Wikipedia:Reference desk/Archives/Science/2011 November 20

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November 20

Morning erections & psychogenic ED

In the Wikipedia article, "Nocturnal Penile Tumescence" it says:

"Nocturnal penile tumescence (informally known as "morning wood" or "morning glory") is the spontaneous occurrence of an erection of the penis during sleep. All men without physiological erectile dysfunction experience this phenomenon, usually three to five times during the night.[1] It typically happens during REM sleep."

But this, from the Cornell Urology Department, would seem to contradict that:

"One of the great myths in sexual medicine is that the presence of a rigid early morning erection indicates psychogenic ED. This is a false concept, as many men with significant arteriogenic ED wake up with good erectile rigidity. The presence of good early morning erections is suggestive only of adequate venocclusive function. (full article: http://www.cornellurology.com/sexualmedicine/ed/evaluation.shtml)

Is this a controversial issue in medicine? — Preceding unsigned comment added by 204.9.109.10 (talk • contribs) 00:17, 20 November 2011‎ (UTC)

I don't see any contradiction between the two texts. Dauto (talk) 00:26, 20 November 2011 (UTC)

Not with the section the OP quoted, but our article goes on to state:

The existence and predictability of nocturnal tumescence is used by sexual health practitioners to ascertain whether a given case of erectile dysfunction (E.D.) is psychological or physiological in origin. A patient presenting with E.D. is fitted with an elastic device to wear around his penis during sleep; the device detects changes in girth and relays the information to a computer for later analysis. If nocturnal tumescence is detected, then the E.D. is presumed to be due to a psychosomatic illness such as sexual anxiety; if not, then it is presumed to be due to a physiological cause.

which does sound contradictory. -- 203.82.66.204 (talk) 01:17, 20 November 2011 (UTC)

Male testosterone is highest in the morning. ~AH1 ^(discuss!) 20:36, 20 November 2011 (UTC)

Strictly, maybe not, but it may be misleading. I doBold text think it would be a useful counterpoint to include that someItalic text men withItalic text physiological ED alsoItalic text wake up with morning erections, according to the CU article. — Preceding unsigned comment added by 67.206.184.166 (talk) 22:33, 20 November 2011 (UTC) [edit shifted and reindented to retain threading -- 203.82.66.198 (talk) 01:23, 21 November 2011 (UTC)]

Just as a comment, I think it might matter what you sleep on. Specifically, I found it practically unworkable to sleep on an air mattress while camping, because it had an effect that seemed to verge on priapism (including the lack of real arousal). Seriously it seems better to sleep on the ground than put up with that ... but I didn't actually find medical discussion about this. Wnt (talk) 04:16, 21 November 2011 (UTC)

For possible help see Ingrid Bellamere's report. N.B. The link is for information and not recommendation. Cuddlyable3 (talk) 19:03, 22 November 2011 (UTC)

Relativistic attraction of current-carrying wires

Let us imagine a situation where we have two parallel current-carrying wires with current pointed in ${\hat {y}}$ direction. Let us idealize this situation by considering a line of electrons moving in the $-{\hat {y}}$ direction with a velocity $v$ (no wire, just movement of negative charges, and negative to take into account for conventional current). As is well known, the two wires will attract each other. Now, let us consider us in a new reference frame of the same situation where relative to our old reference frame we are moving in the ${\hat {y}}$ with velocity $v$. Now our electrons appear to be stationary charges, and since we are considering solely negative charges, the will end up repelling. My first question is: why does a change of reference frame change whether the wires attract or repel?

The movement of these charges will form a magnetic field by the equation $B={\frac {\mu _{0}v\lambda }{2\pi r}}$ for linear charge density $\lambda$ as $I={\dot {q}}=v\lambda$. Now, this magnetic field will reach the other wire and cause an attractive force towards the other by the Lorentz Force ${\vec {F}}_{B}=q{\vec {v}}\times {\vec {B}}$ and thus on a single charge we have $F_{B}={\frac {q\mu _{0}v^{2}\lambda }{2\pi r}}$. In our new reference frame, the electric field of one wire is given by $E={\frac {\lambda }{2\pi r\epsilon _{0}}}$, and thus the force on one charge is given by ${\vec {F}}_{E}=q{\vec {E}}$ and thus $F_{E}={\frac {q\lambda }{2\pi r\epsilon _{0}}}$. Even though I know the two forces are technically pointing in the same direction, for fun I decided to set $F_{E}=F_{B}$. What resulted was $v={\frac {1}{\sqrt {\mu _{0}\epsilon _{0}}}}$, which I recognized as the speed of light/speed of propagation of electromagnetic waves. My second question is: Why is that so and what relevance does the speed of light in the $\pm {\hat {y}}$ direction have in this situation? — Trevor K. — 04:38, 20 November 2011 (UTC) — Preceding unsigned comment added by Yakeyglee (talk • contribs)

"My first question is: why does a change of reference frame change whether the wires attract or repel?" Now, I'm neither a physicist, or a mathematician, so I can't claim to understand the question in detail, but I think that there is an underlying assumption there that needs further investigation. Do you have any empirical evidence that your "reference frame change" actually affects "whether the wires attract or repel"? I can't help thinking that this is on the face of it somewhat implausible. Still, what do I know?... AndyTheGrump (talk) 04:58, 20 November 2011 (UTC)

Yes, you're right in that regard. It seems fishy to me as well, which is why I felt the need to ask it. This is only the result of the equations and relationships of electromagnetism that I am familiar with, and it seems to form a result that contradicts itself. — Trevor K. — 05:22, 20 November 2011 (UTC) — Preceding unsigned comment added by Yakeyglee (talk • contribs)

A line of moving electrons is not equivalent to an wire carrying a current because the wire is electrically neutral but the line of electrons isn't. Dauto (talk) 06:37, 20 November 2011 (UTC)

I think you overlooked that the electric repulsion is present in all frames, and it's always larger than the magnetic attraction (becoming equal as v → c, as you observed). So these "wires" repel each other with respect to any frame. They do repel more slowly at high speeds, by a factor of γ. -- BenRG (talk) 06:43, 20 November 2011 (UTC)

And if you do take wires into account, i.e. you consider electrons moving through a stationary positive ion lattice (then there is no electrical repulsion since the charges cancel), you will get positive ions moving through a stationary electron lattice in the other frame 83.134.178.103 (talk) 08:16, 20 November 2011 (UTC)

There might be an electric repulsion or attraction in a referential other than the wire's referential. Dauto (talk) 15:10, 20 November 2011 (UTC)

Thers an article Relativistic electromagnetism that may answer your questions--78.148.128.218 (talk) 20:55, 20 November 2011 (UTC)

optic nerve damaged and loss of vision

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This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

→Στc. 07:12, 20 November 2011 (UTC)

I think it is appropriate to point out that Wikipedia provides some information about the optic nerve and optic neuropathy. And ethics should compel us to urge anyone with recent vision loss to seek medical help quickly: purely as an example, note the usefulness of corticosteroids when given quickly for treatment of anterior ischemic optic neuropathy. Wnt (talk) 04:04, 21 November 2011 (UTC)

Proof?

In [1] interview, I read a part that said "Nobel laureate Eugene Wigner believed that observations determine existence, and observations require a conscious mind, and hence the existence of the universe meant that there was a cosmic consciousness permeating it. In some sense, he was offering this as a proof of the existence of God." Although there's some difficulty in equating "cosmic consciousness" and God, it seems quite reasonable, is there an article on this in Wikipedia?Are there any atheist answers to this kind of proof? — Preceding unsigned comment added by Irrational number (talk • contribs) 14:45, 20 November 2011 (UTC)

The part "existence = consciousness" is kind of weak. You don't need an atheist to dispute this. 83.37.188.63 (talk) 15:04, 20 November 2011 (UTC)

It's actually "existence=>consciousness" which is kinda different...--Irrational number (talk) 15:11, 20 November 2011 (UTC)

"I am, therefore I think"? Isn't that putting Descartes before the horse? Mitch Ames (talk) 12:20, 21 November 2011 (UTC)

Most physicists don't agree with Wigner's opinion on the topic so atheists may simple point out that this is a controversial interpretation held only by a small minority of physicists. Dauto (talk)

He wasn't expressing an original thought. He was repeating the Vedanta, which he had been studying for a while. -- kainaw™ 15:48, 20 November 2011 (UTC)

I could be wrong, but I don't think the Vedanta says anything about the collapse of the wave function. --Mr.98 (talk) 15:55, 20 November 2011 (UTC)

Perhaps you are REALLY reading into the quote in the question. I don't see anything at all about the collapse of the wave function in it. -- kainaw™ 21:24, 21 November 2011 (UTC)

See also Immaterialism. Deor (talk) 17:34, 20 November 2011 (UTC)

The main issue here seems to be whether a non-materialistic science can actually work and to what extent consciousness be incorporated into the equation – human consciousness seems to have a direct partly-observable effect only at very small scales, ie. the Quantum Zeno effect. Take a look also at theory of mind, Integral humanism (India) and Ghandi's Seven Blunders of the World: science without humanity. ~AH1 ^(discuss!) 20:33, 20 November 2011 (UTC)

The Quantum Zeno effect is in no way related to human (or any other) consciousness. Any device capable of determining whether the quantum pot has boiled will lead to the effect. Of course, nobody will know about it if nobody reads the device, but that's as meaningful as saying that nobody will know that a tree fell if nobody was watching the tree.

Also, I think that "science without humanity" means using science to pursue inhumane goals. I doubt Gandhi meant to imply that scientific laws would be invalid if humanity didn't exist. --140.180.3.244 (talk) 01:25, 21 November 2011 (UTC)

There's no consciousness effect in quantum mechanics. There's a phenomenon called quantum decoherence which manifests itself in experiments as the watched-pot effect (aka quantum Zeno effect), but it doesn't require lab equipment built by humans, much less "conscious observation", to operate. It operates in any thermodynamically irreversible system.

If God was watching everything, we'd know about it, because of the aforementioned watched-pot effect. If there is a God, he's not looking, at least not in the quantum sense. Wigner effectively believed that God was looking in a classical sense (looking at the world at a large scale, not at the details). The idea that there has to be a Prime Observer because nothing can exist without being observed is almost the same as the first cause argument, and the rebuttal is the same.

Michio Kaku is technically a physicst, but he has no reputation in the field. In practice he's a full-time media personality. He says dumb things all the time. Wigner was a prominent physicist, but he had the excuse that it was early in the history of quantum mechanics and it wasn't understood as well as it is now. -- BenRG (talk) 05:56, 21 November 2011 (UTC)

Tsunami

Im going to the Canaries for Xmas and New year (2 weeks). What is the probability of the Cumbre Vieja fault opening up and causing me to get hit by the megatsunami? --78.148.128.218 (talk) 21:10, 20 November 2011 (UTC)

It's similar to the probablity that your plane will crash. Which in turn is a lot lower than the probability that you'll suffer a deadly accident while driving to the airport. Count Iblis (talk) 21:16, 20 November 2011 (UTC)

Actually I would put that as a lot less than the likelihood of the plane crash, more like the chance of being struck by lightning and winning the lottery. Mikenorton (talk) 21:27, 20 November 2011 (UTC)

On this occasion Count Iblis I have to disagree with you. As we (anybody) can't quantify the probability that the local activity 'might' cause a submarine slippage (there ain’t no data) so we can't compare it to any other probability of risk. The Lake district is a nice place to go and it is a long way above sea level.--Aspro (talk) 21:33, 20 November 2011 (UTC)

Read this as to why the risk is much less than some people would have you believe and it is something that some geologists do spend there time trying to put numbers to. Mikenorton (talk) 23:20, 20 November 2011 (UTC)

@Aspro, are you being gently ironic in some way when you compare the Lake District and the Canary Islands in December/January. I go along with Count Iblis, the chances are vanishingly small. Richard Avery (talk) 08:13, 21 November 2011 (UTC)

If any quantifiable probability of a megatsunami swamping the Canaries were known it would be reflected in the price for Travel insurance. Cuddlyable3 (talk) 00:47, 22 November 2011 (UTC)

Crystal Fusion Turbine

I've got a wacky idea for a fusion power plant, so could you'll please point out the obvious flaw?

We know that Piezoelectricity can create surprising large electrical fields over small distances. So this design uses crystals that are rubbed against each other to build up strain that is suddenly released as they "snap back".

This field is then applied to liquid water flowing past the crystals, which by the Self-ionization of water has a tiny fraction of free protons that are accelerated 17 times as much as Hydroxide ions by the same electric field.

These crystals have a large proportion of lithium and boron, which the protons slam into, releasing alpha particles in Aneutronic fusion.

The alpha radiation is contained inside the device and used to boil the rest of the water which is then fed through a steam turbine connected via a shaft to the disks to which the crystals are attached. (The shaft is also connected to an electrical generator or other process to extract the energy for useful purposes.)

The steam then goes through a radiator and condenses back into water which is then pumped back into the device via a water turbine that is connected to the same shaft.

So basically this is a Jet engine, with the combustion chamber replaced by the fusion crystals.

And it doesn't work because what? Hcobb (talk) 21:37, 20 November 2011 (UTC)

Because the Klingons have cornered the market in Dilithium crysyals? Actually, this sounds no wackier than some of the other cold fusion devices being touted around currently. Even if it doesn't work, you could probably earn a few dishonest bucks by claiming it did, and advertising for 'investors'... AndyTheGrump (talk) 21:50, 20 November 2011 (UTC)

I'm not a physicist, but I'm dubious you can scale the crystals up to the size that would be necessary to generate enough protons to generate enough aneutronic fusion to boil water. Without knowing some basic numbers here — the strength of the field you'd, the likelihood of the protons being accelerated, the likelihood of the protons causing aneutronic fusion — it's hard to know exactly how impossible this is, even barring any actual physical errors in the conception (which I'm not qualified to identify). You'd need at least back-of-envelope numbers to even start thinking this made sense. Without those at hand, any kind of energy generation scheme sounds plausible (I rub my feet on the carpet, generating static electricity; I touch a door knob; the door knob connects to a device that uses the current to boil water; steam goes through a turbine; etc.); with them, it becomes clear what isn't ever going to work... --Mr.98 (talk) 00:12, 21 November 2011 (UTC)

This is a creative scheme, but I'm having trouble getting past the first step. According to that piezoelectricity article, the crystals can build up "thousands" of volts. Now even protons properly accelerated with millions of volts in an evacuated chamber are hard to get to fuse with stuff, so I don't see how you have enough power to play with. Of course, if you can start fusion, then the rest becomes very interesting.

I'm vaguely remembering something about a miniature neutron source (I think) that came out ten years ago - is this it? ("Rossi"?) [2] Maybe this is in some way related, but if I remember right the problem was that didn't actually produce very many neutrons for the power input. Wnt (talk) 00:38, 21 November 2011 (UTC)

Requested ref: Pyroelectric fusion Hcobb (talk) 03:27, 21 November 2011 (UTC)

Repeat trauma

Suppose a person receives a gunshot wound in the upper arm (a through-and-through with a full metal jacket round that does not break the bone or sever any nerves), and then three or four days later gets hit with the flat of a propeller blade in the exact same spot. Can this cause any significant complications (aside from the fact that it will hurt like hell)? DISCLAIMER: This is NOT A REQUEST FOR MEDICAL ADVICE. (Also note that the victim gets hit with the flat of the prop blade, NOT the sharp edge -- if it had been the edge, then it's obvious that the victim could end up minus an arm.) 67.169.177.176 (talk) 21:46, 20 November 2011 (UTC)

What -oh-what has prompted you to ask this question? From what context do we approach this? Are you researching for a novel?--Aspro (talk) 22:23, 20 November 2011 (UTC)

Yes, you're right on the money. Specifically, I intend for one of my characters to get shot while escaping from a hostile area after force-landing there, and then a few days later to get struck by the prop blade while hand-propping the engine (the plane's electrical system having been partially sabotaged in a way that is very hard to detect). 67.169.177.176 (talk) 23:30, 20 November 2011 (UTC)

Consider, from your own possible personal experience, that a wound that starts to heal, and then gets re-opened, will take longer to heal than just the one wound. And obviously, anytime a wound is (re-)opened, there is a risk of (further) infection. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:34, 20 November 2011 (UTC)

Am I to understand that the major complication is the risk of infection? 67.169.177.176 (talk) 01:30, 21 November 2011 (UTC)

It might be easier if you told us the outcome that your plot wanted, and we could see if a plausible medical explanation can be generated. TenOfAllTrades(talk) 23:35, 20 November 2011 (UTC)

That's not how I work -- I try to keep it realistic as much as I can. No point stretching the limits of plausibility for just one little episode. 67.169.177.176 (talk) 01:28, 21 November 2011 (UTC)

The outcome is: he gets the Girl – dummy :-)

What era is this set in? If its an ancient Cessna 152 with a fixed pitch -it will slice. An modern turboprop on full pitch (slap-mod) will suck the hero in to the prop and the natives will be able to enjoy long-pig stew for the rest of the week. Should he however, be standing behind the prop he will be blown a**** over t** and away from it. John Wayne was always getting shot in the shoulder and trampled by horses – can't you work that sort of scenario into the story instead? (it made him rich) PS. If doing a hand swinging start, he needs a leather glove. Aluminium props often have little nicks, which will cut into the the naked hand. Also, you could add realism by pointing out that 'contact on' is really 'contact off '– the electrical circuit is shorted to make it safe. For this reason and in reality – both swinger and pilot – must always assume that the ignition circuit is ALLWAYS LIVE in case of a bad shorting contact. Point out too that the fuel should be coloured blue (aviation gasoline) but as it isn't, it means he's running on 'regular gas' syphoned from the baddies limousine, (black, they always drive black limousines) etc., etc., etcetera.--Aspro (talk) 01:04, 21 November 2011 (UTC)

This is set in the modern era, but the aircraft in question is a prehistoric Electra 10-E with 550-hp Wasp engines and hydraulically-operated constant-speed propellers. Hope that helps. 67.169.177.176 (talk) 01:24, 21 November 2011 (UTC)

Which brings up the point that the Wasp engine CAN actually run on automotive gasoline if need be (yes, it's THAT ancient). However, this won't be the case here, because there's NO WAY you could fill up an Electra's 1100-gallon fuel tanks with fuel siphoned from the bad guys' limo. 67.169.177.176 (talk) 01:34, 21 November 2011 (UTC)

Also, as an aside, I don't think it's possible to hand-prop a turbine engine -- the cranking RPM's are just too high and the rotational inertia too big. 67.169.177.176 (talk) 01:36, 21 November 2011 (UTC)

Cumbre Vieja

Hi. Does there exist any geological evidence on the coasts of eastern North America, northern South America, the Caribbean, Europe, Africa, the Mediterranean (less reliable), etc. for a large tsunami across a wide area that coincides with postulated past occurrences of submarine landslides on the flanks of La Palma, El Hierro, or any other of the Canary Islands, dated using such methods as those used for climate proxies or other mud core sample data, or using C-14 dating, or other methods, that provides close correlation between the dates? Thanks. ~AH1 ^(discuss!) 22:33, 20 November 2011 (UTC)

The most recent landslide on the Canaries dates at 15,000 years age from El Hierro and the average repeat interval for such events is about 100,000 years (with a large spread). More details here. Nothing on tsunami deposits yet, still looking. Mikenorton (talk) 23:35, 20 November 2011 (UTC)

No, nothing on such deposits, and people are certainly looking. Plenty of examples of near-field tsunami deposits around groups of volcanic islands though, just not transoceanic ones. Mikenorton (talk) 23:58, 20 November 2011 (UTC)