Wikipedia:Reference desk/Archives/Science/2012 December 24

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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)