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December 24

Balangoda_Man is homo erectus or Homo Sapien

My Question is related to the article in http://en.wikipedia.org/wiki/Balangoda_Man.

According to the article, balangoda man is homo-erectus. But it is dated 37,000 yrs ago. According to graph and the article connected to http://en.wikipedia.org/wiki/File:Humanevolutionchart.png homo erectus were extinct about 500,000 years ago.

These two are contradicting each other. Is balangoda man really a homo erectus. If yes, why wikipedia still say homo erectus extinct 500,000 years ago.

Hope I can get a good answer with new findings.

Thank you. -Achala — Preceding unsigned comment added by 69.132.64.162 (talk) 04:35, 24 December 2012 (UTC)

My reading is that it says Homo Erectus was there before Balangoda man. StuRat (talk) 04:45, 24 December 2012 (UTC)

I agree with StuRat. The article discusses other hominids found in the same place as Balongoda Man. The article, in the first sentence, makes it clear that Balongoda Man is a Homo Sapiens (anatomically modern humans are always Homo Sapiens). The discussion of prior hominids is there to provide context for earlier human and hominid settlement in the area where Balongoda Man was found. --Jayron32 04:50, 24 December 2012 (UTC)

"alkaline gargle"

I remember watching a old film from the 1920's about cruise ship illness that said to treat tonsillitis use a "alkaline gargle" every 30 minutes. What exactly is a "alkaline gargle"?, Also lets say its Sodium Bicarbonate or similar I read of Sodium Bicarbonate causing chemical burns in the mouth (http://www.casereports.in/articles/2/1/Sodium-Bicarbonate-mouth-rinse.html) and would be surprised they would use it every 30 minutes for days without harm.--Wrk678 (talk) 08:16, 24 December 2012 (UTC)

Probably a salt water gargle, probably 1 teaspoon salt to 1 pint water, gargle and spit rather than swallow. --TammyMoet (talk) 09:05, 24 December 2012 (UTC)

I dont think salt is alkaline--Wrk678 (talk) 13:38, 24 December 2012 (UTC)

Indeed! An alkaline gargle is composed of water plus baking soda or potassium carbonate. Our article on baking soda lists several home uses, but doesn't seem to mention gargles. A quick Googling brings up all manner of odd things folks gargle with, of which baking soda is far from the most dangerous. As always, it's the dose makes the poison. Matt Deres (talk) 19:46, 24 December 2012 (UTC)

Wouldn't gargling with it every 30 minutes cause a chemical burn like this http://www.casereports.in/articles/2/1/Sodium-Bicarbonate-mouth-rinse.html Also unlike sodium bicarbonate I thought Potassium carbonate is quite caustic to skin (PH 11.5) and wouldn't work for gargling.--Wrk678 (talk) 20:50, 24 December 2012 (UTC)

That would depend on the ratio of chemical to water. I threw my last link in there more as a gag, but it turns out that that's actually the important one for you to read. In the wrong quantities, anything can be dangerous to consume. In the right quantities, anything can be made safe. For example, botulinum toxin is among the most toxic substances on earth, yet it's routinely used as "Botox" treatments for reducing the signs of aging. Putting pure potassium carbonate into your mouth is a very different proposition to putting a small amount into a glass of water and gargling. Matt Deres (talk) 21:30, 24 December 2012 (UTC)

Yes, but when you are done gargling and the water evaporates the baking soda or potassium carbonate would dry on your mouth/throat and be significantly concentrated. --Wrk678 (talk) 18:35, 25 December 2012 (UTC)

The mouth is usually damp and the chemicals will normally be diluted and washed away by saliva. OR warning: In my experience, sodium bicarbonate will not normally do significant damage even if occasionally applied "neat" to an almost dry surface inside the mouth (I use it to discourage mouth ulcers because they seem to like an acid environment, but please don't take this as medical advice because there are dozens of possible causes!) though I think I've noticed a slight necrosis of the surface layer. Potassium carbonate sounds more risky. Dbfirs 22:46, 27 December 2012 (UTC)

Yes, excessively alkaline gargles should be avoided, and that's no lye. StuRat (talk) 22:53, 27 December 2012 (UTC)

calculate ph change that takeplace when 100ml of .05m naoh and .05m hcl are added to 400ml of buffer soln that is .2m in nh3 and .3m in nh4cl

calculate ph change that takesplace when 100ml of .05m naoh and .05m hcl are added to 400ml of buffer solution that is .2m in nh3 and .3m in nh4cl — Preceding unsigned comment added by 182.185.115.249 (talk) 08:50, 24 December 2012 (UTC)

Why don't you try your own homework, and let us know if you get stuck! Someguy1221 (talk) 09:38, 24 December 2012 (UTC)

Suitable conditions for ventilating a residential property to reduce humidity

Can someone help me by determining a formula that I can use to calculate suitable times to ventilate a house that gets quite damp. I'm thinking that I can't simply rely on hygrometer readings because the air temperature also affects the capacity of air for water. I want to make sure I ventilate on days that the external air has a lower water content than the internal air which presumably is more effective than relying on a dehumidifier (which we also have on constantly, removing about four litres per day). — Preceding unsigned comment added by 92.28.74.239 (talk) 14:58, 24 December 2012 (UTC)

As the weather changes from day to day, for most regions of the World, you will do better to install sensors that sense 1) the inside temperature and relative humidity, and 2) the outside temperature and humidity. The position of the sensor needto be carefully chosen and shielded from sun, reflected heat, etc. For each temperature and relative humidity, the absolute humidity (air moisture load) can be calculated from a psychrometric chart or standard formula. This can easily be programmed into a micro-controller, indeed such programmed controllers are commercially available. Run the ventilation fans whenever the outside air moisture load is less than the inside load.

Depending on the area and on the building, you may find this ineffective, as moisture will difuse back in during no ventilaton periods. It takes only a little infiltration thru cracks, door gaps, and the like, to upset this.

You will get better answers if you sign off posts with a pen-name that you consistently use. Wikipedia is a free world - you don't have to. But you will get better answers if you do. If we recognise the name, we might even do a bit of research and find some good links.

Wickwack 58.169.242.150 (talk) 16:00, 24 December 2012 (UTC)

What you should look at is the dew point. Most good weather sites will list the dew point along with the temperature and relative humidity. If you tell me where you live, I'll try to find a site which lists this info for your area. A dew point below 60°F is comfortable, so you could ventilate on those days. However, I wouldn't say you should ventilate whenever the exterior dew point is lower than the interior. For example, if the external dew point is 80°F and the internal dew point is 81°F, it's going to make very little difference. You'd do better to use dehumidifiers on such days.

Also, you can tell when it's humid out without instruments. Does it feel "sticky" ? Then it's too humid.

Finally, try to eliminate sources of humidity inside the home. If you take a shower, close off the bathroom from the rest of the house and use the exhaust fan, if you have one, or open the window, otherwise. Avoid cooking which generates lots of steam. Keep all pots and pans covered, and use an exhaust fan, if you have one. StuRat (talk) 19:28, 24 December 2012 (UTC)

Stu, the OP used the words "the house gets quite damp" - this suggests he is concerned not about human comfort but about condensation/damp surfaces. This can be a problem, causing deterioration of household items even when the temperature is low enough that humans feel comfortable even at 100% relative humidity. Further, although dew point is essentially the same thing as I described above (the air moisture load) it is gnerally inadvisable to go on the dew point as published by weather authorities, as the dew point varies locally quite a bit. For example, at the time of me writing this, our city weather authority, which measures within a City park and at the airport (both clear sites away from water and buildings) has just updated on their website the data for our area as follows: Temperature 34.2 C, Rel Humidity 29%, Dew Point 14.1 C. The actual data measured on my instruments at my house, which happens to be adjacent to a large river and is surrounded by large trees, is Temp 29.9 C, Rel Humdity 29% - this gives a calculated dew point of 10 C. Dew point sensors are not generally commercially avaliable, but temperature and relative humidity sensors are - that's why I did not mention dew point in my 1st post.

I agree with your advice about eliminating sources of humidity though. It may also be that the OP's real problem is rising damp in the building structure, seeing as we have no idea of his situation. Wickwack 60.230.194.179 (talk) 02:45, 25 December 2012 (UTC)

There might be a language difference on "damp". Here, we might say "the air is damp" meaning the humidity is high. I don't think there's any indoor temperature where 100% relative humidity is comfortable (not at normal air pressure, anyway). StuRat (talk) 21:56, 26 December 2012 (UTC)

I'm quite happy with the language point - there are a multitude of examples of where an Australian (eg me), and Englishman, and an American (eg yourself, Stu) use the same English language words in a different way. However, yes, you can feel comfortable in 100% rel humidity. The body gets rid of heat in 3 main ways: radiation, convection, and sweating. 100% rel humidity will render sweating useless, but if the air temperature is low enough, the first 2 methods still work. We sometimes get 100% rel humidity where I live, quite often at night. I personally feel quite ok at 100% rel humidity if the temperature is below 25 C, althoough if I am physically working hard, I may need it as low as around 18 C. It depends on what you are used to as well. I have a British textbook on airconditioning that states that noticeable sweating is an emergency reaction and may cause some distress. Sweating noticeably is what we do normally in Australia. Wickwack 58.164.228.63 (talk) 01:39, 27 December 2012 (UTC)

Well, you're unusual then. I can provide many sources saying that 100% humidity is outside the comfort range. Here's a few: Relative_humidity#Comfort, [1], [2]. Can you provide any saying it's comfortable, even for Aussies ? There are also a number of devices which have instructions saying the humidity should be limited to 95% (to avoid any possibility of condensation). The lacquer on my wooden floors also becomes tacky during extended periods of 100% humidity. StuRat (talk) 01:45, 27 December 2012 (UTC)

Your cited links don't actually say that humans cannot be comfortable at 100% rel hum. I can't actually think of any online references I can give. It is a fact that humdity can be 100% in certain countries, including some parts of Australia - but we live there anyway - you get used to it. I have several aircon textbooks and none would agree with me, but there is a simple reason for that - they all come from the USA and Britain. Its a bit like what they say about temperature - the British book says temperatures over 25 C may cause distress in some people, and 45 C will kill. There's places in Australia and Soudi Arabia where folk routinely work in 45 C heat (I was one of them, but take me to Alaska and I might die of cold. But folk live there too). I haven't heard of floor treatment problems, but we do have problems with mold. Newspapers and other things printed on newsprint paper tends to accumulate black spots. Things made from cadmium plated steel can rust very quickly. Wickwack 58.164.228.63 (talk) 02:28, 27 December 2012 (UTC)

"Relative humidity above 60% feels uncomfortable wet. Human comfort requires the relative humidity to be in the range 25 - 60% RH." - That seems to quite clearly say that humans can't be comfortable outside that range. If Australians disagreed, I'd expect them to have set their own standards. I think it's just you who disagrees. I can see people from different regions varying their preferences some 10% or so, but not from 60% to 100%. Also, if people lived in an area for tens of thousands of years, then they might have physical adaptations to that humidity, but not after a few hundred years. I'm also wondering if "comfortable" has a different meaning to you, like "not cause death", versus what it means to the rest of us, being the preferred humidity. StuRat (talk) 03:19, 27 December 2012 (UTC)

Certainly, "comfortable" may mean a different thing to an Australian, than it does to (say) an Eskimo. I said as much when I talked about sweating. The British very much don't like being wet with sweat. To us it's normal - you can't aviod it when working. But a point that I have been making is that humans get used to the prevaling environment. It's not a matter of evolutionary adaption, it is a matter of acclimatisation. Last week in Western Australia, there was a catastrophic example, reported widely in local and British media. A teenage son came out from Scotland (a cold country in the middle of winter) to visit his father, who has been working in Australia (a hot country now in summer) for some time. The father took the son for a long walk in approx 47 C heat. The son went into heat stress and collapsed, emergency services were called, but the son died shortly after they arrived. The father apparently had no problems. I was born in Australia of European parents. When cousins and aunts have visited, they came, against our advice, in summer, because that's when the airfares are cheap. All they wanted to do is sit around in the house and not go out and see anything, because what seems pleasantly warm to us is unbearably hot to someone who normally has to cope with snow. Immigrants usually find that by their second summer, they've largely become used to it too. It matters not a whit what European and American textbooks (and wki articles) say - that's how it is. Setting standards has nothing to do with it - you can't change the climate with a pen. Fortunately, while we get very high humidity and high temperatures, we don't generally get both at the same time, or we would be in trouble. Wickwack 60.230.192.16 (talk) 04:16, 27 December 2012 (UTC)

It seems like it should be impossible for a human to survive for long at 47 C in 100% relative humidity, but according to heat index situations like that seem to be too rare to define. I haven't looked to see what experimental data are available, however, and this being a biological issue I don't want to say "impossible" with any conviction.

Note that official HVAC standards in the U.S. are typically written up by ASHRAE, an organization of HVAC manufacturers which wants to sell equipment, and enacted directly into building codes and laws at all levels of government. This is why American cities typically sound like one big fan room, and it is more common to hear of workers being too cold in the summer than too hot. Wnt (talk) 16:16, 27 December 2012 (UTC)

I'm thinking more of the Australian equivalent of OSHA. There must be some organization there which sets health standards for the workplace. StuRat (talk) 19:20, 27 December 2012 (UTC)

As for surviving at 47°C in 100% humidity, I expect you'd need to resort to external cooling, such as drinking and pouring cold water on yourself periodically. StuRat (talk) 19:22, 27 December 2012 (UTC)

The wet-bulb temperature is what really matters in extreme cases. The article points out that a wet-bulb temperature of over body temperature means that even sitting in a shaded room unclothed with a fan, the environment warms you instead of the other way around. The relative humidity would have to be around 50% on a 47 degree day to get a wet-bulb of 37. 209.131.76.183 (talk) 20:45, 27 December 2012 (UTC)

Yes indeed. Wetbulb must be below body temperature or we cannot loose heat. Humans cannot survive 47 C and 100% rel humidity simultaneously. I never said they could, in fact I said the opposite. If you look above, you'll see that in my experince, at 100% rel humidity, I need the temperature below 18 to 25 C depending on my physical effort. Unfortunately StuRat has 2 main faults: 1) he posts without thinking first, and 2) he doesn't read too well. Australia does indeed have the equivalent of OSHA in each State, and a comprehensive set of occupational health and safety laws. But, as I said before, that is of little of no relevance to this discussion. People live in their own houses and my not afford aircon; aircon is a comparitively recent innovation anyway; people need to travel and work outdoors. No government regulation can alter that. Wickwack 120.145.59.12 (talk) 01:35, 28 December 2012 (UTC)

Wickwack's faults are way too numerous to mention them all here, but here's a few: 1) He posts personal attacks here instead of on a talk page, or better yet, not at all, despite numerous requests that he cease this disruptive behavior (and he refuses to create an account, effectively blocking others from responding on his talk page). 2) He doesn't seem to realize that a post of mine indented from and following Wnt's post is a response to Wnt, and not him. 3) He makes absurd statements like 100% humidity being comfortable for those who live in Australia, without any ability to back such statements up with sources. StuRat (talk) 03:24, 30 December 2012 (UTC)

Honestly I skimmed most of this one, seeing that it had turned into a drawn-out debate that doesn't help answer the question. I noticed that there was a bit at the end where Wnt mentioned it seemed impossible to survive at 47/100 but he wasn't sure, and I figured that since I knew the relevant facts I could at least explain why it definitely isn't possible - I didn't mean to make it seem like I thought you disagreed with any of this. 209.131.76.183 (talk) 12:31, 28 December 2012 (UTC)

Sorry if I was confusing. My reservation is only that this is biology. We don't actually know that a high body temperature from fever or physical exercise under high heat is precisely the same as that from purely external heating, or that equal internal temperature with unequal humidity is equally dangerous, or that some miracle won't occur under just these particular conditions and people suddenly start using just the right heat shock protein to survive, or even that there isn't some kind of internal air conditioning under extreme conditions, some exothermic-endothermic cycle to release heat at the skin, that scientists haven't discovered yet. With biology, you would have to literally do the experiment - lock people up in those conditions and measure time of death - in order to know for sure that that's the way it really goes. I know that's a dogmatic thing to say, but it's amazing how often people make reasonable assumptions that don't hold up. Wnt (talk) 15:29, 28 December 2012 (UTC)

Flame is matter or not

Is flame matter or merely energy ? I am confused because of two observable properties of flame: first, if we blow a flame it moves in the direction of wind (I think it is a property of matter) and second, we cannot capture or divide flame in two parts, but we can do this with matter. Sunny Singh (DAV) (talk) 15:33, 24 December 2012 (UTC)

Flame is matter. When something is burnt, various gasses and particles are produced that make up the flame. It is readily possible with the right apparatus to captue these gasses and separate them out. Also, by analysing the emitted light, the individual gasses can be identified. The red and reddish/yellow colour seen in many flames is carbon particles heated so that they are red or red/yellow hot, ie.e, are heated sufficiently to provide visible black body radiation. Various gasses give various colours. Wickwack 58.169.242.150 (talk) 15:47, 24 December 2012 (UTC)

That's a bit like saying dancing is matter, because we can confuse dancing with the body of the dancer if we do not pay attention to the semantics. Flame is probably better thought of as a manifestation of a process than as matter. — Quondum 06:31, 25 December 2012 (UTC)

I tend to agree with this view, though honestly it's an old and complicated question. I think it best put that fire is a state of transition, a self-catalyzing chemical reaction that happens to involve matter but is not defined exclusively by the mass involved but also by the transformative principles resulting from the interactions between the constituents of said matter and their innate thermodynamic properties. Now that's a far cry from a simple intuitive way of stating things, but at the same time I don't think it gets much simpler for this particular phenomena; as common as it may be in our daily lives, fire is simply not all that easy to intuitively comprehend. Snow (talk) 08:21, 25 December 2012 (UTC)

From what I've learnt: A matter is something that (need not have all the criteria):

• Occupies space. Fire does not.
• Has mass. Fire does not.
• Can change state. Fire does not.

So it is not. Hope this helps and cheers. Bonkers The Clown (Nonsensical Babble) 14:48, 26 December 2012 (UTC)

The OP asked is flame matter. Taking Bonker's criteria:-

Occupies space: Yes it does. Flames comprise heated gasses and particles and most definitely occupy space;

Has mass: Yes, the heated gasses and particles certainly have mass;

Can change state: Flames are already in the gasseous and particle state; particles entrained in flames may comprise solids (eg carbon) and liquids (e.g., partly pyrolysed and unpyrolysed liquid fuels such as hydrocarbons) that do change state by evaporation within the flame.

So, yes, flames are most certainly matter - I would have thought that very obvious. Bonkers is indeed Bonkers. Wickwack 58.164.226.231 (talk) 15:51, 26 December 2012 (UTC)

Oh yeah, yeah. I sure am Bonkers. Yes, fire is NOT matter, more of energy... As of flame, I would suppose its some form of plasma. Bonkers The Clown (Nonsensical Babble) 06:07, 27 December 2012 (UTC)

I read in "Encyclopædia Britannica 2009" that -
Matter can be defined as anything that has inertia and that experiences an attractive force when in a gravitational field. What is flame according to this definition ? Sunny Singh (DAV) (talk) 06:24, 27 December 2012 (UTC)

This definition would be more complex. The simple criteria I have listed above. It's actually arguable/negotiable. Flame could be listed as a semi-gaseous/plasma state of matter. Same debate is as to whether light is matter. Or not. It all boils down to the exact definition of matter. Bonkers The Clown (Nonsensical Babble) 06:31, 27 December 2012 (UTC)

Repeating the same false statement does not make it true. As the article http://en.wikipedia.org/wiki/Flame states in the opening sentence: A flame (from Latin flamma) is the visible, gaseous part of a fire. It goes on to say that depending on temperature a flame may comprise ionised gases, and if the temperature is high enough, plasma. Gass, Ionised gas, and plasma are of course all matter, having mass, volume, inertia, specific heat, etc. What do you think comes out the combustion chamber of a jet engine or rocket engine? If it's not matter, having mass, then there can be no reaction force, and such engines must therefore not work. Wickwack 58.169.234.153 (talk) 13:59, 27 December 2012 (UTC)

A flame is made up of matter. One cannot have a flame without matter. A flame is not a special kind of matter, because it can be made up of anything; it is merely any matter that is emitting visible frequencies of light at the moment. (All matter is emitting some frequency of light, AFAIK, well, except dark matter - I think. But in addition, the flame has to be hot because of being in a fire, I think, which narrows it down further by virtue of its history - you could assemble a "flame" by blowing cool exhaust gas through a superheated tube, but that would not be a flame, as the article defines it, because it's not part of a fire. I think...) Blow it out and the flame ceases to exist, but you can breathe in the matter that composed it. Wnt (talk) 16:06, 27 December 2012 (UTC)

A flame cannot be made up of anything though, and ice is a form of matter too, which also implies ice is matter, and there are different kinds of ices, just as there are different kinds of flame. That flames tend to exist for finite periods doesn't mean that flame or ice are not matter. --Modocc (talk) 17:38, 27 December 2012 (UTC)

Thank you guys! It is clear that flame is matter. Bonkers presented his idea about fire and said it is not matter. Is he correct ? I want only "yes or no" answer. Sunny Singh (DAV) (talk) 16:20, 29 December 2012 (UTC)

What you may want and what you get regarding yes no answers shall differ though. ;) Having built many a campfire, I'll point out that the answer is context sensitive. In other words, yes or no. If referred to as a process or an event it is not matter, but it can also be referred to as an object as in one of my fires that is nested between a few rocks, therefore its matter. As an object, the fire, has the mass-energy of matter. Conversely, fire typically refers to combustion, which is a generic description of related processes (such as when my clothes were on fire because I had backed into a candle that was on a window sill!). -Modocc (talk) 17:26, 29 December 2012 (UTC)

I'll try and make this clear one more time. Sunny Singh asked is flame matter?. Yes, it most definitely is. Bonkers talked about fire. Fire is not flame; it is a collective concept that incorporates flames and fuel. Both have mass etc and are matter. The process that others have talked out is combustion - matter seems not a concept applicable to a process. Combustion however is is not fire; as fire is something that incoporates one sort of combustion, and when it does, the combustion part is not the whole fire. Thus, the answer is: No, Bonkers was not correct. Wickwack 120.145.67.99 (talk) 02:54, 30 December 2012 (UTC)

The point you made that a flame is matter was clear enough, however I've pointed out that the term fire can refer simply to combustion. The terms fire and combustion are often synonymous, not always, but frequent enough. For instance, if residual combustion is occurring in the ashes of the fireplace without any flame then the fire (or merely the combustion) is not extinguished. Its because combustion is a process and is not matter, that if Bonkers was to refer to my shirt burning incident as that of me being on fire (as an action, as in the process of burning), then that is as correct as the alternative description of my incident being just one of many fires. Modocc (talk) 15:07, 31 December 2012 (UTC)

Fire in absence of oxygen

Sun is the hot burning ball of fire. If this statement is correct, then my question is reasonable. Oxygen is a necessary condition for fire, but around the sun there is almost vacuum and sun is a ball of fire. Without oxygen how this fire is sustained. Sunny Singh (DAV) (talk) 15:55, 24 December 2012 (UTC)

It's NOT fire. The sun glows due to nuclear fusion. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 16:05, 24 December 2012 (UTC)

The glow at the surface at the sun is purely thermal and has nothing directly to do with nuclear power. This is exactly the same general sort of glow that old Incandescent light bulbs have. They use electricity to generate heat and then glow because of the heat. The switch to LEDs moves us much closer to a direct connection from electricity to light. Old Sol will continue to glow as a White dwarf long after it has stopped fusioning. Hcobb (talk) 16:22, 24 December 2012 (UTC)

And where does that heat come from? Nuclear fusion. (BTW, the switch is to CFLs, not to LEDs.) Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:31, 24 December 2012 (UTC)

(ec)A link to Black-body radiation might help complete the link between nuclear fusion and the glow described above. in my home we've already replaced a few of our incandescent bulbs with LEDs - and a few CFLs with LEDs; LEDs do provide a tighter connection between electricity and light. -- Scray (talk) 20:01, 24 December 2012 (UTC)

Some small part of that heat is still from the gravitational formation of the sun. Hcobb (talk) 19:55, 24 December 2012 (UTC)

First of all, oxygen is not always needed for burning. You think it is because it's a very common element and very powerful oxidant. Fluorine can burn bricks and water without a spark--see this video.

As for the Sun, nuclear fusion occurs in its core, and the energy is carried as gamma photons across the radiation zone. This takes about 200,000 years. When it reaches the convection zone, the heat is carried by convection, meaning "it touches something hot, so it gets hot". The convection zone glows, as other people have said, due to blackbody radiation, just like how iron in a blacksmith's furnace glows. --140.180.249.194 (talk) 21:06, 24 December 2012 (UTC)

Actually, convection means "hot gases rise, cold gases fall" -- same reason why a hot-air balloon ascends even with a heavy load. "It touches something hot, so it gets hot" would be conduction. 24.23.196.85 (talk) 01:06, 25 December 2012 (UTC)

I think what he means is that the gamma photons are absorbed by the ions in the convection zone, which become hot and move outwards, towards the surface of the sun. This heats the photosphere at the surface, which glows as a result. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:57, 25 December 2012 (UTC)

• Shouldn't someone have mention combustion by now? How about plasma? μηδείς (talk) 20:56, 25 December 2012 (UTC)

You just did. These things take time. Relax and enjoy the kudos. -- Jack of Oz ^[Talk] 07:04, 26 December 2012 (UTC)

I have never actually had one. Do they still even market them? μηδείς (talk) 01:36, 27 December 2012 (UTC)

Indeed, our articles define fire specifically as oxidation, flame and conflagration in terms of fire. I wonder if there's some exothermic reaction that looks like a fire that doesn't actually involve redox? But I can't think of one. However, I have no idea whether the OP speaks another language in which the common word counterpart to "fire" is not defined so specifically in scientific terms. An acid test is to look at a plasma globe - the Sun is described the same way as that stuff is, since both are plasma heated by non-chemical means. Wnt (talk) 15:56, 27 December 2012 (UTC) I actually looked up and found wikt:κῦδος from the 5th century B.C. Attic Greek. Kudos (granola bar) was made from 1986 to at least 2006.

Is the electric field a side effect of the Pauli exclusion principle?

Consider two electrons. We have two different reasons why these cannot be squeezed into the same overlapping state. The Electric field shows that it would take an infinite amount of energy to move two point particles each with a -1 electron charge into the exact same spot and the Pauli exclusion principle states that two electrons must differ by at least one quantum number.

So is electrical repulsion simply a distributed application of the exclusion principle? I.e. is it the exclusionary interaction of the fringes of the wave packets what causes like charges to repel each other? Hcobb (talk) 20:20, 24 December 2012 (UTC)

No. The electrical force is completely independent of the Pauli exclusion principle. Both behaviors happen to affect electrons, but otherwise they are not related. Dragons flight (talk) 22:05, 24 December 2012 (UTC)

To put the question another way, what changes would be needed to Exchange interaction to produce an effect that at the classical limit behaved like electromagnetism? Hcobb (talk) 04:29, 25 December 2012 (UTC)

Just to set something straight: The Pauli Exclusion Principle doesn't really say anything about charged point particles occupying the same point in space. The PEP operates on a completely different model of what an electron is. The PEP merely says that two fermions cannot have identical quantum states. The first thing about the quantum model of particles is that particles don't have a defined precise location, so it isn't meanigful, in the world where Pauli operates, to think of an electron as a little point of electric charge sitting around. You're describing two different models of what an electron is, and there isn't a lot of crossover between them. --Jayron32 04:55, 25 December 2012 (UTC)

And to possibly answer your question a little more, there is no way in which one could interpret the PEP such that it remotely behaves like an electric field. For example, two electrons repel each other electrically, regardless of spin (though magnetic effects do depend on whether they are parallel or antiparallel). The PEP changes completely depending on spin being parallel or antiparallel. A further point of interpretation: there is no field (and hence force) generated by the PEP. The only force associated with the PEP should be interpretated as momentum exchange carried by the electrons (i.e the wavefunction), not by an intermediary force field. One would never expect to be able to produce any kind of classical limit that agrees. — Quondum 05:15, 25 December 2012 (UTC)

The wrinkle that might make this work is applying exclusion to all the virtual electrons between the two real charged particles. It's just at the classical limit that the Dirac sea would produce the classical electromagnetic field. Close up things would behave in a more quantum manner. Hcobb (talk) 08:41, 26 December 2012 (UTC)

I fail to see how. What you are suggesting attempts to attribute charge and electrostatic force to the PEP, and thus the idea of the particles being charged in the first place cannot be used. And you would not expect to obtain electrical attraction between positrons and electrons, and would also not expect electrostatic interaction between particles of different types. Fermions of the same type, e.g. neutrons would be expected to repel each other. Besides which, you would have to find a wavefunction for the fermion field that produces the correct expectation value for energy–momentum transfer (i.e. the electromagnetic stress–energy tensor, giving positive, negative and shear pressure of the electromagnetic field). The long-range transfer of momentum requires quite a definite momentum density, which has to propagate at the speed of light; not great for massive transmitting force via their own momentum, virtual or otherwise. Magnetic fields seem to be utterly inexplicable through this mechanism. "might make this work" is being rather optimistic. — Quondum 18:22, 26 December 2012 (UTC)

Highest altitude for manned post-Apollo mission

What is the highest altitude reached in human spaceflight in the last 40 years? The closest I can find in List of spaceflight records is the 1374km altitude record (set in 1966) for a non-lunar mission. Dmytro (talk) 22:21, 24 December 2012 (UTC)

In case you didn't notice, this list specifically excludes lunar missions -- for obvious reasons, the "altitudes" reached in those missions were so high that Earth's gravity field was no longer dominant, therefore the whole concept of "altitude" defined as distance from Earth becomes kind of nebulous in these cases. FWiW 24.23.196.85 (talk) 00:59, 25 December 2012 (UTC)

I think the Hubble launch and service missions. Which one was highest I am not certain. Rmhermen (talk) 02:29, 25 December 2012 (UTC)

I looked at the Hubble Space Telescope shuttle missions, and the highest altitude appears to be around 620km in STS-82 (1997) as confirmed here. Most of that mission was at a lower altitude, but after servicing, Hubble Space Telescope was boosted to its highest altitude ever. Still, this is slightly less than one tenth of Earth radius and is less than 0.2% of Earth-Moon distance, and the lack of higher flights is one of the most remarkable regressions in the history of human exploration. Dmytro (talk) 04:17, 25 December 2012 (UTC)

One should perhaps not be too quick to use lack of manned missions as a criterion of regression in human exploration. The advances in unmanned exploration often make the same amount of effort go so much further in terms of exploration that only a romantic would define progress in terms of manned missions. Far more realistic criteria would be the annual investment in exploration, the amount of support that new exploration enjoys, and the extent of new knowledge gained from exploration. I'm not saying that there has not been regression by these criteria though. — Quondum 09:59, 25 December 2012 (UTC)

December 25

Acetone

I used Acetone in my car. The vapors are so strong that it has irritated my eyes. Is there a vapor suppressing foam I can buy. Do you know any retailers selling this? Is there anything else I can use. What else can I do. Thanks — Preceding unsigned comment added by 174.111.55.161 (talk) 02:45, 25 December 2012 (UTC)

Open doors and big fan for a day or two. --Jayron32 02:47, 25 December 2012 (UTC)

You didn't learn from when you had this problem last year? DMacks (talk) 05:55, 25 December 2012 (UTC)

Twice. --ColinFine (talk) 23:20, 28 December 2012 (UTC)

Or are you saying you can still smell it 16 months later ? StuRat (talk) 06:13, 25 December 2012 (UTC)

Nothing new under the sun, huh? Any chance Keeeeeeith is baaack? μηδείς (talk) 20:55, 25 December 2012 (UTC)

surface tension

why is there a colouring change when soap is reacted with milk? — Preceding unsigned comment added by 117.196.135.236 (talk) 16:40, 25 December 2012 (UTC)

What color does it change into? 76.23.194.179 (talk) 17:16, 25 December 2012 (UTC)

Ordinarily, milk is coloured white because of the Tyndall effect. When soap is added, the colloidal particles are fully dispersed. Plasmic Physics (talk) 20:37, 25 December 2012 (UTC)

balloons and fire

direct contact of a blowed balloon with fire can burst that balloon but when that balloon filled with water show to the fire it does not burst . why ? — Preceding unsigned comment added by 117.196.135.236 (talk) 16:48, 25 December 2012 (UTC)

Gases expand greatly when heated. For most situations, gases are governed by the ideal gas law: pressure(P) * volume(V) = number of gas particles (N) * boltzmann constant(k) * temperature(T). Or given a certain pressure (gas in a balloon will expand until internal pressure equals atmospheric pressure), V = N*k*T/P. If you heat a gas by flame, it will expand so much (the temperature will increase rapidly) that the balloon will burst. Water does not expand that much when heated, in fact it has a very high heat capacity. You have to convert the water into gas (i.e. by heating at 100C) to burst the balloon. 76.23.194.179 (talk) 17:15, 25 December 2012 (UTC)

I think what's more relevant is the heat capacity of the water inside the balloon which prevents the skin of the balloon from so quickly reaching melting point. I have never seen a balloon expand first before exploding due to a flame, which is what you are implying, IP 76, would happen. μηδείς (talk) 20:54, 25 December 2012 (UTC)

Once, my high school chemistry teacher filled a balloon with hydrogen gas and set the balloon on fire. It did not burst until the balloon burned through, igniting the hydrogen. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 07:22, 26 December 2012 (UTC)

Another example that illustrates the heat capacity explanation of μηδείς is a burning candle standing in cold water: you should be able to get it to burn down a little way below the water surface level protected by a thin-walled cylinder of unmelted wax. — Quondum 07:37, 26 December 2012 (UTC)

I agree with Medeis - another common demonstration is placing a paper cup over a candle or bunsen burner. The water absorbs heat from the paper quickly enough that the paper doesn't ignite. You can actually bring the water to a boil this way. This is clearly the same kind of effect you describe, and the expansion of the water or air has nothing to do with it. 209.131.76.183 (talk) 18:01, 26 December 2012 (UTC)

You can boil water over a camp fire in a plastic soda bottle. Vespine (talk) 22:05, 26 December 2012 (UTC)

In fact, with a little skill, you can even melt lead or tin in a paper crucible... 24.23.196.85 (talk) 01:11, 27 December 2012 (UTC)

Those are three interesting demonstrations none of which I have ever seen done. μηδείς (talk) 01:33, 27 December 2012 (UTC)

Interesting idea. I found [3] which makes no big deal of it. Indeed lead has melting point 621.43 F, which is greater than the legendary 451, but I haven't looked into the details. Wnt (talk) 15:47, 27 December 2012 (UTC)

Actually, Bradbury was wrong -- paper burns at 451 Celsius, not Fahrenheit. (Which doesn't negate his main point about the negative effects of censorship.) 24.23.196.85 (talk) 00:53, 28 December 2012 (UTC)

tests for reality

What are some philosophical and scientific tests to help verify that reality is real, i.e. what we perceive is not an illusion? I know a recent one mentioned in the news is some big particle physics experiment or something. 76.23.194.179 (talk) 17:19, 25 December 2012 (UTC)

There are no scientific tests to prove to yourself that you are real. It's one of those things you need to take on faith. Philosophically, it's a question almost as old as philosophy itself. Different philosophers have approached the question in many different ways. Plato had the Allegory of the Cave for example. Rene Descartes took the rather pragmatic "cogito ergo sum" as his approach. If you want the philosophical end of being and existence, you'll want to look into the well-mined field of Ontology which deals with the question in some detail. --Jayron32 17:53, 25 December 2012 (UTC)

Claiming that we are in a simulation can exclude all arguments "pro-reality." Everything that you perceive, feel or think is simply part of this simulation. It's like the belief in god, everything that point towards a materialistic universe without a god is simply the wish of god. OsmanRF34 (talk) 20:35, 25 December 2012 (UTC)

Email me next time you're in New York. I'll come slap you up the head. You can tell me whether it's real or not. (Hopefully you aren't upset by not really being slapped upside the head.) μηδείς (talk) 20:51, 25 December 2012 (UTC)

This is the classic Johnsonian argumentum ad lapidem - the slapping may _feel_ real, but how can the slappee know that it _is_ real? Tevildo (talk) 21:17, 25 December 2012 (UTC)

Ask yourself how a brain in the vat, receiving the same inputs as your brain, would perceive the world any differently. (Answer: it wouldn't.) Contrary to what Jayron says, you don't "take on faith" the assumption that reality is real; you admit that you don't know. That may be hard for people who usually make up what they don't know, but if you don't know, then you don't assume anything.

That said, people have tried to make various arguments about why it's unlikely that we're brains in vats. Most of them reduce to Occam's razor. If we're brains in vats, there must be an external reality in addition to the reality that we experience, with intelligent beings who have the motivation to put brains in vats. Since this scenario is far more complicated and has no more explanatory power, we assume we're experiencing reality. --140.180.249.194 (talk) 21:48, 25 December 2012 (UTC)

There is no difference between taking something on faith and admitting that you don't know. They are two perfect synonyms for the same concept. In either case, you still need to operate as though what you perceive is reality. Either you admit you don't know, but you behave as though it were real, or you accept on faith that it is real. It amounts to the same thing. --Jayron32 23:06, 25 December 2012 (UTC)

The solution is simple. Define what is real by setting some simple parameters and conditions. If something passes those tests, it's real for the purposes of the definition. If it doesn't, it's not.

Now, whether these supposedly real things are really real ... well, who gets to say? It's all subjective. There isn't any such thing as objective reality. If you don't believe me, please provide one counter-example. That's all it would take. Nobody's ever succeeded, and they're never going to, because whatever we know of anything in the universe is what our senses tell us. Those senses are essential for us to perceive or know anything, but they also act as a barrier between us and those things. We can never know those things directly, extra-sensorily. Those things include everything about ourselves that we assume to be real. Descartes might have had a point with his "cogito ergo sum", because it's hard for a non-existent entity to think. But how do we know we're thinking? How do we know a rock or a tree don't think? What is thought, anyway? Do we get to decide what thoughts we have, or are we victims of "some vast eternal plan"? Does the universe really exist? Who could ever provide definitive and incontrovertible answers to these questions? Nobody. Doesn't stop us asking the questions, though. We're left with what we can perceive, and we try and work with that. It seems to be enough for most people. -- Jack of Oz ^[Talk] 22:38, 25 December 2012 (UTC)

I don't know which "big particle physics experiment" you're referring to - but it doesn't matter what it said because it can't possibly prove the existence of "reality" for any individual because you can't know whether the report of it that you thought that you read is "real". It's only your senses that report that this is what it said - and you know that you can't trust those senses. Truly, the only thing that gives you even a hint of a solution is something vague like Occam's Razor. The simplest and most practical and useful thing you can do is to assume that your senses are telling you the truth - until such time as it's proven that they are not.

I'd also like to suggest that it quite literally doesn't matter. So long as it's all consistent and your actions produce results in this seeming reality that seem correct, what do you care if we're really just brains in jars or a part of some alien intelligence's computer game? You still need to do the same things to avoid unpleasant feelings of hunger or thirst - your drives are still "real" to you and need to be attended to.

Conversely - we might find some strong pointers showing that the universe might truly be a simulation running in some mega-computer in the "real" universe. I'm spent my career as both a game programmer and a simulation programmer. It seems quite striking to me that there are a number of things that we observe about our universe that make it seem to have properties very much like the restrictions that a simulation might have:

1. Quantum theory. When you look at the very smallest things - their behavior is random and quantized. In a finite precision computer, that's exactly what you'd expect. There would be randomness due to things like roundoff error and because of that finite precision, you'd see quantised behavior in all sorts of very small system. Old flight simulators from the 1980's used to have a precision of 1/256th of a foot - if you lived in that simulation, you'd say that the laws of physics quantised all distances to a "plank length" of 1/256th of a foot and invent complicated 'laws of physics' to explain that.
2. Relativity. It's very convenient for the simulation for there to be a finite speed of light and a universal speed limit. It constrains the amount of the universe that you'd have to simulate with great precision and covers up the effects of latency between computers simulating different parts of the universe - and it also prevents humans from spreading outwards beyond the region which is simulated at high fidelity into further reaches of the universe where the computer could do a more sketchy simulation and not have to track ever single fundamental particle.
3. The Big Bang. That's a very convenient way to hide the finite nature of time. You can't have the simulation running forever - it has to have a fixed start time. It has to be impossible to see what happened before that time - and starting things off as a singularity makes a lot of sense. This also imposes a limit on the size of the observable universe - which, again, is handy if your computer has finite memory.
4. Why there is so little matter in all of this vacuum. Building your simulated universe like that allows you to have a vast universe with much less computational effort than if it were mostly full of matter.
5. Entropy. Highly organized systems take a lot of simulation time - allowing things to degenerate into low grade thermal 'noise' keeps the simulation within reasonable bounds. If the system became more organized as time passed, the simulation computer would start to run more and more slowly.

SteveBaker (talk) 04:01, 26 December 2012 (UTC)

Steve, none of this makes any sense. Quantum mechanics is not cheaper to simulate; it seems to be impossible to simulate a quantum system on a classical computer without exponential slowdown. Even accurately simulating a single proton is far beyond the ability of any supercomputer. The enormous cosmos we find ourselves in could be eliminated without any practical effect on our lives. Those vast reaches of space are not empty, but filled with CMBR photons, which are not quite randomly distributed but show a slight anisotropy, first seen with COBE, which has been faithfully preserved for billions of years. The universe was not made on a budget. -- BenRG (talk) 17:19, 26 December 2012 (UTC)

I'm not saying that quantum mechanics is simpler to simulate - I'm suggesting that it's an artifact of any simulation on a finite precision computer that you'll see quantisation and other bizarre behaviors if you look on a small enough scale. Of course simulating even a tiny piece of our universe (like one gram of water) is insanely far beyond what any technology we can imagine could to - but remember that the laws of physics out there in the "real" universe could (and almost certainly would) be very different from our own - perhaps there is no speed of light limitation? That would perhaps allow computers to be very much faster than they are in our universe and (conceivably) make simulating vast numbers of fundamental particles - even with quantum mechanics - a fairly simple business. I don't know (obviously) - but it seems to me that some of the stranger things that we find when we look hard enough could be revealing "bugs" or "artifacts" that might reveal the likelyhood that we're being simulated. SteveBaker (talk) 04:07, 27 December 2012 (UTC)

I think that makes a lot of sense, Steve. Actually the real universe could have supercomputers more vast in power than we could comprehend. Their laws of physics... Everything there could be different. We cannot compare what we can do here with what the "real" God-like simulators could. This would explain a lot about our random and mysterious universe. See simulation hypothesis. But even if we were really being simulated, what can we do? Life, whether simulated or not, will still continue. The universe is an enigma, indeed. Bonkers The Clown (Nonsensical Babble) 06:17, 27 December 2012 (UTC)

You still seem to be missing the fact that it's enormously harder to simulate a quantum world than a classical world. Quantization in quantum mechanics has no resemblance to the sort of discreteness you find in a computer. The state of a quantum computer is represented not by integers but by a vector in a complex vector space whose dimension is exponential in the number of qubits. Roundoff error loses data, and data loss at a fundamental physical level would violate the principle of unitarity which is an indispensable part of quantum mechanics. The idea that our world was designed for ease of simulation is idiotic. All evidence suggests exactly the opposite. -- BenRG (talk) 08:12, 27 December 2012 (UTC)

Go easy there. Both sides are making unjustified assumptions, presumably drawn from empirical experience. The so-called probabilistic nature of quantum mechanics does not suggest round-off error at all, but any observation of "glitches" (never observed) would indeed be interesting evidence in this direction. On the other side, to assume that the quantum world is inherently "too complex" for simulation, or that that the "parent reality" even has a time dimension is not justified. A simulation would only need to process the amount of information required to describe a quantum system, which rather counterintuitively does not grow by volume but rather by the surface area of a volume, thus making large systems more efficient to "simulate". — Quondum 09:53, 27 December 2012 (UTC)

@ Tevildo, it's called not the argumentum ad lapidem but the corollary argumentum I'd've slappèd 'im. And it;s hardly a fallacy. μηδείς (talk) 06:41, 26 December 2012 (UTC)

It is a fallacy, as you're not addressing the question, merely making the assertion "It's obvious that reality is real." If we define truth as "Whatever is obvious to Medeis" (or Dr Johnson), then our work here would be a lot easier, if a lot less useful. SteveBaker, as always, has provided an excellent answer - science can't address the general metaphysical question (our article noumenon covers it reasonably well) , but science can address the question "Is the world we percieve a simulation running on a computer in a world with the same characteristics as ours?" Tevildo (talk) 22:45, 26 December 2012 (UTC)

No, it's not a fallacy (not necessarily) unless one assumes that statements are only ever grounded in other statements, not physical/perceptual evidence. It's actually the request to prove reality which is fallacious, since an independent proof would have to be based on something outside reality. Aristotle recognized the futility of such questions, and I have long had the quote of him saying so at the top of my talk page. μηδείς (talk) 01:31, 27 December 2012 (UTC)

• (Not an answer, just a verbose and speculative exploration of the question; note that some of the first part follows on The Mind's I which is the most useful reference work I can think of and spoke of replacing neurons in the brain in a vat by a computer, a choose-your-own-adventure type book, etc.) It occurs to me that if the underlying algorithm of a "brain in a vat" were understood, i.e. that the actual data being "sensed" by "consciousness" could be defined as bits of information, then you could collect all the possible sequences of bits that could be sent to it and lay them out in a numerical table of all the experiences - not just sensory information but memory and belief as well - which any conscious being could ever possibly have. If so, you have a one-to-one mapping between every possible conscious experience and a number, and the laws of physics, any physics, in any possible parallel universe we can imagine (i.e. our method of consciousness, whatever that is) can be laid out as functions which successively map a series of numbers. In this way it would appear that all experiences are real in that they are all mathematical functions which eternally and immutably exist in the sense of any mathematical function. And yet ... we have the sense that not only is there one present but one past, i.e. that one possible physics is more important than the other. Is that merely the sensation of memory and specifically memory of rules, part of the premise for a given moment? What is the difference between such a number as it exists as any number, or when it is written down, or when it is encoded in flesh? Why is the experience of neurons as they fire a kind of 'consciousness' but not the experience of water as it reaches a rolling boil? (or is it?) I suspect that that our religion of causality is not actually based on any fact, that precognition is an important and dangerous phenomenon, and that its carefully regulated expression in the brain permits the effective creation of information via paradoxes, and its time inverse permits the destruction of information, and that these processes define the one and only consciousness, which is shared between all and only seen as distinct from one person to another due to the limitations of the input data. Wnt (talk) 05:19, 27 December 2012 (UTC)

• In case anyone here finds themselves a bit lost, this is a science reference board, not the whatever unlikely fantasy dreamland might exist board. Proofs of reality are far more than just subjective claims, otherwise some smart rocks might be deluded and still be insisting that other rocks have thoughts and that the world is flat and perched atop some animal's back despite some rather adequate evidence against these intriguing notions regarding the existence of even larger flat rocks. Thus, sometimes even sacred cows get burnt occasionally and, like marshmallows, can taste rather bittersweet when done. Yet despite how exceedingly difficult it might be at times to comprehend reality though, there is from within the unvarnished bowels of our esteemed wiki the article on scientific realism. Also, the OP eluded to a recent notable science experiment, which is probably the discovery of a particle believed to be the Higgs boson. --Modocc (talk) 14:37, 27 December 2012 (UTC)

Is the ability to fart in a controlled manner a rare talent or a mundane skill?

Both Flatulist and Flatulence remain silent on the matter. Is the ability to control one's abdominal muscles like this really incredibly rare, or is it a skill which can be achieved through experimentation and practice (at least in principle) by any average person – just like, say, belcanto technique (which doesn't require extraordinary talent to master, as far as I've been told, unless you wish to pursue it on a professional level; it's just really tricky because the muscles involved are so small and numerous and your teacher can't show you directly the way they move them or guide you, the same reason why it's relatively easy to teach a chimp hand gestures/signs since you can shape their hands the way you intend them to move, but talking, no way: same problem with the muscles in your abdomen) –, but that simply hardly anyone bothers to try to learn? Perhaps the real reason why flatulists are so rare is that people believe that you "just can't learn that", you've got to be a freak of nature? --Florian Blaschke (talk) 21:50, 25 December 2012 (UTC)

Le Pétomane indicates that he had some innate ability that was developed through practice. That is, his ability to take up and expel both air and fluids through his anus was something that was inborn, and over time he developed the inate ability into an entertainment act. --Jayron32 23:03, 25 December 2012 (UTC)

So it's like being able to wiggle your ears, except much, much rarer? And you are saying that the overwhelming majority of humanity are just innately completely unable to control these anal muscles (the sphincter?) consciously (at least this precisely)? Making Le Pétomane a genuine freak of nature? OK, but how about the medieval flatulists? The quote from Piers Plowman sounds as if the level of ability a medieval flatulist needed was not all that rare, at least. So perhaps Le Pétomane is not the best example of a flatulist because his case is too extreme/unique.

By the way, Le Pétomane is already halfway there compared to the freak which Knorkator describe in their song Ich bin ein ganz besond'rer Mann, because that man is not only able to suck liquids and other objects into his anus, but even drink and eat with it. Hilarious and brilliant. --Florian Blaschke (talk) 04:11, 26 December 2012 (UTC)

I would not conclude that it innately unachievable in general. There are numerous examples of potential coordination skills that are never practised by the vast majority of people and thus seem unattainable. Those that are never practised tend to atrophy (both the neural and muscular aspects). Like squinting, winking, raising an eyebrow, moving your eyes independently (cameleonlike), riding a bicycle, concious heart rate control etc. – with dedicated effort many of these skills can be acquired later in life, and would probably be acquired naturally if taught/observed from birth or early childhood. I have heard anecdotally of a a sect/group that learns rectal cleansing using this kind of control, which would suggest that this is just another skill that can in principle be acquired by a majority given sufficient effort. — Quondum 07:05, 26 December 2012 (UTC)

Thank you for confirming my suspicion. That's exactly what I was thinking. --Florian Blaschke (talk) 16:31, 28 December 2012 (UTC)

You can't teach a chimp to speak because they lack the equipment to do so. StuRat (talk) 06:57, 26 December 2012 (UTC)

Citation needed. They do not lack the necessary organs or neural pathways, so their inability is not a matter of principle; if anything, they lack the dexterity, which was exactly my point. See Viki (chimpanzee). --Florian Blaschke (talk) 16:37, 28 December 2012 (UTC)

I took the StuRat's comment to refer to the physiological equipment: "chimpanzees are not able to produce the sounds that make up human speech" as it says in the article you cited. This is not just a matter of dexterity, but also the shape of their vocal tract, which cannot produce many of the vowels (and disctinctions of vowels) found in Human language. IIRC Eve Spoke, by Philip Lieberman goes into this in some detail. --ColinFine (talk) 23:42, 28 December 2012 (UTC)

Exactly. Humans seem to have evolved different equipment specifically to support speech. StuRat (talk) 04:16, 29 December 2012 (UTC)

December 26

rare and hazardous research chemicals

Name a few chemicals that are hazardous, used rarely and applied for novel research purposes (ex:certain toxins that are researched in very few laboratories against deadly unusual microbes). — Preceding unsigned comment added by 213.120.141.254 (talk) 06:07, 26 December 2012 (UTC)

Is that what your teacher asked you to do on your homework? -- Jack of Oz ^[Talk] 06:58, 26 December 2012 (UTC)

nope. I am aware that advise and homeworks are not discussed here. — Preceding unsigned comment added by 213.120.141.254 (talk) 09:14, 26 December 2012 (UTC)

If it looks like homework, sounds like homework, smells like homework, it probably is homework. You've asked a question in a way that probably 1000's, even millions, of chemicals, toxins, virus particles, and other substances might qualify. And it should be easy to think of a few if you give it a moment's thought - a few more moments' thought might suggest some words to google. Why don't you just run your eye over the periodic table and look up a few promising elements? Some of the high weight elements have only been synthesied in one or two labs at considerable effort just to get a few atoms. If you narrow it down a bit what you want to class as rare, and tell us what steps you have taken so far to find out, i.e., show us you are not just lazy, we might feel more inclined to do a bit of digging for you. Floda 58.164.226.231 (talk) 11:11, 26 December 2012 (UTC)

Except that those superheavy elements are not really used for what your question seems to classify as novel research purposes – there's not much time to do much with them before they decay, given their short half-lives. Pure research is more like it. Double sharp (talk) 13:49, 26 December 2012 (UTC)

• my favorite Brevetoxin --Stone (talk) 11:27, 26 December 2012 (UTC)

This blog[4] is a source of wonderful stories about chemicals that no sane person would handle, usually because they're explosive, corrosive, or incredibly smelly - all backed up with references to actual research that has used them. AlexTiefling (talk) 10:14, 27 December 2012 (UTC)

Bacterial infection before antibiotics

I know before the discovery of antibiotics, herbs were used to treat bacterial infection. Is there any information available about the success rate of this treatment? --PlanetEditor (talk) 09:24, 26 December 2012 (UTC)

I'm not aware of any quantitative information, but the basic answer is: dismal. No herbal treatment comes anywhere close to penicillin. For superficial infections, the most effective primitive treatments are probably either licking the wound (saliva is a pretty potent antibiotic) or spreading honey on it. Looie496 (talk) 16:18, 26 December 2012 (UTC)

Or Maggot therapy. Ruslik_Zero 18:53, 26 December 2012 (UTC)

Or putting a poultice of moldy bread on it, as the ancient Greeks had done (but that is actually a primitive form of antibiotic treatment, they just didn't know it at the time). 24.23.196.85 (talk) 01:08, 27 December 2012 (UTC)

Researching it takes me to links about how we are almost back to the pre-antibiotics era (due to superbugs). Maybe we will have to use greatpa's antibiotics again. OsmanRF34 (talk) 22:09, 26 December 2012 (UTC)

Train related engineering questions

1) Is it possible to increase train speed by doubling current train width?

2) Why China reduce its train speed from 350 to 300km/h, does reducing the speed by 50km/h also increase the train safety? Why?

3) What's the main propulsion inside fast train? Electric motor?

4) With current technology, is it cheaper to build a bridge or a tunnel below sea? roscoe_x (talk) 14:51, 26 December 2012 (UTC)

I numbered your Q's for ease of response:

1) Doubling width does not automatically allow for an increase in speed. In fact, you want to minimize cross sectional area (≈height×width) to reduce drag.

2) Any decrease in speed increases safety, since it reduces the chances of a crash and also the severity.

3) There are a variety of propulsion systems used, but the best choice, IMHO, is to not have any engine on-board, and instead deliver energy using the tracks, as in a mag-lev train.

4) A bridge is cheaper in shallow water, and a tunnel in deep water (due to the height of the supports needed for a bridge). StuRat (talk) 21:42, 26 December 2012 (UTC)

1) Widening does indeed allow for faster turning.

2) Operating below maximum speed is standard practice, as it allows trains to make up time following delays.

3) High Speed Trains generally use electric motors. Delivery of propulsion from the track, as is proposed above, would incur absurdly large infrastructure costs and is not a sensible proposal for a large network.

4) A bridge is cheaper for crossing water. Building a tunnel under deep water requires a deep tunnel which is also absurdly expensive. A tunnel is used for going under mountains or the like. — Preceding unsigned comment added by 92.11.76.114 (talk) 23:38, 26 December 2012 (UTC)

1) Perhaps, if you mean wider and shorter. But wider and proportionally taller doesn't help.

3) You need to read up on maglev trains: [5].

4) The cost of building tunnels under deep water rises more slowly with additional depth than the cost of bridges does. Hence the Chunnel, as opposed to a bridge. StuRat (talk) 23:43, 26 December 2012 (UTC)

2) Per High-speed rail in China#Corruption and concerns, the official line is that "This was in response to concerns over safety, low ridership due to high ticket prices, and high energy usage." Suspicious people (like me) speculate that it is because of corruption in the construction that may compromise safety. Clarityfiend (talk) 22:21, 26 December 2012 (UTC)

1) The main problem with doubling width is that it would necessitate a change in loading gauge, and almost certainly in track gauge. High speed trains run on regular tracks at least part of the time, if only to be taken for servicing and so on. And I understand that the Chinese authorities are trying to increase the adherence to Standard Gauge throughout Eurasia, to try and let their own network link up with other nations', and thus enable truly transcontinental trains. As Russia currently uses Russian Gauge, as do many ex-Soviet nations, that's quite a challenge. Introducing a variant gauge just for high speed would certainly over-complicate the task. AlexTiefling (talk) 00:08, 27 December 2012 (UTC)

I remember that according to one of Albert Speer's books, Hitler had a plan for trains twice as large in every dimension which his underlings, citing similar concerns, politely convinced him to defer until after he won the war. Wnt (talk) 00:17, 27 December 2012 (UTC)

Stalin had no such inhibitions - see 4-14-4. Tevildo (talk) 00:43, 27 December 2012 (UTC)

1) I recommend you read up on Brunel's seven-foot gauge.

4) Unless built over very shallow water, a bridge is very limited in its maximum span compared to a tunnel, due to requirements for intermediate supports.

24.23.196.85 (talk) 01:33, 27 December 2012 (UTC)

One of the practical limits on the speed of passenger trains on existing track is the lateral g-forces exerted on them in corners. Hence the two ways to increase speeds are:

1. To use larger radius curves - which results in difficulties with using existing track - or even with upgrading existing track without a lot of land purchasing.
2. To attempt what British Rail did with tilting Advanced Passenger Train...which was notoriously unsuccessful.

SteveBaker (talk) 03:55, 27 December 2012 (UTC)

Is it the lateral forces on the passengers or train that's the problem ? StuRat (talk) 04:07, 27 December 2012 (UTC)

On the passengers -- they get thrown sideways. Hence the use of "pendular suspension" in many high-speed trains like the aptly-named Italian Pendolino or the Swedish X 2000. 24.23.196.85 (talk) 06:31, 27 December 2012 (UTC)

Seems like a much simpler fix for that is putting the backs of the seats against the windows (perhaps slanted with the feet forward and head back) and requiring people to remain seated when going through curves. StuRat (talk) 22:17, 27 December 2012 (UTC)

That's supposed to be a joke, right? 24.23.196.85 (talk) 00:48, 28 December 2012 (UTC)

No. Also, looking out the windows at 300 kph can cause nausea even if there's no lateral g's. StuRat (talk) 00:55, 28 December 2012 (UTC)

And just how do you stop people from getting up and walking around, or get them to reseat themselves every time the train approaches a curve? Also, not being able to look out the window on a curve can cause worse nausea than in the scenario you describe. 24.23.196.85 (talk) 01:41, 29 December 2012 (UTC)

The same way you get them to sit on airplanes when they encounter turbulence. StuRat (talk) 04:13, 29 December 2012 (UTC)

Regarding question #4, bridges need not be rigidly anchored to the sea bed. A pontoon bridge design similar to the Lacey V. Murrow Memorial Bridge may be an economic option. Likewise, a tunnel need not be embedded in the sea bed. See submerged floating tunnel. A combination of the two or a bridge-tunnel may be needed to balance shipping and cost considerations. See also transatlantic tunnel. -- Tom N (tcncv) talk/contrib 16:55, 28 December 2012 (UTC)

You can't send a bullet train over a pontoon bridge or through a submerged floating tunnel -- it would break apart. And a bridge-tunnel crossing can only be built in shallow water -- it needs intermediate islands (natural or artificial) for the transition between bridge and tunnel or vice versa. 24.23.196.85 (talk) 01:50, 29 December 2012 (UTC)

Roche limit for black holes

where is Roche limit for any black hole?Akbarmohammadzade --78.38.28.3 (talk) 16:29, 26 December 2012 (UTC)

Black holes do not have Roche limit. They are essentially inviolable. Ruslik_Zero 18:51, 26 December 2012 (UTC)

I think that answer is true, at least in a sense, but it is a bit unsatisfying to me. The Roche limit is a point where part of an object is going to fall away from it. How could something inside an event horizon fall away from the center? To illustrate, the Roche limit article says that a satellite can only be torn apart if its density is less than twice that of the primary, because otherwise the limit is inside the primary - so anything that could bring a black hole to the Roche limit would be darn near one already. And so my assumption is that the black hole + primary become a big rotating black hole. But note that a rotating black hole has a ring singularity, and so one can argue that you have disrupted the innards of the black hole and turned them into an "orbiting ring of debris" in some very, very loose sense. I'm not really giving you an answer with this, just making an appeal for an imaginative consideration by one of the experts. :) Wnt (talk) 20:32, 26 December 2012 (UTC)

This is an interesting question that I've never thought about before. There are a bunch of papers/preprints about it on the arXiv. According to arXiv:0705.1570 (which has pictures), the event horizon is distorted by the tidal force into a cigar shape. This actually surprises me, because the event horizon of a rotating black hole is not distorted: it's a sphere with no equatorial bulge. The singularity remains a point/line (I think), but the Planckian region, where the curvature exceeds the Planck curvature and therefore general relativity is presumably wrong, is flattened like a pancake. The paper mentions that there's a threshold tidal force beyond which the pancake extends outside the event horizon, giving you a naked singularity (more or less). This might imply the existence of a (mass-dependent) maximum tidal force analogous to the maximum rotational speed of a rotating black hole (beyond which you get a naked singularity). I'm not sure how this force could actually be achieved, though, since it seems to require another black hole essentially touching the first.

arXiv:0910.4311 mentions that a black hole orbiting another body will gain mass from tidal friction, and I assume (though it doesn't say so) that it would eventually become tidally locked to the other body. This isn't directly relevant to the question, but it's interesting. -- BenRG (talk) 01:34, 27 December 2012 (UTC)

thanks all. It might be two Roche limit for any black hole .One of them outer than event horizon and other inner it as we know all objects elongate infinitive there. — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 08:52, 27 December 2012 (UTC)

It would be useful to frame the question properly. The Roche limit for a body applies in relation to another, and depends upon properties of both (the mass of the primary, and the density and configuration of the secondary). Thus, the Roche limit of a (normal matter) body orbiting a black hole (the primary) will be the radius from the black hole where the object will disintegrate under the influence of tidal forces, and this will typically be far outside the event horizon of the black hole for smaller black holes, but inside the event horizon for supermassive black holes such as in the centre of the galaxy. The radius of a black hole's event horizon is proportional to its mass. The Roche limit is proportional to the cube root of the ratio of the black hole's mass and the orbiting body's density. The previous answers assumed that the black hole is the secondary, orbiting an even larger primary. Here the (infinite) density of a non-rotating black hole makes the Roche limit zero radius from the primary's centre, though the rotating case (a Kerr black holes as the secondary) might be interesting, since the singularity presumably differs non-trivially from a spherical configuration. — Quondum 09:35, 27 December 2012 (UTC)

When we talk about black holes we imagine some thing absorbing and destroying all around it .This is not reality about them. If it is so that any black hole has infinitive mighty and effect at all distance , this has contraction with nature laws. I want to say (as said last about planets round black hole )that the black hole with mass M and rotating properties , has as gravity field as last star .we say if any black hole was any star which had planets , its members will rotate round it safely . if our sun was able to be black hole ,our earth was rotating round it ,without any difference later and after . why we do such mistake ? black hole sun cannot destroy not only low density Saturn but also near mercury ,then we give some hypothetical properties to it, of absorbing all the things? can any black hole absorb its neighborhood star?never .

have you never calculate Roche limit of any black hole?

excuse me --Akbarmohammadzade (talk) 10:47, 27 December 2012 (UTC)<

Hmmm, there's another problem: there are no stable orbits very close to a non-rotating black hole. See photon sphere. But black holes in such relationships might be rapidly rotating, so sometimes I suppose it is possible... (but I'm out of my depth on this) Wnt (talk) 15:38, 27 December 2012 (UTC)

Shwartz child radius for any star 10 times massive than sun is about 5kilo meters Akbarmohammadzade — Preceding unsigned comment added by 2.187.90.105 (talk) 17:08, 27 December 2012 (UTC) 1.5 times further it will be about 8 kilometers--Akbarmohammadzade (talk) 17:32, 27 December 2012 (UTC)

Past article from the Lancet medical journal.

I require a specific article from a past Lancet journal. The article if from 2005 volume366 pages 29-36.IT IS specifically about the ABCD criteria after a TIA (transient ischemic attack). — Preceding unsigned comment added by 24.185.248.186 (talk) 16:32, 26 December 2012 (UTC)

The article is titled A simple score (ABCD) to identify individuals at high early risk of stroke after transient ischaemic attack. If you search for the title at scholar.google.com, you can get access to several downloadable online versions, including this one. This way of finding things works pretty frequently. Looie496 (talk) 17:23, 26 December 2012 (UTC)

Wikipedia:WikiProject Resource Exchange/Resource Request is the place to request articles that aren't available free online. -- BenRG (talk) 17:52, 26 December 2012 (UTC)

How does it come that this is legal? OsmanRF34 (talk) 21:48, 26 December 2012 (UTC)

We don't give legal advice. But you might want to read fair use. 208.102.63.50 (talk) 23:04, 26 December 2012 (UTC)

December 27

measuring in a hypodermic syringe

How does one accurately measure small amounts of medicine in a hypodermic syringe? Is there medication left in the needle after the injection?Tmary (talk) 01:07, 27 December 2012 (UTC)

(1) The hypodermic syringe usually has markings on the side showing the volume of medicine to be delivered. (2) Yes, there is a small amount of medicine left in the needle after the injection, but it's unusable because it cannot be expelled from the needle, and also because it's mixed with the patient's (possibly infected) blood. 24.23.196.85 (talk) 01:16, 27 December 2012 (UTC)

2) I think what they are asking about is if the unused portion remaining in the syringe is accounted for in the markings. I'm not sure, but guess that this amount is insignificant, either way. StuRat (talk) 01:26, 27 December 2012 (UTC)

(2) All the syringes I've seen are calibrated "to deliver" -- which means that the markings show the volume actually injected. 24.23.196.85 (talk) 01:41, 27 December 2012 (UTC)

also, a standard amount of medicine is in solution by weight per volume in the liquid matrix. So one simply measures a volume of a usually pre-made solution to be injected, rather than measuring some miniscule weight. μηδείς (talk) 01:25, 27 December 2012 (UTC)

Seems like the graduations measure the amount in the barrel - so when you suck the liquid inside, you're getting a little extra inside the needle...then when you do the injection, that exact amount is left inside the needle at the end - so the reading on the barrel should be exactly correct no matter the volume inside the needle. I suspect that the limitations on precision are more to do with the skill and eyesight of the operator than anything else. SteveBaker (talk) 03:46, 27 December 2012 (UTC)

There is a small dead volume in many sorts of equipment. One quick way to avoid it being a problem is to keep its contents constant. That is, if you keep the syringe needle-down, pull the syringe barrel from the 0.0 mL marking to 0.2 mL and then push it out to 0.0 mL, you have picked up and squirted out 0.2 mL. The needle (and the inner part of the Luer lock and other areas) started empty and wind up empty. Or else you could pull to 0.3 mL, invert and push down to 0.2 mL (expelling the air that had been in the needle, etc.). Then when you push to 0.0 mL, you are still ejecting "0.2 mL to 0.0 mL", now indeed wasting the drops in the needle. Either way, you keep the same material in that space, whatever it is does not interfere when the barrel moves a certain number of volume-markings (standard laboratory practice when titrating by volume from a burette). DMacks (talk) 03:48, 27 December 2012 (UTC)

Note that having a constant 'dead volume' in a syringe depends on the contents being liquid (and specifically aqueous, as water is practically incompressible), i.e. the syringe is commonly tapped to bring any air bubble(s) to the top, and the uppermost contents, liquid and gas alike, are expelled down to the desired precise quantity. Wnt (talk) 04:40, 27 December 2012 (UTC)

Something else I should add is that the syringe should be chosen for the amount of med to be given. You wouldn't use a 100 ml syringe to administer 5 ml of meds, as it would be less accurate at that dosage than a 5 or 10 ml syringe. StuRat (talk) 04:43, 27 December 2012 (UTC)

decline of space expansion and exploration

I came across an old (pre-70's) transcript of an Earl Nightingale radio broadcast in which he spoke of Seaborg's predictions for the year 2000. Seaborg predicted that moon trips would be commonplace by 1992, and people would be able to go around the world in 2 hours, and that we would be visiting nearby planets by the year 2000. Interesting that he also predicted the 'internet'... he said that people would be able to use radio technology to read books from remote libraries :) Now my question is - why is mankind not devoting resources into space expansion and exploration? Surely, with the large number of extinction events possible, that we would need a 'backup' of mankind in space bases on the moon and beyond? Yes I know the traditional response to this is that it's 'prohibitively' expensive, but surely there's got to be more to it than this? What's the use hoarding or misusing funds if a comet can wipe us out tomorrow? Sandman30s (talk) 09:51, 27 December 2012 (UTC)

Is the transcript of this Seaborg interview available online? Nimur (talk) 18:16, 27 December 2012 (UTC)

No, they were "Defy" (South African electrical brand) transcripts of the radio show that my grandfather collected. Email me and I will scan and send to you. I should probably make them all available online as there some real gems there and I don't believe there is any copyright. Sandman30s (talk) 20:57, 27 December 2012 (UTC)

There almost certainly won't be any comets wiping us out tomorrow because we're constantly monitoring for any nearby objects of sufficient size to do serious damage. Launching anything into space is ridiculously expensive, even for low-earth orbit. Creating a fully autonomous offworld base (in orbit or on another body) is an extremely difficult task by itself; there's an absolutely vast number of ways in which it could go wrong. The combined cost of developing the necessary equipment and launching it into space would be outrageous. The chances of an offworld colony being wiped out would be much greater than the chances of the entire human race being wiped out. If we really wanted to protect the human race from mass extinction events, I'd imagine building underground cities would presently be a much better choice than colonising space. As for space exploration, we are doing that, except we're using robots instead of humans, because it's just that much cheaper and easier. --Link ^(t•c•m) 11:01, 27 December 2012 (UTC)

Yes I know about monitoring near-earth objects, but we currently would not be able to prevent a large object (kilometres in diameter?) from crashing into earth. What's the use having underground cities (or even cities on the ocean bed) if a comet hits or supervolcano erupts? These events would wipe out all surface life as well as all crops, so how would the subterranean dwellers get food? I would also imagine that creating underground cities would be just as expensive as cities on the moon. Yes I do agree that a space base would be far more dangerous, but that's the whole point of creating backup(s)... if your primary source is gone then at least you do have a backup. Sandman30s (talk) 11:17, 27 December 2012 (UTC)

The ocean would be hard to disrupt, especially not quickly. Yes, if an event leads to the whole ocean boiling you're screwed in the long run, but no dinosaur killer or Snowball Earth event ever did that. (A full fledged runaway greenhouse, maybe...) There is actually extensive military-oriented regulation of trading in even a camera that can see things more than a mile deep, so there must be something down there, though the usual explanation involves crashed nuke sub(s). I don't think we can rule out that one or more such bases to shelter elites haven't already been constructed, though I know of no evidence. Wnt (talk) 15:33, 27 December 2012 (UTC)

Can you provide a link to where I may read more about the trading limitations on such cameras? Are you talking about pressure resistant cameras and housings? -- 41.8.83.148 (talk) 05:30, 28 December 2012 (UTC)

You could move underground during the most turbulent period, and then return to the surface once things start to stabilise again. Getting food would be problematic, but it's not quite easy to do in space either. You seem to be underestimating how incredibly inhospitable space actually is. Once you're out of the protective shell of Earth's atmosphere and magnetosphere, you're constantly pelted by radiation. No planet or moon in the solar system beside Earth has a breathable atmosphere. There's nowhere other than Earth where leaving the protection of a spaceship or space suit is survivable for even a minute or so. It would probably still be easier for humans to survive on Earth in the aftermath of a global disaster than it would be on Mars in the most favourable conditions. Sure, it would be useful to have an off-world colony, but the launch costs alone make it utterly infeasible (a space elevator would alleviate that problem, but we're not quite at the point where we can build one yet). Putting a permanently manned base on the moon is just about at the limit of what we could reasonably do right now. Creating a completely autonomous (i.e. capable of surviving indefinitely even if the Earth were to go kaboom) colony for a minimum viable population of humans is very far out of reach for the time being. Ensuring a few thousand humans could survive a global disaster on earth is easier, cheaper, and likely more effective than creating an offworld colony that can repopulate the Earth later. --Link ^(t•c•m) 16:49, 27 December 2012 (UTC)

You could get by the minimum viable population problem by keeping thousands of frozen embryos (or sperm and eggs), so you'd only need a "caretaker" population. StuRat (talk) 21:23, 27 December 2012 (UTC)

Thank you for your thoughts. Let's say terraforming became viable and feasible in the distant future. Would you still say that underground cities would be better than colonies on a terraformed Mars? Sandman30s (talk) 21:07, 27 December 2012 (UTC)

Well, except the runaway greenhouse. If the oceans actually boil and the water vapor greatly enhances the greenhouse effect, so that the whole planet gets a proper steam cleaning, then anywhere, even underground, will eventually be uninhabitable. Getting the energy to run enough air conditioning to live in an oven when you can't go anywhere seems like a long shot, though I suppose in such a thick atmosphere amazing things can be done with wind power (a little late, tho) Wnt (talk) 17:02, 27 December 2012 (UTC)

I am currently looking at tens of thousands of perfect tomato plants sitting on a cement floor while a foot of snow is on the roof above, so getting food while living underground really would not be a problem so long as one has continuous energy (likely nuclear) and a one time supply of water, seed, fertilizer, and growing equipment. 50.101.153.9 (talk) 21:40, 27 December 2012 (UTC)

Right at this very moment people ARE going round the world in two hours (less actually), in the International Space Station. HiLo48 (talk) 22:14, 27 December 2012 (UTC)

Yea, if you don't count the take-off, landing, prep time, etc. Actually getting from the ground in Australia to the ground in the US takes a lot longer. StuRat (talk) 05:33, 28 December 2012 (UTC)

Link: Glenn T. Seaborg - 41.8.83.148 (talk) 05:44, 28 December 2012 (UTC)

quantum effects in processors

How, specifically, do modern processors use quantum effects? (i.e. "don't work without it", etc). This is not homework. 91.120.48.242 (talk) 11:49, 27 December 2012 (UTC)

If nothing else, transistors depend on quantum effects. It's hard to give a definitive answer, because really every property of matter is a quantum effect if you look deeply enough. Looie496 (talk) 15:47, 27 December 2012 (UTC)

But that's not what I mean. When they're designing a processor, they have modeling software (to lay out the circuits). Does this modeling software include quantum effects? 91.120.48.242 (talk) 15:54, 27 December 2012 (UTC)

No. Looie496 (talk) 16:33, 27 December 2012 (UTC)

Thank you, Looie. Is there a size where it would? I found a stackoverflow answer to the question "Is Quantum Physics used in manufacturing CPU's" (June '11). It says they mostly avoid it: "As component sizes have gotten smaller, tunneling has become an increasingly important limiting factor in the design and layout of chips." Is there some kind of size where you could no longer avoid these effects, but, for example, have CPU modeling software (for laying out new CPU's) that actively includes the quantum effects for you to include in the design? I am not talking about a quantum computer per se, just at what point traditional CPU design will directly work with (use) quantum effects, if indeed there is such a size. 91.120.48.242 (talk) 16:56, 27 December 2012 (UTC)

Modern off-the-shelf processors do not, but see http://en.wikipedia.org/wiki/Quantum_computer#Developments. The article states that, "In 2009, researchers at Yale University created the first rudimentary solid-state quantum processor." It goes on to summarize other state-of-the-art developments. --Modocc (talk) 17:06, 27 December 2012 (UTC)

This also depends on what you mean when you say "designing a processor." In modern engineering practice, a computer architect (or a whole team of them) designs a system architecture, including a low-level digital logic representation/implementation of the instruction set architecture. At this layer of abstraction, transistors are "guaranteed" to work. One could say that we build in a sanity-check any place we use an error correction code, because we handle any generic type of bit error without regard to the source of the bit-flip. That bit error could be due to thermal noise, or analog electromagnetic interference, or a timing error due to imperfect trace length, or a cosmic-ray alpha particle striking the transistor, or a quantum fluctuation... but it just doesn't matter. The computer architect doesn't care why the analog circuit might fail; at this layer of abstraction, we just have ones and zeros. Now, usually it is "someone else's job" to make sure that the bit-error rate is as low as possible. An entire team of engineers worries about each source of error: a layout crew makes sure the traces on the silicon get designed properly for minimum clock skew and best signal integrity. A packaging engineer (or a team of them) worries about using the right type of plastic encasement to minimize RFI and EMI and alpha particle strikes.

And finally, somebody - usually not just one engineer, but an entire company full of engineers - worries about what we calll very large scale integration. These guys don't care at all whether the system architect designed a billion transistors that comprise a processor, or a radio demodulator, or a giant billion-transistor no-op. It's their job to ensure that all billion silicon transistors get built right - as designed. This is sometimes called the "Process." Each manufacturer of silicon has their own process, and distribute large complex computer aided design tools that automatically translate a digital design into the correct number of photolithography masks - one mask for each layer of semiconductor, insulator, and conductor layer. It is the job of the fabrication process company to make sure that their masks properly convert a digital design into the analog world. They worry about such things as the optical resolution of their lithography masks; if they choose to use quantum mechanics to analyze the optical path, it may improve their yield. In fact, current semiconductor processes are so small that it's uncommon to use light during photolithography; the wavelength of light is larger than the features being etched. So, they may use x-rays, or ultraviolet light, or any other strange proprietary technique to get around the wavelength limitation. This method can be called a "quantum" effect: you cannot build a single transistor if the uncertainty principle dictates that your photon is larger than the transistor. Another team of engineers - chemists, electrical engineers, material scientists, and so on - worry about etching. They worry about how many seconds of exposure to various etching chemicals are required to remove photomask, and etch away the undesired parts of the semiconductor structure. Now that nano-layer fab processes have such a small number of atoms, the process of acid dissolving solid surface atoms can be modeled quantum-mechanically. This is a molecular physics problem, or a statistical problem. If a quantum-mechanical analysis of this chemistry helps the engineers etch better transistors, it will affect the yield.

The design of an electronic circuit in semiconductor requires accurate knowledge of the dynamic electrical properties of a material. In semiconductors, things like electrical resisitivity and free electron count and even thermal constants are dictated by atomic processes. In very small transistors, such as the ones in a modern process, these properties might require analysis of atomic physics, because there are so few atoms that we can't "average" everything out (as we do in conventional thermodynamics or large-scale statistical physics). An entire field of quantum mechanics analysis - semiconductor physics - is useful in analyzing the electrical and other properties of structures that are built from just a handful of atoms or molecules.

Finally, we can consider the statistical methods of quantum mechanics - independent of their applications to atomic physics. Quantum mechanics helps scientists speak definitively about uncertainty. It helps analyze quantized (countable) effects while also working with analog (continuously varying) phenomena. So, at very low levels of analysis, or at very abstract levels of analysis, we can use methods of QM to analyze things like defect count per wafer, and use that knowledge to guide and modify our designs.

Now, I often hear the pure physicists say things like "quantum mechanics makes the transistor possible." As a former physicist, turned silicon-engineer, I can say my piece: this is utter baloney. It's physicist-talk. Engineers have historically designed, and will continue to design in the future, without understanding the absolutist view of "fundamental processes" that phyicists continually strive for. Engineers are able to work with problems, analytically and quantitatively, while abstracting away the irrelevant details - any detail that doesn't directly affect the current problem. Most engineers in the semiconductor industry - even the ones down low in the process stack - never ever ever use QM or its techniques. Some engineers do. Unlike pure physics research, where scientists use the most sophisticated analysis possible, engineers only use the analytical tools that are needed to get the job done. When designing computer processor logic, QM is almost totally irrelevant. When working with the implementation of that processor as an analog circuit, QM is often irrelevant. But, there are cases where QM improves the process. And there are probably some areas where methods of QM are absolutely essential to the correct design and analysis. But on the whole, what you should recognize is that QM is a method of analysis, not a physical fact. Like all physics, quantum mechanics is a best-effort to accurately model the world as we observe it. It happens to be the best method we have for analyzing atomic physics, and many similar problems. When atomic processes affect analog circuits, we must use QM. But again, let me reemphasize: engineers work by abstracting problems and worrying only about the details that directly affect them. Only half-in-jest, I say that QM analysis is "always" somebody else's job; everyone knows that somewhere in the machine, QM rears its ugly head, but as long as each engineer can make her/his contribution work right, he/she doesn't need to do any extra mathematical juggling. Nimur (talk) 17:51, 27 December 2012 (UTC)

Thank you. I read all this (in a few sessions :). Basically, you are saying that the part that I am interested in - chip architecture design - does not and probably will not use QM, which is more like "noise" that has to be removed by error checks and carefully embodying the abstract design: it is literally at a lower layer and does not make it into chip design. Thus if I understand you correctly, my question is similar to the question "do Internet Protocols like TCP/IP or UDP make use of the fact that light is both a wave and a particle?" and the answer is "No, not at all", and double not for quantum entaglement. That fact has been abstracted away long before they see it. TCP/IP or UDP doesn't even know if it is going over fiber optics, over copper, or over radio. All it gets is the 1's and 0's. You are basically saying the same thing about QM effects: they are abstracted away long before the chip designers see them. Thank you for your detailed answer, Nimur! --91.120.48.242 (talk) 12:58, 28 December 2012 (UTC)

I too found Nimur's exposition an informative read. There are of course things at the lower layers that do not get entirely abstracted away: simulations of implementations can result in high-level logic design choices, e.g. differences at higher design levels may make a difference to the highest clock frequency at which a circuit implementation will function correctly. At times there are low-level aspects that are exploited at a higher level, e.g. in true random number generators, where noise (sometimes of a quantum nature) is the basis of the functionality required. — Quondum 13:28, 28 December 2012 (UTC)

hair/fur, not pelt

Please list the characteristics of squirrel fiber, squirrel tail fiber, and raccoon fiber.Curb Chain (talk) 12:28, 27 December 2012 (UTC)

Please do your own homework. Your quetion reads like it has been copied straight out of an assignment. If not, show us why not. Wickwack 58.169.234.153 (talk) 13:50, 27 December 2012 (UTC)

They tend to grow outward from the skin, and are long and slender. Does that help? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:34, 28 December 2012 (UTC)

Thanks but can you give more distinguishing charactersitics?Curb Chain (talk) 06:24, 28 December 2012 (UTC)

Hydrogenated Polyisobutene in cosmetics

The entry on Polyisobutene makes it sound like something I wouldn't want to rub on my skin. But I've seen "hydrogenated Polyisobutene" as in ingredient in a number of hand lotions. What properties would make it appropriate for that? --71.189.190.62 (talk) 17:59, 27 December 2012 (UTC)

Let's provide a link to the article in question: polyisobutene. While our article doesn't talk about the hydrogenated version, it sounds like it can be used as a thickening agent to keep the oils from readily evaporating, and doesn't have much of a smell. So, it makes the hand lotion last a long time and not stink. The fact that it's used in chewing gum also makes it clear that it's not toxic. StuRat (talk) 18:07, 27 December 2012 (UTC)

As the article notes, PIB and many related compounds are common synthetic rubbers. I bet you've handled, used, and maybe even worn many things made out of it. We also have an article about hydrogenation. DMacks (talk) 18:39, 27 December 2012 (UTC)

If your cosmetic ingredients gross you out, don't think too much about the urea they frequently add. StuRat (talk) 18:58, 27 December 2012 (UTC)

Daily Comet Ison pic?

I'd like to rig up a picture on my computer's desktop to be a current image of Comet Ison, the one that could become a Great Comet in about a year. Is there a "live" image somewhere on the net I can link to? (By "Live", I mean "taken this week or so".)

Even better would be a time-lapse showing the motion of the comet from its discovery until now, but I'd be delighted just to find a weekly-updated image of what the comet looks like now. TIA - Tarcil (talk) 19:12, 27 December 2012 (UTC)

Mystery mineral

Any ideas?

I've had this item for a number of years, having purchased it from a rocks and minerals gift shop, but have unfortunately forgotten what it was called and have long since lost the handy little label describing it. This may have said something about it being an industrial by-product, perhaps from Eastern Europe or Russia, but I could be misremembering. It's certainly very pretty - the picture doesn't really do it justice. It's iridescent, and the edges are rather sharp. It wasn't too expensive either, around £20 I think, if that helps to narrow it down. Any ideas what it could be? the wub "?!" 21:41, 27 December 2012 (UTC)

Looks like slag. Graeme Bartlett (talk) 21:49, 27 December 2012 (UTC)

Could be schist. --Jayron32 22:19, 27 December 2012 (UTC)

Reminds me a bit of Bismuth crystals.--Gilderien Chat|List of good deeds 22:59, 27 December 2012 (UTC)

Might be silicon carbide. -Modocc (talk) 23:49, 27 December 2012 (UTC)

It seems flat. Is one side different from the other side? If so, how? Also, does it seem especially light or especially heavy for its size, or just of expected weight? I don't know what it is, but I think this information may help more knowledgeable editors to take a guess. Also—is it strong—or would it break very easily if you for instance applied manual pressure to it? Bus stop (talk) 00:04, 28 December 2012 (UTC)

The sides are all similar. I would say that it's quite light, and it's easy to break flakes off it.

Silicon carbide / carborundum definitely seems like the right answer. It looks very like this example, and the fact that it's found on the inside of blast furnaces sounds like what was on the card. Thanks everyone! the wub "?!" 01:04, 28 December 2012 (UTC)

Is it hard? Does it scratch glas? --Stone (talk) 12:11, 28 December 2012 (UTC)

It looks to me like quenched pyrite or galena, both being a sulfide mineral. Plasmic Physics (talk) 02:41, 28 December 2012 (UTC)

To tell some of the above options apart you can do a streak test. Use one of the broken off bits to scratch the rough back of a porcelain tile. bismuth galena and pyrite will give dark streaks, silicon carbide will just scratch the tile. Schist will probably leave a brown or grey mark and slag may leave a gray line of broken glass fragments. Graeme Bartlett (talk) 10:37, 28 December 2012 (UTC)

December 28

Mr Edelweiss type of bird

In the film Nanny McPhee Returns, she has a bird named Mr. Edelweiss. What type of bird is he? — Preceding unsigned comment added by Donmust90 (talk • contribs) 02:05, 28 December 2012 (UTC)

he is a Jackdaw, from what I can ascertain via Google. AndyTheGrump (talk) 05:06, 28 December 2012 (UTC)

Name that fish (Halfbeak -- ballyhoo?)

Name that fish.

I was snorkelling in Cuba last week (near Playa Jibacoa, roughly halfway between Havana and Varadero). Lurking just under the water's surface near the reefs not far off shore, I saw a number of interesting fish, including the character pictured at right. My best guess is that it was roughly a foot long, including the 'beak'.

I'm pretty sure it's some sort of Halfbeak, and I think it might be a Ballyhoo. Is there anyone who knows their saltwater tropical fish who can confirm/narrow that identification? And is there an article that could use the picture? Thanks, KevinHadley (talk) 03:06, 28 December 2012 (UTC)

The ballyhoo article only contains a low-res drawing, so an actual pic would be a definite improvement. StuRat (talk) 05:40, 28 December 2012 (UTC)

It's a Ballyhoo. Darkness Shines (talk) 10:45, 28 December 2012 (UTC)

Indian victim

Did that Indian rape victim thats been in the news attempt suicide? Her injuries are not consistent with rape, for example she would not been able to run away if she had a significant brain injury as said here http://www.bbc.co.uk/news/world-asia-india-20856180 , and here it says only her male friend was beaten up http://www.bbc.co.uk/news/world-asia-india-20765364 --Wrk678

She did not get to run away, she was beaten half to death then thrown off the bus, read the BBC article you linked to. Darkness Shines (talk) 10:40, 28 December 2012 (UTC)

If you read the second article it says the opposite of that. I also think it seems implausible that they were beaten with bars on a crowded bus.--Wrk678 (talk) 18:33, 28 December 2012 (UTC)

The second article says: "A 23-year-old woman is savagely attacked and raped by a group of men inside a moving bus and her male friend is beaten up senselessly. Battered and bleeding profusely, they are dumped near an expressway in Delhi, where they are found by a passer-by. " Doesn't say the opposite of it at all. --TammyMoet (talk) 20:01, 28 December 2012 (UTC)

Read the article 2012 Delhi gang rape case. It wasn't a crowded bus. Other than the victims, the other six people on the bus (including the driver) all knew each other in advance and were all part of the attack. Dragons flight (talk) 22:22, 28 December 2012 (UTC)

Even if she was beaten her injuries are more consistent with swallowing a corrosive substance such as lye or bleach or a pesticide. That region has a tendency to exaggerate stories unfortunately such as the Pakistani girl Malala Yusufzai who was allegedly shot point blank in the head and neck with a ak47 despite pictures showing no marks or injuries on her head or neck, And perfect ability to talk and walk. This article states she may have not been shot at all http://www.telegraph.co.uk/news/worldnews/asia/pakistan/9655417/Pakistani-Islamist-politician-claims-Malala-was-not-injured.html --Wrk678 (talk) 08:09, 29 December 2012 (UTC)

Can a tunnel flood?

Like a major one like the Lincoln Tunnel or the Channel Tunnel. ScienceApe (talk) 07:32, 28 December 2012 (UTC)

I fail to see why wouldn't it be possible. It must have a draining mechanism, which probably stops when everything is flooded. OsmanRF34 (talk) 13:17, 28 December 2012 (UTC)

The Holland Tunnel just flooded in Hurricane Sandy. You can even watch it [http://www.bloomberg.com/video/subway-tunnel-flooding-problems-in-new-york-K5yQpX6ARVKziYi~4HlRiQ.html. Rmhermen (talk) 18:24, 28 December 2012 (UTC)

Lincoln Tunnel was the only one that wasn't closed in NYC. --jpgordon^{::==( o )} 20:03, 28 December 2012 (UTC)

The Midtown Tunnel between Norfolk and Portsmouth, Virginia flooded in 2003 when maintenance crews were unable to completely close the floodgates in time due to (IIRC) a drainage grate or cover plate that had been welded in place. -- Tom N (tcncv) talk/contrib 00:23, 29 December 2012 (UTC)

(YouTube link: How to Knit * Knitted Hat Top Down * How to increase)

The vid shows knitting with 3 or 4 needles. Is it possible to knit with say 7 needles?Curb Chain (talk) 08:18, 28 December 2012 (UTC)

See Circular knitting - no obvious reason why you couldn't use five or more double ended needles (they are sold in sets of four or five apparently), although these days you would most likely use circular needles. Mikenorton (talk) 09:06, 28 December 2012 (UTC)

As someone who always knits with circular needles, I can tell you they are not practical for smaller items such as socks, and 4 or 5 needles are the norm for knitting socks. No reason why 7 needles couldn't be used but it would be very complicated. I wouldn't want to try it. TammyMoet (talk) 09:52, 28 December 2012 (UTC)

Not without a knitting machine, anyway. --jpgordon^{::==( o )} 15:55, 28 December 2012 (UTC)

Those use hooks or latch hooks, not needles. Rmhermen (talk) 18:22, 28 December 2012 (UTC)

Or, as they commonly called, "latch hook needles". --jpgordon^{::==( o )} 19:50, 28 December 2012 (UTC)

Not by me. But they aren't knitting needles whatever their name. Rmhermen (talk) 20:08, 28 December 2012 (UTC)

Can curing of paints change tensile properties

We are painters doing powder and pvdf coatings on aluminum. Normally, aluminum alloy 6063 is used for door, window sections. However, in one specific case, we have got alloy 6082 T6 for pvdf coating job. PVDF coatings need to be cured at a temp of approx 230-240 degree C for 8 to 10 minutes, which, in general is specified by the paint manufacturers.

Would curing at this temperature and time bring some difference in the Fy or elongation/ tensile properties of the metal 6082? If so, to what extend. The mill finished extruded material received by us has a Fy 255 mPa.

Your opinion is awaited.

Regards, Sanjay — Preceding unsigned comment added by 122.161.52.208 (talk) 13:14, 28 December 2012 (UTC)

If you have a look at Steel#Material properties, you can see that heating may cause Recrystallization (metallurgy) of the alloy. Whether or not that will happen at that temperature is entirely dependent on the particular alloy's thermal behaviour. Considering the relatively low melting point of the alloy (555 °C), that does not seem unlikely to me.

For those who are looking for more information on the alloy: [6]. Plasmic Physics (talk) 19:08, 28 December 2012 (UTC)

telling if we are in a Virtual Machine

Suppose the universe might be emulated, just as we might emulate a few atoms of it once we have all the laws figured out. Propose strategies that we can follow to determine whether the physical universe is in fact being emulated in this sense or not. This is not homework. 91.120.48.242 (talk) 14:50, 28 December 2012 (UTC)

Similar questions have been asked here several times before, I recommend a search of the archives. Our most relevant article on the concept is Simulation hypothesis, which gives an overview of the problem and its history. From there you can jump to articles that seem relevant to you or follow the references. I notice that there is an original research tag at the top of the article, so you should be aware that some portions may be user speculation instead of being based entirely on reliable sources. 209.131.76.183 (talk) 15:54, 28 December 2012 (UTC)

If this is not a homework question, why is it worded like one? Propose strategies that we can follow to determine whether you are doing your own work. However, for the record, we can help with your homework, so long as it is in the manner of a library reference desk, ie. pointing you in the right direction. From the link by 209, you want reference 28, which I suppose is obvious since it is under the section "testing the hypothesis". The article is quite advanced, so try to pick up the gist. You may be interested in chaos theory, in particular Chaos theory#Distinguishing random from chaotic data. If the universe were a numerical simulation, there would presumably be limits on chaotic behaviour, since it involves intractable complexity. So your answer could propose ways of testing the universe based on subjecting chaotic processes to tests that determine if they are, in fact, truly chaotic. You will have to do this bit yourself. IBE (talk) 17:53, 28 December 2012 (UTC)

I'm curious what you think of these contributions (left-hand side) - http://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&diff=prev&oldid=530148333 - the part that has been removed from the question. is it the same as what you propose? 178.48.114.143 (talk) 21:33, 28 December 2012 (UTC)

Very interesting, but I'll wait to see what someone smarter suggests. I think it's clear that we are dealing with a fairly bright person who hasn't got his ideas sorted out very clearly, or at least doesn't know how to express them. It is certainly along the same lines, however. IBE (talk) 21:43, 28 December 2012 (UTC)

I would also add that there are many possible configurations of the question itself - does it allow quantum computers, for example? It seems clear from the post you linked that the OP is not considering such possibilities, because quantum computers could definitely generate random numbers. If pseudorandom processes occurred in reality where science expects random ones, then yes, you have some hard evidence of a VM reality. Absence of them could indicate a quantum computer VM, however. I don't know how quantum computers might influence chaos calculations, but I would have thought not on a fundamental level. Please anyone who knows this stuff well, tell us about it. IBE (talk) 21:48, 28 December 2012 (UTC)

OP, have you read Stephen Wolfram's A New Kind of Science? It proposes that the universe is a just a very, very big cellular automaton. To tell if the universe is such a system could prove problematic of course, because if it's true then we are all part of it.. --hydrox (talk) 06:47, 29 December 2012 (UTC)

A drug meant specifically to induce pain

There are plenty of drugs to create a recreational experience, but are there any drugs that cause acute pain after injecting, swallowing or inhaling them?

I was wondering if such drugs could be used to turn recreational drug use into a painful experience via classical conditioning, by mixing the original drug with the pain-inducing one and giving it to the users. (Just to be clear, I didn't ignore the serious disadvantages, and possibly illegality, of this method, and don't expect to see it being applied to rehabilitate drug addicts.)

Thanks, 82.166.216.211 (talk) 23:49, 28 December 2012 (UTC)

Well, there are lots of drugs that cause pain upon being injected; I'm thinking that the vast majority of things you could possibly push into your bloodstream would probably hurt quite a bit. The problem is that drug dealers don't typically try to rehabilitate their users. I also doubt it would work, even if you got by the staggering legal and logistical hurdles. If watching yourself waste away, spitting out all your teeth, and slipping into the occasional coma don't do smarten people up, I'm not sure what will. :( Matt Deres (talk) 00:27, 29 December 2012 (UTC)

Because acute pain is more persuasive than those other things. That's why torture became so popular. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:57, 29 December 2012 (UTC)

That's pretty much the way Disulfiram (Antabuse) works in the treatment of chronic alcoholism. Tonywalton ^Talk 00:35, 29 December 2012 (UTC)

(e/c)You may find this interesting. Not quite what you were looking for, but very similar. Matt Deres (talk) 00:37, 29 December 2012 (UTC)

Ooh! Spooky! Tonywalton ^Talk 00:38, 29 December 2012 (UTC)

Platypus venom would be a wonderful candidate for the drug you seek.--Digrpat (talk) 00:46, 29 December 2012 (UTC)

This has been in the news, see the sadistic suggestions made about oxycontin and capsaicin. μηδείς (talk) 03:54, 29 December 2012 (UTC)

meteorites from EARTH to Mars, rather than vice versa

Hi, what i read is that about a ton of meteorites of mars origin land on earth every year. How often would the reverse happen given Earth's stronger gravity? Less often I'm sure but how less often? Is there an approximate formula based on gravitys and distance from sun etc? Thanks68.65.169.66 (talk) 01:20, 29 December 2012 (UTC)

When was the last time a meteorite impact on Earth was storng enough to eject material into space? This is not just a matter of stronger gravity -- it's also a matter of Earth having a dense atmosphere that all but prevents any Earth material from being ejected into space as meteors. 24.23.196.85 (talk) 01:37, 29 December 2012 (UTC)

I don't know when the last one was, but a meteorite impact on Earth, if it did bang stuff off of earth, even many millions of years ago, could be a continuing source of meteorites to Mars. Also, i wonder about (Earth)volcanoes shooting material away from Earth.68.65.169.66 (talk) 02:09, 29 December 2012 (UTC)

No volcano has ever been powerful enough to launch stuff into space -- the rocks fly thousands of feet into the air at most, while the volcanic ash usually goes up into the stratosphere and just hangs there for some weeks. 24.23.196.85 (talk) 02:51, 29 December 2012 (UTC)

No volcano on Earth. There have been (water) volcanoes that launched material into space. Some of Saturn's rings are from one (see Enceladus (moon)). StuRat (talk) 04:05, 29 December 2012 (UTC)

No volcano in historical times has come anywhere close to achieving an orbital launch. Large modern eruptions send volcanic bombs (i.e. large rocks) up to 500 m or so above the volcano. However, we have good evidence of volcanic explosions 10-100 times larger having occurred over geologic times. This makes it likely that at least occasionally volcanic eruptions might send rocks miles into the sky, and just possibly the very largest eruptions might approach escape trajectories. Back in the early twentieth century, there was a theory in geology that large, suborbital volcanic ejecta was responsible for creating impact craters (e.g. verneshot). We now know that most impact craters have a extraterrestrial origin (i.e. meteors), but I don't think one can completely rule out the possibility of an extremely large, extremely rare (e.g. 1 per 100 million years) volcanic eruption being capable of launching some rocks off the planet. If it has ever happened though, it certainly doesn't happen often. Dragons flight (talk) 05:12, 29 December 2012 (UTC)

What about meteorite impacts?64.9.234.141 (talk) 05:58, 29 December 2012 (UTC)

It would require a pretty big meteorite impact. Still not very common, since big impacts are themselves rare—maybe once every 10 million years or so at most. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:59, 29 December 2012 (UTC)

I thank you for your answer. I'm not sure how you get your estimate, or even if your estimate is at least from intuition gained from experience and study. My original question was how much Earth material gets to mars relative to the reverse process, (which hopefully the scientists who claim about 1 ton/year have their reasons). But if you are correct that such meteorite impacts are on average 1 every 10 million years, how much transfer would we expect to mars? Is it likely or unlikely that there been in the last 100million years meteor impacts that ejected millions of tons of matter from Earth?(I ask the large amount of a million tons because I bet the odds of any given particle of it ever getting to mars, let alone in a given year, are small.) Could we say perhaps then that extremely tiny amounts of Earth end up on Mars, like a teaspoon per year?Thanks again.64.9.234.141 (talk) 08:02, 29 December 2012 (UTC)