Wikipedia:Reference desk/Archives/Science/2006 December 12

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December 12

Investigating the etymology of the term Backhoe

Our backhoe page says, "Similar attachments for [other vehicles] are still called backhoes even though they are mounted on the front. This is because the name refers to the action of the shovel, not its location on the vehicle; a backhoe digs by drawing earth backwards, rather than lifting it with a forward motion". And personally, I completely agree with this on both points, but I'd like to find some really definitive historical sources explaining how the term arose. (This is for my own curiosity, and perhaps for the Etymology section at wikt:backhoe, not because I'm about to start slapping {{cite}} tags on our backhoe article or anything.)

My own hunch -- and this is what I'd really like to confirm, if it's true -- is that the term "backhoe" was coined in direct opposition to the older steam shovel. If you look at a picture of a steam shovel, such as this one of ours, or this cute one, or this classic one, you can pretty clearly see that the digging bucket faces up, and that the machine digs by lifting up and away. A backhoe, on the other hand, digs by pulling down and back towards the machine. The fact that you don't see steam shovels -- or anything else with that same, old up-and-away action -- any more makes me suspect that the pull-down-and-towards action has been found to be much more effective. (But it had to await the development of modern hydraulics, because a cable-hauled backhoe wouldn't work nearly as well.)

Anyway, I suspect that the word "back" in the name "backhoe" was chosen specifically because of the back-towards-the-machine action, which was backwards from the way steam shovels worked. I suspect that the fact that backhoes are often mounted on the backs of tractors is a coincidence which had nothing to do with the term's coinage (though I could be wrong). But the web searches I've done to try to confirm these suspicions have come up dry.

If anyone can dig up any confirmation for any of this (and preferably more definitive than personal armchair speculation, which is all I've really been doing so far), I'd appreciate it.

(I'm going to raise the same question at Talk:Backhoe, and if I get any immediate answers there, I'll propagate them here.) —Steve Summit (talk) 00:20, 12 December 2006 (UTC)

The American Heritage dictionary 2000says "An excavator whose bucket is rigidly attached to a hinged pole on the boom and is drawn backward to the machine when in operation." I see a few other sites mention the "mounted at back" as the reason for being called a backhoe, but the "pull back" idea seems more rational, since it can be mounted in front or at the back. But then, one would may like to find more original references. --Seejyb 01:16, 12 December 2006 (UTC)

That's a very strange comet indeed!

When William Herschel first saw Uranus, did he note that it was much brighter than any comet with the same size? Uranus is also blue-green with a well-defined edge that's not fuzzy; I wonder how many comets are like that. If Herschel observed comets before (I assume he did since he's a serious amateur astronomer), did he ever remark about the strange appearance of Uranus? According to [1], it was the famous comet-hunter Messier who pointed out it didn't look anything like a comet. --Bowlhover 04:26, 12 December 2006 (UTC)

• Herschel's logbook entry for the night of March 13, 1781 described it (what eventually turned out to be Uranus) as "a curious either nebulous star or perhaps a comet." (Herschel's quote obviously did not include the preceding wikilink however ;) His next observation of the new object, on March 17th, revealed that it had "changed its place" therefore convincing Herschel that it was a comet. Yes, Uranus is blue-green with a well-defined edge when observed using modern telescopes however, Herschel was using a small homemade reflecting telescope with a speculum mirror that was far inferior to even the smallest amateur instruments made today. Also, at the time, the idea of there being more planets beyond Saturn did not really exist yet. Comets were the only other object known at the time that moved across the sky relative to the stars. It was not until after the discovery of Uranus that searches for more planets became commonplace eventually leading to the discovery of Neptune (in 1846) and Pluto (in 1930). Many other astronomers (including Charles Messier) soon began to suspect that perhaps the newly discovered object was a 7th planet rather than simply a distant comet. Ironically, Herschel was one of the last to concede the object's planetary status. --Nebular110 17:29, 12 December 2006 (UTC)

Particle Accelerators

If the Diameter increases in a particle accelerator does it increase output or if I had a small diameter and boosted up the power would that have the same effect? I am very confused about this thank you for any answers.67.126.141.245 05:14, 12 December 2006 (UTC)

Larger diameter can achieve greater particle energies for the same amount of input energy. Larger rings can also store larger numbers of particles at a given time, but this is usually a secondary consideration. Dragons flight 09:37, 12 December 2006 (UTC)

The velocity vector of a particle in a synchrotron changes constantly as the particle follows the curve of the circular track. This causes the particle to lose energy as it emits synchrotron radiation. The amount of lost energy is inversely proportional to the square of the radius of the synchrotron. For this reason the bigger the synchrotron, the less input energy it needs to attain a given particle velocity. Weregerbil 12:57, 12 December 2006 (UTC)

Also the magnetic field required would be lower for a larger accelerator, as the radius of curvature required is lower, although you would need more magnets. There's a lot of work on superconducting magnets for new accelerators. But as above synchrotron radiation is a big factor, it's also controlled by mass which is why hadron colliders can achieve much higher energies than electron colliders (e.g. LEP and LHC).

drying a log

hello, I plan on finding a huge yule log in the forest next weekend and bringing it home. I shall attempt to dry it in preparation for burning on the 25th. My question, are there internet sites that concern the process of drying logs at home?

This is what I'm going to try to do:

-bring indoors, surround with electric heaters. -enclose in plastic case with a hole on the top and with salt scattered around it -as the salt absorbs the h2o, I will replace it with more salt

Is there a better method than this? hopefully between the heat and the dessicant salt, the log will dry out before Christmas. Thanks. -John

the rate at which wood dries it primarily a result of surface area and the humidity of the air relative to the wood. I would suggest cutting up a portion of the log to dry totally and then on xmas burning the cut logs to dry the main log. the main log might burn slow but thats no problem. Beckboyanch 06:43, 12 December 2006 (UTC)

I truly hope that you would cut down a dead tree in the forest, and this would solve your problem. Some woods, such as Birch can burn well when green, White Oak only needs a little drying, but something like Spruce can't be burnt until it's very dry. --Zeizmic 12:39, 12 December 2006 (UTC)

yea I'm going for a dead tree. So is there a table somewhere of different woods with how they burn when wet?

Does this help? User:Zoe|(talk) 18:54, 12 December 2006 (UTC)

It would help to split them lengthwise into small pieces then "reassemble" them on xmas day, perhaps with some metal wire wrapped around them. Of course, this effort would all be unneeded had you started a few months ago. Then, just letting it sit where it won't get rain on it would have been sufficient. Considering the cost of running the space heaters, wouldn't it make more sense to buy a dry log and use this one next year ? StuRat 04:40, 13 December 2006 (UTC)

I have never tried to dry anything large and thick like a log. I can easily imagine it taking more time than is available. But when I have to dry something at home that got soaked -- carpets, books, shoes -- I find it always helps immensely to arrange to have air blowing over it (or better yet, if possible, through it). Of course you also want the humidity of the air to be low -- but applying heat to it will already lower the humidity. The desiccant may be a good idea but my guess, and I do mean guess, is that it won't help enough to be better than blowing air over the thing in an open room.

By the way, as a side point, you want to make damn sure that your heaters can't ignite the log (or the floor) if the log could roll over unexpectedly or something like that. --Anonymous, December 13, 06:36 (UTC).

It takes the moisture in lumber or firewood a very long time to leave the wood, like a year or two. It is unsafe and unrealistic to try and turn your living room into a kiln, and unnecessary. Salt on the wood might extinguish the fire or might give color to the flames. Some other chemical might produce lethal fumes. Do not burn preservative treated, Wolmanized or creosoted wood like railroad ties or utility pole sections in a fireplace. See Wood drying and Wood fuel. The Yule log is traditionally NOT a dried out or seasoned log which burns up quickly. It is supposed to be cut green at Christmas. It is supposed to burn for 12 days! A fresh green hardwood Yule backlog can be accompanied by a small amount of seasoned firewood in front of it (you can buy bags of seasoned hardwood firewood at many supermarkets or from firewood vendors). Evergreen logs may burn too quickly, starting the house on fire, and deposit creosote in the chimney. Do not build a huge fire in a fireplace, since the excess heat may start a chinmey fire or shatter the glass doors if it has them. Just put the Yule log in the back, the light a normal little fire in front. The backlog will dry as the fire progresses. When northern Europeans start rituals at Christmas involving trees (Yule logs, singing about "the holly and the ivy" I always suspect the ancient Druids must be chuckling in whatever afterlife they inhabit. A modern Fireplace is definitely not typically designed for large roaring fires. Also note the dangers of carbon monoxide. Edison 17:08, 13 December 2006 (UTC)

Singularity size?

What is the volume of the singularity (not the event horizon) of a black hole? Does it occupy a cubic plank? or does it not occupy space (Does the mass slip through space time? or does it so warp space time to render a conventional view of volume irrelevant? Beckboyanch 06:13, 12 December 2006 (UTC)

Gravitational singularity suggests that a singularity has zero volume, though much of what happens inside black holes is unknown. -anonymous6494 06:46, 12 December 2006 (UTC)

It also suggests that black holes have infinite density and to have infinite density and a finite mass one must have infinitesimal volume and in a quantum world there is no infinitesimal volume so that doesn’t make sense209.112.216.29 07:19, 12 December 2006 (UTC)

I think we can not use the terms "size", "distance", "volume", etc. because the space inside the Schwarzschild radius (beyond the event horizon) is NOT a metric space, so these terms have no meaning. --V. Szabolcs 10:44, 12 December 2006 (UTC)

I don't understand how you can say such things with such certainty. Singularities are theories?83.100.174.70 11:27, 12 December 2006 (UTC)

No, they have been measured via various means. See our article on black holes. Hipocrite - «Talk» 13:02, 12 December 2006 (UTC)

Where is there any evidence there?83.100.174.70 19:49, 12 December 2006 (UTC)

The sections on "Suspected black holes." Hipocrite - «Talk» 19:52, 12 December 2006 (UTC)

But there is no evidence there of singularities etc..83.100.174.70 20:43, 12 December 2006 (UTC)

No there isn't, and there can never be evidence because it's impossible to know what goes on beyond the event horizon. However, according to the gravitational singularity article, general relativity predicts black holes to be singularities. Relativity explains all other phenomena well, but of course if something is unfalsifiable then it isn't considered science. So you decide: do they really exist or not? --Bowlhover 01:33, 13 December 2006 (UTC)

Back on track, so to speak: So the mass of a black hole is down at the bottom of the gravity well, in the singularity, so it really can't be quantified as having a size dimension, or a volume, being in a non-metric space. But if I was able to observe a black hole, I'd see the schwartzchild radius as the "apparent" size, yes? That is, if a black hole was in front of a distant star field, I'd see a perfectly round spot where no stars are visible, and the size of that spot is the diameter of the schwartzchild radius, right? [[192.16 oh bugger, the bot's gonna screw it up anyway...

Not really. What you'll get is more of a perfectly black spot that will be roughly the same size as the Schwarzschild radius, but around that you'll get gravitational lensing, which will create a very distorted view of the stars behind the black hole. In fact, if you see a black spot at all, I think it's guaranteed to have a smaller angular diameter than something the size of the Schwarzschild radius. And as for the mass being in the singularity, that's not really the case. It's more that once the mass goes within the event horizon, all the calculations that can be made about spacetime outside the event horizon are equivalent to what you would get if all the mass was concentrated at the centre (this is completely analogous to Newtonian gravitation, where the gravitational field of a spherical object is the same as the gravitational field of a point mass). Confusing Manifestation 13:45, 13 December 2006 (UTC)

Just look at [2] and [3]. It can be seen that the black spot is quite small. --V. Szabolcs 15:43, 13 December 2006 (UTC)

Excellent! Cool pictures, more proof that a picture is worth a thousand words. Now I understand. 192.168.1.1 9:39pm, 13 December 2006 (PST)

estimate temp of room

I have no access to a thermometer. How can I measure the temp of my room within 10 deg F? it 's very cold. -john

How about a simple solution: buy a thermometer or borrow one from a neighbour. Or is this homework and you are supposed to devise a physics experiment? Weregerbil 12:40, 12 December 2006 (UTC)

Or you could catch a cricket, and follow Dolbear's Law. Unfortunately, that's assuming it's over 50°. -- Plutor ^talk 13:41, 12 December 2006 (UTC)

yea I was thinking of that but it 's too complicated.

My speculative guess is that you could take an ice cube and time how long it takes to melt completely into water in the room. Then somehow figure out what melting at that rate would indicate about the temperature of the room. Not sure if that would work within 10 degrees, though. --24.147.86.187 14:22, 12 December 2006 (UTC)

I like this one, perhaps I shall attempt...

Keep in mind that the humidity and air pressure of the room would affect the results, as well as any airflow. If the room has no circulation, your model must take into account the insulating effect of the surrounding air. If the air is very dry, the ice may sublimate. Air pressure can affect the insulating qualities of the medium the ice cube is in. Finally, drainage is an important consideration. The melt rate would be changed if the water coming off of it was allowed to pool around it. - CHAIRBOY (☎) 18:10, 12 December 2006 (UTC)

Sometimes in a science problem. everything which is not specifically forbidden should be considered as allowed. It does not say you are trapped in a bare room with no access to anything. It just says you do not have a "thermometer," not that you do not have anything in the room the properties of which vary with temperature. So rephrase it as "I have no thermometer, but I have access to other devices which behave in a way that varies with temperature." So you could weigh out a precisely measured mass of a gas, and measure its volume. Then apply the Gas laws to determine the temperature. Or you could measure how long it took a given fluid to pass through an orifice, and apply the Temperature dependence of liquid viscosity. The warmer it is, the faster the molasses will pour out of the bottle. You could dissolve something: the solubility constant will vary with temperature. You could measure the resistance of a coil of wire: the temperature can be accurately inferred from the Electrical resistance. You could measure the length of a metal rod which has a known length at some temperature and a known expansion coefficient. You could measure the output voltage of a Clark cell, which varies with temperature. You could measure the activity of yeast or other cultures, which are temperature dependant. You could select a series of substances with different melting points and note which remain solid. If it is below 0 Celsius, you could see if water freezes, then see how much antifreeze you have to add to the water to prevent it from freezing, and look up Freezing-point depression. You could expose film to a known amount of light, then develop it and see what the optical density is: it will vary with temperature of the developer. Edison 19:06, 12 December 2006 (UTC)

lol, I'm in a residential room, not Oak Ridge Laboratory

How big is the room? Once, in a class, we determined air temp by taking a distance measurement and observed a clapper (something that makes sharp noise, like pieces of wood hit together) and noted the time delay in the sound. Taking altitude from sea level into account, you can rough out the local temperature by calculating the speed of sound. To make it easy for students to get accurate results, we did this outside and measured a distance equal to one sound second. --66.195.232.121 19:52, 12 December 2006 (UTC)

how did you measure the time delay so accurately?

This might be obvious, but any person can tell the temp within 10°F just by how they feel. Did they exclude using this method ? StuRat 04:33, 13 December 2006 (UTC)

yea but the original thought was to bring it up to my landlord, so I needed some unbiased technique. At the worst, I bet my room gets to 50-55 F, right now it's probably 60-65 F

I have heard people say "Look at the thermostat! It is 65 degrees (F) in here! I feels like it's 30!" Edison 17:09, 13 December 2006 (UTC)

One rough estimate method I discovered for one limit when it's cold is if you exhale slowly with your mouth open. I've found that if you can just make out steam coming out of your mouth it's about 12-13 degrees, I'm talking centigrade so google if you want farenheit. If no steam comes out it's above that and if the steam is quite prominent then it's likely below 10 degrees. Vespine 01:08, 14 December 2006 (UTC)

interesting...I observe nothing, perhaps my Dorrito breath affects this test

I believe humidity is also a factor, as any water vapor quickly dissipates in dry air. StuRat 22:33, 15 December 2006 (UTC) AND IS A CACA HEAD WITHOUT A LIFE I ADDED THIS CAUSE IM BORED1!!!!!!! GOT IT!!!!!!

"a constant-amplitude, constant-frequency sinusoid in channel k should have identical analysis phases in all nearby channels."

k is the index of the bin of a stft-transformed signal. Can you explain this? i got it from this pdf, but I think that this should be real for any STFT-transformed signal which is a sinusoid in the time domain. tia --Ulisse0 09:42, 12 December 2006 (UTC)

I think you've asked this several times now. I'm sorry to say, we don't appear to have any expert on that field. StuRat 04:28, 13 December 2006 (UTC)

Perhaps you could contact the author of the dissertation you cite. Edison 17:10, 13 December 2006 (UTC)

If you quoted the page number of the thesis, that may help us to answer.--Light current 22:39, 15 December 2006 (UTC)

Inventor of the scratchie ticket

Hello

I am interested in the history of the invention of the "scratchie" instant lottery ticket?

Thanks

Yaeli

Our article on Scratchcard should be helpful. Hipocrite - «Talk» 12:59, 12 December 2006 (UTC)

That article states: "Such cards are vulnerable to attack by devices which allow individuals to see through the concealing substance without physicically disturbing it."

Does anyone have any info on what type of devices are used? Downunda 00:49, 14 December 2006 (UTC)

aqueous copper

I have Cu(H2O)6²⁺ in solution, I cool it rapidly and bring the entire thing into the solid phase, what is the structure of the complex I end up with? Would this be the equivalent of doping an ice lattice with copper? 14:26, 12 December 2006 (UTC)172.145.201.173

You will have to supply some additional information to get an answer to your question. First of all, Cu(H₂O)₆²⁺ can't exist by itself. There must be a counterion - in this case something with a negative charge. How did you prepare this solution? Also what do you mean by "bring the entire thing into the solid phase"? Do you mean crystallization, evaporation, precipitation, trituration, freezing or something else? --Ed (Edgar181) 14:57, 12 December 2006 (UTC)

Ok, there's trace amounts of zinc, and nickel, with the principle counter ion being chloride, and let's say hypothetically, all I've done at the end is cool rapidly and freeze 22:40, 12 December 2006 (UTC)172.161.40.6 22:40, 12 December 2006 (UTC)

Ok. Point 1 if the principle counter ion is chloride you would most likely have CuCl_4>^2- not Cu(H2O)6²⁺, the latter occurs with weakly complexing ions such as sulphate and nitrate..

That aside - it still depends on just how rapidly you can cool it. If your cooling is not rapid enough then you will get relatively pure water freezing out at first with the remaining liquid becoming more concentrated - eventually leading to a two phase system of water ice and solid (hydrated) complex. If you can cool very rapidly I would imagine that you could indeed get a copper complex incorporated into the ice matrix.. If you haven't already why not take a look at clathrate and look up host-guest complexes, inclusion compounds. Does that help at all?83.100.254.21 16:10, 13 December 2006 (UTC)

Help me prove the Earth (and Universe) is over 5,000 years old

A coworker of mine is an Ultra-Orthodox Jew. He doesn't believe in evolution, but putting that aside, he also says that the Earth is 5,000 years old. I've argued with him about this several times. My favorite argument is that, given the speed of light, the vast majority of stars we see are more than 5,000 light years away. He counters that god could have created the light mid-stream. (To which I've countered, why would he do such a thing -- just to confuse us?)

What other arguments (that a layman would understand) might convince him of the age of the universe? Forget about radiocarbon dating -- he has a paper from a 'theologian' that says that carbon dating is inaccurate.

I know this is a pointless affair -- but I must admit I enjoy the debate a little bit.  ;-) -Quasipalm 15:25, 12 December 2006 (UTC)

Review our article on age of the earth. Hipocrite - «Talk» 15:30, 12 December 2006 (UTC)

It really, truly is a pointless argument. For one thing, if your opponent is willing to posit the existence of an omnipotent god who can fabricate any evidence, then no argument you can possibly ever come up with, whether understandable by a layman, a child, an evolutionary biologist or a quantum physicist, will ever, ever convince him.

More important, I think, is the fact that you and he are arguing from completely different worlds. You might as well be speaking Swahili, and he Martian. Science tries as hard as it can to be objectifiably verifiable and to remove human emotions such as faith from the equation. But religion, of course, depends as heavily upon faith as science does upon rigor. So your arguments with him aren't merely pointless, they are also in a real sense meaningless. (Be thankful that your opponent isn't trying to use "scientific" arguments to "prove" creation, or to disprove evolution, as some fundamentalist Christians I know sometimes try to.) —Steve Summit (talk) 16:27, 12 December 2006 (UTC)

Look at the external articles linked to from Young Earth creationism. yandman 16:55, 12 December 2006 (UTC)

See also Last Thursdayism --TeaDrinker 18:36, 12 December 2006 (UTC)

If he is willing to believe that God would create the world with light in mid-stream, then he is willing to believe in a God who would trade in deception in order to test faith. Which means that no evidence can work; it is an anti-empirical philosophy and one without end. You should ask him if that's the sort of God he thinks the Bible depicts, though, and what the implications of that might be. --140.247.251.173 18:41, 12 December 2006 (UTC)

The above comment is completly unnaceptable for a reference desk, which is not a debate society. Please refrain from making such comments in the future. Thanks. Hipocrite - «Talk» 19:09, 12 December 2006 (UTC)

Can you please elaborate on that? I think it's completely relevant to the question, which is about how to prove Earth's age to a religious person. Therefore, it's completely acceptable. --Bowlhover 23:37, 12 December 2006 (UTC)

Um, all I did was extrapolate from the argument and suggest a way to discuss it which would be fruitful. In my experience most people who believe in the "God rigged the fossils/light/etc." argument (which is a quite common way that Creationists deal with contradictory evidence of this sort) are not willing to really go all the way in that type of God (a God who would deceive people by putting evidence of an old universe all over the place). This line of argumentation is not new (neither the original assertion, nor my probing of it); see the links to Omphalos below. --140.247.251.173 00:41, 13 December 2006 (UTC)

See also Omphalos (book) which introduced the philosophical argument that in the Garden of Eden there would have been inevitable biological references to spurious prior existence. The wavefront of light from the stars, the fossils, the giant eroded canyons, tree rings, all suggest existence before any given moment of creation. See also Omphalos (theology). Edison 18:43, 12 December 2006 (UTC)

By definition, faith-based explanations cannot be argued as science-based explanations are argued. Faith is complete belief without requiring any proof. Science is belief only in that which can be proven empirically. Therefore, your assumption that there is a possible resolution to this argument is, perhaps, not true. 70.50.237.242 19:45, 12 December 2006 (UTC)

It's interesting that you wish to disprove his pig headed theory but yours "My favorite argument is that, given the speed of light, the vast majority of stars we see are more than 5,000 light years away" is equally as faith based - how can you possibly know the distance to the stars etc?83.100.174.70 19:54, 12 December 2006 (UTC)

Stellar parallax is one simple way. DMacks 19:57, 12 December 2006 (UTC)

83.100.174.70, stars get fainter over distance. If you know how much light a star with a certain chemical composition gives out, and you find such a type of star, why not calculate how far the star must be in order to have the measured brightness? --Bowlhover 23:37, 12 December 2006 (UTC)

You should fight FIRE with FIRE. Tell him that he is wrong and the world was created 5000 minutes ago. Demand that he prove it to you that it was not created 5000 minutes ago and that if he fails then he must accept that the world was created 5000 minutes ago. Let him do all the hard work because that's the only way he will ever learn. 202.168.50.40 20:41, 12 December 2006 (UTC)

The existence of all all-power being precludes any scientific explanation. There is literally no evidence you can suggest to which he cannot say "that's how God made it". So any discussion of the age of the Universe must, a priori, exclude supernatural explanations. That's the basis of all natural science, in fact. Or, as the anon above pointed out - ask your friend to "prove" that God didn't create the world yesterday, and with every claim he comes up with, you can simply say "but that's how God made it". Raul654 20:46, 12 December 2006 (UTC)

A good argument against his is that although most of the 1000ds of human culture have developed some form of notion of god(s) and that their conceptions vary wildly, pretty much every one of them has a different version of the origins and places it in different circumstances at a different time. Therefore his conception is no more valid than theirs. Although his Jewish faith might incline him to think he is part of the chosen people and thus is a keepr of the Truth, reminding him that everybody else believes something of the same order but just slightly different might help him to understand that the authority argument is not very practical for a firm understanding of reality. Keria 21:09, 12 December 2006 (UTC)

I was told I was born in 1987... and I don't remember anything before 1991... so I'm pretty sure that the earth was created when I was four.

It's obvious that you're lying! People tell me I was born in 1992, but I don't remember anything clearly from more than 5 minutes ago. Obviously the universe was created 5 minutes ago!

-What I don't understand is why you feel a need to prove him wrong. He is the one claiming that the earth is 5,000 years old. Why should the burden of proof be on you? It should be on him! I mean, can he even prove that God exists? You can explain a lot of the biblical miracles with science. --AstoVidatu 22:39, 12 December 2006 (UTC)

Er, no you can't. That's why they're called miracles. BenC7 02:12, 13 December 2006 (UTC)

It seems that everyone has failed to try to come up for a reasoning as to why this man thinks that the world is 5000 years old. This reasoning comes simply from the fact that in ancient times (or close to there), there were few accurate methods of determining the exact age of the Earth. Certain people agreed that the only way to deduce the age of the Earth was to add up the ages of all of the prominent male figures in the Old Testament through Adam, Noah, Abraham, Isaac, Jacob, etc. It sounds like a logical idea, but it requires that the Creation story and the ages and accurate records of all of the descendants of Adam be plausible. Maybe you can focus on these areas instead. I know that life spans of people in the Old Testament are heavily dilated to well over 100 years due to their methods of measuring time and such. --Russoc4 22:58, 12 December 2006 (UTC)

I think it is silly to say that people back then miscalculated how long a year was (and thereby how many years they lived). Everybody can tell the changing of the seasons as one year and it is not difficult at all to note when the sun gets back to rising at the same point on the horizon for a more exact measurement. If you choose to believe the Old Testament then there is no reason to think they did not know how long they themselves lived.Yaver 21:11, 13 December 2006 (UTC)Yaver

No, like one of the posters said above, the earth was created yesterday. God just implanted all the memories we have of any previous events when he created us all, yesterday. What? You think He couldn't do that? Piece of cake for an omnipotent being. Vespine 23:07, 12 December 2006 (UTC)

Seriously though, we've observed many events from far-away celestial bodies, like supernovae, novae, and even transits by planets across their stars. Why would God manipulate light just to make it seem like these events really happened? Using Occam's Razor, it's more logical to assume that these astronomical events really occured, rather than blaming them on God.

Also, there's a pretty good tree ring record back to about 10 000 years ago (see dendrochronology).--Bowlhover 23:37, 12 December 2006 (UTC)

Ah, that's what God wants you to think - he put those tree rings there to test the faith of doubters ;) Raul654 23:39, 12 December 2006 (UTC)

I started reading this thread about five minutes ago so the earth must be at least five thousand years and five minutes old. --hydnjo talk 02:57, 13 December 2006 (UTC)

You are fighting a losing battle. An omnipotent God can create anything he chooses and the "proof" otherwaise is simply a test of faith. All of the theories are about 'what' but ultimately fail to answer the question 'why'. For all you know, the universe is 10 minutes old. Why was there a big bang? Also, keep in mind that at the end of the 19th century, physics was nearly declared dead because Newton's theories predicted everything. And for the net rambling thought: the apple in Genesys came from the Tree of Knowledge. In a way, the supplanting of faith with science is the Orginal Sin. --Tbeatty 04:25, 13 December 2006 (UTC)

Let your goal be that you get wiser, rather than that you manage to humiliate your friend by proving him wrong. Study the concepts of probability and likelihood. What is the likelihood of there being life on Mars? Make your estimation based on current knowledge combined with an à priori complete ignorance, so that the initial likelihood is 50%. If you do not know the answer, then an observation will modify your estimate of likelihood, upwards towards 100% or downwards towards 0%. If you do know the answer beyond doubt, then the likelihood is either 0% or 100%, and then no new observation can ever change your mind. So there is no point in making observations unless you are in doubt. Study Bayes' theorem. Bo Jacoby 13:22, 13 December 2006 (UTC)

If God is to us like we are to the inhabitants of computerized realms like Sims or the people Captain Picard interacted with in the holodeck (who thought they truly lived in the computer generated reality), consider how the Sims could decide whether their world was really as old as it looked, or whether you just wrote the program today and gave them a huge oak tree in the front yard, fossils, starlight in the skies, and a view of the Grand Canyons, with millions of years of erosion of the mountain peaks. You could design a realm where every test they did said their world was of any specified antiquity, while from your perspective it was of any desired recency. Edison 17:17, 13 December 2006 (UTC)

Tell him that God is trying to make him think that the universe is only 5000 years old, but He really created it whenever the big bang started. Tell him that it's God's way of figuring out who is realy smart or something. The smartest people will figure out the Universe's real age. If that fails, try the old, "well, if the earth is only 500 years old, all of science's observations are wrong, and if all of science's observations are wrong, then we might as well be giant watermelons floating in a rhino's stomach in Dimension X 25,000 years ago after we died at the same time because we drowned in custard. Ilikefood 01:44, 14 December 2006 (UTC)

On a side note, is there any more evidence for, say, electrons, than there is for a 5-billion year-old earth? 80.169.64.22 16:41, 14 December 2006 (UTC)

There's lots of evidence for both. The fact that batteries work (for example), for the Young double slit experiment, or the fact that when you rub a balloon on your head it will stick, or if you run across a carpet while scraping your feet on it you can then shock someone by touching them - all of these are examples of electrons at work. Raul654 21:59, 14 December 2006 (UTC)

One of the main differences is that we can do reproducible experiments in the here-and-now to look for the existence of electrons; we can make observations. We can't reproduce bio/geo/astro evolution; the theory is inferred from the data in the present. BenC7 00:37, 15 December 2006 (UTC)

As I was saying earlier, if the earth is too young, then all of our scientific observations are wrong, and therefore anything that we have based on those observations should not work. If all of the facts that we base, say, the space shuttle on are false, then how come it still works? God? I don't think so. That's how you prove that the universe is older than 5,000 years. Ilikefood 21:30, 14 December 2006 (UTC)

Great thoughts all... Thanks!! -Quasipalm 06:08, 17 December 2006 (UTC)

A mannan-digesting enzyme?

Does anybody happen to know an enzyme that at least somewhat specifically digests mannan? I've been searching through the literature and Sigma catalogue, but I've been unable to find anything satisfactory. I'm hoping that I'm missing something specific. – ClockworkSoul 16:52, 12 December 2006 (UTC)

Prefaced with I know nothing about this topic, Mannanase seems to have some mention of digesting mannan (no wikipedia article on it yet), see [4]. --TeaDrinker 18:47, 12 December 2006 (UTC)

See also alpha-Mannosidase. –mysid☎ 19:30, 12 December 2006 (UTC)

Guns Fired Into The Air

When someone fires a gun up into the air (toward the sky), how hazardous is the falling bullet? I'll leave you to decide what gun and bullet-type since I know nothing of such things. --Username132 (talk) 18:30, 12 December 2006 (UTC)

How stuff works seems to indicate it is a lethal hazard, which is the impression I have as well. --TeaDrinker

The MythBusters covered this in their third season episode "Bullets Fired Up". The wikipedia summary is: "In the case of a bullet fired at a precisely vertical angle (something extremely difficult for a human being to duplicate), the bullet would tumble, lose its spin, and fall at a much slower speed due to terminal velocity and is therefore rendered less than lethal on impact. However, if a bullet is fired upward at a non-vertical angle (a far more probable possibility), it will maintain its spin and will reach a high enough speed to be lethal on impact. Because of this potentiality, firing a gun into the air is illegal in most states, and even in the states that it is legal, it is not recommended by the police. Also the MythBusters were able to identify two people who had been injured by falling bullets, one of them fatally injured." -- Plutor ^talk 18:35, 12 December 2006 (UTC)

It's pretty fatal in Los Angeles. We're always getting warnings on the news, especially on New Year's, about firing into the air. User:Zoe|(talk) 18:58, 12 December 2006 (UTC)

I know of two instances of people getting killed by bullets shot into the air (one by airgun, one by 22long rifle) in both cases (the police finding shot dead people in the street) the most difficult part of the police inquiry was finding the origin of the gun shot. I don't know of any statistics on the subject though. It reminds me of a 3rd case where the police found a woman shot dead in her car all doors locked from the inside no gun in the car nor any broken window or hole through the car (it was found on a road by the beach). After a lot of research and pondering they found that the bullet had left very small traces on the rubber when it entered the car going between the window and the window frame at the top of the car door. It transpired later that a group of young people had been firing a rifle on the beach at the dunes and one bulet had gone over a dune and down on the car. If I'm not mistaken there is a law in texas forbidding the firing of guns in the air after accidents on national celebration days. Keria 20:56, 12 December 2006 (UTC)

A bullet coming down is very dangerous. That said, I'd much rather take a .44 in the head on its way down from a 2-mile flight, than straight out of a Magnum! :) Vranak 01:01, 13 December 2006 (UTC)

See the article Celebratory gunfire. —Keenan Pepper 03:16, 13 December 2006 (UTC)

What about bullets from spitfires and hurricanes in the war? Paul Silverman 21:20, 13 December 2006 (UTC)

There was another TV broadcast that featured a man who fired an old WWI rifle (that's how theyn were finally able to determine what happened) from his boat out in some sound in New York or New Jersey or in New England. The bullet came through the rear side window of a Mustang if I recall and struck a women in the back of the head. Quite a coincidence to the story above. They determined the the type rifle from the bullet in her head and then due to its uniqueness went searching starting in a particular neighborhood and after only a few houses found a man with that type rifle, took in in for examination and foudn that it matched the bullet perfectly. Spooky if you ask me. 71.100.6.152 00:39, 14 December 2006 (UTC)

in the absence of air resistance an object shot skyward will have the same magnitude of velocity falling down as shooting up. This means that (assuming there is no air resistance) the speed of a bullet is the same at the moment fired at the sky as the moment it is at equal height on the path down. However since there is air resistance a bullet will be slower coming down. However a spinning bullet (one from a rifled gun) is reasonable aerodynamicand so the bullet would be quite fastBeckboyanch 05:13, 15 December 2006 (UTC)

Balanced forces

Let's say that the forces in the x direction and y direction and z direction on an object are balanced, but it has net torque. However, if it has net torque it is rotating. Therefore, doesn't it have centripital acceleration? --AstoVidatu 22:43, 12 December 2006 (UTC)

What do you mean by an object "having" centripetal acceleration? Melchoir 01:32, 13 December 2006 (UTC)

Acceleration of the particles that compose the object toward the center of gravity. I was thinking something like a windmill. --71.235.243.114 01:56, 13 December 2006 (UTC)

Well, as the object rotates, yes, its particles execute centripetal motion. That's just a consequence of the rotation, though; you can say the same of a freely rotating object with no torque.

Given that your object is experiencing some torque, its rotation rate is changing, so the centripetal acceleration of a given particle is also changing. The particles also accelerate in the tangential direction, that is, not pointing towards the center of mass. Melchoir 02:31, 13 December 2006 (UTC)

Balanced external forces means that the object's centre of mass is not accelerating. However, some parts of the object may still be accelerating relative to other parts. In the case of a rotating body, centripetal acceleration is due to the internal forces which are stopping the body flying apart. For a non-rotating case, think about a rocket and its exhaust, considered as a single system. If there are no external forces then the centre of mass of rocket+exhaust does not accelerate, yet the rocket can accelerate in one direction while its exhaust is accelerated in the opposite direction. Gandalf61 11:16, 13 December 2006 (UTC)

Miniature nuclear power plant?

A co-worker of mine has a hobby of machining and building miniature steam engines and steam locomotives. Got me thinking... would it be possible to build a miniature, but operational nuclear power plant? Seeing as how small amounts of radioactive material are available for laypersons to purchase, could one (with sufficient technical background and skill) build an operating, albeit small and low-powered nuclear power plant? 192.168.1.1 6:40pm, 12 December 2006(PST)

depends. if you are just using thermocouples etc to harness the heat produced by natural decay, then it is probably possible. but if you want a full blown model fission reactor it's more difficult, because below a certain critical mass the reaction won't proceed. this puts a lower size limit on a working reactor. Xcomradex 03:51, 13 December 2006 (UTC)

The obvious problem with this idea is the difficulty of obtaining critical mass. If you're going to use one of the standard fissile isotopes of uranium or plutonium, you need at least a kilogram in order to sustain a nuclear chain reaction with standard neutron moderators (although doi:10.1016/S0168-9002(01)02108-8 says there's a way to make a critical system with amounts "as low as" 100 g). On the other hand, if you're not determined to use the same fuel as full-scale nuclear reactors, a small radioisotope thermoelectric generator is quite feasible. —Keenan Pepper 03:54, 13 December 2006 (UTC)

Ah, the Radioactive Boy Scout and the University of Chicago Scavenger Hunt! If you have less than the critical mass of nuclear fuel you can use an external neutron source to split the atom. It's just that the nuclear reaction won't be self-sustaining. Dr Zak 04:18, 13 December 2006 (UTC)

I believe there are small-scale nuclear reactors used in many spacecraft. They have the advantage of not having to worry about radioactive contamination, once they are in space, so can eliminate most of the shielding. They just use natural decay, as well, as discussed above. StuRat 04:22, 13 December 2006 (UTC)

And the answer is: Radioisotope thermoelectric generator --Tbeatty 04:44, 13 December 2006 (UTC)

Thanks for all the answers. I'd prefer the miniature power plant be as accurate a replica of a full-size domestic utility powerplant as possible, involving steam turbines (yah, complex, I know). While it would be cool to build a radioisotope thermoelectric generator (and a lot easier), it unfortunately wouldn't be quite what I want. So the natural decay of the plutonium in an RTG does not produce enough heat to boil a small amount of water? 192.168.1.1 10:05pm, 12 December 2006 (PST)

The problem will be to get the highly radioctive starting material! But if you are rich enough: Get a catalog for radiactive elements and search for one with a short half life (not decades like the plutonium used in a RTG). I would suggest some curium, americium or polonium isotope. Buy several gram of the oxide of the element. The rest would be really easy: Get some plans from your nuclear powerplant you want to build, my suggestion would be Three Mile Island Nuclear Generating Station or RBMK-1000 and than start! The decay heats the elements enough to built--Stone 12:51, 13 December 2006 (UTC)

Highly dangerous and illegal. Better to build a non-working model with moving parts and cutaway sections to show the operating principles. Or take a nuclear engineering course at one of the many colleges with a TRIGA reactor, which is quite small compared to utility generators, and which students get to operate. Also read SL-1 to learn what might go wrong with a small reactor which lacks the backups of backups in utility reactors or nuclear navy reactors. Edison 17:23, 13 December 2006 (UTC)

You've seen the picture of the PU pellet at Radioisotope thermoelectric generator, right? They could heat water OK, could you get your hands on them. But the material is in rather short supply (and regulated, too) - remember that after that security scare at Los Alamos they had to launch the New Horizons spacecraft with less nuclear fuel than they would have liked. Dr Zak 18:05, 13 December 2006 (UTC)

Find out when and where the next full scale nuclear power plant will be built and offer to build a working scale model. 71.100.6.152 00:25, 14 December 2006 (UTC)

Per the answers above, it's going to be very difficult – and almost certainly very illegal – to obtain the quantities of fissile nuclear material required to actually build a functioning plant, capable of maintaining a (barely) subcritical mass of uranium and boiling water. Note as well that some things don't scale well; scaling the radiation shielding down to the same scale size as the rest of the plant will probably result in bad things happening to you. Also, you probably have no facilities for disposing of spent fuel....

Instead, have you considered building a scale model that includes all the delightfully difficult-to-build elements (heat exchangers, pumps, turbines, etc.) but replaces the heat source with a resistance heater? You still get to demonstrate the principles, but you don't get the Nuclear Regulatory Commission showing up in your workshop. TenOfAllTrades(talk) 01:17, 14 December 2006 (UTC)

I'm coming to realize that that is probably the best solution. Resistive heaters inside the sealed nuclear core would be an easy and safe solution. And I have learned that nuclear fission doesn't scale down. Now to suggest this to my co-worker, so he'll be willing to machine some very intricate parts for me! 192.168.1.1 9:34pm, 13 December 2006 (PST)

Y'know, if you -really- want Americium, you could always buy a whole lot of smoke detectors -- they all come with a small quantity of Americium-256. Cernen Xanthine Katrena 13:00, 14 December 2006 (UTC)

or Thorium. 64.90.198.6 23:42, 15 December 2006 (UTC)

Science Learning Resources

I'm a freshman in highschool, and I really want to learn about chemistry, physics, and some other sciences. I've aways had a huge interest in them, but my knowledge about them is limited to what I've read in books like The Elegant Universe or tv shows on the science channel. I want to get a more deeper knowledge of the subjects, such as the mathematics behind them. Unfortunately, I can't take those classes until my sophemore, junior, and senior year. I was wondering if there are any good sources where I could learn more about them. Thanks much in advance. :-) Imaninjapirate 03:38, 13 December 2006 (UTC)

• Find a copy of The Feynman Lectures on Physics or anything else by Richard Feynman.
• Ask your teachers to let you borrow some more advanced textbooks. For example, the chemistry book my class used left me with a lot of questions, but my teacher let me borrow a college textbook she was given as a sample, which answered most of them. Always ask for the "nitty gritty".
• See if you can get access to Science or Nature from your library or university (or even buy a subscription, but they're expensive).
• Wikipedia isn't so bad. =P —Keenan Pepper 04:08, 13 December 2006 (UTC)

Do you have a public library you can get to easily? Just wander down the aisles of the Science and Math sections and pull down books that look interesting. If they look really interesting, check them out and try to read them. That's what me and my friend used to do... (I still remember a classic: Mathematics Made Difficult, by Carl E. Linderholm, in which one of the starred, i.e. especially difficult, exercises was: "Show that 17 × 17 = 289. Generalize this result." I don't think I learned a thing from that particular book, other than 17², but it was sure interesting!) —Steve Summit (talk) 05:10, 13 December 2006 (UTC)

Online, try Free High School Science Texts, Free-Ed.net, and Annenberg Media. BenC7 10:48, 13 December 2006 (UTC)

For physics, completely agree with Keenan Pepper's recommendation of anything by Feynman. The Feynman Lectures on Physics will be expensive, but definitely try to find a library copy. Six Easy Pieces, Six Not So Easy Pieces and The Character of Physical Law are more affordable - the first two are selections from the Lectures. Gandalf61 11:05, 13 December 2006 (UTC)

Wow these all sound great, thanks a lot for the help! Imaninjapirate 22:47, 14 December 2006 (UTC)

I suggest looking for "The History of Physics" by Isaac Asimov or the books "Understanding Physics: Motion, Sound and Heat", "Understanding Physics: Electricity and Magnetism", and "Understanding Physics: The Electron, Proton, and Neutron" in that order, by Isaac Asimov. You might be able to find them in a library. I think the "Feynman lectures on Physics" might be too difficult for you to get very far into at this stage, but keep them in mind for later. Cardamon 05:37, 15 December 2006 (UTC)

Depth

What is the shallowest depth below the surface of the sea that an object the size of a boat can escape a storm on the surface ? Adaptron 07:33, 13 December 2006 (UTC)

Depends on how bad the storm is. If the storm is minor, then quite shallow. BenC7 10:51, 13 December 2006 (UTC)

It depends on the size of the waves, so the diagrams in our ocean surface wave article might give you a better idea.--Shantavira 12:54, 13 December 2006 (UTC)

One wavelength below the surface the amplitude has decreased by a factor e^−2·π=0.001867. Bo Jacoby 13:40, 13 December 2006 (UTC)

Paint that generates electricity...

Some years back, a show like Beyond 2000 showed this thick paint that when getting hot, generated electricity. Likewise, when you passed a current though it, it generated heat.

I search every so often but have never found any information about it.

Thank you in advance.

David

There are a couple of thermoelectric processes that convert temperature differentials to electricity and vice versa. Some thermoelectric devices use layered materials or films; I guess you could consider them painted on to a surface. (google: thermoelectric film). Weregerbil 11:56, 13 December 2006 (UTC)

Age of earth

how old is earth? —The preceding unsigned comment was added by Ceolan (talk • contribs).

This is answered in our age of earth article. Hipocrite - «Talk» 15:58, 13 December 2006 (UTC)