Science desk
< April 2	<< Mar \| April \| May >>	April 4 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

April 3

skin disease

I remember a horrifying image on wikipedia of a skin disease in which your skin grows super fast and doesn't fall off, and it foams or something.. there was a picture for the article and it looked like the guy had like feathers over his hands and he looked like a bird; the skin had gone like a foot past the tips of his fingers. What disease is that? :D\=< (talk) 00:01, 3 April 2008 (UTC)[reply]

I think its called Froth —Preceding unsigned comment added by 79.76.255.69 (talk) 01:06, 3 April 2008 (UTC)[reply]

I remember the pic – an Indonesian man I think, and a specialist medic offered to treat him. It wasn't catching, but I can't remember the ref, only that it might have been on the ref desk. Julia Rossi (talk) 01:30, 3 April 2008 (UTC)[reply]

I think the disease was warts, human pappiloma virus. Graeme Bartlett (talk) 02:07, 3 April 2008 (UTC)[reply]

Ah found it thanks http://blog.wfmu.org/photos/uncategorized/easterneuropeskincondition1c.jpg :D\=< (talk) 04:20, 3 April 2008 (UTC)[reply]

You may be thinking of Dede. We used to have an article on him, but it got redirected to Epidermodysplasia verruciformis after an AFD. Bovlb (talk) 05:06, 3 April 2008 (UTC)[reply]

Lemon peel eating rodents

Is there a critter known for eating (very cleanly) only the peel off a lemon? Several (25 or so) lemons were either partially or fully peeled, both on and off the tree. No evidence of any peel pieces or poop. No reference found on the net, experts at the nursery had never seen it. San Francisco Bay area.

milkshark66Milkshark66 (talk) —Preceding comment was added at 00:41, 3 April 2008 (UTC)[reply]

Just my guess, nothing all that specific, but if I'd have to wager a guess, I'd say that it was most likely an insect of some type. I know that's not really helpful, but it might narrow it down some. Wisdom89 _{(_T / ^C)} 03:21, 3 April 2008 (UTC)[reply]

This paper might be helpful [1]. Wisdom89 _{(_T / ^C)} 03:23, 3 April 2008 (UTC)[reply]

Here's another guess: citrus peel miner, but a little out of your area. Call your local agricultural office or a university botany/ag department. I'd bet they'll be all over it (especially if it's new). Franamax (talk) 05:28, 3 April 2008 (UTC)[reply]

Citrus peel miners eat within the peel, they don't remove it, so they are probably not the cause. Milkshark66, you might also consider the possibility it's a prank of some sort. Look for shoeprints, ladder prints, or other indicators to see if the lemons could have been tampered with by people. Generally most insects find the peels toxic and most animals find the peels unpalatable, which is what makes me suspect human intervention (especially just after April Fools' Day). -- Hi Ev 09:48, 3 April 2008 (UTC)[reply]

ZOMG April citrus fool miners! Block all IPs! Stop the site! But wow, chewing the peel off 25 lemons, that's a dedicated trick. Certainly didn't stop the predator, those lemon trees need to do some evolving. :) Franamax (talk) 10:06, 3 April 2008 (UTC)[reply]

Homosexuality

What "causes" it? 143.43.8.32 (talk) 03:24, 3 April 2008 (UTC)[reply]

Read Homosexuality specifically Homosexuality#Why some people are gay or lesbian and you might find Biology and sexual orientation helpful. The Dominator (talk) 03:45, 3 April 2008 (UTC)[reply]

Kevlar

If Kevlar sublimates at 450 degrees Celcius, what are the properties or uses for the gas created? Who would know this? —Preceding unsigned comment added by Nusaince (talk • contribs) 03:35, 3 April 2008 (UTC)[reply]

In an oxygen atmosphere, the decomposed monomers would probably be useless. However it appears that if you do it in argon you can improve batteries! I found this by googling "kevlar heat decomposition". Franamax (talk) 05:21, 3 April 2008 (UTC)[reply]

Kevlar is a polyimide and it does not sublimat, but decompose on heating. The imide bonds break and lead to several compounds like carboxylic acid derivates and others. I have a GC-MS plot of the pyrolysis of Vespel which is not so much different. If you are lucky, by choosing the right conditions (no oxygen), you get a residue which is a carbon fibere. The article mentioned above is about this carbon fiber not about the gas evolving.--Stone (talk) 06:18, 3 April 2008 (UTC)[reply]

Stone, you sound like a good candidate then to update the Kevlar article where it says "At 450°C Kevlar sublimates.", which I found a little questionable (why I said "decompose" above). If you can throw in a reference when you update it, all the better! Franamax (talk) 06:47, 3 April 2008 (UTC)[reply]

inter and intra generalation equity

what is inter and intra generalation equity ? —Preceding unsigned comment added by 211.30.50.68 (talk) 03:55, 3 April 2008 (UTC)[reply]

You mean Intergenerational equity? William Avery (talk) 11:29, 4 April 2008 (UTC)[reply]

Benefits so far from LHC

The space race fuelled the development, amongst other things, of miniaturised computers, communications satellites and (one would guess) detector technology. Do Ref Desk people know of any things so far which have been developed for the LHC and have found wider use? AlmostReadytoFly (talk) 08:04, 3 April 2008 (UTC)[reply]

First of all we should note that the Large Hadron Collider is not yet complete or online. Second, the LHC is meant to deal with large amounts of energy and forces that have never been produced by man before, so much of it has no other application. Also, the LHC is not the first particle accelerator. The Intersecting Storage Rings (ISR) at CERN was the first hadron collider, and it began running in 1971. So, most of the pioneering in design has occurred in the earlier colliders. The ISR, for example, was the first use of stochastic cooling. The real benefits from the LHC will come after June 2008 when the experiments begin, and the big ones are noted in the "Research" section of the LHC page. Due to all of those reasons I would not be surprised if there were no or almost no wider use applications due to the LHC so far. After the experiments begin, then you'll see the benefits probably 10-20 years later. -- Hi Ev 09:39, 3 April 2008 (UTC)[reply]

I know that it's not yet online, but the question relates to the work which has been necessary in the design and build phase, not the research which is planned. AlmostReadytoFly (talk) 09:46, 3 April 2008 (UTC)[reply]

To clarify: I wasn't aiming for abstract future things like everything we predict about the Standard Model being wrong, but important things like better detectors in the x MeV to y MeV range, or yes, stochastic cooling. (the above comment is to be read in a slightly ironic way ;) ) AlmostReadytoFly (talk) 10:00, 3 April 2008 (UTC)[reply]

This page and its links might help you. It mentions:

an innovative micro-duct optical fibre cabling system.
novel 1.8 K refrigeration units based on advanced cold compressor technology.
a novel method of cost-effective rust protection of steel. Gandalf61 (talk) 10:18, 3 April 2008 (UTC)[reply]

Cool, that's just the sort of thing I meant. Thanks. AlmostReadytoFly (talk) 11:21, 3 April 2008 (UTC)[reply]

Particle accelerators, in general, don't have a lot of side commercial benefits, not as many as other areas of research, anyway. Historically the biggest benefits have probably been in the area of mass spectrometry, which is extremely useful for chemical analysis, and the early work on the atomic bomb, which spun in part out of Ernest Lawrence's particle accelerator laboratory in Berkeley. But in terms of investment, they are a lousy way to get commercial benefits, and cannot really be justified in those terms (and, to my knowledge, never are). (They also don't have many direct military benefits either, though historically having a strong experimental physics community and pool of physicists has been seen as indirectly beneficial for military programs. I'm reminded of Robert R. Wilson's justification for Fermilab before the JCAE; see his page for the quote) --Captain Ref Desk (talk) 13:38, 3 April 2008 (UTC)[reply]

I attended a lecture from a guy who worked at the LHC. This was part of a course I did on grid computing, and all the previous lectures had been from other scientists who thought that grid computing was a nice idea but wasn't going to/ hasn't yet actually worked in practice. Anyway, due the mind boggling amount of data that the LHC will produce it will need an equally massive amount of computing power to analyse that data (the only way they could hope to do it when they were planning the LHC was to rely on Moore's law to catch up with what they needed during the time it took them to build it). And it seemed like the people at CERN have been the only people smart enough to actually get grid computing to work in a practical way, and as warm-up/testing to get ready for when the LHC comes online they have been doing various scientific research using their grid computing computer farms. Here is the website for this stuff: http://lcg.web.cern.ch/LCG/ Tomgreeny (talk) 17:05, 5 April 2008 (UTC)[reply]

Protecting a rose petal from coffee

I would like to coat a rose petal with something that does not melt in coffee and leaves the rose petal looking like a rose petal. Is it possible?Bastard Soap (talk) 09:43, 3 April 2008 (UTC)[reply]

Something edible? kwami (talk) 10:01, 3 April 2008 (UTC)[reply]

No, don't plan on eating the rose petal. Why do they taste good?Bastard Soap (talk) 10:09, 3 April 2008 (UTC)[reply]

People can make rose petal jam (preserve) with them. There's [2] and if you google rose petal recipes there's heaps more. But one petal is no biggy---about the petal, couldn't you just let it float on the coffee as it's served? Coating it with something (like crystallised with sugar) could sink it. Just guessing. Julia Rossi (talk) 11:47, 3 April 2008 (UTC)[reply]

It really only needs to float until it is served, correct? Once the person starts drinking, they will likely ignore the rose petal - if they even leave it in the coffee. I would use a wax. They melt at different temperatures, but usually float. There are many edible waxes. Beeswax is one. I'm not sure how well it will float though. -- kainaw ™ 12:34, 3 April 2008 (UTC)[reply]

You might try some sort of water-proofing spray, like you'd find in a camping store. I have no idea at all if that would work. You might try explaining exactly what you're trying to achieve. You could probably entirely enclose a rosepetal in some sort of acrylic cube, also if that's what you're going for. APL (talk) 16:04, 3 April 2008 (UTC)[reply]

Isn't water-proofing spray somewhat toxic? 206.252.74.48 (talk) 16:53, 3 April 2008 (UTC)[reply]

out of the can it is toxic, but set silicones may not be, there are some silicone cooking gadgets, such as muffin tray. A problem with wax is melting in coffee! ALso the petal can cook in a hot drink, so it may have to be impregnated, not just coated. A plastic rose petal might do! Graeme Bartlett (talk) 21:30, 3 April 2008 (UTC)[reply]

Suffice to say, anything you could coat it with would likely either melt, or be toxic to human consumption. Most folks wouldn't recognize a lone rose petal anyway, and complain about something being in their coffee! If this is a romantic gesture, it'd be better to just include the rose itself (maybe with a shortened stem) tied to the handle of the coffee mug with some twine or something. Sans the thorns, of course! -- Kesh (talk) 03:20, 4 April 2008 (UTC)[reply]

Blinking light

Okay, I am Raglan, New Zealand, and I can currently see a blinking light in the sky. It is roughly east-by-northeast of me, and appears maybe 10 cm (rough estimate) above sea level. It is the same size as any star. It somewhat resembles the light of an aircraft, possibly a little brighter. It is maybe as bright as the two or three brightest stars I can see in the sky (clear sky, no light pollution). There is a blinking/twinkling effect to it, but the brightness remains constant. The blinking has a red tinge to it (ie when it pulses, it is distinctly red). The light has been stationary in the sky for at least 10 minutes. I tried looking at it through a telescope, but everything is dark so I could not find it. What is it? --superioridad ^(discusión) 10:17, 3 April 2008 (UTC)[reply]

Oh, and at least one other person agrees with my description of it, so I doubt I am hallucinating or somesuch. --superioridad ^(discusión) 10:19, 3 April 2008 (UTC)[reply]

More: I have not been watching it constantly, rather, checking on it every few minutes, so there may have been some slight movement that I have not noticed. It is currently about 11:20 pm. --superioridad ^(discusión) 10:23, 3 April 2008 (UTC)[reply]

Hmm...I bet a rubber chicken that it's a sateliteBastard Soap (talk) 10:26, 3 April 2008 (UTC)[reply]

I'll take that bet. Bright satellites are in low earth orbit and typically cross the sky in a minute or so. They also have to be able to "see" the sun in order to reflect sunlight, so they're normally visible at dusk and dawn, not 11:00 pm. To remain fixed in the sky, a satellite would have to be in geostationary orbit, and I don't think any of those satellites are visible to the naked eye. Heavens-Above.com can give you a list of bright satellite passes at your location. -- Coneslayer (talk) 11:50, 3 April 2008 (UTC)[reply]

Looks like someone might have lost a rubber chicken. 206.252.74.48 (talk) 16:53, 3 April 2008 (UTC)[reply]

The fact that it's low on the horizon is a clue. I'd say it's a reflection of a terrestrial (or naval) blinking light off the clouds. If it's out at sea I'd say it's a ship or buoy. StuRat (talk) 13:14, 3 April 2008 (UTC)[reply]

If I'm not misunderstanding you, there are 2 problems with the suggestion of a blinking light being reflected off the clouds:

(1) Light spreads out over distance, so the image projected on the clouds would be extremely large in angular size and dim, not at all like a point source of light.

(2) The OP said the light was changing colours but maintaining constant brightness, not blinking. --Bowlhover (talk) 07:59, 5 April 2008 (UTC)[reply]

It could also be a weather balloon.TheGreatZorko (talk) 14:15, 3 April 2008 (UTC)[reply]

I'd be more concerned about your belief that you're a town... Clarityfiend (talk) 19:27, 3 April 2008 (UTC)[reply]

Silly English language, leave out one 2-letter word and the meaning is completely different. —Preceding unsigned comment added by 206.252.74.48 (talk) 20:35, 3 April 2008 (UTC)[reply]

Raglan's not a town, its a way of life :1 Boomshanka (talk) 21:21, 3 April 2008 (UTC)[reply]

Hi. Well, I saw a weird object in the sky last night too. However, let me check the sky atlas to see if it might just be a star. Well, judging by your location, Arcturus and Antares may be close. They're both reddish. Antares would have appeared east-northeast, but are nowhere near the three brightest stars from that location: Sirius, Canopus, and Rigil Kentarus, actually the 3 brightest in the sky. Arcturus would have appeared north-northeast, but is the fourth brightest in the whole sky. However, both would have been well above the horizon, but I suggest you check Yoursky and enter your coordinates and time yourself, as I could be wrong about which star map in the atlas to use, thus they might have been low on the horizon. Why a star? One time I mistook Capella for a UFO. It was blinking red and green, probably a twinking effect, and was about 20 deg above the horizon. Hmm, have you seen this any other night? Maybe it's a faraway but bright tower on a nearby island or something that pulses light, such as a lighthouse. Hope this helps. Thanks. ~A H 1^(TCU) 22:45, 3 April 2008 (UTC)[reply]

It might be a tower, but I don't thiknk it's a lighthouse. This is a map of all lighthouses in New Zealand. The nearest one in the correct direction is #33, which, measuring from Google Maps, is about 70 km away. --Bowlhover (talk) 06:33, 4 April 2008 (UTC)[reply]

Assuming New Zealand lighthouses are about the same size as Atlantic Coast lighthouses in the US, that would put the lighthouse right at the edge of visibility. --Carnildo (talk) 20:26, 4 April 2008 (UTC)[reply]

The OP, though, specified the unidentified light to be "10 centimetres" above sea level. If he or she meant ten centimetres at arm's length, that's about 6 degrees. Assuming the light was from lighthouse #33, a trigonometrical calculation arrives at a minimum height for the lighthouse of 7 km. It's the minimum height because, at 70 km, a significant portion of the structure would be blocked by Earth's curvature. --Bowlhover (talk) 07:59, 5 April 2008 (UTC)[reply]

Diffraction

According to me diffraction can be explained by particle nature. The bending of light can be because of collision of photons (particles) with each other when they move. The dispertion of light when it travels through a door can be explained by the fact that the photons are under the influence of the force of attraction (short range) by the walls of the door. So those photons which passes close to the door frame will experience a outward force which pulls the photons away from their path and this causes diffraction.

If i am wrong , please explain the defect in this theory. —Preceding unsigned comment added by Nkbspidy1991 (talk • contribs) 11:10, 3 April 2008 (UTC)[reply]

It doesn't explain diffraction peaks, and why they are spaced in terms of wavelengths, or why you get them even in single-photon experiments (where photons can't collide.

If you wanted to test the "attraction to doors" part of your hypothesis you could build an experiment with very thick slits. If diffraction works by attraction, then the beam should be pulled into the side of the slit, and not make it out. AlmostReadytoFly (talk) 11:19, 3 April 2008 (UTC)[reply]

Your theory also doesn't explain laser beams, which stay together better than white light because all the light is the same frequency, so there is no wave interference. StuRat (talk) 13:00, 3 April 2008 (UTC)[reply]

Actually no theory explains that phenomenon, StuRat, because it doesn't occur. Laser beams are subject to the same laws of diffraction as any other waves. Because of their high coherence they often operate at the limit of diffraction, whereas white light beams are typically spatially incoherent enough to be limited by geometrical optics, but that is a different story. --169.230.94.28 (talk) 15:42, 3 April 2008 (UTC)[reply]

Gene therapy

Is it possible for or through the use of gene therapy to change a physical feature or characteristic? —Preceding unsigned comment added by 198.188.255.2 (talk) 02:07, 3 April 2008 (UTC)[reply]

I don't think it is, as of today, but if you're asking if it might ever be possible, I'd say yes. Although, unlike in sci-fi, the change won't be immediate, but will take time. This might be years in the case of a major change. StuRat (talk) 12:54, 3 April 2008 (UTC)[reply]

neuronal tracts in our body...

all the tracts in our body after descending from brain cross to the opposite side at some level or other to control the opposite side of the body..what is the significance of that? what will happen if fibres are not crossing? —Preceding unsigned comment added by 59.93.13.89 (talk) 15:16, 3 April 2008 (UTC)[reply]

If you have tracts on the brain, you need to stop answering the door when the cultists knock. :-) StuRat (talk) 16:16, 3 April 2008 (UTC)[reply]

But seriously, I think it's just an accident of biology. There isn't any advantage to doing it this way, but the disadvantage (a slightly longer neural pathway) is so slight that there isn't much evolutionary pressure for it to be changed. My guess is that if anybody ever had nerves that didn't cross over like this, they would be just fine. StuRat (talk) 16:16, 3 April 2008 (UTC)[reply]

If someone injured the right side of our ancestors head and caused slight brain trauma without unconsciousness, the left side of the brain could still see and respond to the threat with the right limbs. Some (tiny) survival value in that. Edison (talk) 18:50, 3 April 2008 (UTC)[reply]

This is a very interesting question, and, in fact, one of great inetrest for neuroscience and medicine. However, first of all, I must note that many, but certainly not all the "tracts" innervate the contralateral (opposite) side. Among the sensory pathways, as far as I know, auditory crosses over almost fully, visual crosses over so that the opposite half of the visual field (rather than opposite eye) is represented, and olfactory crosses over very little or not at all. Among the motor pathways, innervation via the spinal cord is "opposite" but innervation by cranial nerves is not necessarily so. Motor part of the trigeminal nerve is represented bilaterally (that is, on both sides), for example. As far as the "significance" part goes, the significance for the contralateral representation of the visual field was explained by Santiago Ramón y Cajal. The explanation is simple: the lens of an eye produces an inverted image on the retina; if the optic pathway did not partially cross over, the two halves of the image would not have matched. The inervation of limbs then crosses over as well, to match the visual input. The detailed explanation by Rodolfo Llinás is here. Hope this helps. --Dr Dima (talk) 19:27, 3 April 2008 (UTC)[reply]

That last link requires a subscription. Is it available anywhere for free ? StuRat (talk) 20:04, 3 April 2008 (UTC)[reply]

Found it! Here, enjoy. --Dr Dima (talk) 22:19, 3 April 2008 (UTC)[reply]

Thx. StuRat (talk) 14:17, 4 April 2008 (UTC)[reply]

asbestos pipe

Since the risk of death from breathing asbestos is so severe full body protection is used to provide for disposal of any possible secondary sources of contamination, however, contact with asbestos from water in water supply pipes appears to be of no concern. What is the difference in contact of asbestos in the lungs and in the gut? 71.100.173.69 (talk) 19:27, 3 April 2008 (UTC) [reply]

Well, the health problem from asbestos is specifically that long-term exposure deposits asbestos crystals into the lungs, causing asbestosis or mesothelioma, over a long period of time, so of course people who work with asbestos in their jobs need to wear the suits (they are constantly going to be inhaling it otherwise), though that doesn't mean that one time of doing such is going to end up with instant death otherwise. I am not sure, in any case, that asbestos around supply pipes would get into the water supply in appreciable levels—if the pipes allows their insulation to leak into them I doubt they'd be great at holding in water.

Anyway, I don't know if consuming asbestos is a good idea but if sounds like it will just be flushed out of the system. In any case, they won't get into the lungs if they are just in the water supply. When thinking about toxic risks it is important to think about the pathways in which the risks act. All plants, for example, contain a number of radioactive isotopes in them (e.g. bits of polonium, among other things). In food, though, they pass through the body as waste and are not a problem. When burned and inhaled, as in cigarette smoking, they can become lodged in the lungs and sit there radiating, causing great harm over a long time period. Something that is fine in one situation becomes toxic in another; it's probably incorrect to generalize too widely about this, but it seems to apply in particular to things that take a long time to develop into a fatal disease, and in situations where they would in one context be flushed out as waste but in another are allowed to accumulate. --Captain Ref Desk (talk) 18:54, 3 April 2008 (UTC)[reply]

Asbestos -cement pipe was widely used in the US and other countries after World War 2 because it is cheaper than iron pipe and does not rust (although it corrodes in its own way). It is no longer manufactured in the US, but one town at least still imported and installed it in the 1990's. Phoenix New Times 1994 In 1988, 65 million people in the US got their drinking water through asbestos cement pipe totalling 300,000 miles. The pipe was 15 to 25% asbestos by weight. New York Times, 1988 The US EPA sets a max alowable exposure level of 7 million asbestos fibers longer than 10 microns per liter of water US EPA. The same source says one source of such asbestos in drinking water is the cement asbestos water pipes. How many liters of water does one consume in a year? Asbestos is actually a component of some water pipes, rather than insulation around metallic or plastic or concrete pipes as Captain Ref Desk seems to suggest. If the pipe is worked on or damaged, the asbestos fibers become friable and could contaminate the water per [3] . Holes are drilled in large supply pipes to make service connections. The instructions say workers should provide a means for flushing out the fibers downstream before they enter the premises. Do workers always follow official procedures? Asbestos from pipe can also enter the drinking water through corrosion [4] . In some locations where pipes deteriorated, levels of over 300 million fibers per liter were found. Anniston Star, 2005 Asbestos fibers in tapwater may be released into the air and inhaled [5] as from vaporizers. I could not find readily a government or other reliable source that said any of this was a health hazard in general, but there are certainly advocacy groups which are alarmed about it. Edison (talk) 09:41, 4 April 2008 (UTC)[reply]

an extra star in the big dipper?!

Hi. Last night, I was stargazing, when I looked towards the big dipper, I saw an extra star. I'm familiar with the constellation, so I know that star shouldn't have been there. First of all, I estimate its visual magnitude to be somewhere between +2.0 and +3.0. Its celestial coordinates, as I checked on the star atlas, were approximately RA 14h 20m, DEC +52°, with an uncertainty of roughly 2 degrees. I watched the object for about 30 seconds to make sure it stayed, took another 30 seconds or so to check the star atlas and try to point the telescope at it, but it was gone. After this, I thought I saw it again but much fainter, although it could just have been an [illusion or a non-medical placebo, which happens sometimes when I think a really faint star is there but really isn't. I have relatively poor vision, and live within a light-polluted neighbourhood in southern Ontario, if that helps. When I tried to point the telescope toward or near the object or where I thought I last saw it, I keep coming to a scalene triangle of three stars in my low-power eyepiece, most likely Nu Bootis, Iota Bootis, and Kappa Bootis. Checking the star atlas, the object was also likely to have been close to NGC 5480 and NGC 5474. The time was roughly between 9:20 and 9:30 PM EDT, April 2, 2008, which is 1:20 - 1:30 UTC time, April 3. I watched the object for roughly 30 seconds for any obvious movement in case it was a plane or satelite. I noticed no obvious movement, although I may or may not have seen a slight drop in brightness. All I know is, it didn't flash like a plane, and didn't seem to move like a sattelite. I didn't see movement in that time, but if there was any movement, it couldn't really have been faster than 6 arcminutes per second. As for colour, I'm not sure I remember seeing any obvious colour, however it could have been slightly tinted some colour, so don't count that out of the question. I'm not sure about the duration, but I think it probably lasted 30 seconds or longer. All I know is, when I first went outside to stargaze at roughly 8:50 pm, it wasn't there. I calculate the change in brightness at roughly the time of observation to be about 0.2 - 3.5 magnitudes per minute, dropping in brightness at the time of observation. I'm not sure if it was any larger than a pinpoint object, but if it was of any size, it could have appeared no larger than 40 arcminutes in diametre. I thought it was fuzzy at one point, but it could easily be an artifact (when I look at stars, they look like they have rays coming out of them. It makes it difficult to recognise objects like comet Holmes, but wearing glasses at one point turned the comet into a pinpoint light source). I'm not sure, but it's possible I may at one point have noticed an object of roughly magnitude 3, roughly halfway between Mizar and Alkaid, and perhaps another magnitude 4 or so object roughly a degree closer towards Alkaid than the original object, or I could have caught a glimpse of Nu or Kappa Bootis. However, these could easily have been an illusion, although the original object is likely much too bright to have been an illusion. I can often see fainter objects and have better angular resolution when there's less light pollution and glare. So, what could it have been? Let's list and examine some of the possibilities:

a satellite?

Hmm, interesting possibility. Well, the problem is, it likely wasn't the ISS, as the only ISS appearence around that time last night was lower in the sky, close to Cassiopeia and Draco and nowhere near Ursa Major. As for Iridium flares, Heavens-Above only lists them to mag. 0 and brighter. I have no time to check nearby areas for flares, but these flares generally last only 15 seconds or so, and their movement and change in brightness should be obvious. What about other satellites? Well, out of all the satellites brighter than mag. +3.5 visible at this time, only one passes through Ursa Major: Lacrosse 5. This seems to pass pretty much exactly through the place I observed the object, it passed through the area at about 15 arcminutes per second. Also, when I looked again in about 30 seconds, it was gone, and an object that moves so slowly, if at all, shouldn't have dissapeared so quickly (although the that area of the sky was only about 20 degrees from being obscured by a terrestrial object). It was also high enough in the sky to not be one of those bright horizon-hugging satellites that never appear on the Heavens-above because they're so low.

an asteroid or comet?

Well, it looked fuzzy at first, but comets don't just suddenly vanish. Asteroids don't either, and this also wasn't listed on Heavens-above like the other asteroids. In order for it to be an asteriod passing really close to the Earth and naked-eye, as well as covered by the Earth's shadow in order for it to dissapear so suddenly, seems unlikely. JPL nasa lists 2008 FH5 passing near the Earth on April 2, but being 7.6 LD away and 11-24 m is not going to maked it naked-eye.

a gamma-ray burst?

Hmm. Well, there was this burst around two weeks ago in Bootes that was briefly visible to the naked eye for around 30 minutes to maybe a lucky observer. However, that one only reached mag +5.8 or so, and I doubt one could look so bright from Earth unless it was close to us. Wikipedia would probably have an article on such a GRB if it happened, but lists no such thing.

an erratic variable star or nova?

Well, I don't see a variable star like that in the star atlas. Novas are quite often unpredictable, but I don't think one would last mere seconds to no longer than probably half an hour, unless it got covered by dust or something, and such a bright nova would probably have been reported by someone else already.

An illusion or misremembering?

Probably not. I first noticed this object when I glanced at Ursa Major, so it's probably not a floater or similar object, and I didn't require averted vision to look at it for about 30 seconds, and I didn't notice any movement. Although I may have seen similar objects closeby such as the ones described earlier, this one is likely too bright to be an illusion. The combined magnitudes of the three stars in that scalene triangle of Nu, Iota, and Kappa, total about magnitude +3.0, and perhaps I got a glance of that, but it doesn't explain why it appeared just as bright as some of the other Big Dipper stars, why it stayed for a whole 30 seconds, and why I didn't see it before or after this observation. Also, I jotted down notes about the object right after I came back inside, and misrememberings and dreams don't just leave papers titled "unidentified stellar object".

So, what do you think it might have been? Please note that I am not immune to errors in observational astronomy. For example, a few years ago, I mistook the Pleadies for Delphinus, one time I mistook Capella for a UFO, and another time I mistook Venus for Planet X. However, I'm better at this now, and I'm pretty sure I saw this last night. Can someone help suggest what it might have been? Thanks. ~A H 1^(TCU) 22:30, 3 April 2008 (UTC)[reply]

Just 2 random and unlikely suggestions:

A satellite in a high orbit which displayed one of its very rare flares.
A collision of 2 asteroids.

Icek (talk) 23:56, 3 April 2008 (UTC)[reply]

I've two questions for AH:

(1) Was the stellar object as strongly affected by astronomical seeing as the other stars? If so, it likely has a small angular diameter; if not, it likely has a large diameter.

(2) For how long did you were you looking at the object?

Icek: the collision of two asteroids is definitely very rare. I don't think there has even been an observation of such an event before. However, according to http://members.aol.com/_ht_a/hattonjasonp/hasohp/GEO.HTML, flares from a geosynchronous satellite can definitely reach magnitude 2-3. I suppose bright flares are even more frequent for medium-Earth-orbit satellites. I've never observed a flare made by high-orbiting satellites, though, so I have no idea how quickly their brightnesses change. --Bowlhover (talk) 05:55, 4 April 2008 (UTC)[reply]

The other bit regarding the asteroid collision: why would this be visible? We're not talking about movie effect giant-TNT-asteroids-in-oxygen, just two rocks. Nothing would generate light. As to the original question, I'm not enough an expert to offer an opinion. — Lomn 14:20, 4 April 2008 (UTC)[reply]

Any collision of two objects, unless it's totally elastic like two ideal billiard balls bouncing off each other, converts some kinetic energy into heat, and if there's enough heat then the objects will incandesce. Consider an asteroid, with known mass M and speed V, made of solid basalt, with a specific heat c = 0.84 kJ/kg K, or 840 J/kg K in SI units. It collides head-on with another identical asteroid moving with speed V the other way. The relevant reference frame is the one relative to their center of mass. Each object contributes kinetic energy MV²/2 to the collision. The greatest possible temperature increase would be when all of that energy goes into heat (the collision is totally inelastic, like two globs of ideal glue colliding and sticking together). Then if the heat warms all parts of each asteroid equally, the temperature increase ΔT is ((MV²/2)/(Mc) = V²/2c. Note that the M's cancel. So the speed to produce a given temperature increas e is V = sqrt(2cΔT). Making the rock incandescent would require it to be warmed by probably at least 1,500°C = 1,500 K, which would require a speed of sqrt(2×840×1500) m/s (isn't the coherence of SI neat?) That's 1,600 m/s or about 3,600 mph. A collision at 5 times the speed, which is still within the range of possibility, would produce 25 times the energy and 25 times the temperature increase for a totally inelastic collision. Except that a totally inelastic collision at even the lower speed is also totally unrealistic. Asteroids aren't all that strong and they don't have a lot of self-gravity to make the pieces come back together. What would really happen is that the asteroids would be shattered and pieces would fly off in all directions. It's conceivable that some pieces would be heated more than others and might incandescence, but I don't know of a way to easily estimate whether it's really possible. Intuitively, I doubt it. --Anonymous, on Earth, 23:08 UTC, April 4, 2008.

Hi. Well, I didn't see much twinkling in the object or the other stars, either. Also, I watched the object for approximately 30 seconds, although I didn't time it, and also didn't notice any obvious change in brightness, but about 30 seconds or more after, it either dissapeared or faded in brightness. Could it be a flare from a geostationary sattelite, and if so, is there a place that predicts these? I think there is the possibility it may have been tinted a colour, although I'm not sure what colour. Also, do high-orbit satellites' flares last longer? Thanks. ~A H 1^(TCU) 20:46, 4 April 2008 (UTC)[reply]

Geostationary satellites orbit above the equator, is that consistent with your sighting? Here is a NASA tracker, I haven't played with it. Franamax (talk) 21:51, 4 April 2008 (UTC)[reply]

Where was the Jules Verne ATV at the time, and did it have a blinking light? It was recently in space on its way to automatically docking with the ISS. Edison (talk) 00:54, 5 April 2008 (UTC)[reply]

Hi. I can't use Heavens-above right now to search for it, but I remembered looking at the list yesterday, and I think ATV was in it. I don't know how accurate it was as the ATV is a craft that changes orbit. However, the first time I checked, which was about 12 hours after the sighting, the Lacrosse 5 was the only satellite on the list crossing the area, and the exact area where I observed it, but the velocity seemed off. I didn't check the ATV's angular velocity, but I think it did go across the northern area, and was visible within the time indicated. Was the ATV a slow mover? However, although the prediction could have been off, I think it predicted to have been in Draco or Leo or Cassiopeia or something, I don't remember. Also, I checked the object for any movement, change of brightness, or blinking. I didn't notice any obvious movement or blinking, although there would have to have been a change in brightness as it dissapeared shortly after the observation. Thanks. ~A H 1^(TCU) 01:34, 5 April 2008 (UTC)[reply]

If it "was not a satellite", it was not the ATV. The ATV is in a lower orbit than Lacrosse 5, so its angular velocity is larger. The object was too far north to be a geostationary satellite (they appear south of the celestial equator on the northern hemisphere). Icek (talk) 13:44, 7 April 2008 (UTC)[reply]

<off topic>In the manga Fist of the North Star, seeing an extra star in the Big Dipper was a sign that you were about to die...</off topic> --Kjoonlee 09:13, 6 April 2008 (UTC)[reply]

seawater and human skin

What is the effect of seawater on human skin? Can it cure acne, helpus keep it clean, young ? Mr.K. (talk) 23:41, 3 April 2008 (UTC)[reply]

It's not so useful for cleaning, because you smell like dead fish when you're done with your bath. In places where fresh water is in short supply and sea water is plentiful, they will bathe in sea water and then rinse in fresh water, however. Saltwater will tend to dry out the skin, which is somewhat helpful for oily skin. With dry skin, on the other hand, you would need to moisturize after. I don't see sea water as a fountain of youth. On the contrary, if you bathe in it in the sun, the UV damage may age your skin prematurely, especially the parts that stick out of the water, like your face and shoulders. StuRat (talk) 07:10, 4 April 2008 (UTC)[reply]

But, if seawater is full of bacteriophages that will be a treatment against acne, right?Mr.K. (talk) 07:31, 4 April 2008 (UTC)[reply]

Phages in seawater would tend to evolve to infect the bacteria present in seawater, they wouldn't necessarily be adapted to the bacteria that contribute to acne. However the mineral content of seawater might act as a good solvent to clear the pores of sebum, and the salt content might tend to be toxic to bacteria. Franamax (talk) 08:18, 4 April 2008 (UTC)[reply]

Allegedly, special soaps are required when you bathe in salty water, lest no soapy foam be generated. A sailing magazine, shop, or website may have more information.

Atlant (talk) 11:46, 4 April 2008 (UTC)[reply]

I've had good experiences bathing in seawater. I suggest you try it and see for yourself. Vranak (talk) 19:49, 4 April 2008 (UTC)[reply]