Wikipedia:Reference desk/Archives/Science/2008 June 29

= June 29 =

galaxy edge on
what do u mena by galaxy caught edge on ? i am only able to get the pics for my niew but not the explanation —Preceding unsigned comment added by 123.239.149.69 (talk) 08:24, 29 June 2008 (UTC)


 * There are many different types of galaxies, see Galaxy morphological classification. Now, edge-on is simply a term describing the inclination of the galaxy with respect to an observer on earth.  If a galaxy is inclined 90° relative to the earth then you will observe the galaxy directly from the side, or edge.  Jdrewitt (talk) 09:59, 29 June 2008 (UTC)


 * Here's some pictures:
 * edge on [[Image:M104 ngc4594 sombrero galaxy hi-res.jpg|150px]]


 * from 'above' [[Image:M63.jpg|150px]]


 * as you can see galaxies are thin like a plate87.102.86.73 (talk) 10:19, 29 June 2008 (UTC)


 * Please note that the above pictures do not appear to be fully edge-on or fully face-on, although they are quite close. Perhaps the images below illustrate an edge-on galaxy and face-on galaxies with an inclination relative to the earth closer to 90° and 0° respectively.


 * Jdrewitt (talk) 10:49, 29 June 2008 (UTC)

The "edge-on" picture shows lots of light coming from oval regions above and below the disc. A spinning disc shaped arrangement of stars could be reasonably stable, but why does light come from above and below the disc? Are there a significant number of stars in soupbowl shaped regions above and below the disc to create the apparent glowing clouds? If so, what keeps the gravity of the disc stars from pulling them into the disc? If the stars are in the disc and the light is being scattered, what is there to scatter the light in space? If dust, gasses, or small objects, then again why doesn't the gravity of the stars in the spinning discull in the surrounding matter? —Preceding unsigned comment added by Edison (talk • contribs) 11:57, 29 June, 2008 (UTC)


 * See galaxy - it answers these questions and more. PhySusie (talk) 12:17, 29 June 2008 (UTC)


 * The region you are referring to is the galactic halo which exists around spiral galaxies. Its shine is due to the stars and star clusters that exist in that region, but at much lower density to the main disk region of the galaxy. There is a lack of new material in the galactic halo and so there is no new star formation.  The stars that exist in the halo have much different orbits to stars lying in the plane of the galaxy, and halo stars may pass through the disk and nucleus of the galaxy.  See Galactic spheroid. Jdrewitt (talk) 12:53, 29 June 2008 (UTC)


 * Actually - I think this person is referring to the galactic bulge, rather than the halo. But the article referred to by Jdrewitt is a good one to check out. PhySusie (talk) 00:40, 30 June 2008 (UTC)


 * "apparent glowing clouds" suggested the halo to me, however, both answers are valid. Jdrewitt (talk) 08:35, 30 June 2008 (UTC)

Flying Mammals
Which is the only mammal that has no wings,cannot fly, but does fly? —Preceding unsigned comment added by 72.51.78.180 (talk) 12:43, 29 June 2008 (UTC)
 * Is this some kind of a riddle? It sounds to me that you already know the answer. Anyway, humans have no wings and are incapable of flight by themselves, but they still do a fair bit of flying by various means. -- Captain Disdain (talk) 12:48, 29 June 2008 (UTC)
 * Flying squirrels kind of match the question too. -- Aeluwas (talk) 12:51, 29 June 2008 (UTC)
 * Wait, this mammal cannot fly yet does? That seems like you've logically excluded all mammals. --  JSBillings  16:53, 29 June 2008 (UTC)
 * It sounds like it may involve some kind of word play - in which case, original poster, are you sure you've got the exact wording of the question? If not, there could be a vital clue missing. Confusing Manifestation (Say hi!) 23:01, 29 June 2008 (UTC)
 * As said above, this question is impossible to answer, as all mammals are excluded. —Preceding unsigned comment added by Sliver Slave (talk • contribs) 20:17, 2 July 2008 (UTC)

Medicine-Patella replacement.
Whilst looking at a page on the Patella, a sesamoid bone, I wondered whether replacing the Bone with something larger would be beneficial to jumpers or distance runners. The larger bone would create more leverage for the muscle which the primary functional role is knee extension. Obviously after healing and training, it may improve top speed for runners, like a high gear on a bicycle. Whereas jumpers, long or triple jumpers, might find it beneficial for their sport. However you look at it, controversial, cheating or whatever, do you think it possible?

The Patella []

Mike —Preceding unsigned comment added by 88.105.111.27 (talk) 12:49, 29 June 2008 (UTC)


 * I think you´d be hard pressed to find a runner who would undergo a risky knee surgery like that. Replacing the bone would require disconnecting all sorts of tendons and ligaments, reattaching them, then a long rehab which may not necessarily return all function to the limb. I guess it´s possible that it could work, but I think ít´s about as likely as a runner having his legs removed completely and replaced with prosthetics (which apparently can have some advantages over actual legs). You´d probably find Oscar_Pistorius interesting. --Shaggorama (talk) 01:13, 30 June 2008 (UTC)

Human and agricultural uses of antibiotics, and the development of drug-resistant bacteria
Is it known how great the contribution of non-judicious human use of antibiotics is to the development of drug-resistant bacteria, when compared with the contribution of antibiotics use in animal farming? —Preceding unsigned comment added by 71.162.249.44 (talk) 12:58, 29 June 2008 (UTC)


 * Not to me, at least. But I suspect nobody really knows, but the uppers fear it and do everything to reduce the use of antibiotics for humans so they will still work when the important people like soccer players, stock bulls or politicians fall ill. 77.3.168.22 (talk) 15:36, 29 June 2008 (UTC)


 * Heh... "Important people like soccer players"? You make it sound as if they're more worthy of healthcare than anyone else... -- Aeluwas (talk) 16:03, 29 June 2008 (UTC)


 * I think 77* was being sarcastic, though unfortunately so. Antibiotic resistance, it seems to me, will harm people with less money disproportionately.  Rich people will be more likely to have access to the few remaining effective antibiotics.  (And by the way, the article I linked to has a section on use in animals, though apparently it's under dispute.)  --Allen (talk) 16:13, 29 June 2008 (UTC)


 * Hey, yes, I am sarcastic. But soccer players really do get better treatment, so that proves they effectively are more important, at least for those people that decide who gets the real medication and who only get the dopes so they don't feel so much ill any more.


 * But are there any serious alternatives to antibiotics? Washing hands won't get you healthy again once someone else has sneezed his bacteria into you. And phages are natural vectors for genes, including those for antibiotic resistance. Unlike antibiotics they mutate and have a potential to get out of control. 77.3.168.22 (talk) 18:01, 29 June 2008 (UTC)


 * Well, no, there aren't serious alternatives to antibiotics... that's the whole point of fighting antibiotic resistance by discouraging overuse, right? --Allen (talk) 03:59, 30 June 2008 (UTC)

Inseminating Mars
If humans sent spaceships to nuke Mars with bacteria, would new life develop and would this new life eventually generate itw own atmosphere, allowing people to breathe easily ? 69.157.237.196 (talk) 13:53, 29 June 2008 (UTC).


 * This is indeed an area of great interest to scientists, and is studied and theorized about frequently. We have a nice article about it: Terraforming of Mars. Apparently the biggest problem currently is that Mars is waaaaay cold, so we'd need to heat it up considerably. The good thing is that once you get the heating process started, Mars can help along, since there is considerable quantities of CO2 frozen at the poles. When it got warmer, that would be released into the atmosphere and help along the greenhouse effect. It's some sort of irony that the things that would make Mars more like earth is vast quantities of CFCs and CO2.
 * After that it is done, the article says gives essentially your plan for continuing:

''After the heavy dust-storms subside, the warmer planet could conceivably be habitable to some forms of terrestrial life. Certain forms of algae and bacteria that are able to live in the Antarctic would be prime candidates. By filling a few of the rockets with algae spores and crashing them in the polar areas where there would still be water-ice, they could not only grow but even thrive in the no-competition, high-radiation, high CO2 environment.''
 * (I assume that this is what you meant, and not literally nuking the surface of Mars. That would probably not be the greatest plan for allowing life to spread). The article is fascinating, I highly recommend you read it. 217.213.153.218 (talk) 14:08, 29 June 2008 (UTC)

Starting out with electronics...
(not sure if this is more computing than science, but here goes...)

After seeing a bunch of guides and how-tos on the internet about how to easily program microcontrollers to control LEDs or build robots or do whatever (you know, MAKE magazine stuff), I've sort-of become intersted in learning this stuff. I'm great at computers, and I can develop in a number of different languages (including C, which I suppose is the language you'd use to program microcontrollers), and I have a deep understand how computers work. The thing is, I've always concentrated on the software side, I don't think I've ever in my life held a soldering iron in my hand. I know some of the theory behind electronics and basically how it all works, but I don't really know about this stuff in practice (When do you need a power-supply capacitor? How big does it need to be? Where do you put it? How big a resistor do you need not to fry stuff? And how do you read those colorful bars? And how do you solder without burning yourself and your stuff? etc.) I'm betting that out there there's a book for me, called "I'm a pretty smart guy and I want to try to build stuff but don't really know how" or something. Or maybe a website? Can anyone make a recommendation? Like, a beginners crash-course. 217.213.153.218 (talk) 13:56, 29 June 2008 (UTC)


 * I had similar motivations once. I did some research and decided to buy The Art of Electronics.  I kind of fizzled out after a couple chapters, but that was my fault.  The book seemed excellent.  Hopefully someone who's actually finished a book will also respond :-).  --Allen (talk) 15:59, 29 June 2008 (UTC)


 * Allen, you beat me to it with your recommendation for Art of Electronics. Another good one is Electronic Circuits and Applications by Senturia and Wedlock. But I'm not sure either of these books will teach the more-practical aspects of electronics (such as which end of the soldering iron to hold; I'm not sure about reading color codes, but Wiki's article is probably enough there). In the old days, Heathkit, Eico, and Knightkit were the best answers for learning the more-practical skills, but they're gone, of course. You can still buy kits of parts with a PC board from a few electronics parts shops (such as "You-blew-it", err, "You-do-it" Electronics in Needham, Massachusetts ). They can also sell you a soldering iron, electronic test equipment, and the like. (Soldering is like any other skill; practice makes perfect.)


 * It's gotten a lot harder to learn anything about electronics as a hobbyist; the prevalence of VLSI, very-fine-pitch parts, and surface mount devices has made the bar to entry much, much higher than when I joined the trade.


 * Atlant (talk) 17:17, 29 June 2008 (UTC)


 * This seems oddly fitting, since I learned many of my programming skills from The Art of Computer Programming (my dear parents gave me all three volumes my second year in high school; it is the best birthday present I've ever got). I can at least check them out from the library to see if they are what I want :) 83.250.202.36 (talk) 17:22, 29 June 2008 (UTC)

Someone in one of the electronics magazines a couple of years ago noted that electronics became a great hobby when the era arrived in the 1960's that you could build radios amplifiers and other gadgets using transistors and LEDs rather than vacuum tubes with high voltage power supplies. Breadboarding became cheap and easy. People built TVs, oscilloscopes, computers and even robots from Heathkit kits. Ham radio was a popular pursuit for tecchie. Then along came computers as a tecchie pursuit, with people programming them to do amazing things with BASIC programs. Large scale integration meant that there was not all that much soldering to do in building an electronic device. Websurfing seemed to replace ham radio to some extent. Then PCs arrived with less accesss to the lower level functioning and no BASIC. No more games to be typed into the computer from a monthly computer magazine and debugged so they actually worked. Just the running of applications and games. With the passing of the era of big chemistry sets, Heathkits, and other hands-on technology, there seems to be less interest and ability of those entering college today to understand the inner workings of the electronic and computer devices they use. So it is great to see someone interested in tinkering. You can approach electronics from a low technical level of perhaps experimenting with one of the larger Radio Shack electronic experimenter sets, and you can still buy lots of interesting kits from the electronics magazines. Community colleges offer some great courses in basic electronics that are less of a calculus fest than electrical engineering courses. Edison (talk) 19:15, 30 June 2008 (UTC)

Look for the evil genius series of books, like the title Electronic Gadgets for the Evil Genius or 53 High-Tech Pranks for the Evil Genius, Bionics for the Evil Genius (etc.) they all have introductions to electronics and stuff. While not exactly textbooks or courses in electronics, they make learning electronics an enjoyable activity. They have some really phenomenal projects, ranging in difficulty from absolute beginner to experienced. Ilikefood (talk) 01:37, 1 July 2008 (UTC)

SImple pendulum
1.If a simple pendulum with a period of 1 second is set in motion on the moon, determine the new period of this pendulum.

2. will a simple pendulum swing continuosly in air? explain why. suggest the condition required for a pendulum to swing continuoslyMinjiun (talk) 14:21, 29 June 2008 (UTC)Lmj


 * For #1, see the article on pendulum; see also the article on the moon for value of lunar gravitational acceleration. For #2, see the articles on drag and damping.


 * (After edit conflict) 1. Not enough information - doesn't say where the pendulum has a period of 1 second. But let's assume that is on the surface of the Earth. Somewhere in your texbook there is an expression for the period of a simple pendulum in terms of its length and the local acceleration due to gravity (or g) - if you can't find it in your textbook, take a look at our pendulum article. Now, keep everything constant apart from g. Reduce g to 1/6th of its value on Earth (that is approximately correct for the surface of the Moon). What is the change in the period of the pendulum ?


 * 2. Another badly phrased question - the motion of any pendulum is always continuous. But let's assume it means continually or perpetually, not continuously. Think about energy and friction. Gandalf61 (talk) 14:43, 29 June 2008 (UTC)


 * You are assuming the question is badly phrased. It is likely verbatim to what the questioner's teacher said in class, drew a diagram of on the board, and explained would be in the homework - all while the questioner was busy texting his friends about much it sucks to repeat physics class in summer school. --  k a i n a w &trade; 00:27, 30 June 2008 (UTC)
 * There are places on the planet where the regular school year is still in session! —Preceding unsigned comment added by 62.145.19.66 (talk) 08:46, June 30, 2008 (UTC)

mars
can life exist on mars? —Preceding unsigned comment added by 117.97.3.66 (talk) 14:28, 29 June 2008 (UTC)


 * yes. Scray (talk) 14:50, 29 June 2008 (UTC)


 * See the article Life on Mars and Planetary habitability. Jdrewitt (talk) 14:56, 29 June 2008 (UTC)


 * Please clarify what you mean by "life", "exist", "on", and "can". And because I'm feeling mean, "mars". (Translation: Could a human being, without any form of life support, survive for any meaningful length of time on Mars? No. Is it possible that just below the surface of Mars there is a habitat in which single-celled creatures similar to those found on Earth could possibly survive? Definitely. In between? Maybe.) Confusing Manifestation (Say hi!) 22:59, 29 June 2008 (UTC)
 * But is there Life on Mars?--Shniken1 (talk) 16:42, 30 June 2008 (UTC)

Amount of energy on earth remains constant.
Is it true the amount of energy on earth is the same today as when the earth was formed? If so who is credited with the theory that the energy amount is the same only changed to a different form? I believe I remember in my study of Physics years ago that it was taught that if two boxcars were pushed together one was moving the other still that the energy of the moving one was transfer to the other and some energy went into heat and sound as the still boxcar would never begin moving as fast as the moving car.

My question is WHO —Preceding unsigned comment added by 24.19.226.142 (talk) 14:31, 29 June 2008 (UTC)


 * The general idea you're looking for is the conservation of energy, with the conservation of momentum relating a little closer to the boxcar example. However, it is not true that the amount of energy on Earth is unchanging, because the Earth is not a closed system.  Solar energy radiates in (at a changing rate) and heat energy radiates away (at a changing rate).  An ice age, for instance, is a period where the Earth has less energy (though I've no idea what that difference would be in percentage terms -- likely very very small if you start talking about "the whole earth").
 * As for "who", no one man can be credited with fully formulating an explanation of the conservation of energy. The history section of that article should be illuminating. &mdash; Lomn 14:40, 29 June 2008 (UTC)


 * Several energy factors are changing and I doubt it can simply be assumed that the total Earth energy is less during an ice age. Earth picks up more mass from the Solar system (meteors and such) than it looses. If the equivalent energy per mass–energy equivalence is included then it may be important. More heat energy radiates away than Solar energy radiates in. This once caused wrong estimates of the maximum age of the Earth because heat energy from radioactivity in the Earth was not discovered and included in the calculations. PrimeHunter (talk) 15:55, 29 June 2008 (UTC)
 * Excluding meteors (an excellent point, by the way), I think the ice age idea holds up pretty well. Air and surface temperatures decrease, and everything else holds.  Insignificant in a grand e=mc2 mass-of-the-earth example, but a good practical one. &mdash; Lomn 13:01, 30 June 2008 (UTC)


 * Oh no, not another "second law of thermodynamics" mangler. Imagine Reason (talk) 22:34, 29 June 2008 (UTC)


 * The first law of thermodynamics, you mean?. --Bowlhover (talk) 00:11, 30 June 2008 (UTC)
 * No, but I've seen that one too. Imagine Reason (talk)


 * Imagine Reason, have you investigated the articles breeder reactor and fast breeder reactor yet? --arkuat (talk) 08:38, 30 June 2008 (UTC)


 * No. Why? Imagine Reason (talk) 01:17, 1 July 2008 (UTC)


 * Because they produce fissile material from fertile material; that is, they produce more usable nuclear fuel than they consume. However, they're only liberating potential energy stored in the nuclei of (otherwise unusable as fuel) U-238 atoms. So they don't violate conservation of energy, but can easily be mistaken by a novice for doing so. --arkuat (talk) 04:49, 1 July 2008 (UTC)

Space left by crude oil
What is filled to the huge space left by the crude oil and gas? —Preceding unsigned comment added by 62.231.233.151 (talk) 14:55, 29 June 2008 (UTC)


 * Oil doesn't sit in voids in the earth, it is usually in porous rocks. So when oil is extracted, the rocks remain.  Following extraction of the oil, the pores in the rocks will either be filled with natural or atmospheric gases or the oil may be replaced by water, which is either used to force the oil out or naturally seeps into the rock from the natural water table. Jdrewitt (talk) 15:04, 29 June 2008 (UTC)


 * In some cases, the pore spaces contract when you remove the fluids they have been storing. In effect, the land in the regions settles, but in general the amount of such settling is not very noticable for practical volumes of oil/gas.  Dragons flight (talk) 00:55, 30 June 2008 (UTC)
 * wow 125.21.243.66 (talk) 06:43, 30 June 2008 (UTC)

So, geologists take note, if you pump oil or natural gas out of a land area, you may expect that land area's water table to contract naturally as a result. Or am I reading the replies wrong? --arkuat (talk) 08:28, 30 June 2008 (UTC)


 * That is possible, yes. But sometimes the way they get the oil out is by pumping water into the ground, the pressure of which pushes the oil up and out. I doubt that this method has an impact on the water table.  Plasticup  T / C  12:44, 30 June 2008 (UTC)

Very good point. Thanks --arkuat (talk) 04:53, 1 July 2008 (UTC)

Insect
There is an insect at my home in Kentucky. It looks like a cross between a bee and a humming bird or butterfly. Can you tell me what it is? And if it will sting me? 98.19.3.125 (talk) 20:41, 29 June 2008 (UTC)


 * A Hemaris sp. hummingbird moth would be my first guess. It is a moth, it is perfectly harmless. --Dr Dima (talk) 20:56, 29 June 2008 (UTC)
 * You may also want to look at Carpenter bee. It doesn't match the description you gave as closely, but it can sting if you try to catch it; so you may see if that's not it. --Dr Dima (talk) 21:00, 29 June 2008 (UTC)


 * Check out the Sphingidae article for more extremely hummingbirdy bugs in the same family as Dr. Dima's suggestion.  These bugs are not to be trusted!  Look at this Gaudy Sphinx Caterpillar: . --76.182.119.241 (talk) 23:29, 29 June 2008 (UTC)
 * Wiki knows everything. Yay! 125.21.243.66 (talk) 06:42, 30 June 2008 (UTC)