Science desk
< January 23	<< Dec \| January \| Feb >>	January 25 >

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.

January 24

Interplanetary travel

In Kerbal Space Program, players have put together this map, showing the delta-V required to travel between the planets and moons of the Kerbal solar system. There's also this calculator for finding launch windows.

I can't seem to find a similar map or tool for the real solar system. Does anyone know of one? I'm very curious, for example, what the minimum delta-V is to get from Earth to Mars using the Interplanetary Transport Network. --140.180.241.138 (talk) 03:17, 24 January 2014 (UTC)[reply]

From what I remember, once you're out of Earth's gravity well, getting to Mars can be done with close to zero energy, if you don't mind taking millions of years to get there. It's theorized that Martian meteorites got here that way. 50.0.121.102 (talk) 08:53, 24 January 2014 (UTC)[reply]

This is equivalent to the Kerbal map for Earth and Mars. I think it is based on Hohmann transfers, like your map, not the ITN and other delta-V reducing techniques. Katie R (talk) 12:44, 24 January 2014 (UTC)[reply]

Apparently, the same authors have made a delta-v map of the real solar system. You can view it here. Some of it's shortcomings are discussed here where the NASA trajectory browser and how to use it is also discussed. Obviously, NASA is a rather more reliable source for this information if you are actually planning to make that journey. Spinning Spark 13:11, 24 January 2014 (UTC)[reply]

mermaid morphology

Mermaids are mythical creatures with the top half of a human and the bottom half of a fish. However, I noticed that while depictions of mermaids show scales like a fish, the tail is oriented like that of a dolphin (that is, moving up/down (like a dolphin) rather than side to side (like a fish)). Anyone know why there is this inconsistency? I would think that even before any particular scientific classification of the animal kingdom people would be able to tell the difference between a fish and an aquatic mammal. 173.35.158.194 (talk) 03:20, 24 January 2014 (UTC)[reply]

They're often portrayed as sitting on a rock, and generally as human-like as possible. Clarityfiend (talk) 04:04, 24 January 2014 (UTC)[reply]

"Fish" has not always had the strict definition it now has. At one time it simply meant any animal that lived exclusively in water. Hence, eating beavers in Lent, when the only animal allowed to be consumed is fish, has traditionally been allowed for Catholics (in the days when hunting and eating beavers was considered acceptable). Spinning Spark 04:10, 24 January 2014 (UTC)[reply]

Agreed. In Moby-Dick (1851), Melville takes up the best part of a chapter rehearsing the various arguments as to whether a whale is a fish or a mammal, and finally comes to the conclusion that it is a fish. Alansplodge (talk) 11:19, 24 January 2014 (UTC)[reply]

I think the up/down tail is influenced more by the way humans swims, or might swim if they had a tail, see monofin. It would be very hard, near impossible, for a human to swim with a side to side motion. Disney has also played a large part in fixing the mermaid representation. Representations of mermaids prior to the widespread ability to swim amongst people do not always follow this pattern. Spinning Spark 04:25, 24 January 2014 (UTC)[reply]

Have a look at this mermaid - very fishy! Alansplodge (talk) 13:17, 24 January 2014 (UTC)[reply]

See Sirenomelia. Your mistake is in thinking mermaids are a fiction! :) [though I recall that article having a better picture of an otherwise healthy-looking infant ... so far I didn't find it in the history. I ought to write up some python app to run through all the history revisions and extract every image ever posted to an article. Wnt (talk) 14:14, 24 January 2014 (UTC)[reply]

Where you looking for File:Sirenomelia2.jpg? I won't actually post it here so readers who don't want to be grossed out don't have to look at it. Gross-out warning for the present article as well. Spinning Spark 15:50, 24 January 2014 (UTC)[reply]

I suppose it comes about from the thought that human hips and even, perhaps, knees would be present in the mermaid - that would certainly require the movement of the tail up and down rather than side-to-side - and that in turn means that the tail flukes would have to be whale/dolphin-like rather than fish-like. Remember that some cultures believed that the skeletons of large marine mammals like the manatee and dolphin were really mermaid skeletons. Also, note that some varients of the mermaid myth give them two "tails" - appearing as scaley legs, each tipped with a fin that looks like a diver's flipper. SteveBaker (talk) 15:43, 24 January 2014 (UTC)[reply]

This is probably the answer, for the most part anyway.

If you assume that your mermaid has human-like hips, (Necessary for 'sexy' mermaids) then the tail has to be oriented like a dolphin's for the whole thing to "work". (Especially for animation. Disney has probably contributed a lot to the modern mermaid imagery.)

Functional mermaid costumes actually used for swimming are pretty much required to have the flipper move front-back like dolphins, a human couldn't move her legs left and right like a fish.

Less human, Non-'Sexy' mermaids, like the fiji mermaid have all kinds of tails. There's some images in the Mermaid article. APL (talk) 16:50, 24 January 2014 (UTC)[reply]

There's a lot more diversity in mermaids that what you describe. As mentioned above, some have more "fish" style tails, and the cetacean/true fish distinction is not that old. For examples of mermaids that don't fit your description: the famous Starbucks mermaid has two tails, or a split tail:[1]. Some mermaids have fish tops and human bottoms, like this classic Magritte [2]. You also might be interested in this WP user's article on the "Mermaid problem" [3]. SemanticMantis (talk) 16:55, 24 January 2014 (UTC)[reply]

René Magritte would hardly be expected to portray anything "normal" or "standard", or even the least bit functional. All his work is pretty much the antithesis of all those things. Spinning Spark 17:28, 24 January 2014 (UTC)[reply]

Sure, but he wasn't the first to depict mermaids that way, and my main point is that there isn't just one canonical mermaid, there are many depictions of this fantastical creature. SemanticMantis (talk) 17:51, 24 January 2014 (UTC)[reply]

I can well understand Fry's conundrum in an episode of Futurama where he befriends a mermaid, and agree with him that it would be much better if the fish and human parts were transposed. That way, at least, you could consummate the relationship. What, however, would the kissing feel like? Myles325a (talk) 03:32, 28 January 2014 (UTC)[reply]

Human brain question.

Does the human brain work best in pictures? There are phrases such as "a picture is worth a 1000 words" and our society seems to be full of pictures, diagrams, charts etc. However some people are very good with numbers or words. Others are good at reasoning and logical deduction. I know there are alot of articles and research around different types of intelligence and ways the human brain works but is there something which is common for all human brains? For example, do all human brains work best with pictures? Are all other types of intelligence, such as those I've listed just an addition to that? Clover345 (talk) 03:32, 24 January 2014 (UTC)[reply]

We have a very capable visual system and images are able to represent a large degree of data (depending on situation). Beyond that, though, I'm not exactly sure what it would mean to think in pictures as opposed to something else; at least, not in any way that's rigorous enough to attempt an answer. As for the idiom "a picture is worth a 1000 words", I think it's very subjective and very contextual: a picture of starving children will be more compelling than any description of starvation, a diagram of a machine will, probably, be more clear than a description, etc. However, there's plenty of things that we can't picture, or that pictures would mislead us about, mathematics and physics abound with these (picturing an atom usually ends up as imaging a small solar system, that is quite misleading, but also quite hard to avoid - etc.). Vision is a powerful method of presenting information/ideas, but it isn't the only one, nor do I think it is the sole primary one; again, it's a matter of what the idea is and who you are presenting it to. --Note: I have no citations and am approaching your question from a loose concept of "thinking in pictures", I'm sure there are more precise senses and answers, thus, if you had something more narrow in mind, just disregard this:-)Phoenixia1177 (talk) 06:00, 24 January 2014 (UTC)[reply]

You basically answered your own Q, some people think best in pictures, some don't. People blind from birth, for example, probably don't think in pictures. StuRat (talk) 06:47, 24 January 2014 (UTC)[reply]

In terms of raw bandwidth, our eyes are by far the fastest way to get data into our brains. Audio signals top out at around 40kHz, touch, taste, smell, balance, pain, proprioception and thermal senses have speeds in the tens of bits per second - but our eyes can pull in millions of pixels worth of data at tens of frames per second. There is also much more brain matter handling vision than sound or any of the other senses. That's why diagrams can generally convey data much more rapidly than the other options. SteveBaker (talk) 06:49, 24 January 2014 (UTC)[reply]

I think your ears are operating at the Nyquist rate :) . Humans generally are around 20-22 kHz (with good hearing at age before iPod.) --DHeyward (talk) 16:11, 24 January 2014 (UTC)[reply]

Perhaps he's sending separate signals to each ear. Doubling the data rate. APL (talk) 16:58, 24 January 2014 (UTC)[reply]

Nobody's eyes can "pull in millions of pixels worth of data at tens of frames per second". 84.209.89.214 (talk) 23:39, 24 January 2014 (UTC)[reply]

Re other types of intelligence, yes, empathy or emotional intelligence to use the buzzword of a few years back. 50.0.121.102 (talk) 09:09, 24 January 2014 (UTC)[reply]

Also known as the "Hurray! Everyone's a winner!" buzzword. --DHeyward (talk) 16:11, 24 January 2014 (UTC)[reply]

A human may stroll through a forest and catch sight of an ear and a striped tail projecting from the undergrowth. A person inclined to logical deduction would infer the probable size of a hypothetical creature that bears the ear and tail, then would seek in memory knowledge about known creatures of matching size, colour and habitat; that would be followed by estimations of the abilities of the candidate creatures to cause him harm; eventually he would gauge his need to carry out a life-protecting strategy such as retreating along his path. In contrast, a better equipped human in that situation has a lively pattern recognition i.e. "thinks in pictures". He immediately connects the (partial, noisy) evidence of the ear and tail to a vision of a tiger, which immediately stimulates his Fight-or-flight response, likely an escape requiring intense muscular effort, supported by all of the body’s systems. These scenarios demonstrate that A) the (human and animal) brain's ability to think in pictures has evolved as an optimum way to handle incomplete sensory data where any delay threatens survival, and B) the (human only) brain's trained ability to digest and develop logical deduction without emotive bias is the comparatively slow but only way that collective human Knowledge is acquired, validated and eventually preserved for generations in an encyclopedia. Educators are most effective when their teaching activates both types A) and B) of intelligence and they are less effective when learning depends on either A) alone (e.g. textbooks that are literally text-only such as language grammar books) or B) alone (videos without textual reference or formal exam). 84.209.89.214 (talk) 12:29, 24 January 2014 (UTC)[reply]

Roughly half of the human brain is devoted to vision -- processing visual input and controlling eye movements. As Phoenix said, our visual bandwidth is orders of magnitude higher than the bandwidth of any other mode of communication we can perform. Looie496 (talk) 21:10, 24 January 2014 (UTC)[reply]

This general topic is a recurring theme on the TV series "Brain Games": How when we see something only vaguely or partially, our brain uses our previous pattern-recognition experience to fill in the gaps as best it can, and assess the situation. We're not perfect, and that tendency to fill in can sometimes lead to mistakes or failure to see other things. But it's vital for survival. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:32, 25 January 2014 (UTC)[reply]

O2 arena london structural engineering

Is there a reason the O2 arena in london is missing seating stands on the upper tier of the front part of the arena, from a structural engineering point of view? Clover345 (talk) 12:21, 24 January 2014 (UTC)[reply]

While seats full of people would add a significant amount of weight, even more weight could be added if it's filled with standing fans, which could be packed tighter. Do we know what the intended use of that area is ? Maybe it's meant for people in wheelchairs ?

As far as structural concerns, if it has a cantilever design, as opposed to support columns at the front, then the torque created at the cantilever attachment points would be a concern, and weight at the front of the upper tier would contribute disproportionately to the problem. Do we know if it has support columns at the front ? StuRat (talk) 17:33, 24 January 2014 (UTC)[reply]

Science of steaming food

I have a food steamer, which consists of an insert full of holes, placed inside a stock pot. The steamer holds the food and the stock pot holds the water. The problem is, since the holes on the steamer insert are down the sides and on the bottom, small food items or liquids drop through the holes. I'd rather eat them than have to clean them off the stock pot later.

So, my question is, if we eliminated the holes on the bottom, and halfway up the side, leaving only holes near the top, would it work as well to steam foods ? Or, for that matter, if we eliminated the holes entirely, would the air gap at the top be enough to fill the inside of the steamer with steam ? Would it slow the steaming process down, or even stop it, for some reason ? So, let's say we reduce the open area between the two by 90%, would that increase cooking time by 10X ? (I'm guessing no, that it would make little difference.)

(BTW, those who saw my previous post on this topic know I was looking for stainless steel bowl to place in the steamer to solve this problem. I ended up using a ceramic bowl, which works, but the volume is much smaller than if I could use the entire steamer basket. I also tried Crock Pot liners (plastic bag inserts), but they were too small for my steamer basket.) StuRat (talk) 18:56, 24 January 2014 (UTC)[reply]

The problem is that without holes on the bottom, water will condense inside and fill up the steamer. Looie496 (talk) 21:07, 24 January 2014 (UTC)[reply]

Yes, that does happen, especially if I start with frozen ingredients, but I'm OK with that (also tomatoes and other foods will drain their juices). I end up with vegetable soup, with no risk of it burning, which is exactly what I wanted all along. If I make soup the normal way, I have to use excess water and/or watch it like a hawk, to prevent it from boiling dry, and I'd have to stir periodically to prevent burning at hot spots on the bottom, and burning at the waterline can also occur when using a gas stove. But this way, I can "set it and forget it". (Well, it would eventually boil dry, too, but the much larger water reservoir in the covered stock pot would take many hours to boil off.) Of course, this does create excess heat and humidity, but those are welcomed in winter. (I don't make soup in summer, I eat cold food then.) StuRat (talk) 01:13, 25 January 2014 (UTC)[reply]

I feel silly for saying something so obvious, but steamers are made for people who want their food steamed, not for people who want their food simmered. Looie496 (talk) 18:38, 25 January 2014 (UTC)[reply]

Well, call it a simmerer instead of a steamer then. It's actually a bit of both, as the food at the top and near the start is steamed, while that at the bottom and near the end is simmered. I like to put some lentils and rice in the bottom, as that needs to be simmered, while the veggies and salmon fillets at the top can be steamed. StuRat (talk) 02:07, 26 January 2014 (UTC)[reply]

If you don't want to actually steam the food, then you possibly just want a bain-marie. I have a similar stock pot plus steamer, and managed to find a metal bowl which fits in in the same way as the steamer (not designed as such, just happens to be the right width) MChesterMC (talk) 10:13, 27 January 2014 (UTC)[reply]

Yes, that was originally what I wanted, but it was difficult to find a large double boiler (that's what we call those in the US), as they all seem to be designed for melting a bit of butter or chocolate. I already own a small double boiler for that purpose. I actually find this steaming setup preferable, though, as I can steam a salmon fillet on top, which gives a much better result than either boiling or microwaving it.

But, if you independently added a bowl to your steamer, just like I did, this seems to indicate there is a need for a semi-steamer/semi-double boiler setup. Thus my Q, would plugging up most of the holes, only leaving a few open at the top, cause any problems ? StuRat (talk) 02:31, 28 January 2014 (UTC)[reply]

Fingers versus thumbs

I wasn't sure whether to ask this here at the Science Desk or over at the Language Desk. I settled on here. I am just curious, why is it that the thumb is (sometimes) not considered to be a "finger"? At other times, it seems that it is. I read the thumb article, which didn't really address this (unless I missed it). Thanks. Joseph A. Spadaro (talk) 20:28, 24 January 2014 (UTC)[reply]

It's always a finger. Otherwise how could we have five on each hand, and a middle one? Clarityfiend (talk) 20:31, 24 January 2014 (UTC)[reply]

Always? No, I have heard it said (many different times in many different places) that the hand has four fingers and a thumb. For whatever reason, the thumb is not "counted" as a "finger". I just wondered if there was some reason behind this? Thanks. Joseph A. Spadaro (talk) 20:35, 24 January 2014 (UTC)[reply]

According to Wiktionary, fingers are "one of the long extremities of the hand, sometimes excluding the thumb." According to the OED "one of the five terminal members of the hand; in a restricted sense, one of the four excluding the thumb." So yes, the thumb is sometimes excluded. I would have thought that it was fairly self-evident why the thumb is considered separately. Spinning Spark 20:57, 24 January 2014 (UTC)[reply]

Thanks. But, what is the "self evident" part? I obviously know how the thumb is different than the other four; the question is why would it not be considered/called a finger? Thanks. Joseph A. Spadaro (talk) 21:42, 24 January 2014 (UTC)[reply]

Because language is funny that way, which usually is a sign that humans are funny that way. Are Neanderthals human or not? Are dogs wolves or not? Are whales fish or not?Yes, I know the scientific answer.. Is a foil a sword? Pluto a planet? --Stephan Schulz (talk) 21:56, 24 January 2014 (UTC)[reply]

Good examples, especially Pluto. Joseph A. Spadaro (talk) 22:13, 24 January 2014 (UTC)[reply]

It very much depends on the context. In keyboard music, the thumb is not only a finger but is primus inter pares, as it were, being counted as Finger No. 1. -- Jack of Oz ^{[pleasantries]} 03:04, 25 January 2014 (UTC)[reply]

The thumb is the only digit of the hand that is opposable to the other four fingers, has two phalanges rather than three, has greater breadth in the distal phalanx than in the proximal phalanx and is attached to such a mobile metacarpus (which produces most of the opposability). The etymology of the word: "tum" is Proto-Indo-European for "swelling" (cf "tumour" and "thigh") since the thumb is the stoutest of the fingers. 84.209.89.214 (talk) 23:46, 24 January 2014 (UTC)[reply]

The crucial consideration about whether thumbs are fingers here is, do thumbs fing? μηδείς (talk) 03:03, 26 January 2014 (UTC)[reply]

See this silly story for a very confused person.--Auric talk 17:11, 27 January 2014 (UTC)[reply]

Well, in that case, how many toes do I have? Myles325a (talk) 03:36, 28 January 2014 (UTC)[reply]

I'd recommend counting them if you are unsure... AndyTheGrump (talk) 03:43, 28 January 2014 (UTC)[reply]

According to the PIE language, you have twenty toes (originally digits, PIE *deik-) of which anmong the Proto-Germans, the fingers were the ones that caught (like fangs, German fangen), and the swollen ones, were the thumbs. μηδείς (talk) 03:53, 28 January 2014 (UTC)[reply]

Thanks to all. This was very helpful; I appreciate the input. Thank you. Joseph A. Spadaro (talk) 16:38, 30 January 2014 (UTC)[reply]

Red tomatos that are green inside

I was at local deli where they build your sandwich while you watch. I noticed that the gelatinous insides of the tomatoes (where the seeds are) were all greens and very unappetizing. What causes this? --209.203.125.162 (talk) 23:54, 24 January 2014 (UTC)[reply]

With over 7,500 varieties of tomatoes, it's entirely possible that what you saw was simply an odd varietal; appetizing is in the eye of the beholder, after all. It could also be that the tomato really was still green and only the outside of the tomato was reddened, due to incomplete "forced" ripening via ethylene gas. Matt Deres (talk) 00:14, 25 January 2014 (UTC)[reply]

Yes, forced ripening would be my guess. If the tomatoes had naturally ripened, the part by the stem would be the last part to turn red, not the interior. StuRat (talk) 01:06, 25 January 2014 (UTC)[reply]