Wikipedia:Reference desk/Archives/Science/2015 June 14

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June 14

What kind of plant is this?

Plant, Southern Germany.

What kind of plant could this be? Found in Southern Germany. Many thanks. --Edcolins (talk) 10:28, 14 June 2015 (UTC)

Looks like a form of clover to me. --TammyMoet (talk) 18:15, 14 June 2015 (UTC)

It looks more like Aquilegia to me, but it is much easier to identify with flowers. What is the shape of the whole plant? Graeme Bartlett (talk) 22:17, 14 June 2015 (UTC)

Agreed - see this image for comparison. There is a huge list of Aquilegia species, but Aquilegia vulgaris and Aquilegia alpina are native to northern Europe. Alansplodge (talk) 09:27, 15 June 2015 (UTC)

Thanks! It must be an Aquilegia vulgaris indeed. If any flowers show up, I'll take some pictures... The shape of the whole plant is somehow difficult to describe: Not very high, 10-20 cm probably. Growing in the shade of other plants. --Edcolins (talk) 19:08, 15 June 2015 (UTC)

Wisdom tooth timing

So if wisdom teeth assisted our prehistoric ancestors in chewing, one would expect that such teeth should emerge roughly at the same time as other permanent teeth - I don't think the prehistoric men switched to another diet in their 20s or so, to warrant wisdom teeth so late. I.e., the ancestors would have needed wisdom teeth already in their teens at least, but now there's a significant timing difference - my sister had her first wisdom teeth around 18, others in their late 20s, etc. Maybe there was a different timing of wisdom teeth back then and later it evolutionarily shifted when such teeth became redundant? Brandmeister^talk 11:49, 14 June 2015 (UTC)

I'd expect that wisdom teeth were to replace other permanent molars that were no longer effective. Back then, with lots of sand and grit getting in the food, teeth would wear down more quickly than they do now. StuRat (talk) 12:08, 14 June 2015 (UTC)

@StuRat: I have to call "citation needed" on that! Since wisdom teeth typically come in before age 25, and wear typically affects the tops of the teeth without allowing them to come closer together. Wisdom tooth explains that there are quite significant racial differences in their occurrence. Some people, myself included, get them quite early. Wnt (talk) 12:40, 14 June 2015 (UTC)

Keep in mind that life expectancy back then was under 30, so the wisdom teeth would provide a spare set of molars for the "golden years". StuRat (talk) 15:04, 14 June 2015 (UTC)

So why timing varies if our ancestors most likely consumed rough food well before adolescence? One would expect that such teeth should erupt at roughly the same time both in prehistoric and in modern men. Brandmeister^talk 15:27, 14 June 2015 (UTC)

They actually begin to grow at about the age of ten but don't erupt until years later [1]. As they are vestigial and no longer really fit into the modern mouth (see: [2]) maybe the difference in timing in modern humans depends on the actual conformation of the jaw and how well they erupt i.e. are they partially impacted, fully impacted or fully erupted. Richerman (talk) 09:55, 15 June 2015 (UTC)

And many people never develop wisdom teeth at all (like me), due apparently to the PAX9 gene. To me this suggests that evolution is ongoing with regards to wisdom teeth, and those ethnic groups who have smaller jaws (and hence less room for them) and/or lack the need for them (due to less grit in their diet to grind down their other molars) are losing them first. StuRat (talk) 19:14, 15 June 2015 (UTC)

Why is platinum a good material for spark plugs?

As I understand it, plating the tips of the electrodes of spark plugs with platinum causes them to last longer. I presume this is because the platinum does not erode due to the electric spark. I am referring to spark plugs that are used in internal combustion engines to provide ignition. Why does platinum erode more slowly than other metals? 50.43.33.62 (talk) 13:43, 14 June 2015 (UTC)

Electrical erosion depends on boiling temperature (yes, metals can boil), thermal conductivity and density. Each of these should be high in order to minimize erosion. Platinum has a high boiling temperature (3827 C versus 2567 C for copper) and high density (21.5 g/cm3 versus 9 g/cm3 for copper). Platinum has a lower thermal conductivity than copper but the other two properties make up for that. Short Brigade Harvester Boris (talk) 14:46, 14 June 2015 (UTC)

Also, platinum is fairly nonreactive, so it won't form a patina that interferes with the spark, as copper would. StuRat (talk) 15:04, 14 June 2015 (UTC)

Oh, it's more complicated than that! Spark plugs are exposed to the hardest conditions: high temperature, high pressure, rapid thermal changes, corrosive gases! Depending on the engine type, fuel type, and operation, a different thing is going to cause end of life for your spark plug. Even if the platinum is perfectly uneroded, the plug can fail for other reasons. This scanning electron micrograph from Oak Ridge National Laboratory compares different electrode materials in well-used spark plugs. The Platinum/Tungsten metal performance is superb! It barely shows any sign of erosion. (Quantitatively, 30 to 40% of the platinum eroded, compared to 10% of the iridium, but this isn't what caused the failure.) However, the plug electrode is beginning to crack off of its attachment: over time, oxidization occurs at the metal junction, and this aggravates and is aggravated by thermal cycling. The perfect platinum tip is in fine condition, but the plug is no good! Oak Ridge's report calls this oxidation cracking the probable end-of-life causative factor.

On the other end of the spectrum, one aircraft I fly is usually used for local training. Its engine doesn't get to high temperatures over sustained periods of time. This causes spark plug fouling: you can read all about it in this technical publication from the engine manufacturer. In this case, because the aircraft engine idles or operates so frequently at low temperature / low RPM (during landing when the engine is not delivering high power), the ambient temperature in the cylinders is too low to vaporize the tetraethyl lead in our fuel. So, the plugs "wear out" because they get coated in TEL solids (as well as carbonized unburned fuel product). In that case, it doesn't really matter what the plug electrodes are made from: the reactive surface has been coated (replated!) with TEL! The solution is to run the engine at high temperature to burn the crud off the plugs, or just to replace the plugs on accelerated schedules.

So, before we say "platinum electrodes are great" or "terrible" or anything, we need to first focus on a few important details: what type of engine (compression ratio, fuel type, fuel intake mechanism, normal RPM)? What regime of operation (temperature, duty cycle, RPM)? What type of plug failure do you wish to avoid by way of selecting the ideal electrode?

We can talk about platinum's physical properties: it's fairly nonreactive, fairly strong, fairly high melting point... but the same applies to tungsten and just about every other material we use to build plug electrodes. The platinum erosion rate as measured in a lab may be slower than, say, iridium (or not, depending on operating conditions!)... but (for example) the plug may still fail sooner because of cracking at the platinum-nickel interface. In reality, the material properties in isolation don't matter: as a perfect example, re-examine those SEM micrographs, where we see a perfect Platinum electrode that's cracked away from the substrate! We have to look at the entire engineered system.

Here's a catalog and tech note from Champion Aerospace: Spark Plugs. I'm a fan of the massive electrode style plugs: they seem less susceptible to fouling in my engine. Whether this works for your engine is a different question: if you put an aerospace spark plug in an automotive piston engine, I don't know what would happen, but I'd bet the plugs would foul pretty fast.

Nimur (talk) 17:12, 14 June 2015 (UTC)

I also found two publications that are made available at no cost by Johnson Matthey Technology Review (a publication conglomerate and chemicals company). These papers came from the now defunct publication, Platinum Metals Review (a trade journal):

• The Mechanism of Electrode Erosion in Electrical Discharges (1963). This is a great review article that explains the theory of arc discharge, and explores several different causes of erosion; then explicitly studies an empirical equation and its constants for platinum. Trade journals from the '60s are great - they're pure, unadulterated, apolitical empirical science ! If we trust this paper, the primary reason why platinum erodes slowly is because it has a very high boiling point; secondary effects are related to the thermal conductivity of the metal and other factors. Tungsten erodes even slower, which is consistent with its very high melting point.
• Arc Erosion of Electrical Contacts (1957), which is essentially just an empirical data summary.

Nimur (talk) 21:48, 14 June 2015 (UTC)

opium

Do opium poppies contain any opium BEFORE they flower? If not, why not? What causes opium to be produced only after flowering?

Also is it true that the government has been breeding poppies with no opium content and then releasing them into the wild to dilute the wild poppies opium content? — Preceding unsigned comment added by 117.163.61.226 (talk) 13:55, 14 June 2015 (UTC)

Think the simple answer to that is yes. The very bitter tasting ( and opium containing) latex is what protects the poppy from browsing herbivores. The reason for scarring the seed pods, after flowering is that the valuable poppy seed can still be harvested. Yet, put a poppy plant through a mangle before flowering and the juices will still contain opium.--Aspro (talk) 22:59, 14 June 2015 (UTC)

You may find helpful information in Poppy straw which indicates that many parts of the plant contain at least small amounts of various opium alkaloids. Edgeweyes (talk) 15:22, 15 June 2015 (UTC)

Harvesting

If a man is in a permanent coma and his wife want a baby, how do they harvest the sperm?--86.180.139.143 (talk) 14:28, 14 June 2015 (UTC)

Hello Manchester! In an amazing coincidence, this very question was asked by someone from Liverpool exactly one month ago. Please see that question and its answers in our archives at WP:Reference desk/Archives/Science/2015 May 14#Permanent coma. -- ToE 15:32, 14 June 2015 (UTC)

Snowy owl?

Can someone confirm if this bird is a snowy owl? Compared to the other images of snowy owls in the Snowy owl article, it just seems a bit different in terms of head shape and physical characteristics. --Nick⁠—⁠^Contact/_Contribs 15:37, 14 June 2015 (UTC)

Looks more like an immature sparrowhawk. Mikenorton (talk) 18:36, 14 June 2015 (UTC)

I have no idea what it is but I do know that it isn't a snowy owl. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 00:30, 15 June 2015 (UTC)

Perhaps a juvenile red-tailed hawk (see pix) given their variation and presence in all the lower 48. μηδείς (talk) 00:40, 15 June 2015 (UTC)

Triggering emotional memories

There are times we trigger memories or link previous events after observing or hearing another event by chance. Here are some examples:

• Hearing a song with some party that may remind you of an exact snapshot of the same event occurred somewhere in the past.
• Being worried about something and then realizing non-relevant hazard and later on you comeback to find an indecent of what you were worried about.

Are there specific explanations to such phenomena?--Almuhammedi (talk) 15:59, 14 June 2015 (UTC)

We have articles on Trauma trigger and Flashback (psychology) but they're not really what you're describing.. This is specifically addressing your first example Music and emotion#Emotional memories and actions.. My guess is that this seemingly 'simple' question is probably an extremely deep, complex and multifaceted subject. Vespine (talk) 02:03, 15 June 2015 (UTC)

See Memory#Factors that influence memory which describes some of the mechanisms that trigger memories. Richerman (talk) 09:35, 15 June 2015 (UTC)

Looking at Pavlov's Dog, it is how the brain works. The best fitting try to simulate the brain was made by Hermann von Helmholtz, seeing the brain as a statemachine, comparing stored hypotheses with impressions. It was shown at the example of interpreting ambiguous images like rubins vase. --Hans Haase (有问题吗) 12:06, 15 June 2015 (UTC)

Electrostimulation

Is electrostimulation of the male donut safe? I mean a lot of these things produce more than 500mA. Can't that sort of current do permanent damage to a mans donut?--86.180.139.143 (talk) 18:58, 14 June 2015 (UTC)

Our article Electroejaculation has some info on possible dangers. Rojomoke (talk) 19:39, 14 June 2015 (UTC)

I've always kinda thought of Churros as male donuts and ring Doughnuts as female ones. If this question does indeed pertain to experiments involving the passage of electrons through fried pastry products, then what would be the outcome of applying one of the devices mentioned in the electroejaculation article to these? 81.101.142.79 (talk) 21:16, 14 June 2015 (UTC)

(The prostate is donut shaped.)--86.180.139.143 (talk) 11:14, 15 June 2015 (UTC)

Looking for a page about a Holholm (incorrect spelling) Box that traps light.

I recall the article explained as something like the following: Light enters a box through a small opening like a slit along the edge of one side of the box. The light that enters reflects within the box many times before finding its way out the same single opening.

The reason this method is not effective for harnessing light energy is ambient temperature which prevents the small amount of light which entered to effectively heat the larger area of the inner walls of the box no matter how many times it reflects.

I believe this was first explained in the early 1800s by a man named Holholm and so the described box was called the Holholm Box.

I would be grateful if someone can direct me to the article again.

See Black body and the two sections called Cavity with a hole. The people are Otto Lummer and Ferdinand Kurlbaum. Graeme Bartlett (talk) 22:06, 14 June 2015 (UTC)

The word you'e after is hohlraum. --Tardis (talk) 01:37, 15 June 2015 (UTC)

I added a link to hohlraum in the black body article, thanks. SemanticMantis (talk) 17:21, 15 June 2015 (UTC)

More Big bangs -> More (Parallel) universes?

If our universe popped up out of nothing/nowhere, could other universes also exist? Our universe is thought to be the product of one almighty BIG bang. According to the Many worlds Interpretation there may be may parallel universes brought about by the SAME big bang. Now my Q is: Could there have been other big bangs in different 'places' it different 'times' that could also give rise to many more parallel universes. If so, would it be possible to travel to these universes? --86.180.139.143 (talk) 20:37, 14 June 2015 (UTC)

In Many-worlds interpretation you will not be able to travel between the worlds unless it becomes coherent again. Normally this would mean almost identical at the quantum level, so anything that succeeds will have no different memory from being in two different worlds. For example in the two slit experiment two worlds in which the particle goes through either slit merge, but they do not know which one they went through. Place and time are also created in the big bang, so you will not be able to change your position or time to be in a different universe created in some other way. You will have to create your own simulation, ie write a story, or run a computer program. Graeme Bartlett (talk) 22:01, 14 June 2015 (UTC)

That doesnt answer my Q. Could there have been more than one big bang and could we detect the fact and travel to the resulting universes?--86.180.139.143 (talk) 11:12, 15 June 2015 (UTC)

There are theories that there would be more than one big bang, but there is no way to detect it or travel there. But there are theories where one universe runs into another. Have you looked at multiverse? Graeme Bartlett (talk) 12:52, 15 June 2015 (UTC)

So far, all respectable theories in which there are many big bangs, resulting in many universes, state very clearly that we have no means of detecting or traveling to the other universes. As an example, this is a theory that doesn't hold up against scientific observation, but is popular with non-scientists and allows me to avoid writing a scientifically accurate response... The theory is that the big bang is the result of a black hole in another universe. So, it is as though our universe is like a bubble inside a black hole inside another universe. Therefore, every black hole spawns a universe in every universe that has black holes. However, to get from a universe to the parent universe or to the child universe, you must travel through the singularity of the black hole. Doing so will, in simplistic terms, take everything that defines you and turn it into nothing but pure energy. That is a one-way process. You can't put the energy back together to get you again. So, your attempt to travel from one universe to the other will do nothing more than result in little more than a warm fart on the other side. 209.149.113.240 (talk) 13:24, 15 June 2015 (UTC)

• Note that the definition of universe makes answering this question problematic, because you're wandering into the territory of philosophical tautology. If the universe consists (as our article says) of everything that has existed, exists, or will exist, then can another universe exist? No, by definition. When we talk of parallel universes, we must be using some other definition, like maybe "everything that we can affect or can affect us", in which case the possibility of determining whether they exist can occur only in theoretical speculation, and travel to them is impossible, by definition. But can we use a wormhole to travel to some other broad Euclidean region of space not obviously connected to ours by other means, and call that a "universe"? Then that must be another definition. So it's tricky. Wnt (talk) 14:25, 15 June 2015 (UTC)

Why keep food at 0 °F/-18 °C?

What would happen when you increase the temperature coming closer to the freezing point, but still below it? Could some bacteria thrive at 23 °F/-5 °C? --Yppieyei (talk) 21:35, 14 June 2015 (UTC)

Some food with sugar or salt in in freezes below 0 C. Bacteria can live in that too. Also the freezer temperature is not completely steady so you will want to keep it frozen at all times. Food can also dry out, and the lower the temperature, the slower that process. Graeme Bartlett (talk) 22:09, 14 June 2015 (UTC)

Well one has cryophilic bacteria. But the more important reason I think is that polyunsaturated fatty acids will degrade over time dependent on temperature. IE go rancid. Heat pumps (freezers) are most efficient over just a 20 deg range, so -18 is at the limits for a domestic freezer operating in an ambient temperature of +20.--Aspro (talk) 22:50, 14 June 2015 (UTC)

Isn't that a 38 degree range ? StuRat (talk) 03:41, 15 June 2015 (UTC)

Good question. What I am saying is not that they can't operate out of this range but by the time most domestic freezers gets down to -18 the coefficient of performance is dreadful. So the manufacture would have to add more insulation to meet efficacy standards at temperatures below this -which adds to the cost of the appliance. In countries like Australia where electricity is expensive, the extra cost of of such an appliance is worth while, whilst in say the US, the lower power costs there make the purchase price of the appliance more important than the running costs. Even then, large commercial cold stores would be better off with a double stage system. -18 is a compromise.--Aspro (talk) 19:35, 15 June 2015 (UTC)

Starchy foods (such as bread) need to be kept at or below freezing when stored. Above freezing, the starches stale. The colder they are, the faster they stale, until you hit freezing temperature. That is why you keep bread either at room temperature or in the freezer. You do not put it in the refrigerator. Bread is the most common starchy food that people notice to go stale, but you can experiment with any starchy food and see the same thing. For example, my father-in-law used to store his chips in the refrigerator so they wouldn't mold. I explained to him that the excessive salt on the chips kept the mold away and, if he didn't cool them down, they wouldn't taste so bad. 209.149.113.240 (talk) 13:16, 15 June 2015 (UTC)

• The question is not why keep food below the freezing point. But why to keep food way bellow the freezing point.Yppieyei (talk) 15:07, 15 June 2015 (UTC)

Because chemical reactions still continue (although at a ever decreasing rate). By the time one gets to boiling liquid nitrogen it has more or less come to a halt (food wise) but who wants to invest in having a cryogenic flask in there kitchen? Mind you. Dip a few sprigs of fresh mint or other herbs into liquid nitrogen and then its a quick and simple job to pound them in a pestle and mortar to save the hassle of having to finely chop them up.--Aspro (talk) 17:49, 15 June 2015 (UTC)

Foods with a high fat content and delicate texture, such as ice cream, should be kept even colder than that. Even at 0F, the tubs will compress if squeezed since they're not truly solid. -20F for the higher end (read higher fat and sugar) ice creams. Matt Deres (talk) 13:32, 15 June 2015 (UTC)

The answer to the original question may depend on circumstances. From a logistics, distribution, and supply chain management point of view, it is a useful property that items removed from a colder freezer stay frozen longer. The further the food item is below freezing, the longer it will take to thaw - it has to warm up to the freezing point before anything frozen starts to melt. Whenever items have to be moved from one freezer to another during the course of a supply chain, this can make a big difference. Edgeweyes (talk) 15:16, 15 June 2015 (UTC)

As Aspro said, chemical reactions still occur in a frozen (solid) object, but the lower the temperature, the slower those reactions are. And those reactions will eventually spoil the food (fats going rancid was already mentioned, but there are many other reactions that spoil food slowly). StuRat (talk) 19:06, 15 June 2015 (UTC)