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June 28

Gamma ray bursts and extraterrestial civilizations

Could short duration gamma ray bursts be from nuclear pulse propulsion vehicles piloted by extraterrestrials? 202.155.85.18 (talk) 01:33, 28 June 2013 (UTC)[reply]

Do the arithmetic — look up nuclear weapon to get the gamma-ray flux from an explosion of that size. Then apply the inverse square law to figure out how much of it we'd see at the distance from here to the closest star system (Alpha Centauri, I think). Then compare with the brightness described in gamma ray burst and let us know. --Trovatore (talk) 01:37, 28 June 2013 (UTC)[reply]

I can't find any values for the gamma ray flux from nuclear devices, and "that size" is highly variable as the devices could be very compact anti-matter or antimatter catalysed explosives, or large Teller-Ulam thermonuclear explosives, or something else entirely. 202.155.85.18 (talk) 01:44, 28 June 2013 (UTC)[reply]

OK then, work backwards. Consider it a Fermi problem. What's the order of magnitude of gamma-ray flux that might be needed for us to detect a gamma-ray burst? What's the order of magnitude of the size of the detector? What solid angle does that detector subtend, at the distance of Alpha Centauri? Multiply the minimal detectable flux by 4π divided by that solid angle, and get the total flux you'd need at the source. You can throw in a fudge factor for the fact that it's not expanding uniformly in all directions.

Now, is that a plausible value for a spaceship? --Trovatore (talk) 01:49, 28 June 2013 (UTC)[reply]

Ok, so according to [1] the detection limit for the x-ray telescope is 2x10^-14 erg/cm^2/s which is 2x10^-21 J/cm^2/s. I'm going to assume the x-ray equipment is more sensitive than the gamma ray equipment, since no LLD is quoted for that. Short GRBs last for less than 2 seconds so that's 4x10^-21 J/cm^2. Alpha centuri is 4.37 lightyears away, or ~4.1x10^16 m. A sphere of that radius has a surface area of 2.1x10^34 m^2 or 2.1x10^38 cm^2. That gives a total of 8.4x10^17 J of gamma rays. According to [2] a nuclear weapon released 0.13% of its yield as gamma rays, using that factor, the total yield for our device would need to be 6.5x10^20 J to be detected. That's the same as 155 gigatonnes of TNT. Sounds implausible, but in a Medusa type craft the main source of propulsion is from radiation pressure. If the explosives were tuned to give say 50% of their yield as gamma rays, the gross yield could be as low as 400 megatons, just to be barely detected. Ok, sounds like it's not possible. 202.155.85.18 (talk) 02:56, 28 June 2013 (UTC)[reply]

Nice! I was pretty sure that was going to be the answer (at interstellar distances, such a craft would be too dim to see), but I didn't feel like doing the work myself. (I have not, BTW, checked your work.) --Trovatore (talk) 03:45, 28 June 2013 (UTC)[reply]

It would be awfully strange if it just happened to be the case that every gamma-ray burst we've seen that was a spaceship happened to have the same signature we'd expect from a stellar-size explosion.

μηδείς (talk) 01:54, 28 June 2013 (UTC)[reply]

The signatures of GRB are highly variable (File:GRB_BATSE_12lightcurves.png), and the low-red shift short GRB may be closer and weaker than they would be if they were stellar sized. 202.155.85.18 (talk) 02:05, 28 June 2013 (UTC)[reply]

I am entirely disposed to accept your claim. But how does one interpret the chart you linked to, and which signature is the most relevant? Thanks. μηδείς (talk) 03:05, 28 June 2013 (UTC)[reply]

They're all equally relevant. The point is that GRB can only be broadly categorized into short and long. There doesn't seem to be much of a pattern to the rest of the signatures. 202.155.85.18 (talk) 03:22, 28 June 2013 (UTC)[reply]

(OR ahead) If nuclear pulse propulsion was the major source of GRBs, we'd be looking at both red-shifted and blue-shifted pulses, sometimes from spacecraft during acceleration, and sometimes during deceleration.

I'd think that a small source like a glorified H bomb cools quite quickly due to its rapid expansion, while a more massive source (say, several solar masses) would expand more slowly.

Thrid, I always had the idea that accelerated ejecta (i.e. gas and plasma), not the particles and rays from the nuclear explosion would push the NPP spacecraft. The Medusa seems even more ~~particle-driven~~ ejecta-driven, since (caution: WILD WP:OR ahead) a "sail" would not capture as many gamma rays as Orion's pusher plate. - ¡Ouch! (^{hurt me} / _{more pain}) 12:36, 28 June 2013 (UTC)[reply]

(Very tangential contibution ahead) It looks like the Orion is the big ship of the family, while the Medusa is the small ship -- it scales down much better thanks to its long tether, so you don't have to resort to lots of inefficient micro-nukes for small ships. - ¡Ouch! (^{hurt me} / _{more pain}) 17:00, 29 June 2013 (UTC)[reply]

Yeah, that's a good point. Radiation pressure from gamma rays would be insignificant on a thin sail. 39.215.55.222 (talk) 01:17, 2 July 2013 (UTC)[reply]

I am amused to read this discussion. We have no idea what an ET would use as a propulsion source. With all due respect, to assume that their technology would follow the profile of our nuclear bombs or any of our theoretical propulsion systems is half-baked. (Although we have to start somewhere!) We do know that at least 17 billion extrasolar planets exist in our galaxy. If there are any space-faring civilizations among them, then we can expect their technology to leave some sort of mysterious mark in the cosmos. Kortoso (talk) 22:19, 3 July 2013 (UTC)[reply]

STD

A condom can give us 100% protection against sexual terminating disease or not? — Preceding unsigned comment added by 112.79.36.180 (talk) 01:58, 28 June 2013 (UTC)[reply]

No. See Condom#Effectiveness for a breakdown of how successful it is in preventing pregnancy and in preventing the transmission of various diseases. --Jayron32 02:03, 28 June 2013 (UTC)[reply]

side discussion that does not provide any references to help the OP answer their direct question

The following discussion has been closed. Please do not modify it.

The only truly "safe" sex is to abstain. ~~However, condom with spermicidal foam is regarded as highly effective.~~ [Apparently NOT - see below] ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:12, 28 June 2013 (UTC)[reply]

Any reason for including spermicidal foam in a discussion of STD prevention? I think you'll find there is scant evidence for efficacy in preventing infection. Some might try to argue that some pregnancies resemble infections, but that's unfair -- Scray (talk) 05:55, 28 June 2013 (UTC)[reply]

If I recall correctly, nonoxynol-9 used to be recommended as helpful in preventing HIV transmission, presumably on the grounds that it killed the virus in vitro, but then when they actually followed up and checked, it turned out that it made transmission more likely, perhaps by irritating the mucous membranes. This is just my vague recollection and no one should rely on it. --Trovatore (talk) 08:51, 28 June 2013 (UTC)[reply]

Interesting point, and my information was old. The condom + foam should still be nearly 100 percent for pregnancy prevention, but that wasn't the OP's question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:34, 28 June 2013 (UTC)[reply]

Actually, as per the OP's question, this discussion is about sexual terminating disease. 202.155.85.18 (talk) 06:30, 28 June 2013 (UTC)[reply]

There's no such term. STD stands for sexually transmitted disease. Jayron's link leads to information about condoms and STDs. If the OP wants to know about something called 'sexual terminating' disease, s/he will have to come back and explain. - Ka renjc 07:01, 28 June 2013 (UTC) [reply]

If ~~"abstention"~~abstinence is safe is entirely open to debate. It will make it very unlikely to contract an STD (you can still pick up diseases classified as STDs via other ways of transmission - toilet seats ;-), needles, ...). But it might have other detrimental effects on your health, both physical and mental. --Stephan Schulz (talk) 08:46, 28 June 2013 (UTC)[reply]

That wasn't the OP's question. And if you get it from some inanimate source, it's technically not "sexually transmitted" (not directly, anyway) - not that that makes any difference to the microbes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:30, 28 June 2013 (UTC)[reply]

Stephan, your English is normally impeccable, but "abstention" is the noun form of "abstain" in the sense of not voting. When you're abstaining from something fun, especially sex, it's usually called "abstinence". --Trovatore (talk) 08:55, 28 June 2013 (UTC) [reply]

Thanks. I was under the impression that one was the verb form (actively not doing it), the other the noun (the state of not doing it), and was not aware of a difference in usage. Fixed above. Probably not fixed in my mind. Expect more embarrassing errors in the future ;-). --Stephan Schulz (talk) 09:40, 28 June 2013 (UTC)[reply]

Safety is less debatable than efficacy. "Abstinence", like all methods of contraception or STD prevention, has a failure rate. See [3], which estimates the use effectiveness rate at about 50%, lower than most other forms of contraception. A theoretical rate of 100%—assuming perfect use by perfect practitioners—is a useless figure in terms of real world decisions. Studies have demonstrated that teenagers, at least, who pledge abstinence, have sex as frequently as those that have not made such a pledge. -Nunh-huh 09:06, 28 June 2013 (UTC)[reply]

A "pledge" of abstinence does not equate to actual abstinence. I'm talking about actual abstinence. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:32, 28 June 2013 (UTC)[reply]

But then you have to apply the same criterion to other means of prevention. Does "actual use of a condom" exclude those cases where it was not properly put on, or of the contraceptive pill mean only when it is taken exactly as prescribed? These figures will all be real-world figures, not some theoretical ideal. Besides, "actual abstinence" is also fuzzy: where does the boundary lie – when no direct physical contact takes place at all, ever? — Quondum 14:44, 28 June 2013 (UTC)[reply]

Yes, lack of contact is actual abstinence. A "pledge" is meaningless - unless you live up to it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:57, 28 June 2013 (UTC)[reply]

As interesting as this discussion is, it does not provide any additional reading for the OP to go read to directly answer their question. --Jayron32 15:11, 28 June 2013 (UTC)[reply]

Neutrinos that go toward neutron stars

What fraction of the flux of neutrinos that go into a neutron star get "stopped"? Do some of them end up orbiting the star? There's the famous 50 light years of lead claim, true or not, but neutron stars are way different from lead. Thanks.76.218.104.120 (talk) 09:37, 28 June 2013 (UTC)[reply]

A quick calculation using that 50 lightyear figure for lead and the density ratios yields that the fraction that get scattered will be of order 1. If we consider cosmic background neutrinos then the coherence length will be large, of the order of 0.1 millimeters and you'll have a huge number of nucleons within the radius of one coherence length in a neutron star, making the probability of scattering a lot larger than what you would expect using the ratio of densities. Count Iblis (talk) 13:05, 28 June 2013 (UTC)[reply]

Yes, the density of a neutron star being in the order of 5×10¹⁶ times that of lead, and a light-year being about 10¹⁶ m would lead to the same level of neutrino absorption or scattering for 50 ly of lead occurring in 10 m of neutron star material. Would the coherence length of the neutrinos not potentially make the neutron star material more neutrino-transparent just as glasses and liquids are to light (not more opaque as as you suggest)? As to whether scattered neutrinos might end up orbiting the neutron star (and one would want to include repeated scattering of suborbital neutrinos in this), this would not be the case with a normal neutron star: its material would be at such a high temperature that the typical scattering event would impart too much kinetic energy to the scattered neutrino. Incidentally, a Google search finds "A fairly common qualitative statement in physics texts is that the mean free path of a neutrino is about a light-year of lead", which is echoed in more place. I suspect that lead is used precisely because its density is about right to produce this easy-to-remember figure. This would make the mean free path of a neutrino in a neutron star (coherency and any energy-dependency ignored) about 0.2 m. — Quondum 16:49, 29 June 2013 (UTC)[reply]

So could these scatterings be important to the evolution of a neutron star, given all the zillions of neutrinos, almost all of which apparently scatter within the star? Thanks again.76.218.104.120 (talk) 20:50, 29 June 2013 (UTC)[reply]

I'm definitely no expert. The bulk of the significant neutrinos would be generated and radiated as it is becoming a neutron star and soon afterwards, at which stage they are very important: they carry away the bulk of the thermal energy, cooling the interior (or so I gather from Neutron star). If the density of incident neutrinos (e.g. the neutrino remnant from after the big bang) is sufficient, this scattering could serve as a way of cooling the neutron star faster than otherwise, but I really have no idea whether the incident neutrino rate is sufficient to be significant in this regard. I do not expect other neutrino mechanisms (absorption) for low-energy neutrinos to be significant. — Quondum 20:58, 30 June 2013 (UTC)[reply]

Are you guys sure you can use all three dimensions of density for your calculation? Certainly the cube root of 1E16, for the depth, I can believe, but do adjacent nucleons(not directly in the path) coming in closer actually matter? It seems counterintuitive to me that the neutron star would impede a neutrino so vastly much more than the same star unpacked, but then again, my intuition is worthless here. :) Wnt (talk) 17:21, 1 July 2013 (UTC)[reply]

What is the name of this toy?

It's sort of engineering... what is this toy called? Thank you in advance for your superior knowledge and help. Saudade7 14:45, 28 June 2013 (UTC)[reply]

I've not seen this particular toy specifically, but broadly it looks like a type of Mechanical puzzle, like a Disentanglement puzzle, or a something similar. --Jayron32 15:05, 28 June 2013 (UTC)[reply]

The article on Trammel of Archimedes suggests at least some call it a Kentucky Do-Nothing. 88.112.41.6 (talk) 16:23, 28 June 2013 (UTC)[reply]

Yep, more generally it is a type of linkage_(mechanical). For a fun way to kill some time, try these web applets demonstrating various cool linkages: [4], [5], or just google /linkage applet/. SemanticMantis (talk) 16:47, 28 June 2013 (UTC)[reply]

Thanks everyone ! I will check those things out. 64.134.223.233 (talk) 22:20, 28 June 2013 (UTC)[reply]

Effectivity of condoms and other anti-conceptives

why do they state the effective of condoms (and others) in the form of percentage of failure/year? Wouldn't it be more accurate to put it as failures/times used? 80.58.250.84 (talk) 17:31, 28 June 2013 (UTC)[reply]

It is somewhat arbitrary, but as the failure/use rate is rather small, when picking an arbitrary period over which to express a measurement, the measurement is often picked to keep the number within an easy-to-understand range, basically keeping things within about 2-3 digits on either side of a decimal point. For example, I can express my weight as either 95 kilograms, or 95,000,000 milligrams, or any of a number of other measurements, arbitrarily. The human brain does a better job of processing numbers with a small number of digits to either side of the decimal point, so a scale is chosen to keep that in mind. For example, assuming a 2x per week usage, a condom with a failure rate of 2% per year would be expressed as 0.02% per usage, and it's easier for most people to internalize how much "2" is rather than "0.02" --Jayron32 17:39, 28 June 2013 (UTC)[reply]

You mean 0.02 times per usage - not 0.02% per usage. So in your example the failure rate (expressed as a percent of times used) would be 2% - and that seems easy enough to grasp. StewieCartman (talk) 19:39, 28 June 2013 (UTC)[reply]

No, Jayron is correct. His approximation is 0.02 times per year / 100 usages per year = 0.0002 times per usage. -- — Preceding unsigned comment added by 177.120.234.75 (talk) 13:18, 29 June 2013 (UTC)[reply]

I don't think that that's what he meant. He said a "failure rate of 2% per year". That is not the same as 0.02 times per year / 100 usages per year. StewieCartman (talk) 14:09, 29 June 2013 (UTC)[reply]

No, 177 is correct. If something fails 2% per year that's 2/100 chance of failure per year, and at 2 uses per week that's about 100 uses per year, which would be a failure rate of 2/10,000 chance of failure for each usage. --Jayron32 20:15, 29 June 2013 (UTC)[reply]

I see. My apologies for the misunderstanding. StewieCartman (talk) 10:27, 1 July 2013 (UTC)[reply]

The approximation only works, of course, because 0.02 is a relatively small number. You could not, for instance, take the 85% probability that a sexually active woman will become pregnant in one year and conclude that the chance of getting pregnant from a single instance of intercourse is only 0.85%, because the majority of those woman will become pregnant early in the first year of trying. The actual number appears to be more on the order of 5% per instance. [6] -- 189.71.47.213 (talk) 22:03, 2 July 2013 (UTC)[reply]

Yes, but people who have sex 10x/week and people who have sex 1x week will both think: it only goes wrong once every 50 years. Both cannot be correct. If you told me, for each 100 uses, 2x it goes wrong, then everyone would still understand it. And people who have more sex than average would know where they are getting into. 80.58.250.84 (talk) 17:44, 28 June 2013 (UTC)[reply]

The failure rate also acts as a disclaimer. If they said 100 percent effective, they would be leaving themselves open to costly complaints. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:21, 28 June 2013 (UTC)[reply]

I think you've misinterpreted the question. No one is suggesting that they should say 100 percent effective. StewieCartman (talk) 19:34, 28 June 2013 (UTC)[reply]

I didn't look that well at the previous discussion but I know this issue was at least hinted at. Do note that failure rates are complicated. For example, as mentioned in the previous discussion, abstinence has a near 100% success rate at preventing pregnancy or STDs if used perfectly. Similarly condoms alone have a very high success rate. However these figures are often considered misleading or confusing so instead real world failure rates are generally quoted which considers rates when usage is not perfect (in the case of condoms this can lead to slippage or breakage although as with most methods wich require action, simple failure to use is the most common problem as per our article). Determining these rates and what to count is not simple but frequently involves surveys of what people intend to use and in how many cases it failed (as determined by pregnancy, STD transmission etc). (I've heard before of abstinence proponents quoting 100% success for abstinence and so discounting people who were intending to be abstinent but were not, yet if these people were intending to use a condom but didn't including them in the failure rates for condoms. Not that determining rates for perfect usage for condoms in particular is necessarily any easier.) Getting people to estimate how many times they had sex complicates matters (it would likely require more subjects for starters and even then your results may still be more questionable) and the figures could also mislead. While there would be some correlation between failure rate and number of times people have sex, the correlation may not necessarily be that high. Beyond the differences in how effectively the person uses the method, there will also be other confounding factors like how vigiriously the sexual activity is, how long it lasts, the persons susceptibility to the STD etc. In other words, as Jayron32 said, ultimately you have to find some way to meaningfully communicate the info, and it's not clear that a failure rate per usage would be any better than per year in addition to being harder to determine. Nil Einne (talk) 18:23, 28 June 2013 (UTC)[reply]

The neuroscience of waking up

To the best of my understanding, we fall asleep because certain neurons in the ventrolateral pre-optic nucleus crave adenosine, and our bodies manufacture it. The adenosine then goes to those synapses and we fall asleep. How do we wake up? — Preceding unsigned comment added by Bobgustafson1 (talk • contribs) 17:44, 28 June 2013 (UTC)[reply]

I do believe other neurotransmitters are also involved in out sleep. Take for example melatonin or histamine (involved in wakefulness). 80.58.250.84 (talk) 17:51, 28 June 2013 (UTC)[reply]

The science here is not very solidly established, but according to Cliff Saper, transitions between sleep and waking are controlled by mutually inhibitory interactions between the VLPO and a set of "arousal" centers, which combine to form a sort of "flip-flop" circuit. The VLPO inhibits the arousal centers, but the arousal centers also inhibit the VLPO. The VLPO is activated by adenosine (a sort of "tiredness" signal) but also by other factors, including circadian rhythms. When the VLPO is activated strongly enough to dominate, we fall asleep. By morning, though, adenosine levels have dropped and the phase of our circadian rhythm has shifted, and so the drive to the VLPO decreases. At some point the arousal systems escape from inhibition, and when they come on, they inhibit the VLPO, allowing further increases in arousal -- thus we get a rapid transition from sleep to wakefulness. This story is at best oversimplified, and might turn out to be completely wrong, but it's probably the best story we can tell right now. Looie496 (talk) 18:14, 28 June 2013 (UTC)[reply]

(subquestion) - there's one practical aspect of this that continues to intrigue me. Back when I was having trouble with gout (a very painful condition in the legs) sometimes I would awaken, but deliberately maintain sleep paralysis of my legs for up to an hour or so to avoid feeling the pain. For very brief periods it was even possible to move arms, at least a little, without breaking that. I assume this has some relevance to anaesthesia by hypnosis? Somehow I didn't get far trying to figure this out with present sources, but I would wonder even if things as serious as locked-in syndrome could somehow have to do with this weird, seemingly low-level block over motion and sensation. Wnt (talk) 20:04, 28 June 2013 (UTC)[reply]

Firstly, neurons don't "crave" adenosine. There's evidence that adenosine accumulates during sleep deprivation and shifts the brain's sleep-wake circuitry in favour of sleep (see Looie496's "flip-flop" explanation). However it is not the only factor in sleep homeostasis. Circadian rhythms of multiple transmitter/peptide systems cause the brain to shift from wake to sleep and vice versa. A very good, fairly non-technical open-access review in Neuron is available here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3026325/ --Markr4 (talk) 20:22, 28 June 2013 (UTC)[reply]

Wind direction and planetary rotation

Hello! I always remember the phrase, "The sun rises in the east and sets in the west," probably because I remember the phrase, "The land of the rising sun," so I know which direction the world rotates, but what I didn't connect with it is, I know which direction the wind flows too, and rather than being dragged along behind the rotation of the planet, it is pushing forward ahead of it! Is there a name for this specific phenomenon? Is it the same for all gaseous bodies? Can anyone recommend some basic info, perhaps online? ~ R.T.G 20:44, 28 June 2013 (UTC)[reply]

The prevailing wind direction depends on where you are on the planet, and in some places on the season of the year as well. See prevailing wind for a summary of the main patterns. Looie496 (talk) 20:50, 28 June 2013 (UTC)[reply]

I'm not sure I understand you, RTG. Are you asking why the planet's rotation doesn't cause wind? The atmosphere is part of the planet and so rotates along with the rest of it. StewieCartman (talk) 20:55, 28 June 2013 (UTC)[reply]

(ec) The Prevailing winds, Trade winds and Hadley cell articles are a good place to start regarding the prevailing wind patterns in lower Earth atmosphere. See Jupiter and Saturn articles for the atmospheric circulation patterns in the gas giants. --Dr Dima (talk) 20:58, 28 June 2013 (UTC)[reply]

Actually I may have this mixed up. The portrayal of wind direction in history make it seem that winds prevail in the easterly direction, and the articles I looked at did not dispel this impression, however, the diagram in the Trade winds article does make it appear that the central winds move toward the west more powerfully. Makes me re-evalute some reputable documentaries and historic events concerning human travel. Well, if Columbus presented a theory to the Vatican about the world being round they'd have thought he was a slow learner. I guess there is a lot of that today, humans being so clever and all. Thanks anyways. ~ R.T.G 21:39, 28 June 2013 (UTC)[reply]

(Pet hate: Columbus, his crew and the guys in the Vatican all knew that the world was round - (See: Christopher_Columbus#Geographical_considerations) - the problem with his voyages were that the estimate for the radius of the earth was way off. The idea that popular belief in the middle ages was that the world is flat is a myth.) SteveBaker (talk) 04:30, 29 June 2013 (UTC)[reply]

To be even more specific, it was Columbus's estimate of the radius of the Earth that was way off: the mainstream one was pretty good. That's why everyone thought his mission was doomed: he thought he'd get to the Indies in half the actual distance, and everyone was pretty sure he'd actually have to travel the distance we now know that it is. He was just lucky he hit another continent, because he was wrong and everyone else was right. 86.162.68.199 (talk) 18:34, 29 June 2013 (UTC)[reply]

Geostrophic wind is also worth having on your list. Dolphin (t) 22:52, 28 June 2013 (UTC)[reply]

Yes that one is the sort of thing I was wondering about, thanks again Dolphin :). ~ R.T.G 23:00, 28 June 2013 (UTC)[reply]

You might want to look at some time-lapse videos of the Earth's atmosphere, where you can see clouds moving in different directions at the same time. Of course, the motion of the Earth's atmosphere is only visible when it contains clouds, and there's considerable variation/randomness in wind direction at any spot over time. If you look at a larger planet, like Jupiter, the atmosphere is both more visible and consistent in the directions it moves at each location. I've always wondered if this is just a function of the size of a planet, or if Jupiter's consistency is due to other factors, like distance from the Sun. StuRat (talk) 05:47, 29 June 2013 (UTC)[reply]

Actually, realtime satellite videos are great ~ R.T.G 21:08, 29 June 2013 (UTC)[reply]

Clouds move mighty slow when viewed at the global scale, so you'd probably want to speed them up to see the patterns. StuRat (talk) 04:16, 30 June 2013 (UTC)[reply]

See: Coriolis_effect#Rotating_sphere It explains it all.--Aspro (talk) 13:20, 29 June 2013 (UTC)[reply]

Slugs?

I don't hold the copyright, so I can't upload here, but who are these fellas munching on an earthworm? Evanh2008 ^{(talk|contribs)} 22:23, 28 June 2013 (UTC)[reply]

Looks like a Spanish slug, but could be another similar-looking member of the family Arionidae. Looie496 (talk) 22:48, 28 June 2013 (UTC)[reply]

Looks too fat to be a Spanish slug. There are plenty of Google Images of slugs, and oddly enough there's one that looks similar[7] - and was likewise posted by someone wondering about it (not this same picture, though). ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:04, 28 June 2013 (UTC)[reply]

Possibly Arion ater. This slug belongs to a closely related complex which includes Arion rufus and Arion elater which can only be distinguished by dissection of the genitalia, according to this site. Richard Avery (talk) 07:33, 29 June 2013 (UTC)[reply]