply]

First of all, this is really old news, even if the UFO websites are just hearing about it. Here's a NASA story on the topic from more than 15 years ago. Microscopic Stowaways on the ISS.

Secondly, this is something that the NASA manned space flight program has studied really hard for a really long time. The pests are from Earth, not from outer space - they are Earth-based life forms that got on to the ISS hardware and somehow managed to survive on the interior and exterior of the space station, especially in fabrics, despite everybody's best efforts to sterilize the material before launch, during launch, in flight, and so on. Most astonishingly, some of these life forms don't die even if they're stuck on the outside of the station, exposed to harsh vacuum, temperature, radiation, sunlight, and so on.

Nimur (talk) 18:59, 28 April 2017 (UTC)[reply]

Sure, why wouldn't a fungus flourish inside a space station? The environment there is not so different than places molds grow on earth. Here's another NASA page describing how they specifically brought fungus to space to study how it grows there [9]. See research article and photos here [10].

For the *outside* of a space station, that's a little more impressive, but we have a long and growing list of organisms that can survive the vacuum of space. If tardigrades can survive out there, it's not so surprising that some fungi and bacteria can as well. SemanticMantis (talk) 19:05, 28 April 2017 (UTC)[reply]

Question about the Time Dilation[edit]

Is the longer path traced out by a light pulse in the triangle of time dilation REAL or pseudo like fictitious force relative to the stationary observer if I am not missing something in the following?

Please refer to the Time Dilation Triangle diagram in the link or you can make your own

Both upper and lower mirrors of the light clock are firmly attached to the ceiling and floor respectively of the moving frame.

Let the base of the time dilation triangle is AA’=s=vt’ where t’ is dilated time

Relative to the stationary frame

• The velocity of the moving frame is v in time t where t is not dilated. This means mirrors also move at v in time t (where t is not dilated).

• Length contraction also affect the exact position of the mirrors inside the moving frame

• The spatial distance covered by the moving frame at any time t is s=vt (where t is not dilated). Thus

• The spatial distance covered by upper mirror of the moving frame from B to B’ is s=vt (where t is not dilated)

• The spatial distance covered by lower mirror of the moving frame from A to A’ is s=vt (where t is not dilated)

Since the aforementioned spatial distances covered in t and t’ (BB’= AA”= s = vt’ and s = vt) are not equal therefore what would be the real distance of upper and lower mirror (or any stationary object) inside the moving frame from its original position B and A respectively relative the stationary observer 2001:56A:7399:1200:131:8B26:E7B6:F63 (talk) 23:25, 28 April 2017 (UTC)eek[reply]

The "real" distance traveled, from the perspective of the stationary observer, is vt. You would never calculate it as vt', since that value for time belongs to a different observer. To your original question: yes, the path traced is real, it has to be. How else is the light to pass between the mirrors from the perspective of the stationary observer? It's not clear to me what you are missing. Someguy1221 (talk) 00:08, 29 April 2017 (UTC)[reply]

If vt and vt’ are not equal then why the base of the triangle = vt’ in the article. — Preceding unsigned comment added by 2001:56A:7399:1200:219C:17B5:F876:9F02 (talk) 03:54, 30 April 2017 (UTC)[reply]

Because I had the coordinates backwards. In the article, t is the time in the moving reference frame, and t' is the time in the stationary observer's reference frame. Someguy1221 (talk) 18:24, 1 May 2017 (UTC)[reply]

The article is correct for t and t’ (dilated) but keep in mind that the mirrors do not trace out a longer path, therefore, the REAL spatial distance traced out by the lower mirror is vt not vt’ (as you admit earlier) therefore vt should be the base of the triangle not vt’ made from the perspective of stationary observer.

The REAL spatial distance covered by a pulse of light is the two hypotenuse (ct’) and the REAL spatial distance covered by a lower mirror is vt, the base of the triangle in the moving frame relative to the stationary observer. Aforesaid REAL DISTANCES can't even make a triangle. Let

Relative to the stationary observer.

The light clock of the article is at rest and the position of the lower mirror is at x. Thus Delta t = 2L/c where t is a time but not t’ or dilated

Now let the light clock starts moving with v relative to the said stationary observer,

The lower mirror is moved from its original position x to its new spatial position y in time t not t’ or dilated

This means REAL horizontal spatial distance covered by a lower mirror from x to y = vt not vt’. Thus

Shouldn’t the base of the triangle be observed vt instead of vt’ while deriving the equation of time dilation from the triangle? 2001:56A:7399:1200:CAA:8A25:E7D:8890 (talk) 02:24, 2 May 2017 (UTC)Eclectic Eccentric Kamikaze[reply]