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July 25

Anti Armor Weapons

I read in a forum that Kornet uses a low energy laser beam to guide the missile so that it cannot be discovered , my fist question is : does the TOW 2 have the same ability to be undiscovered ? My next question : are there any other methods to guide missiles - within SACLOS systems not fire and forget systems - which is resistant to jamming and detection ? 92.253.61.250 (talk) 08:11, 25 July 2014 (UTC)[reply]

See BGM-71 TOW for our article on the missile. According to the article, the wireless version of the TOW-2B employs a "stealth one way radio link", but no details are given and the statement isn't cited. The standard version uses a wire link for guidance, so there's no radiation to indicate the missile's presence - I'm not sure if that makes it "undiscoverable". Tevildo (talk) 09:03, 25 July 2014 (UTC)[reply]

Ask yourself this: Is a Sidewinder missile undiscoverable just because it uses passive infrared guidance? And this will answer your question whether any missile can ever be truly "undiscoverable". 24.5.122.13 (talk) 10:07, 25 July 2014 (UTC)[reply]

Hardening against coronal mass ejections?

I just read a story saying that a 2012 coronal mass ejection could have put Earth "back to the stone age" if it had hit us. Which makes me wonder: what would people need to do to prepare against them?

To start with, where would they do their damage? (This would be good to add to the article also) I had a clearly ludicrous notion of wrapping computers and power cords in tinfoil, but from very not-Wikipedia-grade sources it appears that the damage is mostly to big features, long transmission lines.

Is this true?
Would Germany, with its advanced state of conversion to solar power that I assume is more decentralized, be spared from the event to the degree they have done so?
Would underground power lines be unaffected?
Which power generation facilities would be affected?

Last but not least, since we've now seen an event like this, can we begin to estimate how long it is until we are hit by this? Wnt (talk) 12:51, 25 July 2014 (UTC)[reply]

It is true that we use computer-controlled machines to build machines to build our technology, so that if all surface computers were to be destroyed we would be in trouble. However, there should be computers in Cheyenne Mountain nuclear bunker, and its Russian/Chinese equivalents that will survive. There will be details of how to (re)build our technology stored on surface CD/DVDs that will survive, and on tape/hard drive deep in old salt-mines as long-term backups (Iron Mountain etc use old mines if available). The question is, can our just-on-time supply network provide sufficient food etc for us to survive the few years before we can rebuild everything? CS Miller (talk) 13:28, 25 July 2014 (UTC)[reply]

Our Electromagnetic pulse article should cover much of this. StuRat (talk) 14:08, 25 July 2014 (UTC)[reply]

Another one just missed us, according to this Guardian report ---- CS Miller (talk) 14:50, 25 July 2014 (UTC)[reply]

Don't see any mention of another one. Far as I can tell, the report just refers to the same 2012 event Wnt refers to (along with one in 1859 that we have an article on Solar storm of 1859). The report itself is from the past few days, as I'm sure is Wnt's report, that's just because NASA just put out the PR about it [1] and everyone is reporting it now. Nil Einne (talk) 15:48, 25 July 2014 (UTC)[reply]

BTW, the NASA PR has useful information. In particular it mentions a NSF study. Some quick searching ('National Academy of Sciences solar storm') finds [2] which is probably referring to the same study and gives a title which suggests it's [3] or NSF workshop report (working without registration copy).

The other papers referred to are [4] (wrong date but all the other details seem right so I guess NASA or someone who gave them the date screwed up) and [5] + [6] (found with a search for 'Nature Communications Janet G. Luhmann'). However as the first is about estimating the probability of such events and the second two are about an analysis of the 2012 eruptive event, it looks like they only briefly mention or don't mention at all the possible effects.

Also this is the related PR about the 2014 study [7] and has some cost and recovery estimates. Of course as a press release not a great source (amongst other things, very few details) but it does mention a study in the previous year (i.e. 2013). The NSF workshop report is from 2008 or so unless they do go their dates mixed up it's probably not what they're referring to. But again a quick search for '2013 solar storm 2.6 trillion' finds [8] which mentions a $2.6 trillion Lloyd's estimate from 2013 so the details match up with the Berkeley PR. The same search (or I guess the details from Telegraph) finds the report Lloyds report. They don't actually talk about the figure much, more about other stuff.

Oh and due to misremembering what the Berkeley PR said, I also looked for '2011 solar storm recovery' which found [9] which mentions and links to an OECD report OECD report.

I didn't look at these that well but the 3 reports, particularly the NSF and OECD ones look like they provide a resonable amount of information on what could happen. I think all 3 agree the effect could be fairly disastrous. I doubt any of them say anything about "back to the stone age". It doesn't look like that's even in the NASA PR. I'm not sure who came up with it, but I suspect it may have been a journalist somewhere. I did find one newspaper quoting a researcher but the full quote is "back to the stone age for days" [10] (however it looks to me like this only came after every paper and their dog were already talking about "back to the stone age").

Nil Einne (talk) 16:59, 25 July 2014 (UTC)[reply]

Note that the damage is not done directly by geomagnetically induced currents, these are too weak to cause damage. The problem really is that power transmission through the generators of a powerplant has to be extremely efficient. A 1 GW powerplant with 10 generators will be transporting a power of 100 MW through the generators, so 99% efficiency won't be good enough as that would mean that each transformer would be dissipating 1 MW of heat. This would cause the tranformer to explode. So, the transformers used in powerplants are extremely efficient and that comes with a big price tag. Power companies are not going to keep spare transformer on standby, they are just too expensive.

Then the effect of a geomagnetically induced current is to cause the core of transformers to get magnetized which will make the power transmission slightly less efficient. But that is then enough to cause the transformer to explode. What happens is that beyond a small threshold, a slightly less efficient transformer will lead to more heat to be dissipated and thus a higher temperature. But at that higher temperature the power transmission becomes even less efficient, causing even more heat to build up, eventually the whole thing explodes. If this happens to many powerplants, then you'll have problems operating the factories that are needed to make new transformers.

The best defense is to cut the power when a solar storm is predicted to hit Earth. Count Iblis (talk) 01:26, 27 July 2014 (UTC)[reply]

An electromagnetic potential of Brownian motion

Did a Brownian motion always had been an electromagnetic potential? Why the Wikipedia don’t include that?--Alex Sazonov (talk) 13:54, 25 July 2014 (UTC)[reply]

What the devil does Brownian motion have to do with electromagnetism??? 24.5.122.13 (talk) 17:14, 25 July 2014 (UTC)[reply]

I _think_ Johnson noise is what the OP's getting at. Tevildo (talk) 17:29, 25 July 2014 (UTC)[reply]

If been seek a Brownian motion as movements of electromagnetic charges, we been seek that Brownian motion always had a electromagnetic potential. But I have asked a question about a make been resonances by Brownian motion in which an electromagnetic charges lost’s or had their mass. Why's the Wikipedia don’ting include that?--Alex Sazonov (talk) 18:51, 25 July 2014 (UTC)[reply]

Which why losted mass of electromagnetic charges in Brownian motion up to had mass a twice?--Alex Sazonov (talk) 19:50, 25 July 2014 (UTC)[reply]

Don’tly been mind if a Brownian motion is been a low point of the theory of relativity?--Alex Sazonov (talk) 07:12, 26 July 2014 (UTC)[reply]

As all been know, in a Brownian motion an electromagnetic charges always been change to divide their volts by themselves.--Alex Sazonov (talk) 18:22, 26 July 2014 (UTC)[reply]

Hmmmm, part (c) of the illustration for Johnson noise has me wondering: can you use this noise to transfer heat energy? I understand of course that the noise source in a loop with a resistor is not really going to produce perpetual motion; but it seems like the resistor ought to heat, so the noise source ought to cool ... shouldn't it? Right now our article on solid state refrigeration is synonymous with the Peltier effect or other thermoelectric materials, but could you somehow make a system like this very noisy electrically, and find a way to apply power so as to somehow transmit a meaningful amount of energy this way? Wnt (talk) 19:28, 26 July 2014 (UTC)[reply]

Wnt, I been speak about a nuclear electromagnetic resonance, but you is been speaking about a electronical resonance which always been consists in an electronically transaction.--Alex Sazonov (talk) 20:08, 26 July 2014 (UTC)[reply]

Figure (c) is the Norton equivalent circuit for a noise source, not a practical circuit diagram. The ideal current source and the ideal resistor it depicts are both implemented by the real resistor in figure (a), not separate components. That being said, it would be possible to use the noise voltage produced by a resistor to power another circuit, but not to transfer a "meaningful" amount of energy, compared with simple thermal conduction between the two systems. If you wanted to transfer energy from a hot system to a cold system, where the only possible connection between them was electrical rather than mechanical, _and_, for some reason, you didn't want to use a thermopile or other device that uses the thermoelectric effect, it would work. But I can't see that ever being a practical requirement. Tevildo (talk) 19:58, 26 July 2014 (UTC)[reply]

I understand that Johnson noise is a really small amount generally, and hence the amount of heat moved would be infinitesimal... nonetheless, is there a law of physics that says it must be a small amount? Are we sure there's no way to make the circuit noisy enough that the electrical sort of "thermal conduction" might outstrip the ordinary sort, and begin to make inroads against the inefficiency of a standard thermopile? (Mostly these questions come from having no real appreciation for how the electrical noise decides on its amplitude - I keep thinking "what if we had a room temperature superconductor" and suchlike wishful thinking) Wnt (talk) 22:42, 26 July 2014 (UTC)[reply]

The (Johnson) noise power depends only on the temperature (and Boltzmann's constant), even if the resistance is zero, so that is a "law of physics" limit. The noise is due to Brownian motion of the charge carriers in the device, which will always exist for any conductor above absolute zero. There are other sources of electronic noise that might add some extra power, but Johnson noise will be the dominant component for a passive, non-semiconductor, device. The _efficiency_ of the transfer will be close to 100%, but the _rate_ of transfer will be very low - in a (fairly) realistic situation, where we have two insulated boxes, each with a resistor in them, with the resistors connected with ordinary wires, the major route for heat transfer will be the thermal conductivity of the wires, rather than the tiny noise power generated by the hot resistor. If we had wires with low electrical resistivity but high thermal resistivity, the noise power might become a significant component of the heat transfer. Tevildo (talk) 23:20, 26 July 2014 (UTC)[reply]

Not the answer I wanted to hear, but it does sound convincing. :( Wnt (talk) 00:13, 28 July 2014 (UTC)[reply]

If in nuclear physics a science quest about a safe’s energy always been decide, why in electronically physics this quest not been decide at now.--Alex Sazonov (talk) 20:27, 26 July 2014 (UTC)[reply]

The USSR almost had the thermo-resistors in which always been a low thermoresonance, but why the safe’s energy is not been powered in, I don’t know.--Alex Sazonov (talk) 10:13, 27 July 2014 (UTC)[reply]

Because thermo-resistors don't GENERATE energy -- they vary their electrical resistance with temperature, so they actually DISSIPATE electrical energy under ALL conditions. That said, there HAD been a proposal to generate electricity by surrounding blast furnaces and such with blankets of thermocouples (this was one of Khruschev's pet projects), but nothing came of it because the capital costs would have been too high and the power generated too small. 24.5.122.13 (talk) 02:05, 28 July 2014 (UTC)[reply]

See RTG and this article for practical examples of thermoelectric generators. However, these all use the thermoelectric effect (with dissimilar metals), rather than the electricity generated by heat in a single homogenous component. Tevildo (talk) 07:50, 28 July 2014 (UTC)[reply]

Odd cat behavior

Unlike dogs, which wag their tails when happy, cats normally wag their tails when angry. But I know a cat that wags it's tail when happy, for example, when being petted and purring. So, how rare is this ? Do cats raised with dogs pick up this behavior from the dogs ? StuRat (talk) 14:16, 25 July 2014 (UTC)[reply]

Cat's have different ways of moving their tails. Some mean that they are happy, some mean that they are annoyed. Just part of the enigma of having a cat share its home with you. [11] ---- CS Miller (talk) 14:36, 25 July 2014 (UTC)[reply]

Our cat is almost constantly twitching its tail, whether it's happy, uncomfortable, impatient, or whatever. I think it just likes twitching its tail. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:25, 25 July 2014 (UTC)[reply]

There's more than one way to wag a tail of course. When my cat is getting perturbed, it swooshes its tail side to side in very quick motions; when it's in attack mode, the tail lays more or less straight but quivers; when it's happy and relaxed, the tip often curls about like someone keeping time to slow music. It also seems that cats have a particular mood where they're contented but very close to getting extremely pissed off; in those case, my cat both purrs and swooshes his tail "angrily". Continued petting in those cases might lead very quickly to a bite while backing off calms down the tail. Matt Deres (talk) 15:49, 26 July 2014 (UTC)[reply]

MSF and Scotlands free ride

If Scotland vote for independence, will the MSF transmitter be moved back to central England (Rugby) like it was before? I assume it was moved up north to give better coverage over Scotland so if they are independent, why cant they build their own time reference and stop riding on our backs for free?--86.171.5.136 (talk) 16:03, 25 July 2014 (UTC)[reply]

I never knew that the Multi-Stage Flash desalination process required any sort of transmitter! But yes, if Scotland declares independence, they'll no doubt have to build their own desalination transmitters (whatever that is)... 24.5.122.13 (talk) 17:20, 25 July 2014 (UTC)[reply]

^{[citation needed]}. (EC) Questions begining with "I assume" (or for that matter "if") are rarely good questions for the RD. Most sources about the move e.g. [12] [13] [14] mention the move of Time from NPL (MSF) to Anthorn Radio Station was a result of changing the contract from BT to VT Communications (which occured concurrently with an upgrade meaning less maintenence) and don't mention at at all about Scotland or coverage which is kind of weird if that was the intention. Particularly since from what I can tell, these come from before the SNP 2007 Manisfesto was published so I'm not sure there would even be much controversy then. Plus a quick search doesn't find anything 'anthorn NPL scotland' so it doesn't seem likely it was said much by anyone. So basically you're making a claim which few people involved seem to have said which is very weird given the reasoning you claimed. Note that in case there's any confusion to other respondents, the transmitter remains in England, just a different part. Nil Einne (talk) 17:22, 25 July 2014 (UTC)[reply]

Well certainly the move to Anthorn has reduced signal strength in most of England, so why was it moved to a central part of the island as a whole if it was not to benefit the Scots?--86.171.5.136 (talk) 17:34, 25 July 2014 (UTC)[reply]

Um did I not already say quoting 3 sources? Or do you really need a link to Pound sterling and free market as well? In case you're still confused, you are of course nominally correct. Since Scots must (currently) pay for NPL in some way, just the same as those in Northern Ireland, England and Wales it was ultimately intended to benefit them, just as it was ultimately intended to benefit the people of NI, England and Wales. But not in excess proportion (actually since I suspect England pays more on average for the NPL, because amongst other things they probably use it more on average, it was probably intended to benefit England more. Sort of. Nil Einne (talk) 17:40, 25 July 2014 (UTC)[reply]

Sorry, you lost me there. care to explain?86.171.5.136 (talk) 17:47, 25 July 2014 (UTC)[reply]

After EC. Your answer makes sense now.86.171.5.136 (talk) 17:48, 25 July 2014 (UTC)[reply]

Just from curiosity... how well can you synchronize time over the Internet? I've done a few traceroutes long ago and I know that transit times are variable, but if you choose the right routes to analyze simultaneously, and have a network of a few thousand users' computers analyzing the results after the fact for each experiment, I'd think you could get something pretty precise. I feel like this MSF service ought to be obsolete already. Wnt (talk) 00:11, 28 July 2014 (UTC)[reply]

The MSF signal is mainly used as a frequency standard, rather than a time standard. The GPS frequency standard is an alternative, but MSF is still a useful backup. Tevildo (talk) 07:53, 28 July 2014 (UTC)[reply]

Would a "mirrored" human body work?

Hi. A 2-dimensional surface with an R on it can only be made to show an Я if rotated in 3-space; similarly, a 3D cube with R on the sides can only show an Я if rotated in 4-space. H G Wells wrote The Plattner Story, in which a man passes through a fourth dimension and returns with his body mirrored: the heart is on the right-hand side, his eyes are reversed, and so on. Suppose that this actually happened to a person: could they still live and function normally, or are there reasons (perhaps e.g. Stereoisomerism) why they could not? Thanks. 86.136.110.44 (talk) 17:25, 25 July 2014 (UTC)[reply]

There is a physiological condition where the internal organs are reversed, the name of which escapes me. Slightly shorter life experience is noted in those with it, but that might be because pain localises to the wrong side of the body, making diagnosis harder. 92.40.248.127 (talk) 17:56, 25 July 2014 (UTC)[reply]

His body would have the wrong chirality of amino acids, so I don't think he would get the proper nutrition from normal food. Chemical chirality in popular fiction covers some other stories where this happens. Katie R (talk) 18:06, 25 July 2014 (UTC)[reply]

Having all molecules mirrored, it seems perfectly feasible that perfect mirroring would produce a fully functional being, since physics is almost exactly symmetrical (there are subtle asymmetries, e.g. in the weak interaction, but I expect that this would have no effect at the chemical level and above). Katie's point about nutrition is of course valid: a source of chemically mirrored food, not only amino acids, would be necessary. For example, the stereoisomer of vitamin C is useless to the human body. —Quondum 18:51, 25 July 2014 (UTC)[reply]

Might it be useful to the mirror image of a human, though? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:43, 25 July 2014 (UTC)[reply]

Yes, the R-ascorbic acid would be exactly what the mirror image body would need, and our normal L-ascorbic acid would be useless to it, just as R-ascorbic acid is useless to us. —Quondum 22:00, 25 July 2014 (UTC)[reply]

Wow, I can't believe "Chemical chirality in popular fiction" is an article. WP really has everything. Thanks for that. 86.136.110.44 (talk) 22:24, 25 July 2014 (UTC)[reply]

Yeah, that one's on my list of favorite article titles now. List of animals with fraudulent diplomas is still my favorite, although I preferred it when it was "cats" instead of "animals." I agree with Quondum that there aren't any fundamental reasons a mirrored body wouldn't function. 3D movies wouldn't look right unless they put the glasses on upside-down, but that's a pretty minor problem. :-) They might also have trouble writing at first. Katie R (talk) 13:53, 28 July 2014 (UTC)[reply]

CATS: "All your degree are belong to us" ? - ¡Ouch! (^{hurt me} / _{more pain}) 07:58, 29 July 2014 (UTC)[reply]

Or actually the movies probably would be fine... This is confusing to think about. Katie R (talk) 13:54, 28 July 2014 (UTC)[reply]

It would depend on whether somebody is born mirrored and grows up that way (their 3d perception would be fine) or you have an adult who is suddenly mirrored. All their 3D perception, not only 3D movies, would be screwed up, because their "right" eye is now their left eye and vice versa. A real-life example of nausea fuel. It could be remedied with 3D TV, by wearing a mirrored version of the 3D glasses, but nowhere else.

OTOH, if everything (in Treknobabble, "down to quantum level") is mirrored, their memories would be mirrored, too. They would think everything else (writing etc) was mirrored; however, their 3D perception would be fine.

Although I'm not 100% sure about the latter; there are certain asymmetries at the quantum level, which would mean that particle A could become particle B when mirrored, and other assorted nastiness. - ¡Ouch! (^{hurt me} / _{more pain}) 07:58, 29 July 2014 (UTC)[reply]

Yeah, being born and raised that way would be fine. I have trouble thinking through what the exact effects would be on an adult. If you tried to turn your head right, would it turn left? Would it turn right, but your mirrored vision makes it seem like you're turning left? Is your stereoperception reversed or not? I hadn't really thought of structure below the chemical level. What would reversing the spin of every particle do? Katie R (talk) 11:44, 29 July 2014 (UTC)[reply]

See "Situs inversus".—Wavelength (talk) 18:08, 25 July 2014 (UTC)[reply]

Note that that condition involves reversal of the organs from right to left, but no change at the molecular level. StuRat (talk) 00:36, 26 July 2014 (UTC)[reply]

Flatfish have already evolved a 90° rotation of one eye to join the other "topside" eye. This could have occurred (may still be occurring) in either direction. If a single human should suddenly reverse his Chirality it would cause a ±180° Angular momentum problem that doesn't rate a Wikipedia article. 84.209.89.214 (talk) 18:33, 25 July 2014 (UTC)[reply]

Technical Error, Arthur C. Clarke, 1950. Wnt (talk) 02:20, 26 July 2014 (UTC)[reply]

Mediterranean & South China Sea poles of inaccessibility?

Where are the Mediterranean and South China Sea poles of inaccessibility (points farthest from any land above the surface) and which one is farther from that land?Naraht (talk) 18:22, 25 July 2014 (UTC)[reply]

I doubt that reliable sources for this question will be found, so I'm going to attempt the forbidden Original Research instead. It's easy to get an approximate answer to this sort of question by just moving a circle (cut out or drawn on thin paper) over a map, provided that it is large enough in scale to show all relevant islands. (It would be useful if the map showed water depths so you could be sure you weren't missing an island, but I'm going to use Google Maps, which doesn't.) If you make the circle the right size, you just need to place it so that you can see by eye that it's equidistant from three points of land in different directions, not all on the same half of the circle, and that nowhere else you put it has the points of land so far away. (For geometrical reasons the desired point will always be equidistant from three points in that manner.) After a bit of experimenting in Google Maps, I find that in the Mediterranean the point 35.15°N,18.45°E seems to be near the correct answer, about 340 km from the nearest points of Italy (at Pachino, south of Syracuse), Greece (at the island of Schiza), and Libya (at Tocra, east of Benghazi) and somewhat farther from Malta and from western Libya near Misrata. The South China Sea is tougher because there are so many different groups of islands, but my best attempt is 18.45°N,117.95°E; this is about 260 km from the island of Luzon, Philippines (at Cabugao, south of Laoag) and from two islands whose names Google Maps doesn't have (one of those is C-shaped, probably a coral atoll, ~~one~~ at about 20.6°N,116.9°E; the other is round, one of the Zhongsha Islands, at about 16.3°N,116.7°E). Hope this helps. --50.100.189.160 (talk) 06:30, 27 July 2014 (UTC)[reply]

Thank you. Trying to get a feeling for in a fictional story whether the Mediterranean for our World War II or the South China Sea in this story (France doesn't fall, Italy stays out) would be more "cramped" for World War II era combat.Naraht (talk) 21:23, 27 July 2014 (UTC)[reply]

@Naraht: Reading about Operation Pedestal may help to give an idea of how the physical size (or lack of it) of the Mediterranean affected World War II style naval combat operations. In particular, the conditions were ideal for the use of torpedo boats, E-boats, and land-based air attack. They also made naval mines a greater threat, and indeed submarines, although of course the submariners' own escape would end up being more tricky as well. There's still a fair bit of sea out there though; plenty to have survivors of sunken ships bobbing around in the water for a few hours before being rescued by other ships from the same side, then going on to assist other crippled ships from the same side, and so forth.

Another significant difference from the war in the Pacific and (to some extent) Atlantic was that, in the Mediterranean, rather than seeking out an enemy fleet or convoy and then throwing everything you had at it in a strike which would largely either be decisive or not, in a number of the Mediterranean convoys, including Pedestal, the attacking Axis air forces would find and attack the convoy with everything they had, but if that attack failed, the available sea space was sufficiently limited that they would still have a very good idea where the convoy was (unless it turned back), so could basically re-fuel, re-arm, and attack repeatedly - for days on end - until they either ran out of planes or the convoy reached Allied land-based air cover. --Demiurge1000 (talk) 19:07, 28 July 2014 (UTC)[reply]

Fusion > Fission?

Will nuclear fusion deliver the era of almost limitless, almost free energy that fission promised but didn't deliver? --129.215.5.255 (talk) 20:39, 25 July 2014 (UTC)[reply]

This is a request for speculation, so isn't really answerable. See Fusion power for our article. Tevildo (talk) 20:51, 25 July 2014 (UTC)[reply]

Well, it definitely makes for more destructive bombs, if that's considered a plus. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:55, 25 July 2014 (UTC)[reply]

So at the very least it's a possibility which cannot be immediately discounted? --129.215.5.255 (talk) 21:36, 25 July 2014 (UTC)[reply]

The sun is a naturally-occurring fusion reactor which provides us with effectively limitless energy. It can't be controlled any more than the H-bomb can, but at least its energy can be captured. I'm curious to know what promises fission failed to deliver upon? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:41, 25 July 2014 (UTC)[reply]

I'm not interested in the Sun! I'm interested in terrestrial fusion reactors. Atomic age discusses fission's broken promises. 129.215.5.255 (talk) 21:54, 25 July 2014 (UTC)[reply]

The electricity too cheap to meter was just marketing hype, it was not the serious belief of the engineers. From the Electrical Engineer's Reference Book, Malloy, Say and Walker 6th ed. 1952, I see that an atomic power station is estimated to cost 4 times as much as a coal-fired plant, and it is estimated that the energy will cost 25% more than that from coal. There were other reasons for nuclear power: diversity of supply (necessary to keep the miners in their place), gaining the technological expertise, obtaining fissile isotopes for weapons and national prestige. --catslash (talk) 23:37, 25 July 2014 (UTC)[reply]

That's interesting: Too cheap to meter related to fusion all along; people just assumed it referred to fission (and I still did 60 years later). Amazing what you learn on WP. --catslash (talk) 23:53, 25 July 2014 (UTC)[reply]

The idea of anything being too cheap to meter seems faulty. Tap water is pretty darned cheap, yet we still meter that. If we didn't, people would waste it to such a degree that it would become a major expense. Same is true of energy. There are all sorts of wasteful things you could use an unlimited amount of energy to do, and if people didn't have to pay for it, they would do exactly that. StuRat (talk) 00:42, 26 July 2014 (UTC)[reply]

There are lots of services where the amount that people are charged in/by one city/country/company or another is not related to usage. Tap water is in fact one of them; others include telephone calls, health care, emergency services, garbage collection, and Internet usage. The idea is as logical for electricity as for any other plentiful resource, and in the case of electricity, a limit is imposed on any particular customer by the wiring feeding their home or office. --50.100.189.160 (talk) 08:20, 26 July 2014 (UTC)[reply]

I'd be interested to know if runaway usage is a problem where tap water is free. I've wondered the same thing about unlimited phone calls or internet usage. I'd expect some to take advantage and abuse those privileges. For the others, those aren't the kind of things where you can abuse them as easily. You can't just produce a cubic mile of garbage, for example. Perhaps in the case of a hypochondriac they might manage to overuse medical services, and ambulance services do sometimes seem to be overused by those who just can't get a ride for their regular medical appointments, but there they can just charge for nonemergency usage.

And I still insist that un-metered electricity just makes no sense. People would do stupid things like leave their window open in winter in rooms that are overheated by their electric heating unit. Of course, there could be a limit placed on usage just due to the fact that the wires can only deliver so much electricity per house, and that might make it work, even if technically "un-metered", provided something limits usage below the level that would make the wires melt. There are many unwritten limits, too. For example, I found out my car insurance had a limit of 5 tows per year, when I had a rather defective car and they canceled on me after that many. They never stated that in any of their communications. StuRat (talk) 09:52, 26 July 2014 (UTC)[reply]

If the resource is plentiful enough, that kind of "stupid thing" is not important. You persist in thinking in terms of real life instead of embracing the "too cheap to meter" ideal. --50.100.189.160 (talk) 21:08, 26 July 2014 (UTC)[reply]

A confident technical prediction does not necessarily give an infallible socio-economic prediction. Thomas Edison predicting development of the light bulb said "We shall make electricity so cheap that only the wealthy can afford to burn candles."[15] 84.209.89.214 (talk) 13:27, 26 July 2014 (UTC)[reply]

Isn't that essentially true? Candles are essentially luxury items now - while I suppose you can try to read for a few hours by the light of a 50-cent candle, even conventional light bulbs were something like $5 a month, and the high efficiency ones are only a fraction of that - for much more light and no fire risk. So I'd call this one "confirmed". Wnt (talk) 19:19, 26 July 2014 (UTC)[reply]

It may be nearly limitless (as close as infrastructure allows), but it certainly won't be free. Like with fission, the majority of the cost will be the capital costs of building the power plant, rather than the fuel. Whichever design ends up being used, a fusion reactor will be an extremely large and complicated device requiring expensive components like superconducting magnets or huge capacitor banks. ITER is expected to cost €15 billion. It's a research device designed to work out the best design, so "industrial" reactors will (hopefully) be cheaper. But they will still be extremely expensive compared to a natural gas turbine. Maybe in 100 years the technology won't be so exotic and it won't cost very much. But the materials and time required to build it will still have a non-zero cost. The main benefit to fusion is that it's "clean." The main byproduct is helium. Some of the reactor components will be made radioactive by the neutron radiation produced, but the half-lives will be much shorter than spent fission fuel. And it would require less physical space than other "clean" power methods like solar or wind while being able to produce a consistent amount of power. Mr.Z-man 15:03, 26 July 2014 (UTC)[reply]

July 26

quantum immortality

this is what i found in simple english wikipedia, see question below:

Quantum Immortality is an idea in which it is put forward that the consciousness stays alive even though the conscious being dies. For example, someone sets off a bomb beside the victim, that victim survives in an alternate universe by being injured but living, or by the bomb not blowing up. However, in the original universe, the victim "dies" in the blast. The consciousness continues to exist in another, perhaps many alternate universes. This is related to the thought experiment of Schrödinger's cat.

The idea is that if you use a special gun that goes off, something called a quark is spinning one way, but not if it spins the other way. However, the quark somehow manages to spin both ways at once, so the universe splits into two separate possibilities as the person pulls the trigger. In one universe, the person survives, in the other, the person dies. The person themself does not notice anything different.

my question is, is that (bold text) true and what does that mean? Dannis243 (talk) 01:25, 26 July 2014 (UTC)[reply]

The entire passage is somewhat confused and not very accurate. The bold text is correct, though: it just means that the person never experiences the outcomes in which he dies. In the few outcomes where he somehow survives, he just experiences a narrow escape, just as in any situation where someone has a close brush with death. --Amble (talk) 01:58, 26 July 2014 (UTC)[reply]

I wonder about the same thought experiment done with quantum unconsciousness. The apparatus randomly determines each 10 seconds whether to anaesthetize the experimenter. So in some universe, the events that would render him unconscious never happen, and so he remains awake for the experiment.

What is the difference between someone being rendered unconscious, returning with an at least someone different configuration of nervous system later, and someone who dies, but leaves behind some other member of his species who can then pick up and read about the experiment? Wnt (talk) 02:34, 26 July 2014 (UTC)[reply]

This sounds like a variant on the old expression, "Blown to kingdom come." ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:06, 26 July 2014 (UTC)[reply]

The idea is that some variations of quantum theory maintain that every possible outcome to every event happens in one or other of an infinity of alternate parallel universes. Since you can't reason about what's going on in universes in which you died, then by analogy with the anthropic principle, "you" must exist in a universe in which you survived. What this is claimed by some to mean is that you will live forever - dodging bullets and surviving catastrophies by increasingly crazy and unlikely means. At first sight, this seems like a good thing - it predicts that you'll live forever. But if it's true, the idea might mean that we're going to find ourselves in a literal living hell. This idea would only mean that you survive to observe the universe in this state - not that you are healthy, happy, comfortable or anything else. So, for example, it seems likely that in this view of the universe, the insane series of coincidences actually FORCE you to survive. You can't die even if you try. However, it doesn't prevent you from going blind, deaf, losing all of your limbs, being in continual agony, having all of your family, all of the rest of humanity dying around you, etc, etc. We'd better hope this isn't true - because it means that every single one of us winds up in their own, individual hell-universe. It quite literally dooms us all to the worst hell imaginable for all eternity!

Fortunately, there are many get-out-clauses that most people who've seriously considered it believe will ensure that it isn't true. SteveBaker (talk) 04:41, 26 July 2014 (UTC)[reply]

it calld "the next world" , thanks water nosfim — Preceding unsigned comment added by 192.117.12.48 (talk) 05:05, 26 July 2014 (UTC)[reply]

All of this depends on there being a non-zero probability of you surviving. What if the probability really is zero?--92.251.220.98 (talk) 12:37, 26 July 2014 (UTC)[reply]

The notion of quantum immortality was developed by among others MIT Professor Max Tegmark whose other achievements include writing a word processor in Z80 machine code and proposing his Mathematical universe hypothesis whose postulate is "all structures that exist mathematically exist also physically". Wikipedia's article is Quantum suicide and immortality. 84.209.89.214 (talk) 13:04, 26 July 2014 (UTC)[reply]

The mistake made here is that it assumes that time exists in some objective way which is unlikely to be true (it contradicts most of modern physics). So, while you can write down a wavefunction and consider how it behaves under time evolution, it is wrong to say that just because in a superposition of different outcomes you are not present in some of the states, that you must be in one of the other states where you are present. This is only true of you redefine "you" to limit it to you experiencing one of thse future states, making the statement trivial. However, that's not consistent with how you would want to consider the probability of you experiencing one of the possible states you can be in.

What about quantum insomnia? There is always a probability that I could experience the time that I should be not experience if I would not fall asleep in time. Quantum theory yields a finite amplitude for that, and yet I usually sleep well. The hidden assumption made in quantum immortality predicts that we should all suffer from chronic insomnia.

The correct way to think about these issues is to stop considering time as fundamental, the universe doesn't evolve in time. What we consider to be time evolution is just a mapping from one universe to another that preserves information. All these unverses exist a priori. So, it's not true that the dinosaurs don't exist, that's only true in our universe, just like in some other universe it is the case that we are dead and burried for millions of years. Count Iblis (talk) 18:21, 26 July 2014 (UTC)[reply]

A related issue is that we don't know whether our universe is infinite or finite. In any given volume of space, there are only a finite number of arrangements of energy and fundamental particles that are possible. So with literally infinite space, you'd expect to find infinite numbers of copies of the exact same piece of space for any sized volume you happened to choose. That means that there are infinite numbers of large collections of entire galaxies that are utterly identical to ours. So infinite numbers of earths orbiting infinite numbers of suns, with infinite numbers of Steve's typing this same paragraph. Of course, there will also be infinite numbers of earths with copies of me that make a typo in this sintence instead of typing it correctly. This leads to another variation of quantum immortality, which is that in an infinite universe, we all exist in infinite variations - including those variations where we survive every terrible thing that can possibly happen to us. The same anthropic principle says that all of us exist without having died in any of a million possible ways because we are the copies who survived. So "quantum immortality" is very similar to "infinite universe immortality". SteveBaker (talk) 19:34, 26 July 2014 (UTC)[reply]

Either the infinite universe thing or split universes seem like they can really get out of hand and make a hash of the laws of nature. I mean, if the universes are infinite I suppose there's a universe where I jumped out the window thinking I could fly. There's a universe where I've done so and think that I am flying by flapping my arms, despite normal gravity. There are an infinite number of universes where I do all this and I have the delusion I've been doing it for hours. And if you take the copies of me from all those universes you can put together a nice motion picture where I am indeed in every stage of the wingbeat, flapping my way around town, with a delusional memory that perfectly matches the preceding frames in the picture you've spliced together. So in what sense is it not occurring as an "actual physical phenomenon"? Wnt (talk) 22:49, 26 July 2014 (UTC)[reply]

More than that - there are an infinite number of duplicate Earths where not only does a freak wind gust allow you to fly briefly but there are an infinite number of THOSE Earths where by a truly astounding number of consecutive coincidences, you can actually fly whenever you want to. Infinity is a strange concept! SteveBaker (talk) 00:22, 27 July 2014 (UTC)[reply]

Some of these wild hypotheses, invented to support other wild hypotheses, remind me of the logic gyrations astronomers had to go through in order to retain the notion of planets orbiting in crystalline spheres. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:37, 28 July 2014 (UTC)[reply]

How Steroids eliminate Fungal infections or Hemorrhoids?

If Steroids help to "Construct" tissues... How is it that they "Eliminate" Fungal infections or Hemorrhoids? --- Such actions sound a bit different for me than "Constructing" tissues\enhancing the Biosynthesis of tissues... Ben-Natan (talk) 15:25, 26 July 2014 (UTC)[reply]

The problem is your "if" statement; there are hundreds of varieties of steroid, with a multitude of different actions. For more detailed information about steroids acting as an anti-inflammatory, see Glucocorticoid and Cortisol, among many others. Other kinds of steroids inhibit fungi by inhibiting Lanosterol 14 alpha-demethylase (see here for a list). Matt Deres (talk) 16:02, 26 July 2014 (UTC)[reply]

The article Hemorrhoid notes that steroid-containing agents should not be used for more than 14 days, as they may cause thinning of the skin. It is more appropriate to prescribe Non-Steroidal (NSAID) drugs to relieve pain and inflammation. 84.209.89.214 (talk) 23:15, 26 July 2014 (UTC)[reply]

In reality steroids do not 'get rid of' haemorrhoids, they reduce the inflammation that is causing the irritation, this may give the impression that they have gone, but the swollen anal veins will still be there. Richard Avery (talk) 10:47, 27 July 2014 (UTC)[reply]

What kinetics?

By what a physico-mathematical mean of the kinetics always been different from a physico-mathematical mean of the statics?--Alex Sazonov (talk) 17:57, 26 July 2014 (UTC)[reply]

Those are all English words, but I don't understand what you are saying at all. Is there another language you speak as a native tongue? Perhaps you should find a question answering service in your native language? --Jayron32 20:03, 26 July 2014 (UTC)[reply]

If you're Russian, as your name suggests, maybe it would be better to post your questions in Russian. I can think of several users here who understand Russian and might be able to translate your questions for us. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:20, 26 July 2014 (UTC)[reply]

I think the intended meaning of the question is something like "How does kinetics physically and mathematically differ from statics?" I don't have time right now to tackle providing an answer, though. Red Act (talk) 22:39, 26 July 2014 (UTC)[reply]

Well, the simplest way to explain it is that kinetics is the study of things that are moving, while statics is the study of things that are not moving. --Jayron32 23:13, 26 July 2014 (UTC)[reply]

Yeah, that basically sums it up in one sentence. There's a slightly more detailed comparison at Analytical dynamics#Relationship to statics, kinetics, and kinematics. Red Act (talk) 02:47, 27 July 2014 (UTC)[reply]

It's a spamming troll, its posts on Ruwiki are similar, coherency-wise. It just likes stringing sciencey-sounding words together Asmrulz (talk) 05:02, 27 July 2014 (UTC)[reply]

Hmm but they're also targetting the Russian wikipedia? I long suspected this was our Argentinian friend who I suspect can't speak a word of Russian and who's native language is probably either Spanish or English. But may be the troll really is Russian although their real English level is obviously far better than they show here (as I guess is their Russian). Nil Einne (talk) 07:48, 27 July 2014 (UTC)[reply]

Dose the mass been move in a static’s?--Alex Sazonov (talk) 05:31, 27 July 2014 (UTC)[reply]

Perhaps. Statics deals with objects that are in "static equilibrium", which for sure only includes objects on which there is no net force and no net torque, and therefore no linear or angular acceleration. However, it depends on the author as to whether or not the phrase "static equilibrium" includes objects which are moving at a nonzero constant velocity. Wikipedia articles are inconsistent about this; the Statics article says an object moving at a non-zero constant velocity counts as being in static equilibrium, but the Mechanical equilibrium article says it does not. Of the physics textbooks I have on hand that talk about equilibrium in the context of classical mechanics, one of them defines "static equilibrium" in such a way that it would include non-zero constant velocity objects, and one of them defines just the word "equilibrium" the same way, as does this web page[16]. None of those three sources defines "mechanical equilibrium", or distinguishes between mechanical equilibrium and static equilibrium. Looking online, it looks like in places where "mechanical equilibrium" is also defined, "static equilibrium" is defined such that it only includes objects with zero velocity, but in contexts where "mechanical equilibrium" isn't defined, then "static equilibrium" usually but not always is defined in such a way that it also includes objects with a nonzero constant velocity. It really just depends on the author. Red Act (talk) 07:33, 27 July 2014 (UTC)[reply]

Sorry, if the mass been move in a static’s it been a static’s or kinetic's potential? I’m been study in the physics of the USSR which always been a physics of Ideal Cases.--Alex Sazonov (talk) 08:03, 27 July 2014 (UTC)[reply]

I been see, that science mind of the kinetics always been in a constant moving in static’s!--Alex Sazonov (talk) 08:52, 27 July 2014 (UTC)[reply]

Operations sector

What I the best way for a graduate to get into the operations sector whether in events, travel, leisure, airports industries etc? And does operations involve future planning as well? For example would a job in event operations involve the planning and managing of it too? What about for a fixed building such as an airport, shopping mall or station? Is planning and management also part of operations/operations management or is it separate? — Preceding unsigned comment added by 90.201.185.72 (talk) 23:33, 26 July 2014 (UTC)[reply]

Those are all quite different industries, even if they share some skill-sets or similar sounding titles. Operations is a very broad field; it often draws people who have academic backgrounds in mathematics, business, management engineering, engineering management, industrial engineering; or people who are farther along in their careers after starting out with a technical specialty in a specific industry.

If you're totally lost, start with the Occupational Outlook Handbook, a service and publication of the United States Department of Labor. That can help you narrow down the exact kind of occupation you're looking for. For example:

... and thousands of related types of employment prospects. These types of careers typically imply that you have completed a bachelor's degree and/or additional higher education in a relevant field.

If you're outside the United States, you might find your local government service office helpful. For example, the Career Skills and Training website, produced by the UK government, might also be informative.

Nimur (talk) 23:59, 26 July 2014 (UTC)[reply]

July 27

Bubonic Plague

What is the chance of contracting Bubonic plaque from a bite from a rat infected with Bubonic plague? Hypothetically in this scenario infected fleas of the rat didn't bite the person (the normal vector to host transferal for yersinia pestis). --KAVEBEAR (talk) 02:07, 27 July 2014 (UTC)[reply]

I hope this isn't actually a request for medical advice. If you or someone you know has been bitten by a rat, please see a doctor!

The CDC has a number of web pages about plague linked from this page. This page about its "Ecology and Transmission" lists three transmission modes: fleas, airborne droplets in the case of pneumonic plague, and "contact with contaminated fluid or tissue". Well, being bitten is a form of contact, so it would depend on whether the rat's mouth and saliva contain the bacteria. This page about its "Symptoms" says that bubonic plague bacteria multiply in the closest lymph node, but "can spread to other parts of the body". So it makes sense that a rat's bite could indeed be infectious. I was not able to find anything directly addressing the question "What is the chance?", though. --50.100.189.160 (talk) 09:38, 27 July 2014 (UTC)[reply]

Also, I believe many people have at least a partial immunity to bubonic plague by now, which is why, despite there still being many areas of the planet where people, rats, and fleas all live closely together, it's not the type of pandemic it once was. Of course, if a new strain develops, people may lack any resistance to that, and it could once again become widespread. StuRat (talk) 13:06, 27 July 2014 (UTC)[reply]

There are nearly always a few people immune to almost any disease; consider the case of AIDS-resistant sex workers. Why bubonic plague doesn't flare out into Black Death any more is not well understood, but the existence of a few resistant people is probably not a significant part of the explanation. Antibiotics, advances in vermin control, and greater separation of people from animals probably all play a much larger role. It's also possible that the bacterium itself is now different. I recall reading a article which noted that, during plague epidemics, everything involved is sick - the people, the rats, the fleas, and even the bacteria themselves. Matt Deres (talk) 19:01, 27 July 2014 (UTC)[reply]

Unlike AIDS, bubonic plague has been around for well over a thousand years, and killed off a substantial portion of many generations, giving human survivors time to develop immunity, assuming it hasn't mutated to prevent this. And, of course, a population develops herd immunity without every individual being immune. StuRat (talk) 19:45, 27 July 2014 (UTC)[reply]

Oddly enough, the reverse seems to transmit the disease well - cats and dogs biting infected animals get the disease via the mucous membrane in their mouths ref. I haven't found anything that directly answers your question, but that does point to the disease passing through the mouth. Matt Deres (talk) 18:51, 27 July 2014 (UTC)[reply]

I think a bigger reason is that people are more hygienic and don't have fleas as a general rule. Fleas biting people was the transmission route during the black death periods. When the rat die, fleas went to a new host and Europeans didn't particularly care or bathe regularly. Compare that with Japanese culture in the same time period. --DHeyward (talk) 19:48, 27 July 2014 (UTC)[reply]

Rats don't bite humans unless they are rabid or need to defend themselves. They are a prey animal. Looie496 (talk) 14:46, 28 July 2014 (UTC)[reply]

It only takes once. Doctor to patient: "The good news is, you don't have bubonic plague. The bad news is, you've got rabies. It was nice knowing you." ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:18, 28 July 2014 (UTC)[reply]

LAMI

What does a matrix isolation setup look like where the guest species is generated by pulsed laser ablation, and where post-deposition photosynthesis is facilitated? Plasmic Physics (talk) 12:50, 27 July 2014 (UTC)[reply]

What does LAMI stand for here? Matrix isolation is an experimental technique in chemistry and physics where a material is trapped within an unreactive matrix. A host matrix is a continuous solid phase in which guest particles (atoms, molecules, ions, etc.) are embedded. Here are various images. 84.209.89.214 (talk) 01:07, 29 July 2014 (UTC)[reply]

Scientists talking outside of their area of expertise?

Is there are name for those situations where someone with a solid scientific background attempts to speak with authority on a subject matter far outside of their own particular area of knowledge - and ends up talking utter nonsense of the 'not even wrong' variety or perpetuating horrible bunk, yet nonsense which is taken seriously by the public because the person advancing the idea is an otherwise well-respected doctor, or a professor, or whatever?

For example, you might get a theoretical physicist claiming that he has discovered proof that Jesus walked with dinosaurs, or a chemist stating that he has discovered a method of curing cancer with magnets. Things that many people in the real world would dismiss as 'probably hooey', if the source had just been 'some random guy with a website'. --Kurt Shaped Box (talk) 20:39, 27 July 2014 (UTC)[reply]

Ultracrepidarian. See also argumentum ad verecundiam and junk science. Tevildo (talk) 21:11, 27 July 2014 (UTC)[reply]

Thanks. I could name some examples, but WP:BLP. I'm sure that you can all think of a few though... --Kurt Shaped Box (talk) 21:50, 27 July 2014 (UTC)[reply]

Well, since he's dead, we can name Linus Pauling. StuRat (talk) 14:28, 28 July 2014 (UTC)[reply]

Indeed, and this leads to the answer to the OP: "the Linus Pauling effect". --Heron (talk) 19:47, 28 July 2014 (UTC)[reply]

So, is he the reason for the 'take your vitamin CD - there's something going around' (or 'eat lots of oranges when you have a cold - because you need the vitamin C') thing? --Kurt Shaped Box (talk) 22:32, 28 July 2014 (UTC)[reply]

Appeal to authority and Ad hominem are articles referring to related concepts. They describe the error in saying "What this scientist said about the history of Rome sounds a bit strange but he is a highly respected nuclear physicist so he must be right." Dolphin (t) 01:40, 29 July 2014 (UTC)[reply]

The other day someone told me that Buzz Aldrin doesn't believe in evolution. They didn't seem to care when I pointed out that his degree was in engineering. Katie R (talk) 15:34, 29 July 2014 (UTC)[reply]

Does Newton's law of cooling apply to a hot car?

An automobile's interior on a sunny day will heat up, but eventually will have a limiting temperature after a few hours. I'm not sure if the law applies here, since the temperature rise is due to external radiation rather than conduction alone, but a graph I've seen has shown that without air conditioning, the rise appears to be of the form A-exp(-at). Is my intuition correct?--Jasper Deng (talk) 20:58, 27 July 2014 (UTC)[reply]

Yes -- as a car heats up, it will lose more heat to its surroundings until eventually the rate of cooling will equal the rate of heating. 24.5.122.13 (talk) 01:58, 28 July 2014 (UTC)[reply]

That doesn't really answer my question, since there are an infinite number of functions with finite initial condition and a finite limit as t→∞.--Jasper Deng (talk) 03:01, 28 July 2014 (UTC)[reply]

To a first approximation, yes. The external heat source (the sun) in not involved n the law of cooling; it is merely a constant power source. In your exponential model, you have assumed that the interior of the car acts as a single thermal mass. However, under some conditions, you might get the system acting according to differential equations of higher order. For example, if the body absorbing the bulk of the solar radiation is a metal object of substantial thermal mass inside the window, the interior of the car would initially warm up very slowly, with temperature gain accelerating as the metal object grew hotter, after which equilibrium would be reached. This would be expected to result in interior temperature rise being the sum of two decaying exponentials with different time constants. Nevertheless, for each heat flow path, Newton's law of cooling would remain fairly accurate. —Quondum 03:14, 28 July 2014 (UTC)[reply]

Some complicating factors:

1) The sunlight will not be constant, but will vary as the Earth rotates, clouds move over the car, etc.

2) There are multiple forms of cooling. At a low temperature difference, thermal conduction from the car to air will occur. At higher differences, the air outside the car will start to rise as laminar flow, assuming no wind, setting the car up like a cooling tower, using convection to cool the car faster. Wind has the potential to cool the car even quicker. Then, at high temperature differences, radiation of infrared/heat from the car will become significant.

So, other than in lab conditions, I wouldn't expect to see a smooth graph of interior temps. StuRat (talk) 14:40, 28 July 2014 (UTC)[reply]

In my local newspaper, I saw a graph consistent with Newton's law of cooling (but note again my comment about the existence of other such functions)- it was only for the first hour or so, when the change in the sun angle is small enough to be neglected, it would seem.--Jasper Deng (talk) 15:45, 28 July 2014 (UTC)[reply]

That seems reasonable. In most physical systems, simplifying assumptions can be made, and the simplified model then remains a reasonably accurate description. If your question is whether a first-order model is a reasonable for the typical parked car, the answer would be yes, mostly. One can argue that in the time span involved the typical car on a typical day can be adequately modelled as a single thermal mass with a constant power source and a cooling function that obeys Newton's law of cooling. Over very short and very long times, or with atypical configurations or nonconstant heat source profiles, the complicating factors become significant. So, in effect, for the typical configuration, your intuition is correct. —Quondum 16:11, 28 July 2014 (UTC)[reply]

Aftermath of the 79 A.D. Mount Vesuvius eruption

This could be an appropriate question for the Humanities desk too, but I decided to ask here.

Following the Eruption of Mount Vesuvius in 79, the deaths of 16,000 people and the loss of several towns and villages to the volcano, I presume that the Roman authorities will have launched an investigation to determine exactly what had happened there - and that learned men of the day would have been sent forth to the area soon afterwards to investigate and tasked with devising plausible explanations for the mechanism of a volcanic eruption. As far as I'm aware, this would have been the first major European volcanic eruption in over a thousand years and at the time, no-one would have the slightest idea about what had just occurred.

Now, I suppose that there would be a lot of people who simply believed that it was punishment from the gods, or somesuch - but I'm curious as to what the scientists of the day concluded about the disaster. Anyone know? Or has this information been lost to history now? --Kurt Shaped Box (talk) 22:26, 27 July 2014 (UTC)[reply]

I would have thought the the authorities would have considered it self-evident what happened. The idea that they would see a need for "devising plausible mechanisms" is an attitude that mainly developed after the scientific method became widely adopted during the Renaissance. But if you want the historical facts, you probably do want that other desk. --50.100.189.160 (talk) 22:46, 27 July 2014 (UTC)[reply]

Well, self-evident in that 'a mountain exploded and hot stuff came out', I suppose - but even back then, I'd have thought that there would be much in interest in finding out 'why?' for the purposes of then figuring out 'is it possible to know in advance if this is going to happen again, either here or with another mountain upon which lots of people are living?'. --Kurt Shaped Box (talk) 22:52, 27 July 2014 (UTC)[reply]

Of course, the classic description of that particular eruption was in the letters of Pliny the Younger, in which he recounted the death of his uncle Pliny the Elder in the Vesuvian eruption. But the Romans were quite familiar with volcanic eruptions, particularly those of Mount Etna. The Romans in general (at least those of a scientific bent) usually attributed volcanoes to the interaction of subterranean fires and winds; see Volcanology#Greco-Roman science. Deor (talk) 23:58, 27 July 2014 (UTC)[reply]

July 28

Ecological footprint awareness and self-esteem

Have any studies examined how awareness of one's own ecological footprint impacts self-esteem? I doubt I'm the only one who's ever wondered how many tons of carbon dioxide I'm worth to the rest of humanity. Neon Merlin 02:41, 28 July 2014 (UTC)[reply]

Not that I'm aware of, though the negative ecological footprint of a single person is approximately zero. You're much more likely to affect the rest of humanity with communicable diseases than anything to do with carbon. I'd be more worried about your anti-biotic footprint if it makes you feel better. Plus your footprint is all within your control with use of fossil fuels. I'd question you're awareness if it was affecting you self-esteem, mot the other way around. --DHeyward (talk) 09:12, 28 July 2014 (UTC)[reply]

Well, let's think of a few examples, people who fly all over the world to lecture us about how we shouldn't be flying all over the world. Al Gore, Tim Flannery,Michael Mann for example. If one were to try and limit one's CO2 output to the average worldwide number , you'd be allowed the energy intensity per capita of Cuba, for example. Greglocock (talk) 10:35, 28 July 2014 (UTC)[reply]

And everyone in Cuba is happy ("or else"). ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:16, 28 July 2014 (UTC)[reply]

People who care about their carbon footprint probably try to minimize it, and thus feel good about themselves, while those who don't care are unaffected. However, there may be some who care about it and feel depressed no matter what, as they can never get their carbon footprint low enough to be happy. StuRat (talk) 14:45, 28 July 2014 (UTC)[reply]

Some folks aren't happy unless they aren't happy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:16, 28 July 2014 (UTC)[reply]

Debbie Downer ? StuRat (talk) 17:40, 28 July 2014 (UTC) [reply]

Yep. Where is she now? Working for Fox News, maybe? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:45, 28 July 2014 (UTC)[reply]

You obviously don't watch Fox or only watch Judge Jeannine, Bugs. Harris Faulkner and Megyn Kelly (!) ? Unfortunately, not only is a certain person I won't name an angry drunk, Mom's also never happy unless she's unhappy. I've advocated a carbon tax in the form of a tax on fuel and packaging an other inefficiencies for years. The problem is while you could easily get most Americans to agree to a large tax on shipping and packaging costs in exchange for an end to sales taxes, the left wants to keep the latter on top of the former. μηδείς (talk) 21:47, 28 July 2014 (UTC)[reply]

I should have put that one in small print. And I know who you're talking about. He's on leave, so to speak. As regards taxes, I'm like any American, in that I strongly support taxes on things I don't use. And as regards a carbon tax, you'll never get conventional industry to accept it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:00, 28 July 2014 (UTC)[reply]

We have just the reverse issue here in Michigan, where the right wants to repeal a business tax. They argue that this tax is unfair, since businesses not only have to pay sales tax when they buy equipment, but must pay tax on it every year after, too. That would be a reasonable argument, iff they would increase another business tax to make the bill revenue-neutral. But, of course, they made no such proposal.

As for a tax on packaging, that might have some other benefits, like reducing the amount of garbage overfilling our landfills. A deposit is another approach. The 10 cent Michigan bottle deposit on carbonated beverage containers has worked wonders to clear the sides of roads of returnable bottles, as homeless people will collect them if anybody tosses them out there. Nonreturnable bottles and other packaging continue to lead to littering and illegal dumping, though. For example, some kindly individual was nice enough to donate a vodka bottle to us last week by leaving it for us on our front lawn. I accepted his generosity, rinsed out the bottle, and put some flowers in it. StuRat (talk) 12:07, 29 July 2014 (UTC)[reply]

How good is satellite image?

If we put a printed newspaper outside, could satellite capture a picture of that newspaper with readable text?--115.73.31.225 (talk) 10:46, 28 July 2014 (UTC)[reply]

Well, see Satellite imagery#Resolution and data. For current commercial satellites the answer is certainly not. The maximum resolution available from spy satellites is not something that countries publicize, but is unlikely to be that good because of having to look having to look through the atmosphere. --50.100.189.29 (talk) 12:12, 28 July 2014 (UTC)[reply]

Imagery intelligence#Satellite discusses the Rayleigh criterion limit for resolution, and says that IMINT satellites are believed to have a resolution of about 10cm. So the answer appears to be "no" even with spy satellites. Red Act (talk) 13:41, 28 July 2014 (UTC)[reply]

The US military has been filled with stories of satellites with ungodly resolution. One frequent claim is that they can read car license plates from orbit - another is that newspaper headlines can be read from orbit. Both of those claims were made during the cold-war era when the actual photographs were conveniently labelled "Top Secret" and nobody could be called upon to prove this capability. Probably those are both apocryphal. The US Military certainly do have 10cm imagery, I've worked with it - it's not even secret...but that's not enough to do either of those things. An entire newspaper would be only a handful of pixels and you'd be lucky to tell whether a car even has a licence plate - let alone be able to read it!

The highest resolution Google Maps images are also around 10cm - but they mostly use aircraft-derived photography.

Right now, the US Department of Commerce places a ban on commercial satellite photography with resolutions under 50cm - on grounds that this is the highest resolution that doesn't allow you to see individual humans - hence preserving some sort of anonymity. That limit is currently being appealed by at least one commercial provider (DigitalGlobe) [17] who could provide 40cm resolution with satellites already in orbit - and who plan to launch new satellites with 25cm capability sometime next month! The US Military and the Whitehouse have already lifted their versions of the resolution cap - and it seems that the Department of Commerce may finally eliminate all restrictions sometime this year. Some people are horrified by the privacy implications - but since Google Maps already provides higher resolution than that from manned airborne photography, and the un-banning the use of commercial drone aircraft is probably going to happen just as soon as the FAA can figure out the flight rules for such craft - it seems pointless to disallow satellites from doing the same exact thing.

But no, I don't think reading the text on a newspaper from orbit is possible right now...maybe not ever. That said, I would imagine that even with 10cm imagery - you could get a good enough image of the page to recognize which newspaper it is, and infer which page was being looked at by comparing the blurry image you got from orbit to images of all of the pages of all of the newspapers printed in that part of the world within a week or so of the date that the photograph was taken. In a sense, perhaps that's good enough.

SteveBaker (talk) 14:19, 28 July 2014 (UTC)[reply]

Is that 10 cm limit just for visible light ? How about if we move to the non-visible parts of the spectrum ? StuRat (talk) 14:52, 28 July 2014 (UTC)[reply]

Those are either outside the Optical window or longer, hence worse. Jim.henderson (talk) 16:26, 28 July 2014 (UTC)[reply]

In addition to Earth's atmosphere blocking above-visible-light frequencies, the solar spectrum cuts off quickly below violet. Unless we posit a giant orbiting ultraviolet flash bulb, it would be photographing in the dark through an opaque wall. 88.112.50.121 (talk) 19:14, 28 July 2014 (UTC)[reply]

Thank you all for very detailed responses. I have one more question. I watched an American movie describing an American POW who notifies his superiors his location by facing the sky (to let a satellite see him). In real life, is this possible to identify a man through satellite if he faces the sky?--115.73.31.225 (talk) 16:57, 28 July 2014 (UTC)[reply]

Based on the resolution described above, no. I think a better method is to spell something out on the ground. If spread over a large enough area, it won't be noticeable from the ground. StuRat (talk) 17:22, 28 July 2014 (UTC)[reply]

This comment reminds me of a science-fiction short story by Timothy Zahn. Unfortunately, by mentioning it in this context I have revealed the ending, so if I reveal the title as well, it becomes a spoiler. Follow this link if you would like the story identified anyway. --50.100.189.29 (talk) 22:28, 28 July 2014 (UTC)[reply]

There's a new film called Lucy, based on the debunked notion that we only use 10 percent of our brains. The notion of being facially identified by a satellite was also used in a movie starring Gene Hackman and Will Smith, I forget the title. Basic preposterousness never stops writers from writing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:31, 28 July 2014 (UTC)[reply]

Enemy of the State, incidentally. Tevildo (talk) 18:16, 28 July 2014 (UTC)[reply]

Somewhere in the attic is my college physics text, which if I recall correctly, had a way of calculating the maximum resolution based on aperture size, and i recall calculating long ago that a spy satellite would have to have unrealistically huge optics to allow reading wristwatches, newspaper headlines, or even license plates. This is a limit regardless of atmospheric effects or the quality of the lenses or sensors. Edison (talk) 19:44, 28 July 2014 (UTC)[reply]

How about a precisely placed array of smaller lenses ? StuRat (talk) 20:06, 28 July 2014 (UTC)[reply]

That would be the Rayleigh criterion, that I mentioned above. Red Act (talk) 20:48, 28 July 2014 (UTC)[reply]

I think the digital world has changed most of that at least for static images. In the same way that audio oversampling can have a 1-bit Sigma-Delta converter can shape noise out of the band of interest and achieve 18 bits or more of audio dynamic range, digital cameras with multiple images of the same object can be used to push resolution. Focus stacking is one technique. I believe there are others, that, even though single images are at the Rayleigh limit, multiple images at difference points in space and different focal planes can be combine mathematically to create a static image with much greater resolution than any individual one. I believe this is similar to having a much larger aperture with much less aberrations. --DHeyward (talk) 23:17, 28 July 2014 (UTC)[reply]

I'm not sure it works that way, but I work with audio-like signals, I'm not an expert in the image-processing field. Oversampling the image in the time domain simply allows you to reduce the noise at the source resolution, but not reveal smaller detail. See Oversampled binary image sensor for an example. Oversampling to increase resolution would have to happen in the spatial domain, which could theoretically work by snapping many quick images as the camera drifts over the subject, so the grid of pixels shifts slightly between each shot, but I would be very surprised to hear that the small number of samples would be enough to make an appreciable difference in resolution. I do vaguely remember hear about using a similar technique to get higher-quality stills out of blurry security camera footage, but I'm having trouble tracking down a good source. Katie R (talk) 13:54, 29 July 2014 (UTC)[reply]

It's possible to get a very high angular resolution with an array of separated telescopes; that's the principle behind astronomical optical interferometry. I can't find any evidence that optical interferometry has been tried from satellites, but interferometry at microwave wavelengths from satellites exists; see Interferometric synthetic aperture radar#Spaceborne. Red Act (talk) 15:02, 29 July 2014 (UTC)[reply]

So it's impossible at this time although there are some theoretical ways to do so. Thank you all for this interesting discussion and explanation. I've got what I want :).--115.73.31.225 (talk) 00:57, 29 July 2014 (UTC)[reply]

Rivers

I have two questions, each of which drives toward the same basic point: 1. If the Nile dried up today, what physical evidence would exist a thousand years from now to tell us that it flowed south to north rather than north to south? and 2. Can you determine the direction of flow of a dry river without knowing where its source was or where it emptied? Evan ^{(talk|contribs)} 23:51, 28 July 2014 (UTC)[reply]

You might want to ask the members of Wikipedia talk:WikiProject Rivers.

—Wavelength (talk) 00:04, 29 July 2014 (UTC)[reply]

Wavelength, we shouldn't encourage people to ask knowledge questions on pages meant for discussing improvements to the encyclopaedia. The whole reason the reference desk was set up was to keep those questions off the project pages. SpinningSpark 00:46, 29 July 2014 (UTC)[reply]

Spinningspark, I meant that the original poster would invite editors with specialized knowledge to comment at the reference desk.

—Wavelength (talk) 01:20, 29 July 2014 (UTC)[reply]

The Nile has a prominent delta which shows where it carried sediment into the Mediterranean. 84.209.89.214 (talk) 00:41, 29 July 2014 (UTC)[reply]

The topography of the land, i.e. which way is "downhill", might be a clue. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:05, 29 July 2014 (UTC)[reply]

I hope we aren't facing confusion here because the Nile appears to run UP maps. HiLo48 (talk) 03:19, 29 July 2014 (UTC)[reply]

That would be more pathetic than I can imagine. In any case, the OP is talking one thousand years, which is fairly short on the geologic scale. Dry Falls, for example, has been around for like 20,000 years, and it's still pretty easy to figure out which way the river was flowing. The much less dramatic human-made earthworks leading away from Stonehenge are visible from the air (se Google Maps) ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:15, 29 July 2014 (UTC)[reply]

Spacecraft on Mars are able to measure properties of the dried up rivers located there that haven't flowed for a million years. Figuring it out at the Nile after such a relatively short period of time should be a piece of cake. Erosion patterns would distinctively show flow direction - a protruding surface will be more highly worn on the side that the water is flowing against, and less worn on the sheltered lee side. Ancient river beds are occasionally frozen in time as "Mudstones" that show the ripples in the muddy bottoms - which also makes it really easy to figure out the water flow direction. SteveBaker (talk) 04:36, 29 July 2014 (UTC)[reply]

I saw examples on a recent trip to Central Australia. In Kings Canyon there are large areas of rippled rocks one finds oneself walking over. Nearby, is the Finke River, claimed by some to be the world's oldest river. It still runs sometimes, after really heavy rain, but most people just see a dry river bed, starting in a desert, and ending in a desert. The forms of erosion on rock surfaces can show which way the water has flowed. HiLo48 (talk) 04:53, 29 July 2014 (UTC)[reply]

I believe every river connected to the ocean flows into the ocean, and not inland from the ocean. The reason is simple: land is almost always above sea level, which is to say higher than the sea. Water in a river flows downhill, which is towards the ocean. Anybody who saw a dried-up Nile can immediately conclude that it flowed into the ocean, absent overwhelming evidence to the contrary.

The basic shape of the river should also tell you which direction the water flowed. Generally, small streams merge into tributaries, which then merge into rivers, which then merge into giant rivers like the Nile. So "uphill" is the direction where the river branches off and becomes smaller; "downhill" is the direction where the river merges into a bigger river. --Bowlhover (talk) 07:23, 29 July 2014 (UTC)[reply]

This question pertains to sedimentology, and can be partially addressed by the articles, Sedimentary structures and Paleocurrent. Plasmic Physics (talk) 08:06, 29 July 2014 (UTC)[reply]

Anecdote: A geology professor I once had (a stratigrapher) told the story of his finding, in some exposed strata, what he thought were imbricated pebbles indicating a direction of flow. Excavation revealed that they were, instead, the remains of the ribcage of a fossil whale. Deor (talk) 11:26, 29 July 2014 (UTC)[reply]

July 29

Calculating the distance between two planets on a given date

The title is pretty self-explanatory, I guess. I'm looking for an easy and simple way to do this, preferably online and preferably without installing any software. Thanks in advance. Evan ^{(talk|contribs)} 00:15, 29 July 2014 (UTC)[reply]

The JPL Solar System Simulator has the information you want. You will have to play around with the display settings and turn lots of things off to be able to actually read the distance figures. The information is obscured by a too-busy display on the default settings. There is a much simpler caculator at Wolfram but it is beta and doesn't give the date used so it's accuracy is probably suspect. SpinningSpark 01:10, 29 July 2014 (UTC) and 01:14, 29 July 2014 (UTC)[reply]

If you want high accuracy, use JPL's HORIZONS interface: [18]. For each planet, you can get the planet's right ascension, declination, and distance from Earth. This defines a spherical coordinate system, and you can calculate the distance using the planets' coordinates. I might write an app that automatically does this, if nobody finds a pre-existing one. --Bowlhover (talk) 01:32, 29 July 2014 (UTC)[reply]

Wolfram|Alpha will calculate it, for example distance between Venus and Mars on 31 December 2015 gives 0.9553 au. ---- CS Miller (talk) 08:46, 29 July 2014 (UTC)[reply]

I assume that it takes account that the planets' orbits are elliptical, rather than circular, However does it take account of perihelion precession, orbits slowly increasing, and other effects needed for calculating the planets' locations in the distant future/past? CS Miller (talk) 08:56, 29 July 2014 (UTC)[reply]

Full body burns and infections

I've heard of people who have received full body burns being in the ICU and being unable to survive due to their skin having been peeled off and due to the resulting scabbing (all over their body), eventually die from infection. Is this have any basis in fact? I've researched but I couldn't find this specific scenario. Thanks. Tutelary (talk) 02:55, 29 July 2014 (UTC)[reply]

Burn#Prognosis explains that burns over more than 90% of the skin have an 85% fatality rate - and goes on to say that the most common complication is infection...so, what you've heard seems reasonably correct - although it's by no means the only possible outcome...after all, 15% survive - and of the 85% that die, some at least must die of the less common complications. SteveBaker (talk) 04:14, 29 July 2014 (UTC)[reply]

"Red" and "blue" stars

From the articles about stars, I get the impression that most "red" stars are even more infrared than red, and blue stars are usually more ultraviolet than blue.

My reasoning:

The peak wavelength is around 2.9mm divided by the surface temperature. So, 5000K - 580nm (yellow-orange), 4000K - 725nm (red), and many stars are way below 4000K and thus mainly infrared.
Going the other way, one finds 5800K - 500nm (green-blue), and 7250K - 400nm (violet-ultraviolet). The radiation of the latter is already 50% ultraviolet, and even A-type main-sequence stars are hotter.

So, is it correct that the 7250K star emits half its energy as UV, and a 3600K star half its energy as infrared? The figures look OK, but I'm not sure if I can take the peak as 50/50 mark.

Of course, names like "infrared dwarf" and "ultraviolet giant" are unnecessarily long; the dominant visible color avoids that problem nicely. I'm asking because somebody claimed that you couldn't see any stars in front of you when moving at 0.5c; their claim was that all colors would been blue-shifted out of the visible spectrum. Now, if most "red" stars emit lots of infrared, that issue doesn't even. - ¡Ouch! (^{hurt me} / _{more pain}) 09:55, 29 July 2014 (UTC)[reply]

Note that A-type main-sequence stars emit lots of infrared from the dust clouds surrounding them, so they would be visible too. 24.5.122.13 (talk) 10:04, 29 July 2014 (UTC)[reply]