Wikipedia:Reference desk/Archives/Science/2011 March 13

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March 13

Changes in personality test results and IQ when the subject is drunk

It is common knowledge that people change their apparant personality when drunk, but are there any research papers that compare the results obtained on Big Five personality traits personality tests and IQ tests for the same subjects after consuming alcohol and when completely sober? Thanks 92.15.8.206 (talk) 00:24, 13 March 2011 (UTC)

There is a lot more research on the effects of personality on alcohol consumption than on the effects of alcohol consumption on personality. There seems to be a general consensus that drinking increases impulsiveness, but I didn't spot any research that assesses this using standard personality tests. Looie496 (talk) 01:30, 13 March 2011 (UTC)

I suppose the problem with personality tests is that they ask the subject to recall their past behaviour or attitudes, eg "Do you like parties?" which would not be much affected by current intoxication. 92.15.26.29 (talk) 21:35, 13 March 2011 (UTC)

Why do nuclear reactors have batteries for cooling?

They could obtain all the energy they wanted from the heat of the rector. —Preceding unsigned comment added by 212.169.190.126 (talk) 03:12, 13 March 2011 (UTC)

As far as I understand, normally that's exactly what they do - they need to power the pumps that take the water in, but when the tsunami hit they shut down the reactor and went to diesel to continue cooling. The diesel then failed and they had to go to battery to power the pumps. Again, as far as I know, that's the main power need - pumping, venting, etc. SamuelRiv (talk) 03:52, 13 March 2011 (UTC)

The first backup, before they had to go their diesel generators, is to take power from the grid. This was impossible because the earthquake had caused all the power stations along the coast to go into auto-shutdown, including their own one. This left them on tneir own with only their own diesels and batteries, which worked fine until the subsequent tsunami flooded them. SpinningSpark 11:29, 13 March 2011 (UTC)

Also note that according to (most of) the news stories, the batteries were for instruments and controls, and were not for running the cooling pumps. -- 119.31.126.69 (talk) 12:06, 13 March 2011 (UTC)

Yes, I get the idea that a shut-down generator won't generate electricity directly. However, a shut-down reactor still generates heat (right?), so you could connect a Stirling engine with a cooler to generate all the electricity that you want. A part of the cooling would be passive, through the cooler of the Stirling engine, and the rest would be through the power generated through this process. 212.169.183.128 (talk) 12:53, 13 March 2011 (UTC)

Whether you could even do that in theory would really depend on how you had the plant set up. Have you actually been inside a nuclear power plant? They are not like those idealized reactor diagrams you see that explain how they work. They are massive industrial facilities, the size of many factories put together, with miles of pipe, concrete, and so forth. The turbines themselves fill gigantic rooms, deafeningly whirring away. They are quite a spectacle and I do recommend trying to visit one at least once in one's life, just to get a sense of the scale of the things and the work that goes into running them. I went on a tour of one awhile back and was bowled over by the complexity — you're not just going to rush in and tinker with them, especially not in an emergency situation. It sounds to me like you are either proposing that they'd have such a system already in place (which is probably not economical, considering the specific situation in which it would be useful, which would be quite rare) or adding one on the fly, which seems totally impractical, and not as easy as just using batteries. --Mr.98 (talk) 15:41, 13 March 2011 (UTC)

"Not as easy as using batteries"?? The technical implications of the size & complexity of a NPP plant have obviously gone over your head! Batteries are just about THE most impractical solution available. Bigredtoe (talk) 03:56, 17 March 2011 (UTC)

No, I was not thinking about an on-the-fly solution after an accident and also not an add-on solution to an already built nuclear power plant, but as an ideal solution. You need a backup cooling anyway, and this cooling system needs to be connected to the reactor somehow, so generating power shouldn't be a problem for it. You are right at pointing out that the nucleus quite rarely melts out (even if it might be happening right now). But, if it does, then the harm is apocalyptic (at least on a local scala). 212.169.183.128 (talk) 15:59, 13 March 2011 (UTC)

What happened in Japan (earthquake + Tsunami) is probably rare enough, so no one was prepared for this specific case. Once again, accidents happen, when people think they are prepared for something.Quest09 (talk) 16:58, 13 March 2011 (UTC)

If I understand things correctly, tsunamis are highly correlated with earthquakes; an earthquake that moves the seafloor is highly likely to create a tsunami. Why should one expect the combination to be rare? –Henning Makholm (talk) 20:50, 13 March 2011 (UTC)

It's the 8.9 earthquake that's rare. --Mr.98 (talk) 00:27, 14 March 2011 (UTC)

Yes. I expressed myself poorly. The combination (earthquake + Tsunami) is not rare. The violence of both (which also correlates) is not rare. But having such a violent earthquake and violent tsunami is quite uncommon. Quest09 (talk) 02:02, 14 March 2011 (UTC)

Batteries strike me as being far more flexible and adaptable (and I'm failing to see why they are insufficient). In any case, why assume your engine is going to not be damaged by the quake that damages the plant to that degree? --Mr.98 (talk) 00:27, 14 March 2011 (UTC)

They had diesel engines as backup power source. The batteries are said to be for other purposes. Quest09 (talk) 02:02, 14 March 2011 (UTC)

Undersea nuclear reactors - all the emergency cooling you want. 92.15.26.29 (talk) 21:36, 13 March 2011 (UTC)

The batteries and the diesels are not necessarily for different purposes! Although with a BWR plant they maybe. Power backup systems generally work thus: Immediately main power fails battery energy is automatically used to maintain power and the process of starting and bringing up to speed of the diesel driven generators is commenced. Only when the generators are running correctly (engine speed = output frequency etc)can the system "cut over" to run off the diesels. (You always have at least half of your diesels "ready to run" - some places i've worked at 1 unit was always started and brought up to speed before any servicing/repairs where commenced on the 2nd unit and first unit kept running until serviced unit was bought back into service, started, run and proved!) Assuming the diesels have enough capacity the battery banks then go into recharge mode.

With a sensible amount of diesel fuel stored on site you can run for days or weeks, and with the relative ease of obtaining diesel refueling you could run for months/indefinitely. You generally have 2 gensets or twice as many as you need. There is a lot of energy in a 44gallon(200 litre) drum of diesel. On the other hand to run for weeks or even days on battery alone you would need a stack of batteries of an insane size. (Mr.98 wrote "Batteries strike me as being far more flexible and adaptable (and I'm failing to see why they are insufficient).") That's why. I heard that they had enough battery capacity to run for 8 hours. "..but when the tsunami hit they shut down the reactor and went to diesel to continue cooling.." That is not quite right. Immediately the quake happened all 3 reactors automatically did an emergency shutdown, as did most if not all other reactors in the region. (The other 3 reactors at the site were not running and in a cooled down state.) As the generators driven by all the reactors went offline the power in the main grid would have browned/blacked out, even if the grid itself was undamaged by the quake itself. The transition to diesel power via battery appears to have gone ok and they were running ok "for about an hour"?? then water flooded the diesel gensets AND it seems associated equipment (switchboards, cabling, junctions etc). That appears to be complicating attempts to connect other power sources?

Where batteries may have a special separate roll in a BWR plant is to directly power special emergency backup pumps whose only job is to inject "neutron poison" (boron, boric acid etc) directly into the reactor if other measures to shut it down fail. Not a step operators want to rush into because it means a big cleaning job/lots of work if you ever want to start that reactor again!

But whether the reactor is shutdown by control rods or neutron poison or both, there is still a lot of cooling to be done over an extended period which requires a lot of pumping which is an energy hungry pastime. Using battery power for this is just not feasible. — Preceding unsigned comment added by Bigredtoe (talk • contribs) 23:11, 14 March 2011 (UTC)

Bigredtoe (talk) 19:11, 14 March 2011 (UTC)

Batteries were used to operate steam driven pumps (located in the reactor building) to flood the core and to monitor key parameters of the reactor. But with no Diesel generator the cooling function was actually lost since sea water pumps were flooded by the tsunami.--Franssoua (talk) 13:51, 14 April 2011 (UTC)

production of hydrogen from cooling water in nuclear accident -- was it a thermal decomposition?

It couldn't have been alpha particles or free protons finding electrons, right?

I know how to find the equilibrium reversal temperature to be 2300K. But obviously the pressure conditions are higher inside the nuclear reactor, and both temperature and pressure are increasing at the same time. How do I find the temperature where the equilibrium constant is 1?

Suppose I did start at some reactor pressure T1 -- perhaps I could draw a pressure-temperature curve as the reaction proceeds to T2? How do I calculate the total heat capacity of this reaction? (Is the heat capacity constant within this range, or do I have to account for this too?)

Also, does the presence of thermal decomposition provide a natural sort of "superboiling point" for water? That is, if I were superheating steam initially at 2300K at 1 atm, and suppose pressure were constant (the rxn is taking place in a large bladder or a balloon), would the steam basically stay at this temperature until all of it had converted to 2300K? John Riemann Soong (talk) 03:50, 13 March 2011 (UTC)

Is it accurate to model water as an ideal gas at 2300K and 600 kPa? John Riemann Soong (talk) 03:59, 13 March 2011 (UTC)

Fukushima I Nuclear Power Plant mentions caesium-137 as a fission product. It is radioactive, but as long as it hasn't decayed yet, it reacts chemically as an alkali metal -- like sodium except more so -- dissociating the cooling water into H₂ and OH^-. My understanding is that the systems that ordinarily disposes of the released hydrogen safely failed due to the loss of power. –Henning Makholm (talk) 04:45, 13 March 2011 (UTC)

A nuclear scientist on BBC News last night (sorry, don't remember his name) speculated that the hydrogen was produced, after the cooling pumps had failed, by the oxidation of the zirconium cases drawing oxygen out of the water leaving hydrogen as a by-product. SpinningSpark 09:10, 13 March 2011 (UTC)

Right. The zirconium is a not very reactive at low temperatures, but at higher temperatures it readily converts with water to the oxide leaving the hydrogen. This is a known problem in nuclear reactors.--Stone (talk) 20:01, 13 March 2011 (UTC)

say me what are you thinking about this subject

about formation of planets in solar system--78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

Akbar Mohammadzade wrote:

According to recent 30 years observations and increasing knowledge of man about the earth and planets in solar system , some astronomers are trying to give suitable theory about the formation of planetary system . My study has one difference with those theorems , for my goal of finding any solution for several paradoxes that i had list in my last article . from the angle of sun pole with planetary system quarter to existing of heavy elements in our system and the inner heat of earth ,..... Noticing to the recent studies about the origin of heavy elements in first solar nebula I focused on the properties of super novas , if there was this complex of element in thus nebula , that might be huge part of them in sun , but it has made of helium and hydrogen in general , this fact together with defragments of matter in terrestrial planets and giant planets says us some new rules about planetary system . I found out an approach for solving this problem , that it might be this system had created in two or three steps , first the sun and gas giant planets , second the creation of terrestrial planets with matter sent by neighborhood exploded supernova (in place where that conjunct with sun and solar system )and final creation of satellites and moons . In this sent article I say that supernova was send matter toward sun by 17degree angle(orbit of Pluto) and that reached here molten and changed sun quarter angle 7 degrees . akbar mohammadzade Iran university of science and technology --78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

That would appear to be an attempt to explain why the Sun and gas giants have fewer heavy elements than the terrestrial planets, moons, and smaller objects. However, that is already explained with a simpler theory, in that small planets, having insufficient gravity, lose their lighter elements, like hydrogen and helium, and thus become proportionally enriched in heavy elements. So, to propose an alternate theory (and expect it to be accepted) you would need to find a way to discredit the existing theory and prove your own. StuRat (talk) 08:46, 13 March 2011 (UTC)

(after edit conflict with StuRat) It is difficult to give a proper view on the works of Mr Mohammadzade without seeing the full paper, but I presume that it is not available in English as you appear to have translated an abstract yourself. The standard theory of planet formation is explained at nebular hypothesis, and we also have an article on star formation. A few comments on specific points:

• It is quite correct that the universe is 90% hydrogen and 10% helium with very little else. It is not true that this is not the make-up of our own solar system. Most of the mass is in the sun and jupiter which are both mostly hydrogen. The reason that on earth there is little hydrogen (other than in compounds such as water) and virtually no helium is that these elements are too light to be bound by the earth's gravity and 'evaporate' into space.
• It is correct that the heavier elements originate from supernovae. Elements up to iron in the periodic table are produced by nuclear fusion in large stars. These are later spread around by supernovae explosions. Heavier elements are produced by nuclear fission in the actual supernovae explosions themselves. The standard theory would have these heavier elements in place at the time of formation of the solar system, not arriving later as seems to be suggested by Mr Mohammadzade.
• It is quite unlikely that the curreent position of Pluto is where it originated (see Pluto#Origins and cannot therefore be taken as evidence of early solar system events as Mr Mohammadzade suggests.

SpinningSpark 09:01, 13 March 2011 (UTC)

notice this discussion :

The mater is separated such as spectrum from mercury to Neptune ,the question is this :suppose one element or particle at any place of first nebula , how did it found that’s same particle from distance which light spends in 22 hours to produce core of earth from nickel and iron?--78.38.28.3 (talk) 09:49, 13 March 2011 (UTC)

I'm not sure what that is saying, I can't quite parse the sentence. First of all, in a nebula material is drawn inwards and may eventually form stars and planets; material does not travel outwards from the centre. If the question is concerning the differing structures of the planets, there is general principle that the innermost planets have the largest nickel-iron cores (Mercury's core is particularly large in proportion to its size) and the outer planets have the smallest. This is simply because metal is more dense than rock or ice. Likewise rocky structures give way to ices in the outer reaches of the solar system. SpinningSpark 11:51, 13 March 2011 (UTC)

Hypertension and Asthma

How important are the blood pressure readings for a person who is suferring from hypertension and asthma? What is the significance of blood pressure in a person suffering from hypertension and asthma ? aniketnik 08:22, 13 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

I'm not sure if high blood pressure itself causes or triggers asthma. However, stress may cause both, so there could be a linkage between BP and asthma that way. StuRat (talk) 08:39, 13 March 2011 (UTC)

In case you don't already know, "hypertension" means high blood pressure. thx1138 (talk) 12:32, 13 March 2011 (UTC)

Yes, I do know that. I was using them as synonyms in my reply to avoid sounding repetitive. Or was that comment meant for the OP, and just indented improperly ? StuRat (talk) 13:02, 14 March 2011 (UTC)

Regardless of asthma, hypertension must be controlled because it leads to other comorbidities, primarily diabetes and high cholesterol. Therefore, it is important to get a hypertensive patient's blood pressure below 140/90 (the current standard) or 130/80 (for patients who are diabetic or have chronic kidney disease). Many studies have shown that controlling blood pressure limits progression to other comorbidities and greatly reduces cardiovascular disease risk (see Framingham Risk Score for information on how blood pressure is used to calculate CVD risk). So, knowing blood pressure is very important for hypertensives. -- kainaw™ 18:25, 13 March 2011 (UTC)

Hypertension leads to diabetes? And high cholesterol? Rather than all being correlated with obesity? So, someone who is overweight but has lower than average blood pressure is not at increased risk of diabetes and high cholesterol compared to someone not overweight? 86.163.4.134 (talk) 22:09, 14 March 2011 (UTC)

All three are heavily correlated. Having one leads to gaining another (and then the third if you live long enough). It is true that obesity is an underlying factor. There are many other underlying factors as well, so there is no single "cause". Note that I did not state that uncontrolled hypertension causes diabetes. I only stated that having uncontrolled hypertension leads to diabetes. In other words, a lifestyle that includes uncontrolled hypertension is a lifestyle that often includes diabetes and high cholesterol. -- kainaw™ 05:33, 15 March 2011 (UTC)

Why so cloudy on Venus ?

That is, why hasn't the thick atmosphere been lost to space, since Venus has no substantial magnetic field to deflect the solar wind ? StuRat (talk) 09:08, 13 March 2011 (UTC)

Our solar wind article says "...planets with a weak or non-existent magnetosphere are subject to atmospheric stripping by the solar wind. Venus, the nearest and most similar planet to Earth in our solar system, has an atmosphere 100 times denser than our own. Modern space probes have discovered a comet-like tail that extends to the orbit of the Earth." Which implies that it is being stripped but presumably will take a long time because the atmosphere is so dense. SpinningSpark 09:27, 13 March 2011 (UTC)

If it's been blowing off for billions of years, shouldn't it all be gone by now ? Or is it being resupplied in some way ? StuRat (talk) 10:04, 13 March 2011 (UTC)

Multiple sources confirm that it is being stripped, but I could not find anything to give a timescale (other than it is a lot slower than at Mars). Closest I could find was

"The precise evolution of Venus' atmosphere is not known. Nevertheless, it seems that there is an agreement among specialists that the terrestrial planets' atmospheres result from an evolutionary process which takes several hundred million years (Walker, 1975, Hart, 1978, Melton and Giardini, 1982, Zahnle et al, 1988, Hunten, 1993, Pepin, 1991, 1994). The present atmosphere of Venus is then a secondary atmosphere that acquired its major properties about 1 Gyr after the formation of the Solar System (eg. Hunten, 1993, Kasting, 1993)." [1].

SpinningSpark 10:58, 13 March 2011 (UTC)

Why is it slower than Mars ? Shouldn't the solar wind be much greater at Venus ? StuRat (talk) 12:10, 14 March 2011 (UTC)

Venus has Earth-like gravity. Mars doesn't. --Carnildo (talk) 02:00, 16 March 2011 (UTC)

OK, the gravity on Mars is 0.376 g while Venus is 0.904 g, so that's a valid point. However, Mars is approximately twice as far from the Sun as Venus is from the Sun, so I'd expect the solar wind to be four times stronger at Venus. So, how do gravity and solar wind figure into the calculations ? Do we have a formula for the rate of atmospheric loss ? StuRat (talk) 07:27, 17 March 2011 (UTC)

Note that Venus is believed to be still geologically active. Count Iblis (talk) 14:35, 13 March 2011 (UTC)

Also note that on Earth, volcanoes are the dominant source of non-anthropogenic and non-biological CO2. On the early Earth, they accounted for virtually all of Earth's greenhouse gases. There might also be other sources of CO2 production; for example, see this paper about the calcite + quartz reaction. --99.237.234.245 (talk) 23:26, 13 March 2011 (UTC)

Is Venus hot enough to drive CO2 out of Calcium Carbonate? Perhaps it has Calcium Carbonate in its geology that releases CO2. Googlemeister (talk) 13:00, 14 March 2011 (UTC)

Video

I'm trying to watch one of my video tapes, but every time I play it, it just grinds to a halt. How can I fix this? jc iindyysgvxc (my contributions) 11:24, 13 March 2011 (UTC)

Sounds like there is something wrong with the tape itself. I used to work at a video rental store (back when they used to rent videos!!), and it is relatively easy to take them apart and check if everything is spooled correctly. This post explains how to do it. If it were me, I would take it apart, see if everything looks right (nothing is jammed or twisted). I'd also try playing another VHS in the player, just to make sure it isn't the player that is broken. --Mr.98 (talk) 11:53, 13 March 2011 (UTC)

(ec) Take it to a TV repair shop? Sometimes this is due to the tape becoming loosley wound. If your player will fast forward it without sticking, try winding it fully to the end and then fully rewinding before attempting to play it again. If your player won't do this you could try manually tightening it, but this can be quite tedious. Have you checked if your other tapes play ok? If they don't there is probably something wrong with your player so it needs repairing; if the others do play ok you could also look for dirt or obstructions fouling the tape cassette mechanism. SpinningSpark 11:59, 13 March 2011 (UTC)

To boldly go, though dead, where no man has gone before...

Suppose I wanted my ashes, or to make this quite silly - my brain - to leave the solar system and voyage between the stars like the Voyager probes. Is it within the realm of private citizens to create a rocket that could escape the Sun's gravity? Can I fling my remains out of our solar system? The Masked Booby (talk) 11:58, 13 March 2011 (UTC)

Not sure about out of the solar system for the price of $995 you can have them sent into space.--NortyNort (Holla) 12:51, 13 March 2011 (UTC)

For current state of play see space burial (we really do have an article on everything !). The only person whose remains are currently en route out of the solar system is Clyde Tombaugh - approximately one ounce of his ashes have hitched a lift on the New Horizons spacecraft, which crosses the orbit of Uranus in a few days time. To escape the Sun's gravity you either need a dumb payload and a *very* big rocket, or you need a smaller rocket and a mission plan that include one or more gravity assists, which in turn assumes a capability for deep-space tracking and in-flight manoeuvres. Or you could develop a very efficient but highly sophisticated inter-planetary propulsion system, such as an ion thruster. Any of these routes is beyond the reach of any private citizen. Your most affordable option is to pay NASA to put a small portion of your remains on their next flight out of the solar system - I imagine that would cost you around $10 million (the going rate for a space tourism trip on the ISS is $15-$20 million). However, in the current economic climate, you might have a long wait for the next bus. Gandalf61 (talk) 13:17, 13 March 2011 (UTC)

Well, to expand on the OP's idea, why does it have to be ashes? Why couldn't an uncremated human body make the trip? --KägeTorä - (影虎) (TALK) 13:22, 13 March 2011 (UTC)

It could, but it might be significantly more expensive, as long as the commercial price tags for lifting stuff into space (even just geostationary orbit) lie at tens of dollars per gram. Of course if you can't find an existing interplanetary probe to hitch a ride on, the cost lifting the payload into Earth orbit might not even dominate. –Henning Makholm (talk) 15:50, 13 March 2011 (UTC)

I hope the moon is not being contaminated by people's ashes, as the first link claims. 92.24.186.239 (talk) 13:28, 13 March 2011 (UTC)

The Moon is already "contaminated" by 6 Apollo Lunar Module descent stages, 3 Lunar Roving Vehicles, 2 Lunokhod rovers and umpteen other lunar probes. Compared to the hardware already left on the Moon, a few grammes of sterile human ashes will have little impact. I would be more concerned about the waste of resources involved in a dedicated lunar burial flight (as opposed to hitching a lift on a pre-existing science mission) - it is the complete opposite of a green burial. Gandalf61 (talk) 13:49, 13 March 2011 (UTC)

See List of man-made objects on the Moon. 75.41.110.200 (talk) 19:16, 13 March 2011 (UTC)

I hope the moon will never be used as a deliberate rubbish-tip, even if its for human ashes. It would not be nice to look at the moon and think that it has been despoiled with waste. Exploration-related artifacts are a different matter. I hope governments forbid its use in that way. 92.15.11.100 (talk) 12:23, 14 March 2011 (UTC)

Why bother? The Earth is, sort of, a giant spaceship... Count Iblis (talk) 17:10, 13 March 2011 (UTC)

There are not a lot of probes leaving to the interstellar space New Horizons spacecraft was the last one. With 2 billion dollar you would be on the save side. NASA or ESA would make a nice mission to a Kuiper belt object and would take your (sterilized) brain with them if you donate the money with a good contract attached to it. Cheaper would be to become the discoverer of Nemesis (hypothetical star) and die well before a mission to that place, like Clyde Tombaugh the discoverer of pluto, who is just now on the way to pluto. Even cheaper would be that your brain gets a Tire balance for a space craft. before launch the moment of inertia is determined and a few weights are installed to adjust the rotation axis. If you can talk NASA into using your brain this would get you to interstellar space.--Stone (talk) 23:38, 13 March 2011 (UTC)

Since probes are expensive people want to be sure that they reach interstellar space, instead of crashing in somewhere, but suppose one just gives the best shot to create a rocket that can go as fast as needed for leaving the solar system - wouldn`t that just take a large load of fuel and building materials for the rocket? ~~Xil (talk) 02:47, 14 March 2011 (UTC)

(edit conflict with Xil) You're vastly overestimating the cost, I think. New Horizons is expected to have a 15 year mission cost of just 650 million USD, and that includes the launch costs + spacecraft cost (design and materials) + mission operations + data analysis. If your just sending your body into space, the cost for everything but the launch vehicle is negligible. I can't find a good cost breakdown for that particular rocket configuration (Atlas V 551), but it's certainly less than 300 million USD, probably closer to 200 million USD (the slimmer 401 configuration is cited at 187 million USD). And New Horizons weighs about 1000 lbs. If you can find 5 close friends to get launched into a solar escape trajectory with you, you can cut the costs to less than 50 million USD a piece. If you're cremated (ashes weigh , on average, ~5 lbs per person), you can send about 200 sets of remains into a space, for a per capita cost of under 1.5 million USD. Of course, that means you have to find 200 millionaires who want to be sent out of the solar system after they're dead. Buddy431 (talk) 03:00, 14 March 2011 (UTC)

Re-read Gandalf61's post, above. To get out of the solar system with a rocket like the one that launched New Horizons, you have to do gravity assists, which means you need a sophisticated spacecraft with onboard engines and computing power, and active tracking and management of the craft from Earth. You need, basically, the whole New Horizons mission except for the scientific payload. If you want to just use a dumb rocket and get onto a solar escape trajectory, that rocket has to be much more powerful and expensive. It takes a lot of energy to get from Earth's surface to a solar escape trajectory.--Srleffler (talk) 03:47, 15 March 2011 (UTC)

Re-read New Horizons. New Horizons did use one gravity assist (Jupiter), but it was on a solar escape trajectory before it even reached Jupiter. The gravity assist made it's trip to Pluto faster, but it was not necessary. Buddy431 (talk) 17:58, 15 March 2011 (UTC)

With so many power plants out of commission, how will Japan import the needed power in the shorter term?

In the longer term, they replace or repair the damaged plants. Right now, nearly all(?) of Japan has rolling blackouts 3 hours a day. (Hopefully from 2-5 AM, but probably not.) That can't keep happening until the power plants are fixed/replaced.

Couldn't they use undersea cables to import power from other nations? What are some other power solutions in the meantime? --70.179.169.115 (talk) 14:57, 13 March 2011 (UTC)

You must know Japan's Asia-facing side is much less developed than the Pacific Ocean-facing side. Tokyo and Osaka, two largest Japanese cities are facing the Pacific Ocean and they are separated from Continental Asia by mountains and pretty wide seas. On the other hand, many Korea-facing Prefectures, such as Niigata and Toyama are much more fishery or agricultural. You must know a very great percentage of Japan's lands are nothing but mountains. There are only pockets of small plains. Unfortunately, these Asia-facing areas are generally very narrow strips of rice paddies backed by very very very high mountains. You can ride a Suzuki from the sea shore to the nearest mountain foot within an hour. If you take train, you can see the sea on one side and the mountains the other side. These areas are usually not industrialized. They use much less energy than the Pacific Ocean side. Flat lands like Tokyo and Osaka are rare and mostly on the Pacific Ocean side. Please consult Google Maps. They have terrains. I think the most likely candidate for direct energy importation is Fukuoka which is very close to Korea's Busan City. To long haul electricity under salt water, you must use high-voltage direct current (HVDC). -- Toytoy (talk) 14:59, 15 March 2011 (UTC)

I imagine that a more efficient model that undersea cables would be to just import big generators and fuel for them. You can move a lot of coal very cheaply and very efficiently on big boats, more cheaply than building undersea power cables, I imagine. But this is just a guess — I haven't run the numbers. --Mr.98 (talk) 15:32, 13 March 2011 (UTC)

Rolling blackouts have to happen all through the day. Different places get power at different times - that's what "rolling" about them. They could use underpower cables, but only if they are already there - it takes a long time to lay such cables. We have an article, Electricity sector in Japan, but it doesn't cover this question. Since it doesn't mention electricity imports (just fuel imports), I guess there aren't many, which means they won't be able to increase them quickly.

They will have to reduce demand instead. That usually means cutting off the supply to big factories. They've probably already done that (if any big factories are even able to operate at the moment), but this disaster is on a scale much greater than anything they are prepared for, so it's still not enough. They'll probably get things sorted out over the next few days in terms of supply. What will take longer is fixing the distribution network - there are downed power lines all over the place.

--Tango (talk) 16:45, 13 March 2011 (UTC)

Perhaps they won't have to cut the power, or maybe have. Grandiose (me, talk, contribs) 20:55, 13 March 2011 (UTC)

I was thinking a similar thing (as well as it's entering spring and the temperatures are more mild) but per the OP and news reports, they are instituting rolling blackouts and encouraging people to save power so clearly the reduced power usage due to factories etc shutting down to assess damage (or because they are damaged) isn't enough. On the other hand, I would guess precisely how many power plants are sufficiently damaged that they can't be used remains unclear. I would presume many are shut down at the moment for the same reason as the factories, so the damage can be properly assessed and some of these could potentially be safely operated whether at reduced or full capacity while they are repaired. While likely a high priority task, they are also have tasks with higher priority so this may still take a while yet. Of course other then power plants offline I would guess the national grid has suffered some damage Nil Einne (talk) 00:14, 14 March 2011 (UTC)

In most places a proportion of theoretically active power plants are down for maintenance, refueling (for nuclear), etc. Those can be brought back on line and restore some capacity, but it takes time to complete whatever the work might be. Lots of utilities keep plants in reserve to meet peak loads. Even so, twelve (?) 500mw - 1 gw plants being off-line, particularly since nukes are considered "baseline load" plants for normal production is hard to make up for. I'm certain that some fossil plants are off-line, and bringing up a damaged grid is a slow process, to ensure that surviving generating units aren't harmed. Acroterion _(talk) 02:17, 14 March 2011 (UTC)

According to the Telegraph, Russia will supply power through an existing undersea cable [2]. Acroterion _(talk) 14:05, 14 March 2011 (UTC)

I have mentioned above, Japan's Asia facing side is much less industrialized than the Pacific Ocean facing side. Russia may lay a section of HVDC cable to Hokkaido. But it's a very long haul. Between Korea's Busan and Japan's Fukuoka you may lay another piece of HVDC cable. However, this part of Japan is least affected by the earthquake and tsunami. It helps, even though it's not very helpful. Importing energy from North Korea is out of the question. They are in an even worse shape. From China is really not very feasible. China is way too far from Japan. Even though Japan has a long history of invasions. I really don't think it's technologically feasible to transfer electricity from China to Japan. Between Russia and North Korea, there's a very small tip of China facing the sea. That part of China does not touch the sea and you have to lay cables over North Korean or Russian lands to reach the sea. It was supposedly Chinese land taken over by Russia more than a century ago. Anyway, China is unlikely to provide direct help because of the very long distance between two countries. -- Toytoy (talk) 15:14, 15 March 2011 (UTC)

You guys may have already noticed that the Tokyo Bay's opening to the sea is facing south west, shielded from the tsunami by a whole Chiba Prefecture. As a result, Japan's largest harbor and metropolitan area are protected from the quake and tsunami by the geography. If this tsunami occurs in July or August when people are going to the seas for fun, the death toll could be several times higher. The epicenter is about 400 km from Tokyo and it occurred in winter when very few people go to the seas probably saved countless lives. -- Toytoy (talk) 15:26, 15 March 2011 (UTC)

Form work of Plinth Beam or Shuttering of Plinth Beam

How to Calculate Form work of plinth beam in Running Feet. —Preceding unsigned comment added by 182.178.71.47 (talk) 20:11, 13 March 2011 (UTC)

Note: this question was also asked on the math desk. I don't understand it well enough to figure out which desk is the proper one, but whomever can offer an answer, please add a pointer to the other copy. –Henning Makholm (talk) 20:46, 13 March 2011 (UTC)

I suggest you consult a professional engineer on how to build formwork for a plinth beam. I suspect there are too many variables involved for us to be able to provide a useful (and safe) answer here.--Shantavira|^{feed me} 21:26, 13 March 2011 (UTC)

This appears to be a question concerning estimation of materials quantities ("shuttering" or "forrmwork"), rather than a structural question, but Wikipedia's not really the right place for this question in either case. Acroterion _(talk) 00:28, 14 March 2011 (UTC)

R68: Possible risk of irreversible effects

What does EU R-phrase 68 actually mean? It seems pretty vague to me. I mean, thanks to entropy pretty much everything has irreversible effects. Horselover Frost (talk · edits) 21:54, 13 March 2011 (UTC)

And there's R39, too: "Danger of very serious irreversible effects." (Somewhat less vague at least;). WikiDao ☯ 22:07, 13 March 2011 (UTC)

I think that any answer to this question would have to come from the official specification. They never define "irreversible", but it appears to refer to bodily damage that never heals, as you'd expect. -- BenRG (talk) 23:07, 13 March 2011 (UTC)

Like pulmanary scarring from enhaling corrosive vapours? Plasmic Physics (talk) 23:45, 13 March 2011 (UTC)

Relativity postulates/ Frames of reference/ Escape velocity

As we all know that the laws of physics are the same in all inertial frames of reference but since speed of light (pulse) is way way greater than its Escape velocity in any inertial frame of reference except black hole therefore shouldn't a pulse of light clock be moving freely and independent of frame of reference of spaceship or any other arrangement carrying the light clock assumably74.198.150.224 (talk) 23:03, 13 March 2011 (UTC)Khattak#1-420

There is such a thing as a light clock, but it follows the usual rules of time dilation. I'm not sure I understand your question. -- BenRG (talk) 23:09, 13 March 2011 (UTC)

Thanks for your swift response. As we all know that in order to "break free" from any inertial frame of reference (gravitational field) an escape velocity/ speed is needed. Therefore laws of physics are not the same  in aforementioned reference frames for something if at or greater than escaping speed.

Simple example

An object on the surface of earth if to be freed from its reference frame needs an escaping velocity of 11.2 km/s.

Thus if this correct then

1- A pulse emerging from top mirror in spaceship moving close to c should follow the same original downward path instead of vertical for inside and inclined for outside observers. 

2- Similarly in relativity of simultaneity the two strobe of light striking the front and rear would be the same for both inside and outside observers74.198.150.224 (talk) 04:22, 14 March 2011 (UTC)khattak#1-420.

Inertial reference frames and gravitational wells are totally different things. There's no such thing as "escaping from an inertial reference frame". -- BenRG (talk) 05:05, 14 March 2011 (UTC)

The comoving frame of an object on the surface of the Earth is not an inertial frame of reference. For example, if you're standing on the Earth, as measured in an inertial frame of reference you are being accelerated upward, due to the force exerted by the Earth's surface on the bottoms of your feet. An inertial frame of reference is the comoving frame of an object in free fall. Red Act (talk) 12:14, 14 March 2011 (UTC)

Bus travel

Is it generally safer to sit in the front or back of the bus? Imagine Reason (talk) 23:59, 13 March 2011 (UTC)

Safer from what? Crashes? Mugging? Molestation? Travel sickness? All risks combined? {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 01:34, 14 March 2011 (UTC)

Google searches generally seem to say that any forward facing seat is fine, with some people opining that the seats immediately behind the driver are safest, but none of that seems to have any statistics or any objective research behind it. This guy says that the best seat is towards the middle, though it's played more for humour. Matt Deres (talk) 02:22, 14 March 2011 (UTC)

Seats at the rear of aircraft or trains are safer, so I expect that rear of buses is also. Wear the seatbelt if the bus has one. But I think bus travel is safer than car travel. 92.15.11.100 (talk) 12:28, 14 March 2011 (UTC)

If it's 1955 in Alabama and your name is Rosa Parks then it would be less bother for everyone if you sit at the back of the bus. Cuddlyable3 (talk) 13:29, 14 March 2011 (UTC)

But Rosa did the right thing and made it difficult for everybody - for a while - and now it's a whole lot easier for a whole lot more people. The poster seems to be in London so we might need to consider upstairs and downstairs as well as front, back or middle. Richard Avery (talk) 16:33, 14 March 2011 (UTC)

Is this guy seriously referring to the civil rights movement as 'bother'. Disgraceful. —Preceding unsigned comment added by 92.20.217.50 (talk) 23:03, 14 March 2011 (UTC)

Well, Rosa Parks not sitting in the back was quite bothersome, which is precisely why it was so important and catalytic when she did it, and why she is honored for it. Yes, it would have been less of a bother for everyone had she sat in back. She probably ruined everyone on that bus's day, made a scene and a fool of herself, and made the rest of the ride awkward for everyone else.

As for bus safety in collision, though, it really depends on the type of impact that occurs. I'm not sure if the front has a crumple zone in case the driver veers off and smashes into a pole, but my bus was hit on the side by a car whose brakes failed on a snowy day, thus running a red light. Luckily the collision was relatively low-speed, but it still left a good dent at 20mph - perhaps it would have just been a jolt had it hit the bumper. SamuelRiv (talk) 08:57, 15 March 2011 (UTC)