Wikipedia:Reference desk/Archives/Science/2013 September 28

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September 28

Mould growth from artificially increased humidity

Can putting water in a bowl on a radiator, to moisturise a room, contribute to mould growth? Clover345 (talk) 00:46, 28 September 2013 (UTC)

No, because putting water in a bowl on a radiator isn't an effective way to moisturise a room. What you need to do is to poor that water on one or more towels and put these wet towels on the radiator. Count Iblis (talk) 01:38, 28 September 2013 (UTC)

That could be a fire hazard, once the towels are dry, depending on how hot that radiator gets. StuRat (talk) 11:07, 28 September 2013 (UTC)

Filled radiators don't get that hot! Electric convector heaters might overheat if covered, and of course electric radiant bars get very hot, but you shouldn't put towels anywhere near these. Dbfirs 15:59, 28 September 2013 (UTC)

A bowlful of water won't increase humidity by much, I agree, but every bit helps the mold grow. BTW, more effective ways to increase humidity, short of buying a humidifier, are to run the shower with a fan blowing air into the bathroom, or to boil water on the stove, but there you have to be careful not to let it go dry. Various forms of cooking also have the side effect of increasing humidity. StuRat (talk) 11:05, 28 September 2013 (UTC)

I doubt that most people would want mold growth, seeing as it is a health hazard. Mold growth, assessment, and remediation has more on the topic. Lack of ventilation, humidity above 50% and cold spots where condensation can form seem to be the main factors; also a previous flooding that caused mold would be a source for fresh mold whenever the conditions are right because the infected spots will have a lot of dormant spores. Ssscienccce (talk) 14:02, 28 September 2013 (UTC)

Agreed. If your room needs "moisturising" then most moulds won't grow there except in damp corners. A bowl of water on a hot radiator will help to gently increase humidity, and is unlikely to have a significant effect on mould growth unless the moisture is then condensing on a cold spot, as explained above. Dbfirs 15:59, 28 September 2013 (UTC)

What animals besides spiders have evolved more than two eyes?

75.75.42.89 (talk) 13:50, 28 September 2013 (UTC)

Anableps Richard Avery (talk) 14:33, 28 September 2013 (UTC)

Those don't really have four eyes, in spite of the name. See however our parietal eye article. Looie496 (talk) 14:44, 28 September 2013 (UTC)

I'm not sure how reasonable it would be to give a complete list of the known animals with more than two eyes. Many, many species of insects have more than two eyes (I think the most common number is two compound eyes and three ocelli). Mollusc eyes says that scallops can have a hundred eyes, and chitons can have thousands. I'm sure there are others. Effovex (talk) 14:43, 28 September 2013 (UTC)

Some echinoderms have multiple eyes, and some use their entire surface as a type of compound eye. μηδείς (talk)

Scyphozoa have multiple eyes; since they are the most diverged animals, it is possible that this is the ancestral condition, and various lineages have settled on two as a matter of natural selection. (Some authorities have suggested that eyes could have evolved and reevolved independently, but the common usage of Pax6-related genes makes me think some authorities just underestimate the Urbilaterian. (Dinoflagellates only have one, so far as I know, and I'll reluctantly accept that one is truly a separate evolution of the structure. :) ) Wnt (talk) 22:17, 28 September 2013 (UTC)

Scallops. Technically, they are animals. Plasmic Physics (talk) 09:30, 29 September 2013 (UTC)

This article might help: Simple eye in invertebrates. Vespine (talk) 03:28, 30 September 2013 (UTC)

Compactified on S₅ or T*S₃

In the context of string theory, in the phrase "compactified on S₅ or T*S₃", what exactly are S₅ and T*S₃? Red Act (talk) 15:13, 28 September 2013 (UTC)

P.S. The phrase is used about 15 seconds into Bohemian Gravity, so I presume the terminology isn't anything too obscure. Our Compactification (physics) article, however, is no help. Red Act (talk) 17:52, 28 September 2013 (UTC)

As a non-physicist and non-mathematician, I would assume that S₅ refers to the Randall–Sundrum model and T*S₃ refers to normal Minkowski space. But this conjecture is not receiving support from any of our articles. Tevildo (talk) 22:27, 28 September 2013 (UTC)

I think S_5 and S_3 are Symmetric groups. I'm not sure about T. Dauto (talk) 13:05, 29 September 2013 (UTC)

Are you sure it wasn't S⁵? I'm guessing that they're talking about the 5-sphere and the join (see [1] for more) of the torus and the 3-sphere. You may have seen ADS₅, in which case take a look at Anti-de Sitter space. Random sources: [2], [3], [4]. Note: I'm guessing that "*" is the join, I'm not familiar with the source you mentioned, it could be something else, but I think the join makes sense.Phoenixia1177 (talk) 13:37, 29 September 2013 (UTC)

I didn't think that one out, T*S3 is the Cotangent bundle, see here [5]. Sorry for that, I don't know why I thought the join made sense...! Anyways, cool video (I realized you linked to it:-) ).Phoenixia1177 (talk) 14:41, 29 September 2013 (UTC)

Thanks! Red Act (talk) 22:25, 29 September 2013 (UTC)

How do you show stacked staircases in a building plan?

In the plan for a floor of a building, how do you graphically show it when the same part of the floor (viewed from the top) has stairs connecting to the floor above and stairs connecting to the floor below? — Preceding unsigned comment added by 173.49.18.74 (talk) 15:35, 28 September 2013 (UTC)

Well the bottom of the stair up and the top of the stair down can't be in exactly the same place, so you show the stairs there, possibly with an right-angled arrow to show which way they turn. Rojomoke (talk) 18:30, 28 September 2013 (UTC)

I think the OP wants to know about a situation like this:

            _|
          _|
        _|
      _|                              
    _|
  _|
_|                              
--------------|
             _|
           _|
         _|
       _|                              
     _|
   _|
 _|                              

where the two staircases are vertically above each other, and "up" is the same direction for both. Our architectural drawing article states that stairs are only shown up to the plan level, and that the plan level is "three feet / one meter" above floor level, without (unfortunately) citing a source for this. (Most of the links from the article are dead, as well.) Based on our article rather than a definitive source, I would therefore say that the plan should show the first three feet of the staircase to the upper floor, and the last [room height - 3'] of the staircase from the lower floor, with arrows indicating the "up" direction on both. However, this may be incorrect. Tevildo (talk) 21:51, 28 September 2013 (UTC)

What does this mean in a floor plan:

____
|===|===|
|===|===|
|===|===|
|===|===|
     ----

? Plasmic Physics (talk) 23:08, 28 September 2013 (UTC)

This is the more conventional arrangement, where the "up" and "down" staircases are next to each other rather than above each other, and the user only has to turn through 180° to get from one to the other, rather than having to walk the length of the corridor. Normally, there should be arrows on each staircase indicating which is "up". Tevildo (talk) 23:26, 28 September 2013 (UTC)

Stairs normally are built in a sort of corkscrew ascending arrangment, requiring small landings where the user makes simple U-turns. Stairs such as the OP apears to describe would be very unusual, and would require a sort of extended mezzanine or landing where the user makes a u-turn, a straight walk, then another u-turn. It would require an excessive number of steps in each flight in order to retain sufficient soffit in the stair well, and so would not pass building regulations. As it is unusual, I would expect it to be drawn as a few steps truncated in each floor plan, with a text notation "Stairwell: See sub-drawing A" and include a special plan of the mezzanine if required and elevation of the stair & landing arrangement. 121.215.63.7 (talk) 23:45, 28 September 2013 (UTC)

Stacked escalators are not uncommon in shopping malls, where they help save floor space , and compelling shoppers to walk the extra number of steps (past some display items) is a desirable feature. A plan drawing for such an arrangement is shown on page 17 of this PDF. Also in houses, the stairs leading to the upper floor and the basement from the "main level" are often stacked (since, again, it saves floor space, and traveling from the basement straight to the upper floor is relatively rare); see plan drawing in Figure 16-70 of this book. Abecedare (talk) 00:21, 29 September 2013 (UTC)