Wikipedia:Reference desk/Archives/Science/2011 August 23

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August 23

How good is Scientific Learning Corporation's Reading Assistant?

Scientific Learning Corporation currently redirects to one of their products in which I am not interested. I need independent evaluations of the 'Reading Assistant' product they acquired from Soliloquy Learning some years back. Where can I find those? 208.54.5.213 (talk) 05:14, 23 August 2011 (UTC)

From http://www.scilearn.com/products/reading-assistant/ under "Q&A":

Is Reading Assistant research-based? Yes. According to the report of the National Reading Panel, "classroom practices that encourage repeated oral reading with feedback and guidance leads to meaningful improvements in reading expertise for students—for good readers as well as those who are experiencing difficulty." With Reading Assistant, the computer becomes the supportive listener that ensures all students can regularly practice oral reading while receiving immediate, individual feedback from Scientific Learning's advanced speech verification software.

Is Reading Assistant research validated? Yes. The impact of Reading Assistant on fluency growth was evaluated with mainstream students in Grades 2-5. Half of the classrooms in two schools used the software in thirty-minute sessions, once or twice a week over 17 weeks. Across all four grades, fluency gains were significantly greater for students who used the software than those who did not, averaging 43% (E.S.=0.91) greater than normative expectations over grades. Project sponsored by the Carlisle Foundation and NICHD.

76.254.20.205 (talk) 08:24, 23 August 2011 (UTC)

What does "E.S.=0.91" mean? 76.254.20.205 (talk) 09:31, 25 August 2011 (UTC)

tomato, hot pepper - why are they toxic?

Tomatoes and hot peppers are flowering plants, and thus designed to attract animals and insects to feed of them and so disperse their seeds. In this case, why were tomatoes, or some species of them, poisonous (being related to the deadly nightshade family)? How would being poisonous help a plant to disperse it seeds? Then too, I've read that the toxicity of tomatoes was highly overrated, and that no one was seriously in danger. With hot peppers, most animals would not be able, or want to, eat fruits such as these. I've read in WP, that because birds do not have pain receptors to the capsaicin which causes the burn, then they become the preferred carriers of the seed. Why would this plant discourage other animals from eating its seed, and leave it to the birds? Do the birds help to pollinate the plants? And in any case, if so, why do no other plants encourage birds but discourage non-birds to eat their fruit? Myles325a (talk) 07:01, 23 August 2011 (UTC)

Apparently mammals like mice will digest the seeds if they eat hot peppers. Birds will not digest the seed, and will pass it through, transported to a new location! Graeme Bartlett (talk) 07:07, 23 August 2011 (UTC)

Birds can't taste the capsicumcapsaicin in chilli peppers. Assuming Graeme is right (I have no knowledge either way, but it seems sensible), then it is in the plants' interests that only birds eat its seeds. CS Miller (talk) 10:11, 23 August 2011 (UTC)

The missing piece seems to be, why is it that mammals keep the 4-vanilloid receptor that responds to capsaicin? If it's not harmful intrinsically, then it's odd that the receptor that causes the pain wouldn't be selected out.

The vanilloid_receptor_subtype_1 receptor is activated at well over normal body temperature (43°C), and seems to part of the the thermal homoeostasis mechanism in mammals. Capsaicin interferes with the calcium channel in it, and causes it to activate at around body temperature. So, mammals will need to develop another thermal regulation system before they can remove the receptor. Until the major source of food are capsicums there is not enough selection pressure for this. CS Miller (talk) 10:57, 23 August 2011 (UTC)

Thanks; that seems reasonable. --Trovatore (talk) 20:42, 23 August 2011 (UTC)

Then you get the paradoxical cases of humans who eat the stuff deliberately for the endorphin glow that comes with it. I wonder if that happens with mammals in the wild, as well. --Trovatore (talk) 10:27, 23 August 2011 (UTC)

Do you have a reference for any cultivar or variety of tomato being toxic? Yes, they contain small amounts of toxic substances, as do most foods, but as far as I'm aware their reputation for toxicity was never anything but a flat mistake. Calling it an "exaggeration" is too mild; it was just wrong. --Trovatore (talk) 07:34, 23 August 2011 (UTC)

Op myles325a back live. Yes, I've checked up and you are right. Tomatoes are related to, and look like, deadly nightshade, and apparently ALL parts of it including the leaves and roots are indeed poisonous, except for the fruit. This makes sense, as the fruit is the only part of it that the plant needs to have eaten. Myles325a (talk) 07:48, 23 August 2011 (UTC)

Members of Solanaceae are just naturally very rich in alkaloids. And alkaloids are usually used as the anti-herbivore chemical defenses of plants aimed at indiscriminate feeders (animals who will eat the whole plant if they can), most notably insect and mammalian grazers. Birds are obviously not usually indiscriminate feeders. So yes, that's why concentrations of different alkaloids can vary in different parts of the plants and why they sometimes exclude specific groups of animals. It's not only birds though, some fruits of poisonous Solanum are only poisonous (or at least far more poisonous) when unripe.

And for what it's worth, other plants do have the same kind of targeted toxicity. It's actually fairly common when it comes to berries, especially the brightly colored ones. Pokeweed, Mistletoe, Baneberry, and Holly for instance have berries or seeds poisonous to mammals, but not to birds. Elderberry are also toxic only when unripe. Poison ivy is another good example, they have contact toxins in their vegetative parts but their fruits are perfectly edible for birds. Cashews also have edible fruits but the seed shells are protected by contact toxins even if the seeds themselves are also edible. Milder examples of this kind of repulsion/attraction mechanisms for seed dispersers also includes the extremely sour unripe fruits of some plants and plants with edible berries that are covered with specifically anti-mammalian defenses (like spines). All of them are not members of the nightshade family. Some plants also use different classes of chemical compounds like saponins which are toxic to insects and unpalatable for livestock, even when their fruits are quite edible. Also seed dispersal, while important, is usually less so when compared to the need for fertilization and sheer survival. The bulbs of members of Liliaceae (lilies) for instance are highly poisonous to mammalian grazers and they don't exactly need other species to disperse their seeds.

It's also an ongoing war, so some animals have circumvented those defenses or even coopted them (ragworts and cinnabar moths for instance), others are specifically targeted or excluded (as discussed above, and birds and capsaicin), others have actually evolved with it (the mutualistic relationship between Manduca hawkmoths and Datura is one fascinating example).

All in all, you could simply say that in the plant kingdom, nightshades are armed to the teeth.-- Obsidi♠n Soul 10:56, 23 August 2011 (UTC)

For what it's worth, it's not clear that the indirect allergic reaction of most humans to the urushiol in poison oak, poison ivy, and the like, is adaptive for the plant. Most animals don't seem to react that way, or at least not as strongly (deer, for example, will eat poison oak branches). The twenty-four-hour-or-so delay before the reaction shows up is not ideal as a chemical defense, and there are similar chemicals in the skin of the mango fruit, which would seem to have no objection to mammals (or indeed humans) as seed dispersers.

Also, urushiol polymerizes into a strong lacquer (in fact, lacquer in the original, strict sense is polymerized urushiol oops, from the lacquer article it appears this is not the original sense) so it's plausible that its function for the plant is simply to close up wounds. --Trovatore (talk) 21:07, 23 August 2011 (UTC)

Hm didn't know that. Scratch Anacardiaceae then :P At least the contact toxins defense theory, urushiols are also resins and thus might still function as plant defense against insects. -- Obsidi♠n Soul 02:14, 24 August 2011 (UTC)

Aside from digestive issues, some plants may favor birds as seed dispersers for other reasons. Birds generally can disperse seeds to farther and more varied locations than mammals can (e.g. mountain tops, islands, etc.), and this can aid in long-term persistence of a population. SemanticMantis (talk) 14:30, 23 August 2011 (UTC)

I'll mention in passing that there have been experiments in the past where tomatoes have been grafted on to jimsonweed root stock, with the intention of producing a tomato plant with the inherent frost and insect resistance of the jimsonweed: [1]. Such experiments were abandoned when it was found that toxic concentrations of (hallucinogenic) alkaloids migrated into the tomato fruit. The experiment has occasionally be independently repeated by farmers and gardeners who don't know better, often with unpleasant and dangerous results: [2]. TenOfAllTrades(talk) 14:54, 23 August 2011 (UTC)

Op myles325a back live. You pay a lot more for a tomato like that. This is a case where if you cook it, YOU get stewed, not the tomato. Myles325a (talk) 10:23, 25 August 2011 (UTC)

From what I've heard about jimsonweed, it's not a good trip. Basically you're sick and delirious. I don't think many people do it for pleasure. --Trovatore (talk) 09:50, 26 August 2011 (UTC)

(I'm a layman). It occurs to me that since birds don't chew their food the seeds have a much better chance of making it out the other end intact, aside from other digestive issues. --Sean 16:54, 23 August 2011 (UTC)

Myles325a back live. That makes excellent sense. Also, the digestive tract of a bird is very much shorter than that of most mammals. Myles325a (talk) 10:23, 25 August 2011 (UTC)

Take a read of Bugs put the heat in chili peppers for a reference on the topic. Graeme Bartlett (talk) 11:15, 25 August 2011 (UTC)

event horizon

Is the solar equivalent radius the black hole's event horizon? --DeeperQA (talk) 13:06, 23 August 2011 (UTC)

I only find the term "solar equivalent radius" used with respect to describing galactic evolution, which is unrelated to an event horizon. For the basic case of a nonrotating black hole, the event horizon is the Schwarzschild radius, a value proportional to the mass of the object in question. — Lomn 13:34, 23 August 2011 (UTC)

if the mass of the Sun and the mass of a Black Hole were the same would the event horizon of the Black hole be the same radius as the solar radius? --DeeperQA (talk) 14:28, 23 August 2011 (UTC)

No, it would be significantly smaller. --Goodbye Galaxy (talk) 14:41, 23 August 2011 (UTC)

Goodbye Galaxy is correct. If the Schwarzschild radius of a solar-mass black hole was the radius of the Sun, then the Sun (being of solar mass) would be a black hole. Obviously this is not the case. Our SR article, linked above, notes that the SR for a solar mass body is 3 km; the Sun has a 700 000 km radius. — Lomn 15:51, 23 August 2011 (UTC)

So... Obviously the surface of the star is not the radius of the black hole it would make, other wise nothing from beneath the surface would ever be able to escape... Our sun is not large enough to MAKE a black hole, but on a star that CAN make a black hole, say it makes a black hole that's 10km wide, it's going to have similar gravity to the original star right? (minus any matter that's lost in the nova or whatever)... Does that mean, that in the original star, there was essentially already a black hole in the middle 10km? As in no material would have ever been able to escape from that region? Vespine (talk) 23:10, 23 August 2011 (UTC)

How would such a region avoid growing if things could enter it but not leave? The substitution of a point mass at an object's center of mass is only valid when considering the effects outside the body (and is also only strictly valid for spheres, though at large distances it is approximately true regardless of the shape). --Tardis (talk) 04:37, 24 August 2011 (UTC)

Duh! Of course, the star has to collapse 1st... Thanks. Vespine (talk) 01:25, 25 August 2011 (UTC)

What would happen if you injected fat into a vein?

I guess the subject is basically the question. I assume different types and amounts of fat will have different answers too. Egg Centric 17:51, 23 August 2011 (UTC)

I expect it would cause a nasty embolism and probably kill the person if we are talking about more then a microscopic amount. Googlemeister (talk) 18:59, 23 August 2011 (UTC)

See fat embolism. Dragons flight (talk) 19:06, 23 August 2011 (UTC)

Total amount of platinum

What's the total amount of platinum in/on Earth, including both what's already been mined and what's still in rocks somewhere? --75.10.48.39 (talk) 17:53, 23 August 2011 (UTC)

Well, our article says "Platinum is one of the rarest elements in the Earth's crust and has an average abundance of approximately 0.005 mg/kg" The crust is about 0.5% of Earth's mass, which is 6x10²⁴kg. So that's about 3x10²²kg; or 1.5x10²⁰mg of platinum, 1.5x10¹⁷g, 1.5x10¹⁴kg. This is, of course, rather a guesstimate, I wonder if there are any other estimates out there. Grandiose (me, talk, contribs) 18:00, 23 August 2011 (UTC)

I'd expect there to be substantially more in the core, and also a bit in the oceans, although those sources may be unavailable to us for quite some time. StuRat (talk) 01:46, 24 August 2011 (UTC)

The total mined is about 180 million toz according to http://www.howstuffworks.com/question213.htm. Googlemeister (talk) 18:57, 23 August 2011 (UTC)

Online seismograph reports?

It feels like we just had an earthquake (in Connecticut). Is there an online seismograph report for the region that I can check? RJFJR (talk) 18:03, 23 August 2011 (UTC)

Oh, USGS NEIC at [3] RJFJR (talk) 18:06, 23 August 2011 (UTC)

5.9 in Virginia, time seems right. That's pretty far away but this building may be particularly susceptible to sway. RJFJR (talk) 18:07, 23 August 2011 (UTC)

I felt it also in Syracuse, New York, on the ground floor.. It's not unusual for earthquakes of that magnitude to be felt very far away. —Akrabbim^talk 18:21, 23 August 2011 (UTC)

On the US East coast anyway. If a 5.9 hit in California, it probably wouldn't be felt 100 miles away. Different geology knocks them down quick out there. Googlemeister (talk) 18:53, 23 August 2011 (UTC)

A 5.9 is big enough to be felt 100 miles away even in California -- that's a big quake. This is really remarkable: this quake comes just hours after a series of pretty large quakes in Colorado, which also gets very few. Looie496 (talk) 20:14, 23 August 2011 (UTC)

In the most literal sense, this is a "coincidence" - a "near-simultaneous" incidence of an earthquake in two unusual places. Before we jump to calling it "really remarkable," though, we should do a thorough statistical analysis to determine how improbable a coincidence this really is. There's no shortage of research into remotely triggered earthquakes, or induced seismicity, teleseismic interactions, etc. Here's a few: Remotely Triggered Earthquakes Following Moderate Mainshocks (or, Why California Is Not Falling into the Ocean), from the US Geological Survey; Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake, from the journal Science (1993); and Remotely Triggered Seismicity on the United States West Coast following the Mw 7.9 Denali Fault Earthquake. It's difficult to produce convincing evidence that distant earthquakes are causally related, and this is an active area of research subject to scientific dispute. But it's at least within the realm of possibility that two earthquakes in unlikely, not-very-seismically-active areas, might be linked. I'm sure in the next weeks and months, seismology journals will be hosting a flurry of research papers into this fairly large earthquake in an otherwise seismically-quiet area. Nimur (talk) 03:02, 24 August 2011 (UTC)

@Louie & Googlemeister: According to a Berkeley Seismologist, quoted here: [4] an earthquake of the size that hit Virginia would "rarely" be felt farther than 30 miles from the epicenter; the very different geology of the Eastern U.S. compared to California explains the difference in travel. --Jayron32 03:38, 24 August 2011 (UTC)

lizards

What is the best place and time of year in Ireland to find Lizards that are native to Ireland and also legless lizards. — Preceding unsigned comment added by 86.45.169.42 (talk) 18:37, 23 August 2011 (UTC)

As you probably know there are only two reptile species in Ireland, the Viviparous lizard (Zootoca vivipara) and the legless lizard, better known as the slow-worm (Anguis fragilis). The lizard is widely distributed across the island and can be found in dry heathland, dunes, grassland, bogs and even gardens. The slow-worm is confined to The Burren. The best time to see them is during the warmer weather of spring and summer when they are more active. I'm sure there must be a Natural History Society or club around the Cork area that could offer you local advice. Good luck. Richard Avery (talk) 22:21, 23 August 2011 (UTC)

Required muzzle velocity of a cannon to shoot any target on Earth

What would be the minimum muzzle velocity required for a projectile fired from a cannon to be capable of hitting any target on the planet? Lets say it's being fired from some kind of futuristic cannon like a railgun or a massdriver. ScienceApe (talk) 19:17, 23 August 2011 (UTC)

About 70% of earth's escape velocity which is about 7.9 km/s, assuming no air friction. Dauto (talk) 19:45, 23 August 2011 (UTC)

(ec) Ballpark, ignoring air resistance, you need orbital velocity which, at sea level, is about 8 km/s. Technically you don't need quite this much, as (assuming you can rotate your cannon) you only need to get a projectile halfway around the world, but that won't change the final answer by more than a percentage point or two. — Lomn 19:54, 23 August 2011 (UTC)

If you don't ignore air resistance, then only needing to get half-way round is a big advantage. It means you can reach the opposite side of the planet at ground level, rather than needing enough altitude to counter the drag on the second half of the trip. --Tango (talk) 22:03, 23 August 2011 (UTC)

Project Babylon?--92.28.71.6 (talk) 20:53, 23 August 2011 (UTC)

Just because an object circles the Earth once does not mean that it is in orbit, see Space shuttle abort modes#Abort Once Around (AOA) for an example of this. Whoop whoop pull up ^{Bitching Betty | Averted crashes}`

With an AOA, they do achieve orbit. The orbit is just too low so the drag from the atmosphere is too high and the orbit decays before they can get around more than once. You still need orbital velocity to AOA. --Tango (talk) 21:57, 23 August 2011 (UTC)

They do not. With an orbit, it will circle the Earth forever neglecting air resistance. With an AOA, even without air resistance, it will come down where it was launched. An AOA is basically just a suborbital trajectory where the distance traveled downrange is equal to the Earth's circumference. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:33, 27 August 2011 (UTC)

• Can I butt in with a follow-up question? To hit a target on the exact opposite side of the earth using minimum muzzle velocity, what direction would you fire in? Ignore air resistance. 86.179.3.58 (talk) 22:18, 23 August 2011 (UTC) PS: I was assuming that the target could be attained with some muzzle velocity in numerous directions, but actually I'm not even sure if that is correct.

Ignoring air resistance, possible obstacles such as mountains, and earth's rotation, a very low shot in any direction will do the trick. Dauto (talk) 22:38, 23 August 2011 (UTC)

I wonder if this is actually possible... I mean, wouldn't there be an "upper limit" to how fast you can shoot an "un-powered" projectile in the atmosphere? and how quickly it would decelerate? I remember reading something about theoretical mass driver naval guns and they still said the range would only be in the order of hundreds of miles. Vespine (talk)

Slightly pedantic, maybe, but such a cannon would not be possible, as it would be unable to shoot down its own barrel, and would therefore not be capable of hitting any target on Earth, whatever the speed of the projectile. Likewise with the 'other sides' of mountains, etc.

What do you mean by shoot down its own barrel? Dauto (talk) 23:39, 23 August 2011 (UTC)

@Dauto, are you saying that a very low shot in any direction would be the optimum shot in terms of minimising muzzle velocity? I ask again because on a level surface, a given distance is achieved at minimum velocity by firing up at 45 degrees, isn't it? So, when the whole round Earth is considered this changes and a low shot is best? 86.179.3.58 (talk) 23:43, 23 August 2011 (UTC)

Combine the Vis-viva equation $v^{2}=G(M+m)\left({\frac {2}{r}}-{\frac {1}{a}}\right)$, The standard equation of an elipse in polar coordinates from Kepler's laws of planetary motion $r={\frac {p}{1+\varepsilon \,\cos \theta }},$ and the relation between the Semi-major axis and the Semi-latus rectum $a={\frac {p}{1-\varepsilon ^{2}}}.$ to get $v^{2}={\frac {G(M+m)}{a}}\left({\frac {1+2\varepsilon \,\cos \theta +\varepsilon ^{2}}{(1-\varepsilon ^{2})}}\right)={\frac {G(M+m)}{p}}(1+2\varepsilon \,\cos \theta +\varepsilon ^{2})$ where $p\,$ is the semi-latus rectum which is the radius of the orbit half way between apogee and perigee (90 degrees away from each). In our problem that coincides with the radius of the earth $R\,$. Setting theta to 90 degrees (0 degrees is the perigee while 180 degrees is the apogee) we get the equation $v^{2}={\frac {G(M+m)}{R}}(1+\varepsilon ^{2})$. Clearly the speed is minimized by choosing the eccentricity $\varepsilon =0$. That's the eccentricity of a circular orbit. Dauto (talk) 03:18, 24 August 2011 (UTC)

Why do you want the semi-latus rectum to be the Earth's radius? Assuming your target is on the surface, you want the radius of the orbit when it's above the target to be equal to the Earth's radius. I can't see why you would need to have the apogee and perigee be 90 degrees away from that point. The simplest method (from a mathematical, not engineering, viewpoint, and ignoring air resistance) is to fire horizontally at a speed between zero and circular orbital velocity (which makes the firing point the apogee). If you fire at zero speed, you'll hit yourself. As you increase the speed, you'll go further and further around until you reach the opposite side of the Earth at circular orbital velocity (actually, you would be in a circular orbit and wouldn't hit at all, but that's just the limiting case). By varying the angle you fire at, you can move the agogee (and make it higher, obviously). I would need to do some maths to work out whether another angle would allow a slower launch speed, so I'll leave that to someone else. --Tango (talk) 11:45, 24 August 2011 (UTC)

You don't need to leave the math to someone else. I already did the math in the post right above yours. My post is correct. read it carefully. The apogee is actually the half way point of the trajectory, not the initial point as you stated. Remember that we are assuming that the canon is at the surface of the earth - not at the top of a mountain. That puts the canon and the target at the same level. Obviously, the solution to this problem is a degenerate one because the circular orbit, as pointed out by others, skims the surface of the planet all the way around. Dauto (talk) 15:07, 24 August 2011 (UTC)

As far as I can see (and I'm by no means 100% sure), the only way to reach the antipodean point is by firing exactly horizontally. Any other trajectory headed for the antipodean point would inevitably hit some other part of the Earth first. The lowest velocity horizontal-firing case would be a circular orbit, which would skim the antipodean point, but also skim all other points on the Earth's circumference, so would not in practice be achievable even if the Earth was a perfectly smooth sphere. 86.183.4.36 (talk) 12:02, 24 August 2011 (UTC)

There is clearly an infinite family of elliptical orbits that pass through a point and its antipodes, with one focus at the Earth's center. 69.234.120.192 (talk) 13:00, 24 August 2011 (UTC)

Sure, but show me one that doesn't hit another part of the Earth first. 86.183.4.36 (talk) 13:21, 24 August 2011 (UTC)

Um, none of them do. Each ellipse crosses the earth's surface exactly twice (only at the two points of interest). In general, an ellipse might intersect a circle in four places, but none of those ellipses has a focus at the center of the circle. 69.234.120.192 (talk) 13:51, 24 August 2011 (UTC)

Sorry, I realised later that I made a silly mistake. I was making the centre of the ellipse coincide with the centre of the earth, not the focus. 86.181.200.231 (talk) 17:03, 24 August 2011 (UTC)

If air resistance is included, I'd think you'd want to minimize that by firing at a steep angle, over 45 degrees. You might still have a problem with your projectile burning up in the atmosphere even then. StuRat (talk) 01:38, 24 August 2011 (UTC)

The trajectory needs to be similar to that of an ICBM:

...the flightpath is part of an ellipse with a vertical major axis; the apogee (halfway through the midcourse phase) is at an altitude of approximately 1,200 km; the semi-major axis is between 3,186 km and 6,372 km; the projection of the flightpath on the Earth's surface is close to a great circle, slightly displaced due to earth rotation during the time of flight; the missile may release several independent warheads, and penetration aids such as metallic-coated balloons, aluminum chaff, and full-scale warhead decoys. reentry phase (starting at an altitude of 100 km): 2 minutes—impact is at a speed of up to 4 km/s (for early ICBMs less than 1 km/s); see also maneuverable reentry vehicle.

Count Iblis (talk) 02:05, 24 August 2011 (UTC)

Unreal Creatures in Cave paintings

1. How often did our ancestors draw imaginary creatures in cave paintings (e.g. dragons, gods, etc.)? Where can I find such paintings' images on the web?
2. Is this painting a fake?

Thanks, Oh, well (talk) 19:59, 23 August 2011 (UTC)

Although [5] is supposed to teach you that humans walked the Earth with dinosaurs, which is absurdly false, it does have a nice collection of ancient dragon depictions. And, that FSM painting is almost certainly a fake. Authentic cave paintings almost never use separate full outline and full fill color pigments as is popular with drawing and painting today. 76.254.20.205 (talk) 20:20, 23 August 2011 (UTC)

A recent feature movie about cave paintings, "Cave of Dreams," portrayed drawings of what appeared to be "Monkeys on Wheels," a type of creature which never was manifest tens of thousands of years ago. Three members of my family watched the movie and agreed that some of the cave drawings appeared to be monkeys on wheels. Maybe it was just inept and unskilled drawings of mammoths. Or maybe the ancients dreamed of monkeys on wheels and drew them accordingly, thousands of years before they put any practical device on wheels. I seriously considered changing my Wikipedia name to "Monkey on wheels," so it is no idle observation. Edison (talk) 04:25, 24 August 2011 (UTC)

I assume you're referring to Werner Herzog's Cave of Forgotten Dreams --George100 (talk) 08:25, 24 August 2011 (UTC)-

Our article: Cave of Forgotten Dreams -- 110.49.235.213 (talk) 12:15, 24 August 2011 (UTC)

Some anthropologists, such as David Lewis-Williams, have theorised quite persuasively that some rock paintings depict hallucinatory visions seen in dreams or trances deliberately induced by drugs, extreme exhaustion caused by ritual dancing, etc. In such dreams and trances the shaman (or whatever equivalent term one might use) likely saw/sees imaginary entities, often composite animals (bird-headed men are I believe common in African rock paintings) as well as realistic ones. {The poster formerly known as 87.81.230.195} 90.197.66.45 (talk) 07:38, 24 August 2011 (UTC)

Because all the races of man diverged long before recorded history, we should be confident that ancient humans possessed the same capacity for art, imagination, delusion, hallucination, and guesswork as those who live today. Because so many of our own artworks are made with ephemeral materials, it seems reasonable to suppose that what survives on cave walls is only a tiny and probably a low-quality subset of what was available. But it's also worth mentioning that the ancients sometimes had a penchant for paleontology (such as the Greeks who hunted for "giants' bones" to display as local relics - see e.g. [6]) Of course, they had fewer scientists, much poorer communications and archives - they couldn't develop the kind of comprehensive insights that people take for granted nowadays. But I would not rule out the possibility that a well-preserved skeleton led to a dinosaur artwork on more than one occasion in prehistory. Wnt (talk) 22:53, 24 August 2011 (UTC)

vehicle skid marks

could a car travelling 10-15 km/hour leave 5-10' skid marks that end 10-15' behind the vehicle's final stopping point on dry pavement? 24.69.118.194 (talk) 21:37, 23 August 2011 (UTC)

I don't see why not. There are loads of factors that determine things like that. The weight of the car, the type and condition of the tyres, the type and condition of the brakes, what the driver does, etc.. I can't see why there couldn't be a combination that results in what you describe. --Tango (talk) 22:26, 23 August 2011 (UTC)

here is a stopping distance calculator. Having a bit of a play around with that, and having done a few skids myself, I think 10-15' skid sounds extreme for going only 10-15km/h. As the above says, it's not "impossible" if you plug in appropriate variables (over loaded car, bald tyres, loose surface), but with a normal weight car, road worthy tyres and a sealed dry road, I think you'd be lucky to get 2-4' skid, even if you tried to break very violently. To get 10-15' skids, I think you'd need to be going more like 20-30km/h. Another factor to consider is that a lot of cars these days have Anti-lock breaking so it's quite hard to actually skid in them, especially at such a low speed. Vespine (talk) 22:44, 23 August 2011 (UTC)

Just because you have ABS does not necessarily mean that it will work. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:35, 27 August 2011 (UTC)

That sounds like you need to consult an appropriate forensic specialist with expertise in vehicular accident reconstruction. TenOfAllTrades(talk) 23:24, 23 August 2011 (UTC)

Sounds like the skid marks are too long for that speed, unless another vehicle then pushed it along, which can happen in multiple vehicle accidents. StuRat (talk) 23:32, 23 August 2011 (UTC)

You you were stopping on a steep downhill grade. Googlemeister (talk) 14:49, 24 August 2011 (UTC)

Yes, yes. Right, right. StuRat (talk) 22:08, 24 August 2011 (UTC)

rainfall and earthquake

We've had extreme rainfall on the East coast of the United States this summer. Could large quantities of water entering the ground contribute to the triggering of an earthquake? Links: [7], [8]. Bus stop (talk) 21:45, 23 August 2011 (UTC)

Large bodies of water created behind dams can produce some seismicity, injecting fluids deep into the crust can also trigger earthquakes, but it's hard to imagine that rainfall (however intense) would have such an effect - most of the rain will simply run of into rivers, rather than end up in the ground. Mikenorton (talk) 22:23, 23 August 2011 (UTC)

It might be relevant that the depth of today's earthquake was 1km. I'm not geologist but it seems awfully deep for rainwater to have an effect. Dismas|^(talk) 02:51, 24 August 2011 (UTC)

The focal depth has been recalculated to 6 km, so not that shallow - I should have linked to our article on induced seismicity. Mikenorton (talk) 07:07, 24 August 2011 (UTC)

There's an article in Tectonophysics that looked at this issue.

"Correlations between streamflow and intraplate seismicity in the central Virginia, U.S.A., seismic zone: evidence for possible climatic controls"

Sean.hoyland - talk 13:35, 24 August 2011 (UTC)

Well I've never heard of hydroseismicity before, but always something new out there. This study found an effect at Mt. Hood in Oregon, but note that there was a delay of 151 days between the spring melt and the peak in the seismicity, as it takes time for the pressure change to reach the level at which earthquakes initiate. Mikenorton (talk) 19:11, 24 August 2011 (UTC)

We've been having a severe drought on my part of the east coast. We hoped we'd get some rain from Irene, but no. Bubba73 ^{You talkin' to me?} 02:53, 27 August 2011 (UTC)

Pressure sores

Is it possible to get pressure sores just by remaining seated for too long on a regular basis?--92.28.71.6 (talk) 21:49, 23 August 2011 (UTC)

Our article says "A simple example of a mild pressure sore may be experienced by healthy individuals while sitting in the same position for extended periods of time" bit this is unsourced. Grandiose (me, talk, contribs) 22:03, 23 August 2011 (UTC)

http://www.foxnews.com/health/2011/03/31/obese-ohio-man-dies-fused-chair-2-years/ μηδείς (talk) 22:51, 23 August 2011 (UTC)

I'm not sure the Fox News link has anything to do with pressure sores. It smells of hoax - among other things! Richard Avery (talk) 07:16, 24 August 2011 (UTC)

Not just from remaining seated, no. You have to not change positions, either. Even a slight change in position can allow any pooling blood to move on. StuRat (talk) 01:28, 24 August 2011 (UTC)

Identical Universes

Would it be possible in principle to create another Universe identical to ours (at some instant of time)? Would such a Universe inevitably evolve in exactly the same way as ours, and, if not, what would be the cause of the divergence? I'm not sure whether things at a quantum level (or whatever) may exist unknowably or happen randomly in the sense that they are not even in principle replicable or determined by a replicable "state of the Universe"... 86.179.3.58 (talk) 22:12, 23 August 2011 (UTC)

I don't know what you mean by creation of an universe in principle, but there is a general theorem called No-cloning theorem which forbids the creation of a clone of an unknown quantum state. Bell's theorem states that no hidden variable theory can reproduce QM so whatever randomness is provided by QM must be really random since any unknowable internal variable producing the apparent randomness would violate Bell's theorem. Dauto (talk) 22:28, 23 August 2011 (UTC)

Creating universes is obviously not within our abilities. However, the article determinism will help answer the rest of your question. --Tango (talk) 22:31, 23 August 2011 (UTC)

Thanks. In case it is unclear, "in principle" means ignoring all practical difficulties, and the fact that it is of course not actually within our abilities. Kind of like a thought experiment. 86.179.3.58 (talk) 22:39, 23 August 2011 (UTC)

Whether the universe is deterministic at the quantum level is unknowable. Even in principle, we can not recreate the conditions of the big bang (e.g., there is no principle which could reverse the metric expansion of space.) If we could, the aforementioned unknowability prevents us from saying whether it would turn out the same. 76.254.20.205 (talk) 02:21, 24 August 2011 (UTC)

If you could create a universe identical to our own that would evolve in the same way, then your copy in that universe would necessarily have to create another such identical universe etc. etc. All your copies are identical, so you cannot locate yourself at one particular level in this infinite hierarchy of universes. Count Iblis (talk) 03:54, 24 August 2011 (UTC)

Sorry, I should have mentioned that the new Universe is created instantaneously. If it takes time to build then the question gets much messier, in a way not relevant to the question I wanted to ask. 86.183.4.36 (talk) 12:17, 24 August 2011 (UTC)

"Instantaneously" is difficult to support if you have to take relativity into account. Sounds as if your universe creation scheme requires the suspension of so many physical laws as we understand them that you might as well call it magic, in which can anything is possible. Gandalf61 (talk) 14:04, 24 August 2011 (UTC)

Yes, you can imagine many aspects of this universe creation to be magic that "just happens". Although I didn't originally know the terminology, my question was really about determinism and the theoretical possibility of cloning of quantum states, rather than any ancillary issues. 86.181.200.231 (talk) 17:08, 24 August 2011 (UTC)

The definition of a universe is a deep philosophical question, but as a barbaric supposition it seems fair to say that anything that exists which is subject to the laws of physics as we know them is part of our universe. So the creation (and generally, I'd say, the contents) of another universe is outside our laws of physics. This makes it either impossible or meaningless (probably the latter) for us to say any operation you propose in this realm is possible or impossible. Wnt (talk) 20:31, 27 August 2011 (UTC)