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= October 29 =

== ANTIBIOTICS ==

WHAT IS ANTIBIOTICS?
WHO DISCOVERED ANTIBIOTICS AND HOW? 

WHAT ARE ITS SIDE EFFECTS?
HOW CAN WE STOP THE MISUSE OF ANTIBIOTICS?  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/59.92.244.18|59.92.244.18]] ([[User talk:59.92.244.18|talk]]) 03:47, 29 October 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->

:We will not do your homework here.  Try searching for the answers yourself by typing a key word or phrase (hint: "antibiotics") in the search box near the top left of this page.  -- [[User:Tcncv|Tcncv]] ([[User talk:Tcncv|talk]]) 03:58, 29 October 2008 (UTC)
::Please do not post in ALL CAPS because it is the equivalent of shouting. See the article [[Antibiotics]] which discusses side effects and misuses. For "who discovered antibiotics and how" see the History section of [[Antibiotics]] as well as [[Timeline of antibiotics]] and read about the various antibiotics, who discovered them , how, and when. Questions of "who discovered" something are often subjects of debate. There are many tentative and ultimately abandoned experiments before someone gets it right and comes up with a practical product. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 05:24, 29 October 2008 (UTC)

== Engineering Drawing ==

Why are the French Curves used in the Engineering Drawing called so, ie.why French why not English curve,etc.?  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/203.153.35.130|203.153.35.130]] ([[User talk:203.153.35.130|talk]]) 11:19, 29 October 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->

:Wasn't this answered comprehensively on another desk? Why, here it is[http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Miscellaneous#French_curves] [[User:Julia Rossi|Julia Rossi]] ([[User talk:Julia Rossi|talk]]) 11:55, 29 October 2008 (UTC)

::Well it was ''asked'' on another desk - and I suppose you could say it was ''answered'' (there were replies to the question) - but we didn't come up with any satisfactory (yet alone 'compehensive') answer...which is a shame - because I'd quite like to know too.  However, I doubt there are many people who respond on the Science desk who don't also patrol the miscellaneous desk - so I doubt we'll get any further here. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 17:23, 29 October 2008 (UTC)

:::I for one do not stalk the misc desk.  Just because you seem to think you know everything, doesn't mean you can make such generalisations.  With regards to the answer, Dmcq's answer actually sounds quite reasonable. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 07:52, 31 October 2008 (UTC)

:::: The only reference I can really find that could back up Dmcq's answer is a manual of engineering written by Professor Thomas E. French of the Ohio State University in 1911, the full text of which is available [http://www.archive.org/stream/manualofengineer00frenrich/manualofengineer00frenrich_djvu.txt here] in which he describes how to use the French curve.  I can't find any concrete evidence that they are named after him though. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 18:29, 1 November 2008 (UTC)

== Textile Testing ==

Why is the Beesley balance used in testing of yarn count in fabric called so, i.e.,whether it was named after the inventor "Beesley" etc.?  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/203.153.35.130|203.153.35.130]] ([[User talk:203.153.35.130|talk]]) 11:30, 29 October 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:Have you tried google[http://www.google.com.au/search?q=Beesley+yarn+count&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a]? There are about 700 ghits. [[User:Julia Rossi|Julia Rossi]] ([[User talk:Julia Rossi|talk]]) 12:02, 29 October 2008 (UTC)

== Bridge question ==

[[Image:Sutliff bridge Iowa.jpg|200px|right]]

Posting this here because it's the closest RD topic to engineering...

The bridge pictured to the side was badly damaged in [[Iowa flood of 2008|flooding this summer]], as is obvious; but how properly should the bridge be described?  Destroyed, because obviously it can't be used?  Or damaged, because 2/3 of the bridge is still there?  I'm loth to use "destroyed" because most of it is there; "damaged", because that's not specific enough (after all, minor vandalism to a bridge can legitimately make it "damaged"); "washed out", because (at least to me) that conveys less than this bridge has sustained; and "irreperably damaged" because (aside from the fact that I probably spelled it wrongly) I suppose the state could come along and fix it back up again, so such a pronouncement would be crystalballish and perhaps OR-ish.  What's the most accurate term of these, or is there a better?  [[User:Nyttend|Nyttend]] ([[User talk:Nyttend|talk]]) 14:09, 29 October 2008 (UTC)

:"Partially destroyed", "one-third destroyed"?  [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 14:29, 29 October 2008 (UTC)

:: If you want to be more descriptive or specific then you'll need to think about phrases like "damaged by having one of three spans destroyed". Incidentally, I think you really needed the language desk because your problem is not one of engineering but of words - but hey, who's worrying. [[Special:Contributions/86.4.187.55|86.4.187.55]] ([[User talk:86.4.187.55|talk]]) 14:35, 29 October 2008 (UTC)

What about "Rendered Unusable"? [[Special:Contributions/88.211.96.3|88.211.96.3]] ([[User talk:88.211.96.3|talk]]) 15:22, 29 October 2008 (UTC)

::To say that the remaining 2/3s are "functional" is not necessarily accurate either.  Any structure that has had a partial collapse may have other non-visible structural problems elsewhere.  I would not assume that the standing pieces are "undamaged", they are just "less damaged" than the collapsed span.  [[User:Nimur|Nimur]] ([[User talk:Nimur|talk]]) 17:05, 29 October 2008 (UTC)

: Truly - this is neither a science nor an engineering question - it's linguistic - and it belongs on the language desk.  I suppose - if forced to describe it - I'd say that one span was destroyed and the other two appear intact. "Damaged" works for me too - and since we didn't say how damaged, there is indeed considerable ambiguity between a small scratch on the commemorative plaque at one end of the scale - and just a small amount of the bridge remaining at the other.  So "heavily damaged" might be a better choice.  I suppose we really need a word like "incapacitated" ... "non-functional" maybe?  But it's not science - nor yet engineering.

: To quote (my hero)[[Richard Feynman]] who is talking about a walk through the park with his father when he was just a little kid:
::"'' `See that bird?’ he says. ‘It’s a Spencer’s warbler. (I knew he didn’t know the real name.) ‘Well, in Italian, it’s a Chutto Lapittida. In Portuguese, it’s a Bom da Peida. In Chinese it’s a Chung-long-tah, and in Japanese it’s a Katano Takeda. You can know the name of that bird in all the languages of the world, but when  you’re finished, you’ll know absolutely nothing whatever about the bird.  You’ll only know about humans in different places, and what they call the bird. So let’s look at the bird and see what it’s doing - that’s what counts!' ''"
: So - who cares whether the bridge is "damaged" or "destroyed"?  That tells you nothing about the state of the bridge - but only how humans perceive it to be.  The real issue - is how much will it cost to repair - and do we want to do that? [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 17:20, 29 October 2008 (UTC)
:::The reason I ask is that it's notable (on the [[National Register of Historic Places]]) and I think I'm going to write an article on it soon; and I was guessing that there might be some sort of specific term used to describe it for use in the article.  The article will include this photo, so I'll not need just words.  [[User:Nyttend|Nyttend]] ([[User talk:Nyttend|talk]]) 20:34, 29 October 2008 (UTC)

::One of the more common ways of differentiating between "damaged" and "destroyed" is "Is it cheaper to repair it, or to tear it down and build a replacement?"  If it's cheaper to repair, it's been damaged.  If it's cheaper to replace, it's been destroyed. --[[User:Carnildo|Carnildo]] ([[User talk:Carnildo|talk]]) 23:35, 29 October 2008 (UTC)
:::But that dichotomy is rooted in the originally designed/intended function, not the thing itself. "The thing" is only damaged, not destroyed, until it's completely reduced to rubble. Rendered unusable as intended and unable to be repaired to such a state ≠ demolished. [[User:DMacks|DMacks]] ([[User talk:DMacks|talk]]) 01:34, 30 October 2008 (UTC)

== General Relativity and Tides ==

Does the theory of general relativity explain ocean tides?[[User:Parsecs1|Parsecs1]] ([[User talk:Parsecs1|talk]]) 14:36, 29 October 2008 (UTC)
:Yes. [[Special:Contributions/12.10.248.51|12.10.248.51]] ([[User talk:12.10.248.51|talk]]) 16:10, 29 October 2008 (UTC)
::I'm sure it does in some way but I thought because we're dealing with things on such large scales (Earth, Moon, Oceans) that Newtonian laws were good enough? —'''[[User:Cyclonenim|Cyclonenim]]''' ([[User talk:Cyclonenim|talk]] · [[Special:Contributions/Cyclonenim|contribs]] · [[Special:EmailUser/Cyclonenim|email]]) 16:26, 29 October 2008 (UTC)


: Technically - I suppose - general relativity is SLIGHTLY involved - but that's a really silly, misleading and quite utterly useless answer.

: For all practical purposes, the answer is "No".  Straightforward gravity - per Sir Isaac Newton - suffice to explain the tides without mentioning general relativity.  Science has known how tides work perfectly well - and has been able to calculate their properties for a hundred years before Einstein.

: The gravity of the moon decreases with the square of the distance from it.  Hence, the gravity on the side of the earth nearest the moon is slightly greater than over the rest of the planet - so water is pulled harder towards the moon on that side.  It's actually a bit more complicated than that because there are actually TWO high tides - one on the side nearest the moon - and another on the side furthest from it.  This is because the earth-moon system rotate around a common center of gravity that's not at the center of the earth - but a bit closer to the moon. If you imagine this pair of large objects spinning around a point somewhere between their centers - than you'll see that the part of the earth that's furthest from the moon is subject to some centrifugal force (yes, I know there is no such thing as centrifugal force - it's a handy shorthand and I have no compunctions in using the term in casual explanations).  That centrifugal force throws the water on the side OPPOSITE to the moon outwards - hence there are TWO tidal bulges - one that is strongest when the moon is overhead - and the other that's strongest when the moon is directly below your feet.  The daily rotation of the earth places the moon overhead and beneath the ground roughly twice per day - so the high tides are roughly 12 hours apart.  In fact - because the entire earth-moon system rotates around it's center once a month, that means that there is actually one extra pair of tides every lunar month - so the interval isn't quite 12 hours.   To throw some more complexity into the mix - the sun's gravity also produces tides - although not so strongly as the moon.  So you get smaller solar tides added to the lunar ones.  The combination of the two means that the strongest tides are when the sun and moon are close together in the sky at midday - or close together underground at midnight.

: None of that explanation requires reference to general relativity - but doubtless there are TINY, MINISCULE effects due to relativity - which would be much too small to measure against the other properties of the ocean that can cause the tidal changes to be either more or less than you'd expect (eg the shape of the coastline - or the slight changes in the temperature of the water between summer and winter).

: Hence the best answer to your question is a resounding "No" - although some pedants might like to say otherwise.   To the pedants...please don't let pedantry get in the way of a clear and useful answer to a simple question.

: [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 17:05, 29 October 2008 (UTC)
::Actually, the question was "Does the theory of general relativity explain ocean tides?" not "Is Newtonian physics good enough to explain ocean tides.".  Anyway, it's all good. :) [[Special:Contributions/12.10.248.51|12.10.248.51]] ([[User talk:12.10.248.51|talk]]) 20:18, 29 October 2008 (UTC)

::I don't understand your centrifugal-force explanation of the tide on the far side, and I think it's incorrect. The tide on the far side happens for the same reason as the tide on the near side: because things nearer the Moon are pulled more strongly. The water nearest the Moon gets pulled more than the Earth, so it separates slightly from the Earth; the water farthest from the Moon gets pulled less than the Earth, so it separates slightly from the Earth.

::I'd never argue that general relativity is needed to explain the tides, but I might argue that the "philosophical framework" of general relativity is better for understanding the tides. In general relativity the gross acceleration of gravity is fictitious, just like the centrifugal force. When you're weightless, you're weightless; a gravitational acceleration you can't feel doesn't exist. The ''real'' gravitational field, i.e. what's left when you subtract out the fictitious part, turns out to be exactly the tidal force. <small>(Not quite true, but close enough. I don't want to be pedantic...)</small> The tidal force tries to "[[spaghettification|spaghettify]]" you, by stretching you parallel to the direction of the gravitating body and squeezing you in the perpendicular directions. So in general relativity it's very simple: the Earth is in freefall, and there's a tidal-force contribution from the Moon and another from the Sun. They both spaghettify the water, which is why they cause two high tides on opposite sides of the Earth and a ring of low tides in between. (Or would, anyway, if not for all the confounding factors mentioned in the [[tide]] article.) -- [[User:BenRG|BenRG]] ([[User talk:BenRG|talk]]) 23:36, 29 October 2008 (UTC)

The viscosity of sea water affects tides. It slows down the flow of sea water into the high tide regions on both sides of the earth. This makes high tides lower and low tides higher. Also, land masses deflect tidal current, causing variations in tidal height and timing. See "Tide" in Wikipedia.

== Glassmaking kiln explosions? ==

Hi - I'm writing a scene where I need a disastrous explosion of a kiln in a sixteenth century glassmaking workshop - was such a thing possible? - if so, how? 

ta - [[User:Adambrowne666|Adambrowne666]] ([[User talk:Adambrowne666|talk]]) 19:23, 29 October 2008 (UTC)

: The glassmakers of Wimpole Street were the best in the business - they've been commissioned to make an enormous glass snowglobe for a rich nobleman - it's a wedding present for his new wife who comes from Sweden and misses the snow terribly.  It's 3 gallons of water enclosed in a two foot sphere of inch-thick glass - soon to be engraved with the nobleman's vows to his new wife (just as soon as they get that Swedish translator in).  It's held in an delicate, ornately carved wooden frame that's perfectly weighted so the enormous globe is easy to turn over to make the snow fall.  The glass blowers have been struggling to make it for months - there have been many attempts and many failures.  It's the hardest thing they've ever had to produce.  But finally they have something so perfectly round and amazingly clear that nobody has seen the likes of it before.  They fill it up with water and fake snow (maybe some kind of wax-based concoction) and their top glass-guy is melting a small disk of glass into the very top to invisibly block the hole that they used to fill it through.  His apprentice looks on at the most impressive object they've ever made - realising that he'll never again be in the presence of something so beautiful - despite it's deceptive simplicity.  The glass plug is in place and is cooling off nicely when the klutzy apprentice rests his hand atop the globe.  It's still pretty hot and he recoils in pain...trips and falls against the ornately carved (but flimsy) wooden frame.  The frame snaps and the globe rolls slowly and ponderously towards the furnace while everyone looks on in horror - they don't have time to make another before the wedding day.  They are all frozen to the spot as the globe wobbles on the edge of the kiln...then falls in.  It doesn't break - the glass is too thick.  But it's too hot inside the kiln and the globe is FAR too heavy to lift out with the tools they have.  Try as they may, they can't get it back out again.  The glass on the outside won't get hot enough to melt because the water inside is absorbing the heat and keeping it under 100 degC...until the water boils...then KABOOOOOOM!!!!!  Glass, fake snow, steam and white-hot coals from the kiln go everywhere - most of the building is levelled by the explosion.  The only person to survive (inevitably) is the klutzy apprentice who "learns a valuable lesson".

: The big problem with that is that snowglobes weren't invented until the 1800's sometime...so no good for you.  But maybe you can come up with something similar?  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 20:29, 29 October 2008 (UTC)

The glass makers may have used [[Sulphur]] (or brimstone) as pigmentation in the glass.  To form a [[glass]] you need to rapidly quench a melt.  So the Sulphur will need to be heated to above its melting point.  Since Sulphur burns easily in air, it will have to be sealed in a container with the other glass constituents to prevent exposure to air.  The vapour pressure of Sulphur is very high and so it is quite likely the container would explode!  Since molten Sulphur is extremely flammable there will be quite an explosion and resulting fire. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 21:39, 29 October 2008 (UTC)

:But sulphur boils at 444 degC - but glass doesn't melt until 1500 degC.  How are you going to get even liquid sulphur into the liquid glass if it boils before you can get it in there?  As our article [[Glass_production#Colors]] says - the Sulphur is added in the form of "iron polysulphides".  It can't just be pure sulphur...no way!  iron sulphides melt at temperatures similar to the glass - so they aren't going to do anything exciting in the kiln. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 03:06, 30 October 2008 (UTC)

::Sorry but you are incorrect.  I have made plenty of [[chalcogenide|chalcogenide glasses]] using pure '''elemental''' sulphur.  I have also had a few ampoules explode! The fact that Sulphur boils at 444 degC is irrelevant, since once it has been melted it will react with the other glass constituents.  These don't necessarily have to be in the liquid-state.  Also, you mention "glass" melts at 1500 degC.  This is a complete fallacy.  It depends what glass composition you are talking about! Many glasses have melting temperatures much much lower than the temperature you are talking about. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 13:39, 30 October 2008 (UTC)

:::Just to clarify, the glass constituents, including elemental Sulphur are sealed in a container and heated, this could be done through a series of furnaces at different temperatures so to gradually raise the temperature.  However, since the vapour pressure of Sulphur is very high, the pressure is too much and the container '''explodes''', exposing the molten Sulphur to air, and any the other constituents.  The Sulphur immediately ignites and destroys the glass workshop. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 08:02, 31 October 2008 (UTC) 

::::Oh man, I'm already picking apart Steve's sphere explosion theory on his talk page. Do I have to go after this one too? Sigh. What size pressure vessel and how much elemental sulphur are they using? What other components are in the sealed vessel? When will people learn the simple answer - snow-globe technology was developed by the [[Picts]] and suppressed by the [[Knights Templar]] until [[Charles Dickens]] rediscovered it when he found [[The Pickwick Papers]] in a Welsh [[tumulus|barrow]]. [[User:Franamax|Franamax]] ([[User talk:Franamax|talk]]) 09:23, 31 October 2008 (UTC)

:::::Sorry but I'm not sure whether you're being flippant or serious.  Which part of the theory do you disagree with. I don't expect you would need too much elemental sulphur to produce some nice colours.  But it would need to be heated in a vessel since otherwise it would just react with the air.  Other glass constituents?  Well that depends what they are making but lets just go for a silica based glass but this is really not very important since its the vapour pressure of sulphur which will produce the explosion.  I have made some sulphide glasses up to 3 g sealed in ampoules.  If these are heated too quickly, the vapour pressure of the sulphur causes the ampoules to explode, '''violently'''.  I have witnessed this and was glad I had appropriate shielding in place.  Scaling this to an industrial scale and can easily envisage a large scale explosion. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 10:15, 31 October 2008 (UTC)
::::::I'm being both flippant and serious, as usual. We're talking 160 lb. or so of glass, so it's going to be a lot of sulphur anyway. This glass needs to be extracted as a melt though, and shaped into a globe, right? - so it has to be an openable container at the very least. But why would you use a sealed container anyway - unless you knew you had to contain vapour pressure during the melt process, in which case you would use a freakin' big cast iron lid, because you already knew what happened when you did it with 3g of sulphur? Questions along that line is where I would start, then I would look at the vapour containment efficiency of the openable container to estimate at what point it would start venting gas. Then I'd go back to what you already said about how as the sulphur vapourized, it would begin reacting with the other solid components, and I would wonder about why the Renaissance glassmakers would be trying to use elemental sulphur instead of compounds with a better melt compatibility. I don't doubt what you're saying about vapour pressure of heated sulphur though, nor its reactivity - just trying to figure out how the glassmakers got killed. [[User:Franamax|Franamax]] ([[User talk:Franamax|talk]]) 10:35, 31 October 2008 (UTC)
:::::::Where does it say the glass makers are trying to make a globe?  That was just SteveBaker's suggestion - which by the way I'm not very impressed with (but I think my impression is tainted by the fact that he told everyone that you can't make glass using elemental sulphur when you/I clearly can!)  But anyway, I was thinking along the lines that they just want to make some coloured glass for some reason - any reason, the OP didn't specify.  So they would heat up the consituents in their container to the melting point of Sulphur.  When I speak of vapour pressure, I mean at its melting point.  Sulphur has a very high vapour pressure at its melting point, see the article on [[Vapor_pressure]] to see what I mean.  I'll try and find an article that actually states the vapour pressure of Sulphur. So anyway, the majority of Sulphur is still molten and will react with the other constituents while still molten.  The reason I thought they might use elemental Sulphur is purely because I think it would be readily available. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 10:53, 31 October 2008 (UTC)
:::::::Oh yes, and the reason you need to contain the glass constituents is to prevent the sulphur reacting with the air.  It would just burn if left in the open. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 11:05, 31 October 2008 (UTC)
::::::::(e/c) You're indented under the snow-globe, so I thought it was the same story :) There's still the issue of the need for an openable container, if they wanted to ''shape'' the glass - so what is the failure mode of the container? Now using elemental sulphur is a possibility, but wouldn't they then throw the sulphur into the melt at full temp? Some (or most) would burn off, but the molten part could be mixed in. Or heat the sulphur to molten in a container that could off-gas, then add the molten sulphur to the melt? But to get a uniform mix in the melt, seems to me it would be more practical to use a compound with a higher melt point, so as to be more compatible with the process. These are practical people after all. I'll go with your story, you just need to flesh it out a bit :) Personally, I think the easiest way to go is that rain built up on the roof, which collapsed and dumped cold water into the kiln - if we're talking 1500 C, that should make a nice mess. [[User:Franamax|Franamax]] ([[User talk:Franamax|talk]]) 11:24, 31 October 2008 (UTC)
::::::::And wouldn't you heap the other components on top of the sulphur to prevent it being exposed to air? And maybe heap some lime on top, or ash, or whatever will segregate from the melt, either top or bottom, to prevent air exposure during the melting process? [[User:Franamax|Franamax]] ([[User talk:Franamax|talk]]) 11:24, 31 October 2008 (UTC)
:::::::::Many of your points are valid but I really don't care enough to make any further comment :)  It's not my story after all, I agree it needs fleshing out but the OP can do that themself! I have provided a possible cause of an explosion in a glass making workshop and am not saying its the best explanation but it is possible nonetheless.  Your water explanation would indeed be disastrous also. [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 13:15, 31 October 2008 (UTC) P.S. I have adjusted the indentation of these posts.
::::::::::Well, we've killed these people three different ways now, I guess that's enough - and the OP is happy. Another RefDesk question successfully beaten unto death! :) [[User:Franamax|Franamax]] ([[User talk:Franamax|talk]]) 13:37, 31 October 2008 (UTC)

See "Shattered" by Dick Francis [http://www.guardian.co.uk/books/2000/oct/27/digestedread] for a hint about what unannealed glass can do. An explosion involves potential energy suddenly released. [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 04:31, 30 October 2008 (UTC)

:::I agree annealed glass can be very dangerous, but the OP is asking for an accident inside the kiln, which will be before the glass has been made.  Maybe there is a chance that something could go wrong in the annealing kiln though, maybe if it is heated too quickly or something? [[User:Jdrewitt|Jdrewitt]] ([[User talk:Jdrewitt|talk]]) 10:21, 31 October 2008 (UTC)

: Wouldn't a glassmaking workshop have a large supply of coal on hand?  Perhaps they get careless with it, and somehow their coal store fills with explosive coal dust?  This seems like rather a stretch. [[User:APL|APL]] ([[User talk:APL|talk]]) 05:14, 30 October 2008 (UTC)


::Not sure about exploding, but you might be interested to know that in 1291 the city of Venice forced their famous glassmakers to move their workshops to the [[Murano glass|island of Murano]] because they feared the dangers of fire in their mostly wooden city.

All great stuff - I'm extremely grateful for the detail everyone - Steve Baker's story's fantastic - I might try a variation on that - not a snowglobe, but another waterfilled glass sphere - I love the sulphur and rain ideas too - will keep them for future use - thanks, all [[User:Adambrowne666|Adambrowne666]] ([[User talk:Adambrowne666|talk]]) 11:39, 31 October 2008 (UTC)

:If you're seriously going to go with it - you should probably take a spin over to [[User talk:SteveBaker|my talk: page]] where [[User:Franamax]] and I were engaging in some side-discussions on the subject.  It's certain that I didn't do any kind of math (bad, bad, bad!) in proposing the idea - and I got a '''lot''' wrong that Franamax can help to correct.  A two foot sphere would contain around 20 gallons of water - not three - so we might want to go with a smaller sphere in order to give it a chance to explode before they can put out the fire in the kiln.  Franamax has some convincing math that shows the kinds of pressure it would take to rupture a 1" thick sphere - and in retrospect, that may be WAY too thick.  But I'm convinced that some variation on the numbers would correctly produce the kind of situation you need...at least to the degree necessary to convince 99% of the readers of your work!  The business of snow globes not being invented for another 200 years is actually a nice thing you could weave into the story.  These guys invented the snow globe - but the explosion resulting from the disaster kills all but the young apprentice - so the idea for making such things (along with the not-inconsiderable technology needed to make one this big) would have been lost in the explosion...not to be re-invented for another 200 years.  So it's at least a consistent story - if not historically accurate.  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 18:45, 31 October 2008 (UTC)

== Maximum visual acuity ==

In conventional optometry you increase visual acuity by correcting the curvature of the cornea, or by using glasses to bend the light in a similar manner. The upper limit on the [[visual acuity]] provided by these methods seems to be the exactness of the lens and the precision of the prescription, but I am wondering whether there is an upper-bound imposed by the density of receptors on the retina. Ignoring changes in the shape of the eye and assuming a perfect lens, what is the limit of human visual acuity? [[User:Plasticup|<b><span style="color:#0080FF;">Plasticup</span></b>]] [[User_Talk:Plasticup |<span style="color:#2A8E82;"><sup><small>T</small></sup></span>]]/[[Special:Contributions/Plasticup|<span style="color:#2A8E82;"><small>C</small></span>]] 22:21, 29 October 2008 (UTC)

:We have around 120 million 'rod' cells (and a lot fewer cones) so we can resolve brightness (but not color) at roughly 11,000 x 11,000 pixels - that's pretty amazingly good (consider that we think a 10 megapixel camera is pretty nifty - but we have two 120 megapixel devices in our heads!) - but we can actually do even better than that.  The eyeball never stays precisely still - it's always moving around a teeny-tiny bit.  This means that each of those 120 million detectors is able to sweep over a small area around the point it's nominally aimed at.  By noticing how the brightness changes over time as the eyeball wobbles, we can get even more precision.  The precise resolution is hard to deduce since it depends on complicated aspects of how the data is compressed and encoded in the layers of cells behind the retina and down the optic nerve.  However, within a roughly 50x50 degree region that we can take in with a single glance - so we can resolve better than 16 arc-seconds when the lens is good.  Color resolution is not so good - 4.5 million cone cells.  But they are more concentrated in the center of the retina - perhaps 2,000x2,000 pixels.  A pretty standard 4 Megapixel camera can do color about as well as we can - but our huge lead in brightness precision wipes that out in terms of image sharpness.  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 02:29, 1 November 2008 (UTC)

== Proving that the moon exists to doubters ==

Is there a simple experiment that can be carried out at home, requiring no complex/expensive scientific equipment, that can conclusively prove that the moon, our moon, is in fact a genuine, bona-fide moon (in the 'celestial body' sense) - and not a man-made construct, floating above us, at most a couple of hundred miles away? --[[User:Kurt Shaped Box|Kurt Shaped Box]] ([[User talk:Kurt Shaped Box|talk]]) 22:34, 29 October 2008 (UTC)

:Is [http://homepage.mac.com/dtrapp/ePhysics.f/labII_4.html this] the sort of thing you were looking for. [[User:Theresa knott|Theresa Knott]] | [[User talk:Theresa knott|token threats]] 22:54, 29 October 2008 (UTC)

:Proof is a mathematical concept, there is no such thing in science. All you can do is collect evidence to support or oppose a theory. You then pick the theory that is most likely given the evidence. The fact that there is documented evidence of the moon existing before we developed the technology to create anything that would look like that is pretty conclusive. If anyone truly believes that the moon isn't real then they are basing their belief on something other than reason so no reasoned argument will ever persuade them. --[[User:Tango|Tango]] ([[User talk:Tango|talk]]) 23:15, 29 October 2008 (UTC)

::If the moon were only a couple of hundred miles above the Earth, what are the chances that it would pass over ''your'' house every night? If you ever take a vacation you will notice that the moon is visible from all over the planet, and must therefore be very far away. [[User:Plasticup|<b><span style="color:#0080FF;">Plasticup</span></b>]] [[User_Talk:Plasticup |<span style="color:#2A8E82;"><sup><small>T</small></sup></span>]]/[[Special:Contributions/Plasticup|<span style="color:#2A8E82;"><small>C</small></span>]] 23:19, 29 October 2008 (UTC)

:::That logic only works if you assume the Earth is large and round.  ;-)  But yeah, the fact the moon looks the same from two widely seperated vantage points is an argument for it being a great distance away.  [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 23:26, 29 October 2008 (UTC)

::::Unless the moon is following you... --[[User:Kurt Shaped Box|Kurt Shaped Box]] ([[User talk:Kurt Shaped Box|talk]]) 23:28, 29 October 2008 (UTC)

:::::::*The fact that it can be seen simultaneously by people in different places would take care of that objection -- and incidentally also provides a proof that the Earth is not flat, because which way up you see the Moon depends on your latitude.  However, this really falls outside of the category of household experiments, because it requires long-distance communications. --Anonymous, 05:52 UTC, October 30, 2008.

::::::I've been followed by a moon shadow. I used it to navigate in the woods at night. Does that count? [[User:Edison|Edison]] ([[User talk:Edison|talk]]) 04:28, 30 October 2008 (UTC)
:::::::I'm being followed by a moon shadow too! A moon shadow, moon shadow. In fact, I'm leaping and hopping on a moon shadow…moon shadow, moon shadow. Oh wait, [[Cat Stevens|that wasn't me]]. [[User:DMacks|DMacks]] ([[User talk:DMacks|talk]]) 04:38, 30 October 2008 (UTC)
:::::"The" moon? The contraptions are obviously all over the place! [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 23:33, 29 October 2008 (UTC)

:I was going to give the parallax answer, but Theresa beat me to it.  On the other hand, you don't even need that measurement to determine that the Moon is very far from the Earth.  The equipment-free solution is to go outside and look up at the Moon.  Wait five minutes, and look up at the Moon again.  Notice how it's in the same place relative to the background stars?  Any small body in low Earth orbit would have swept across the entire sky in that time.  (For comparison, the International Space Station, orbiting at an altitude of rougly 400 km, completes one orbit of the Earth about every ninety minutes.  Most folks would notice pretty readily if the Moon rose and set eight times over the course of a single evening.)
:For more precision, one could use a camera to take pictures of the Moon on consecutive evenings.  Measuring the movement of the Moon between images against the background stars would allow you to calculate its orbital period, and from that its altitude.
:Proving that the Moon is not man-made is left as an exercise for the reader.  [[User:TenOfAllTrades|TenOfAllTrades]]([[User_talk:TenOfAllTrades|talk]]) 23:39, 29 October 2008 (UTC)

::That only proves that the fusion reactors and anti-grav drives on the lunar station are able to keep it moving in such a way that it looks like it is far away.  [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 23:59, 29 October 2008 (UTC)

:::[[Occam's razor]]. [[User:Plasticup|<b><span style="color:#0080FF;">Plasticup</span></b>]] [[User_Talk:Plasticup |<span style="color:#2A8E82;"><sup><small>T</small></sup></span>]]/[[Special:Contributions/Plasticup|<span style="color:#2A8E82;"><small>C</small></span>]] 00:03, 30 October 2008 (UTC)

::::My point, which obviously escaped you, is that if someone is already engaging in fantastical thinking to disbelieve in the moon then they are likely to invoke similar nonsense to counter any proof one might offer.  [[User:Dragons flight|Dragons flight]] ([[User talk:Dragons flight|talk]]) 00:07, 30 October 2008 (UTC)

:::::Thank you, [[wiktionary:facetious|I could never have figured that out on my own]]. [[User:Plasticup|<b><span style="color:#0080FF;">Plasticup</span></b>]] [[User_Talk:Plasticup |<span style="color:#2A8E82;"><sup><small>T</small></sup></span>]]/[[Special:Contributions/Plasticup|<span style="color:#2A8E82;"><small>C</small></span>]] 05:28, 31 October 2008 (UTC)

:Probably the easiest proof that the Moon is large and far away is that the apparent size does not change over the course of the night. If the Moon is only 500 miles up and 4.3 miles across, then (assuming the Earth is 8000 miles in diameter) the apparent size should be about five times larger when the Moon's overhead than when it's on the horizon. Incidentally, this works regardless of if the Earth is flat or round, and doesn't require that either Einstein's or Newton's law of gravity be correct. --[[User:Carnildo|Carnildo]] ([[User talk:Carnildo|talk]]) 23:46, 29 October 2008 (UTC)

:Tides.  It takes a monumental amount of force to move a bajillion tons of water 10' vertically upwards.  If the moon isn't really a chunk of matter 1/6th the size of the earth - then how do the tides happen precisely in sync with that white circle up there in the sky?  So - no fancy hardware.  A measuring stick - a beach and someone to watch where the "moon" is in the sky when the tide is at it's highest.  QED.  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 02:44, 30 October 2008 (UTC)

::1/6?!  It's over 1/4 of the Earth's size by diameter, and under 1/80 by mass.  --Anonymous, 05:53 UTC, October 30, 2008.

::If the Moon's orbiting the Earth once per month at an altitude of 500 miles, you can't assume that gravity is behaving according to Newton, so the tides aren't proof of anything. --[[User:Carnildo|Carnildo]] ([[User talk:Carnildo|talk]]) 08:25, 30 October 2008 (UTC)

::I thought the moon was [[Hollow Earth#Concave hollow Earths|inside the earth]]. :) [[User:Dmcq|Dmcq]] ([[User talk:Dmcq|talk]]) 11:02, 30 October 2008 (UTC)

:No, you can't prove that to a determined doubter.  See [[brains in vats]], [[Plato's cave]], [[solipsism]], [[The Matrix]].  --[[User:TotoBaggins|Sean]] 13:52, 30 October 2008 (UTC)

:The moon does exist.  Otherwise, how would they mine all that cheese? [[Special:Contributions/12.10.248.51|12.10.248.51]] ([[User talk:12.10.248.51|talk]]) 15:11, 30 October 2008 (UTC)


'''Occam's razor''' doesn't tell you to '''ignore evidence'''.  In this case the evidence is '''overwhelming'''.  Let me cut and paste:
{{cquote|'''THE MOON: RIDICULOUS LIBERAL MYTH'''<br>
It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- <i>with the same side facing us all the time</i> -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! <i>Daddy's Roommate?</i> God Almighty!) <br> <br>Documentaries such as <i>Enemy of the State</i> have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, <i>the liberals will see it!</i> These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you. <br> <br>Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for <i>that</i> particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who <i>dare</i> to make use of their God-given rights at night! <br> <br>Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, <i>there is no mention of the "moon" anywhere in literature or historical documents -- <strong>anywhere</strong> -- before 1950.</i> That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down.}}  <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/82.124.209.97|82.124.209.97]] ([[User talk:82.124.209.97|talk]]) 14:06, 31 October 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
::Wow - so "''The moving Moon went up the sky, And no where did abide: Softly she was going up, And a star or two beside.''" (Samuel Taylor Coleridge, The Rime of the Ancient Mariner) must refer to the launching of the "moon" - and since it's claimed (in those Liberal "public schools") that Coleridge died 120 years before the "moon" was launched in 1950 - we have proof that the school system is covering up for "big government".  Since he's also claiming that one or two of the stars were launched on the same day - we have to wonder what other things are being looked at?!   But "''When I consider thy heavens, the work of thy fingers, the '''moon'' and the stars, which thou hast ordained...''" comes from Psalm 8:3-4.  This means that they even rewrote bits of the Bible!  Is there no depths to which they will not sink?  If we can't trust the bible then maybe the Theory of Evolution is true too!  Where does the rabbit hole end?  [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 18:27, 31 October 2008 (UTC)

''THE MOON:...  '' but isn't this Ed Anger, the great columnist of [[Weekly World News]]? --[[User:PMajer|PMajer]] ([[User talk:PMajer|talk]]) 10:30, 4 November 2008 (UTC)