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December 15

Blood Pressure differential

A person registered a blood pressure with a wide differential between systolic and diastolic pressure (say 150/60), what physiological conditions (if any) would that indicate?

Full disclosure: past test question.

Thanks in advance. — Preceding unsigned comment added by 174.113.7.240 (talk) 01:32, 15 December 2011 (UTC)

See Pulse pressure#High .28Wide.29 Pulse Pressure. --Tango (talk) 01:41, 15 December 2011 (UTC)

And if you have concerns about your health, see a doctor. No one here is qualified to diagnose medical conditions over the internet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:26, 15 December 2011 (UTC)

Aren't you making quit a leap here Bugs, assuming that the OP is suffering from hypochondriasis of medical students? Reliving past tests may well affect one's pulse, but there is no indication that is happening here. -- 19:51, 15 December 2011 (UTC) — Preceding unsigned comment added by 203.82.91.133 (talk)

Medical students' disease is the applicable link (search on Google for 'isolated systolic hypertension')--Aspro (talk) 20:03, 15 December 2011 (UTC)

Exploding electrode

What would cause a pure graphite electrode to explode during use? Explode may be the wrong term - it suddenly cracked open lengthwise and briefly thereafter disintegrated, sending shrapnel flying everywhere. The electrode was cylindrical, about 3 mm in diametre, and was used in a modified Castner reaction. Plasmic Physics (talk) 11:13, 15 December 2011 (UTC)

Was it a (very) porous electrode. Could metal ions have had enough time to diffuse into it. Is their a chance that the polarity got reversed. Had it been immersed in an acid solution previously. Did this cell involve any carbonates. The lengthwise split suggest the outer surface expanded (like putting wedges in a wooden log). What exactly where the chemicals involved. In other words - Need more info. Who said chemistry wasn’t exiting.--Aspro (talk) 19:39, 15 December 2011 (UTC)

It is the chemists who "exit" suddenly when things start exploding.Edison (talk) 01:24, 16 December 2011 (UTC)

Please blame my spell checker for losing the 'gh' there in the last word. And agree also, that they do from time to time they disappear in a puff of smoke with a loud report (or should that be a loud retort) :-)--Aspro (talk) 14:59, 16 December 2011 (UTC)

Exighting? That would be a cool word, if it actually, er, existed. What you need is "exciting".  :) -- Jack of Oz ^{[your turn]} 06:29, 17 December 2011 (UTC)

Were you trying to make that sodium metal electrolytically? Graeme Bartlett (talk) 22:36, 17 December 2011 (UTC)

Yes, I did try to make sodium metal electrolytically. No, the electrode was not exceptionally porous. Prior to being used in this way, the electrodes were cleaned and dried. The chemicals used was 98% sodium hydroxide monohydrate, and an initial quantity of water to initiate the process. The reaction ran according to plan for some time, before this happened. Plasmic Physics (talk) 07:09, 18 December 2011 (UTC)

After repeated reactions, it only occured once yet. Plasmic Physics (talk) 11:12, 19 December 2011 (UTC)

how can i get :- a)ammonia gas ---- b)potassium hydride

how can i get :- a)ammonia gas ---- b)potassium hydride from :- water - oxygen - carbon dioxide - potasium - nitrogen ("Note : you can use some or all the previous substances")

---

My try to solve this : a) 6K + N₂ -----> 2K₃N then K₃N + 3H₂O -----> 3KOH + NH₃ but i am not sure from the reaction between potassium and nitrogen , is it true reaction???

b)i don't know how to get this :( — Preceding unsigned comment added by Mido22 (talk • contribs) 12:47, 15 December 2011 (UTC)

I have no idea how "practical" (vs "write a balance reaction") an answer this is, but our article on potassium notes that nitrogen is used to extinguish potassium fires--therefore they do not likely react with each other. Looking up what K₃N would be, we have an interesting article about nitride chemicals, which addresses whether this one is likely (with a side-note about Li₃N being easy to make by the type of reaction you propose. Looking in the lithium#Chemistry and compounds section, you can find the answer to whether direct reaction between potassium and nitrogen is expected to occur. DMacks (talk) 15:19, 15 December 2011 (UTC)

I doubt K and N would react. How about adding K to water which IIRC will produce KOH and H2. You could then react the H2 with N to make ammonia (assuming you have the apparatus for the haber process. SmartSE (talk) 16:48, 15 December 2011 (UTC)

If we can get a source of carbon monoxide, we can generate hydrogen gas from the Water gas shift reaction. That's often a precursor for Ammonia production. --Jayron32 23:52, 15 December 2011 (UTC)

Potassium hydride or Potassium Hydroxide? Dropping water on potassium gives potassium hydroxide and hydrogen gas. If you want potassium hydride, you need to collect the hydrogen, then heat the potassium up and blow the hydrogen over it (as per Humphry Davy). Ammonia's harder - the nitrogen needs to be fixed. SmartSE is right about direct combination of nitrogen and hydrogen in the Haber Process, but you need high pressure, temperature, and typically a metal catalyst. Buddy431 (talk) 04:05, 16 December 2011 (UTC)

If you put your nitrogen through an electric discharge you can react this active nitrogen with potassium to make K3N. This reacts with water to make ammonia. A very expensive way to make it. Graeme Bartlett (talk) 04:44, 20 December 2011 (UTC)

Gasoline fuel cell

Do these exist? How do they compare with ICE? I know they are more expensive, but performance wise. ScienceApe (talk) 12:58, 15 December 2011 (UTC)

I'd like to better answer the question but that means that I'd have to better understand it as well. And I don't.

I've often heard the term "fuel cell" used to refer to a small (a couple gallons) fuel tank in a street legal car that is used for racing on weekends. But looking at ICE, I have no idea what you're comparing a gasoline fuel cell to (or my definition of it).

And finally, in the first question, you asked if they exist but in the final sentence you say that they are more expensive. So which is it? Do you wonder if they exist or know they do and therefore wonder if they are worth the cost? Dismas|^(talk) 19:49, 15 December 2011 (UTC)

ICE is almost certainly, from the context, an internal combustion engine, driving an alternator. A fuel cell converts a fluid fuel directly into electricity. They have three chambers, separated by two metallised semi-permeable membranes. The fuel is pumped into one of outer chambers, air/oxygen into the other. The 'burn' at membranes, and the exhaust is removed from the middle chamber. Methanol/ethanol fuel cells were going to be the next laptop power supply, a few years ago, but seem to have dropped of the radar. I'm also not sure how well they scale to the 1 hp (750 W) plus of gasoline engines. CS Miller (talk) 20:37, 15 December 2011 (UTC)

While proton exchange membrane fuel cells are what most people think of when someone says "fuel cell", they aren't the only type of fuel cell. Due to their low operating temperature (which makes them attractive for automotive applications), PEM fuel cells primarily use hydrogen fuel. There are some PEM variants which directly use methanol or ethanol as fuel (Direct methanol fuel cells and direct-ethanol fuel cells), but those are less developed than the hydrogen fueled ones. In contrast to PEM fuel cells, there are also solid oxide fuel cells and molten carbonate fuel cells. These operate at much higher temperatures, and as a consequence can easily use gasoline directly as a fuel source (there are some prototype PEM systems which use gasoline fuel, but they almost all use a separate step to first reform the gasoline into hydrogen). The drawbacks to using SOFC & MCFC for automotive applications are that their high operating temperatures mean that they take a long time to start up, so aren't good for the intermittent usage inherent in cars. Additionally, their construction tends to be more fragile than PEM fuel cells, so are better suited to stationary applications, rather than being bumped around in a car. Researchers are working on both the robustness and the operating temperature of SOFCs & MCFCs, so it's possible that at some time in the future there will be a direct gasoline fuel cell that is suited toward automotive applications. -- 140.142.20.101 (talk) 00:33, 16 December 2011 (UTC)

Indeed. I figured anyone who didn't know what ICE stood for, probably wasn't qualified to answer my question anyway :P ScienceApe (talk) 19:46, 17 December 2011 (UTC)

In what way is the Higgs mechanism not a fundamental force?

Seems that all the bosons of the standard model are mediators of forces, so why not the Higgs boson? What makes it different from the others? Goodbye Galaxy (talk) 15:36, 15 December 2011 (UTC)

The Higgs boson is a spin-0 boson (AKA scalar boson). All other Standard Model bosons are Spin-1 Gauge bosons (AKA gauge vector boson). The key word here is gauge, not boson. The Higgs boson is not a gauge vector boson so it is not associated with a gauge interaction (AKA fundamental force). Dauto (talk) 15:52, 15 December 2011 (UTC)

Odd math

Let's take an event which lasted 4 years, say from 1941 to 1945. Now if I want to briefly describe this event year by year, I arrive to the odd number of 5 years (including 1941). Is there some reference in math to such an odd division?--46.204.24.211 (talk) 18:41, 15 December 2011 (UTC)

It depends on if/how you count the end points, also known as inclusive vs. exclusive counting. If the event started on Jan. 1 1941, and ended on Dec. 31, 1945, then it will have lasted five years. On the other hand, 1945-1941=4, but this is "not counting" the year 1941. So we get a duration of four years if the event starts on Dec 31 1941 and ends on Dec. 31 1945. There's some relevant info at Counting#Inclusive_counting, and also at Closed_interval#Excluding_the_endpoints. SemanticMantis (talk) 19:02, 15 December 2011 (UTC)

See also: fencepost error. --Carnildo (talk) 02:10, 16 December 2011 (UTC)

December 16

principal stress

"Hydraulic fracturing in rocks takes place when the fluid pressure within the rock exceeds the smallest principal stress plus the tensile strength of the rock".

What does this mean? Does principal stress increase with depth? When fracture occurs -- is there negative feedback inhibiting further fracture? Or is there positive feedback (other than that there are now more cracks for fluid). elle _{vécut heureuse} ^{à jamais} (be free) 00:37, 16 December 2011 (UTC)

Does Stress_(mechanics)#Principal_stresses_and_stress_invariants help? --Jayron32 04:14, 16 December 2011 (UTC)

It's literally all Greek to me. I don't understand tensors. I'm a biochemistry student. Basically, what governs crack propagation in hydraulic fracturing deep underground? At what point does the rock stop fracturing? elle _{vécut heureuse} ^{à jamais} (be free) 04:44, 16 December 2011 (UTC)

Hey, if it were greek I may have understood more of it. I'm a chemistry teacher. I also never got to much of the higher algebras either. It was what I could find on the topic when I searched. Knowing what you are looking for, does the Wikipedia article Hydraulic fracturing or any references therein help? --Jayron32 04:49, 16 December 2011 (UTC)

It is basically just a fancy way of saying that a rock will break when the force applied to it is greater than the minimum force required to break the rock. Fractures propagate easily within a single crystal / rock, but geology is sufficiently heterogeneous that such advantageous fracture growth tends to be limited in extent. In general, when you apply a hydraulic overpressure to a geologic formation the effective overpressure will decrease with distance from the well (often as something around 1/r), which limits the distance over which hydraulic fracturing is generally possible from a single well. Dragons flight (talk) 08:53, 16 December 2011 (UTC)

Because of the way that rocks are laid down, there is often a direction of least stress. For example a rock might have been formed from sand and shale particles laid down in a prehistoric river. Over centuries the sand which would later form a rock would tend to become oriented in the direction of the river. After the sand in the now dry river bed is buried and compacted to form rock, secondary effects start to happen. The rock will may be tilted, or bent by faulting and mountain uplift. The tilting and bending will usually be in different directions than the river, so the rock ends up with a variety of stresses. Additionally, due to the weight of the rock above it, other stresses will be created. So, what that statement means is the rock will fracture in its weakest direction. If the rock has been bent enough by geologic forces, there will be millions of microfractures in the rock, which will also help start fractures.

When someone attempts to hydraulically fracture rock, they will first run sensors to try and determine the least stress direction and mechanical properties of the rock. They then create a model of the pressure required and the direction that the fractures should go. They use casing and perforations to control where the fractures began and then start pumping fluid downhole. When the pressure exceeds the strength of the rock, the weakest spot cracks open. The surface pressure will suddenly drop and the frac engineer will know that the fracture has started. They then play with pressure, pump rates and what types of sand that they pump downhole to try and extend the cracks. As Dragon flight says, the pressure decreases with distance, due to friction between the fluid and the rock and also due to an increasing surface area. Since pressure is force per unit area, if the area increases it takes more force to keep the same pressure. Eventually it becomes too expensive to open the fractures up any more, and the process stops.Tobyc75 (talk) 18:37, 16 December 2011 (UTC)

That quote originally comes from here, but not all of the relevant parts are visible (at least to me), so it lacks a full explanation. To produce a tensile fracture (that is a fracture in which the direction of opening is perpendicular to its length - also known as an 'opening mode' or 'Mode I' fracture in fracture mechanics) at depth in a wellbore (borehole), it is necessary to overcome the effects of the weight of the pile of rock sitting above, which produces what is referred to as a confining pressure. By raising the pressure of fluid it offsets the confining pressure until the rock eventually reaches the necessary condition for tensile fracture to happen. This happens naturally in the formation of mineral veins, where the high fluid pressure comes from metamorphic reactions that produce fluids, particularly water. The fracture orientation will be in the plane of the maximum and intermediate principal stresses and perpendicular to the minimum stress direction. Accidental or deliberate hyrofracturing is sometimes used in boreholes as a way of determining the orientation of the stress field at depth. Mikenorton (talk) 20:38, 16 December 2011 (UTC)

the meaning of isogene and examples are welcomed

Hi,everyone,

What i am puzzled was the exactly meaning of the term "isogene".

Dose anyone give me an answer? An detailed explanation will be appreciatedLiujem (talk) 04:33, 16 December 2011 (UTC)

There are several unrelated concepts which use similar terms:

• Isogeny is a mathematical term from Algebraic geometry, that refers to a method of mapping one object to another.
• Isogenicity is a synonym for Zygosity, which is a genetic term refering to the relationship between genes on the two homologous chromosomes in a genome.
• Isogenic human disease models are simpler genomes used to study various diseases, especially cancer.

Does any of those help? --Jayron32 04:44, 16 December 2011 (UTC)

Isogene has two meanings: (1) a line on a map showing the distribution of a gene, by analogy to an isobar, isotherm, etc[1] (2) a copy of a gene that occurs multiple times in an organism's genome - this sense is common in biology[2][3] but I can't find a reference for a definition. --Colapeninsula (talk) 14:31, 16 December 2011 (UTC)

Gas cloud entering black hole in milky way

Would this be visible to any extent other than massive space telescopes; http://4.bp.blogspot.com/_YuR6V_Yr7Bk/S_0PvCTAelI/AAAAAAAAFF4/wNBkqw_INTM/s1600/black+hole.jpg Something like what the link looks like? — Preceding unsigned comment added by 109.224.25.14 (talk) 06:41, 16 December 2011 (UTC)

There's no fundamental reason why you couldn't see it if conditions were favorable. Such observation depends, particularly, on how far away the black hole is. Assuming that we're talking about something with the approximate visible-spectrum luminosity of the sun, it would have to be within 50 light years or so to be naked-eye visible. Mostly, though, such phenomena radiate in the x-ray spectrum, which you're not going to see except via specialized equipment. — Lomn 13:48, 16 December 2011 (UTC)

The centre of the Milky Way is heavily obscured by dust along the line of sight. At visible wavelengths (i.e. those that the human eye can register), essentially everything is absorbed. At infrared wavelengths, the absorption is much less severe which is why scientific observations of the centre of the Milky Way, such as the one that identified the gas cloud, are done in the infrared, which is essentially a matter for professional telescopes (not necessarily space-based - the interesting observations are made from the ground, notably with ESO's Very Large Telescope, and adaptive optics). In addition to X-ray emission, there may also be radio emission, presumably on a longer time scale, though. --Wrongfilter (talk) 14:53, 16 December 2011 (UTC)

how are promoter sequences discovered?

A rather urgent question-- thanks!

You mean, as (concisely) described here? --Ouro (blah blah) 12:45, 16 December 2011 (UTC)

Celsius vs. Kelvin

what ias thew relation bitwin Celsius and Kelvin degree — Preceding unsigned comment added by 77.28.22.143 (talk) 14:49, 16 December 2011 (UTC)

The Kelvin is exactly the same as a degree Celsius. See Kelvin#Use_in_conjunction_with_Celsius. The difference is where the two scales start. 0 Kelvin means absolute zero, but 0 degrees Celsius is the freezing point of water (at least historically, there are some minor modern modifications to the definition of 0 degrees C). Note that "degrees Kelvin" is not proper usage, a Kelvin is the unit. For example, we say "100 Kelvin", but "100 degrees Celsius". SemanticMantis (talk) 15:09, 16 December 2011 (UTC)

... so, just in case this is not clear from the linked articles, to convert degrees Celsius to Kelvin, just add 273.15 Dbfirs 17:13, 16 December 2011 (UTC)

Looking for details behind a Mr. Wizard science trick

One time when I was a kid, I was watching Mr. Wizard on TV and he did this thing where he took one clear liquid and poured it into a pitcher holding another clear liquid, mixed them around a little (the mixture stayed clear), and then had a kid assistant hold the pitcher high while pouring it into another pitcher, and he counted down "three, two, one..." and clapped his hands (for dramatic effect, not that that has anything to do with it), and all at once, the liquid in the bottom pitcher, the liquid in the pouring arc, and the liquid still in the pouring pitcher, all turned a dark purple in an instant. What were those two liquids? 20.137.18.53 (talk) 15:07, 16 December 2011 (UTC)

That's an iodine clock. Classic, performed it a few times myself :) Grandiose (me, talk, contribs) 15:11, 16 December 2011 (UTC)

Thanks!20.137.18.53 (talk) 15:14, 16 December 2011 (UTC)

Damastes--redirects to Procrustes, but recommends "Huntsmen Spider"

Hello!

I am just wondering why "Damastes," one of the names for Procrustes, is suggested in addition to "Procrustes."

What is the connection between the word "Damastes" and the Hunstman Spider?

Or between proctrustes and the Huntsman Spider?

THANK YOU SO MUCH!

Jennifer — Preceding unsigned comment added by 98.97.183.38 (talk) 17:41, 16 December 2011 (UTC)

If you see the Huntsman spider#List of genera section, you can see that Damastes is also a genus of Huntsman spider. We don't yet have an article about the spider genus. -- Finlay McWalterჷTalk 19:01, 16 December 2011 (UTC)

If you're curious as to why there's a spider genus called Damastes (which seems to contain at least the species Damastes nossibeensis), we don't appear to have that information (and what little non-wikipedia info I can find on the spider online doesn't help either). -- Finlay McWalterჷTalk 19:10, 16 December 2011 (UTC)

It's a good question. The opening of the Procrustes article is a bit garbled and hard to follow, and could probably do with rewording. The Damastes page should possibly be made a Disambiguation page rather than a Redirect, and then the Damastes redirect template in Procrustes could be removed. Might do this later. --jjron (talk) 05:28, 17 December 2011 (UTC)

I've started the page for the genus in Damastes (spider) and tweaked the hatnotes for the articles.-- Obsidi♠n Soul 17:58, 17 December 2011 (UTC)

As for etymology, I think it's pretty obvious that the spider is named after the greek mythological figure. Happens a lot in scientific nomenclature. Procrustes itself is also a subgenus (previously a full genus) of the carabid (ground beetle) genus Carabus. However, subgenera do not generally get articles so a hatnote is not needed for it. -- Obsidi♠n Soul 18:09, 17 December 2011 (UTC)

My last two sentences read like tongue-twisters. :D -- Obsidi♠n Soul 18:56, 17 December 2011 (UTC)

Thank you, everyone. I am very grateful not just for the information, but also for the conversation! Do you think there is any way to find out who named the spider after Procrustes? I am writing a novel about Shakespeare that uses the metaphor of the Procrustean Bed . . .

Extracting work from a positive current

So in a fuel cell, hydrogen is ionized into a proton and an electron and the electron then passes through a circut and does work. Ok fine, but the proton passes through an electrolyte and doesn't do any work. Why not? Why can't we extract work from the proton? Is it possible? ScienceApe (talk) 18:02, 16 December 2011 (UTC)

You can extract work from such an electric current. It just so happens that in the practical setups you're typically thinking of, the efficiency would be very low. This is because in most configurations, the maximum current density that can be carried by positive ions is very low.

If you could construct a large current of positive ions flowing through an electrolyte, you could generate heat (for the same reasons that electron flow produces waste heat), and you could, e.g., drive an incandescent light. You could use positive ions as carriers of an electromagnetic wave in an antenna, and propagate a wave (converting energy from the current into electromagnetic energy carried away as a propagating wave). You could, with some effort, build devices that operate with positive ions flowing through wet electrolytes, but otherwise behave analogous to the ways that we extract energy from electron currents in copper wires. You could even create a terrifically inefficient wet-chemistry semiconductor, limited only in practicality by its poor noise, power requirements, and frequency response - but not fundamentally very different from a solid-state semiconductor.

In most cases, including most plasmas and most wet electrolyte solutions, positive charge carriers are less mobile than negative charge carriers; so for optimum efficiency, we use electrons to carry current. This invariably just comes down to the fact that protons are more massive than electrons. Nimur (talk) 18:25, 16 December 2011 (UTC)

It's a little disingenuous to say that you extract work from the electron current and not from the proton current. You can't have the electron current unless you also have the proton current. In reality you're extracting work from the entire system (the complete circuit). There's only a limited amount of energy to extract from the conversion of a set amount of hydrogen, so what you're likely to find is that if you try to extract energy from the proton current directly, the current and/or voltage of the electron current will go down, reducing the amount of work you're able to extract from it. Given the difficulty of extracting from the proton current directly, you'll likely find the best way to extract the greatest amount of energy from the system is to place the load in the electron current, and minimize the resistance in the proton current path. -- 140.142.20.101 (talk) 19:49, 16 December 2011 (UTC)

December 17

Transatlantic travel

By what means (what type of ship) - and for how long - would a Briton (specifically, a Scot or an Englisman) of high social standing have travelled from Great Britain to America in a.) 1767 and b.) 1909-1913? My query pertains to A.) John Witherspoon, signer of the American Declaration of Independence and B.) P.G. Wodehouse, author. How long did the trip take, and what was it like? 82.31.133.165 (talk) 00:41, 17 December 2011 (UTC)

For the latter, one would travel on a liner such as RMS Lusitania; that article details the accommodations on board (which varied in quality greatly by the class of ticket bought). In ideal conditions (such as an attempt to break her own Blue Riband record) Lusitania could cross the Atlantic in less than 5 days. -- Finlay McWalterჷTalk 01:00, 17 December 2011 (UTC)

During the age of sail, common Atlantic-going trading vessels were ships like Galleons and Fluyts and Carracks. I'm not sure there were ever dedicated passenger ships; they wouldn't have been very economical; instead people merely booked on any merchant ship that was headed in the right direction. If there were a large group traveling together, they would essentially book the whole ship (see Mayflower for an earlier example of such a usage). The Mayflower took 2 months to cross the Atlantic; though it was beset by some bad traveling conditions; under ideal conditions about 4 weeks seems to be more standard, especially once Transatlantic travel became more common. --Jayron32 06:16, 17 December 2011 (UTC)

Deploying lifeboats

I think this is the right place to ask this question, kinda fits in with engineering. If not that's fine, I'll move it to miscellaneous or something. But at any rate, on a cruise ship, where do ship employees (if that's the right word) go to actually deploy lifeboats? I emailed a Queen Mary 2 website asking that question but no one had replied. Would it be deployed at the site of the lifeboats (possibly with a control panel near by or something) or would it be near the engine room? Any help would be amazing. 64.229.180.189 (talk) 01:08, 17 December 2011 (UTC)

I can't imagine it being controlled anywhere but where the lifeboat is. You want to be able to see what's going on, when it's level with the deck so people can get aboard, when to stop it if there's some problem, etc. This youtube video (part 1 of 3) seems to go through it step by step (for a US Navy oiler, not for a cruise ship, but the procedure should be about the same I think). Clarityfiend (talk) 01:46, 17 December 2011 (UTC)

From someone who has clocked in a good few nautical miles, and is the offspring of a seaman: I've never seen a lifeboat being controlled remotely from any location from where you couldn't see it. Be it small or large lifeboats, they are deployed directly from their physical location, where the control panel, winch, launchpad or whatever, sits. --Ouro (blah blah) 08:39, 17 December 2011 (UTC)

Another good reason for close proximity is it greatly lessens the risk of wires being cut in whatever calamity the ship is facing. Clarityfiend (talk) 01:39, 18 December 2011 (UTC)

How far can you pull quarks apart

According to Color confinement, you can't pull them apart, but they will stretch and finally form quark antiquark pairs. How far can they be pulled till this happens? ScienceApe (talk) 04:53, 17 December 2011 (UTC)

I'm not sure you can measure such "distances" functionally, nor can you "pull" quarks apart, that would imply you had some means to grab them individually. See Jet (particle physics), which is the only way that the existance of quarks can be inferred, no quark has ever been directly observed. --Jayron32 05:46, 17 December 2011 (UTC)

No isolated quark have ever been observed, but deep inelastic scattering experiments on protons show, for example, that protons must be composite particles made from three subunits. This is similar to the way that the existence of an atomic nucleus was originally inferred. There is a lot of evidence for quarks beyond simply the existence of jets. Some of this evidence is described in quark. Dragons flight (talk) 14:52, 17 December 2011 (UTC)

If you could pull them apart, theory suggests you could go a distance on the order of a few femtometers (10^-15 m). Dragons flight (talk) 14:52, 17 December 2011 (UTC)

Why is traffic on long open roads "lumpy"?

Why do cars on long road sections occur in groups with relatively long gaps between them, instead of being more evenly spread? Roger (talk) 09:42, 17 December 2011 (UTC)

There a couple of reasons for this. First, cars will get on and off of the road (not sure if this counts on long open roads, but it does on highways), thus you get areas where new traffic "spawns"; since these new cars are added at discrete intervals, this leads to some lumping. On the same vein, faster cars will get stuck behind slower cars; new slower cars added, even if going faster than some slower car ahead, may never reach it, thus, giving you clumps. Also, wrecks, or other such, will cause people to cluster, most people will stick to the cluster, thus, causing it to take a while to disperse. Finally, most people seem to have an interval of speed in which they feel safe, so when coming up on a slower driver/cluster, that is not going too much slower than them, they would probably not use the passing lane. There are other reasons, I'm sure; I would imagine a lot of them center around the fact that if some group of traffic is forced to slow down and another not, then the faster group is going to become closer to the slowing down group; depending on the course and reasons, this should lead to various bunching ups of groups. Phoenixia1177 (talk) 11:22, 17 December 2011 (UTC)

A good summary there, and you might be interested in following the links at traffic wave. Yes, there's even an article on this one. And I did an assignment on it once, too, but I wouldn't call it revolutionary - it is definitely part of applied mathematics. IBE (talk) 14:51, 17 December 2011 (UTC)

Traffic engineers call such a lump a "platoon" (Wikipedia has a platoon (automobile) article, but that only discusses proposals to deliberately engineer the formation of platoons, and as ramp meter shows, they also use the term for platoons that aren't wanted). In addition to the scenarios Phoenixia1177 mentions, specific road designs can induce platoons (pedestrian crossings, level crossings, traffic lights) and some can break them up (ramp meters, roundabouts, 4-ways stops). Traffic engineers are clearly in two minds about the desirability of platoons. They're desirable in some cases - if you have a complex signalled junction like a SPUI the traffic lights form platoons and the junction is designed to efficiently push the platoons around the junction - platoons are an efficient use of very limited road space, and they're deterministic (so the traffic modelling software like TRANSYT can predict how a junction will behave). And on highways platoons can be desirable - consider overtaking a platoon of slow lorries in one go, rather than moving back and forth to overtake a succession of widely spaced lorries. But platoons can be undesirable too - if you're waiting at a junction for traffic to pass, you get stuck when a platoon comes along (whereas you might find a space if the traffic was more even), and joining a motorway (on short urban ramp) and encountering a platoon of trucks can be a scary thing. Traffic engineers use queueing theory to try and model dense traffic flows, and (as with other applications of queueing) there's often a balance to be reached between efficiency and fairness. -- Finlay McWalterჷTalk 15:06, 17 December 2011 (UTC)

Sometimes the traffic may just be randomly distributed, with only the illusion of grouping. Mitch Ames (talk) 03:48, 18 December 2011 (UTC)

I also think there's a psychological reason. That is, when you've been passed, you feel like you're going too slow, so speed up. When you pass others, you feel like you're going too fast, so slow down. When everyone does this, the result in clumping. StuRat (talk) 05:34, 18 December 2011 (UTC)

I think that there is strong statistical evidence that traffic isn't randomly distributed. In fact, given the known limitations of a road network, a truly random distribution would be impossible, as long as vehicles were sufficiently close together to interact. As to how much is 'psychological' (per StuRat), and how much is due to 'physical limitations' (maintaining braking distance, needing excess speed to overtake etc), I'd not hazard a guess, though I suspect that the former may account for some of the more serious multi-vehicle collisions that have occurred on UK motorways: there seems to be some evidence that drivers encountering fog will speed up to keep the car in front visible...

(And yes, I know, 'citation needed' - I'm sure I've seen this somewhere...) AndyTheGrump (talk) 05:50, 18 December 2011 (UTC)

...And here's an abstract at least that supports this: "ISOLATION DUE TO THE LOSS OF THE VISUAL STIMULII REQUIRED IN ORDER TO REMAIN ALERT. SUCH A CONDITION OFTEN LEADS TO A SUBCONSCIOUS INCREASE IN SPEED, MOTIVATED BY AN INSTRUCTIVE NEED FOR VISUAL STIMULII (SIGNS, JUNCTIONS, OTHER VEHICLES ETC.) [4]. I've not got access to the original document, but it seems plausible. AndyTheGrump (talk) 06:07, 18 December 2011 (UTC)

A different but related effect is Bus bunching. Vespine (talk) 00:27, 19 December 2011 (UTC)

Implications of the Higgs boson?

Are there any practical applications or implications of the discovery of the Higgs boson or its mass? If so, what are they? 67.6.163.68 (talk) 10:16, 17 December 2011 (UTC)

There are none, yet. --Mr.98 (talk) 13:10, 17 December 2011 (UTC)

And there will probably be none for a long time to come. Dauto (talk) 16:06, 17 December 2011 (UTC)

There may not be any direct applications any time soon. The point of looking for it is to figure out how particles in general work and, by extension, how everything works. That could be quite useful. It is difficult to say what the answer will be useful for because we don't yet know what the answer is, but particle physics has had lots of useful results so far and I'm sure it will continue to do so. Take Positron emission tomography, for example. Doctors find it extremely useful and they wouldn't be able to use it if particle physicists hadn't discovered the positron. --Tango (talk) 00:11, 18 December 2011 (UTC)

The Higgs is thought to carry all mass. See also Higgsless model. ~AH1 ^(discuss!) 03:21, 18 December 2011 (UTC)

How does the GRW theory in quantum mechanics handle multiple hittings?

In the Ghirardi–Rimini–Weber theory of quantum mechanics, spontaneous localisation of quantum particles occurs whenever there is a "hitting", which is a random event happening once in a hundred million years or so for a single particle. It is proposed that this explains how stable macroscopic states emerge from quantum measurements, because any large body (including a measuring apparatus) will have a huge number of particles, and hence many hittings. What happens if, in a rigid body, two hittings occur simultaneously, each one tending in a different direction? I suggest that this might happen for a measuring apparatus of relatively few particles, which would get into an entangled state when measuring a quantum particle. It would enter a superposition for a split second, then have two spatially separated particles undergoing hittings. The spontaneous localisation thus induced could easily be different for the two particles. Which one wins? IBE (talk) 13:56, 17 December 2011 (UTC)

Thankfully the Relativity of simultaneity keeps different events from sharing the same absolute time reference.

BTW: There is no Measurement problem. The so-called Wave function collapse is simply a process of averaging quantum "weirdness" over enough particles, that the effect becomes minimal. Classical mechanics is a delusion. Hcobb (talk) 14:39, 17 December 2011 (UTC)

Re: the measurement problem, I think you'll find it has occupied a good deal of physicists' time over the last 80 years or so, hence I think it is still debatable at least. As far as relativity is concerned, a good thing to note, but in this case they are not moving with respect to each other, so they can agree 1. on simultaneity, and 2. that neither had time to confer when the hitting happened. It does present on the surface as a problem, but it would have been thrashed out quite a bit, so I'm wondering what they've come up with. IBE (talk) 14:46, 17 December 2011 (UTC)

Wavefunction collapse can propagate faster than the speed of light Dauto (talk) 16:03, 17 December 2011 (UTC)

The Invisible Pink Unicorn also travels faster than light. BTW, what's with this mythical "rigid body"? If it isn't held together by electromagnetic forces then what's keeping it rigid? Hcobb (talk) 16:07, 17 December 2011 (UTC)

I confess I'm not an expert on unicorns, but the rigid body is something that is held together so that if one part of it goes one way, so must the rest of it, or there will be a strong force somewhere. It is an idealisation, not a precise description. Dauto - thanks for the explanation, but does that mean it must propagate instantaneously? Otherwise, there would seem to be a chance that at least some pairs of hittings would happen at almost exactly the same time, and thus give rise to the problem I mentioned. IBE (talk) 17:39, 17 December 2011 (UTC)

But these so called "collapses" WILL be observed to occur in different orderings by different observers. Action_at_a_distance_(physics)#Quantum_mechanics, etc. All this FTL garbage means is that quantum physics does not every violate the Conservation laws. If you measure a certain angular momentum then I will measure exactly the opposite change in angular momentum on my member of our shared particle pair, in order to keep from violating the law of Conservation of angular momentum. It doesn't matter if I measure my value first or you measure your value first. In fact if neither of our measurements are in the past Light cone of the other one, then different observers could see mine first, yours first, or both at the same instant. Hcobb (talk) 22:09, 17 December 2011 (UTC)

My interpretation of the wavefunction collapse is that multiple realities are relatively-simultaneously superimposed, and the observer causes the wavefunction to "collapse", thereby making one of the possible realities "real". Is this correct? ~AH1 ^(discuss!) 03:19, 18 December 2011 (UTC)

Summing up some threads here, I think, Hcobb, you are exactly right about the reference frame, as per your first sentence. From my understanding of the rest of your post, it develops this point further. So, my understanding of GRW is that it is at odds with special relativity, for the reason cited, and the solution is that it needs a preferred frame, which no one likes, but they are also trying to solve the quantum measurement problem. As far as AstroHurricane's comment goes, I'm not sure here, but it sounds like you are advancing a particular interpretation of QM, which would not be agreed upon by all physicists. You are saying that observation causes collapse, but the question is how and why. I think many physicists would agree roughly with your statement, without saying it solves the QMP, and some would disagree, such as Many Worlds theorists. Perhaps Dauto can help more? I'm still curious about my further question, whether collapse must propagate instantaneously. IBE (talk) 05:15, 18 December 2011 (UTC)

Angle of the shadow across the moon

Hello. I've looked across our articles on the moon, and done some internet searching, but can't find an answer for this one. The line between the light and dark sides of the moon during it's various phases seems very horizontal recently, compared to the more vertical division I see in most diagrams on here. Is this because at the moment we are near mid-winter/summer and the earth's tilt is at it's maximum (layman's wording) so the view of the moon is different? Can you therefore tell the season from the angle of the moon's light/dark divide? Or am I being foolish? Ta, S.G.^(GH) _ping! 15:01, 17 December 2011 (UTC)

Many factors are at play here. The angle of the moon's orbit relative to Earth's horizon is the obliquity of Moon's orbit, determined by both Earth's axial tilt, and Moon's orbital inclination. The illumination is determined by Moon's obliquity relative ro the ecliptic, in other words by compositing the moon's orbit around Earth with Earth's orbit around Sun. We have articles on axial tilt, orbital inclination, and other orbit parameters.

These parameters are discussed in great detail in our article, orbit of the Moon. There is some relation to Earth's season, insofar as the angle of illumination relative to the horizon is affected by our axial tilt, and latitude, of course. But, there are many other lunar orbit periodicities that do not correspond to any Earth calendar phenomenon - because no Earth culture historically designed such a calendar. This is why lunar eclipses occur at "irregular" intervals during Earth years/seasons. Despite all the tidal locking, many of our Moon's orbit parameters have no integer relationship to Earth month, year, nor to lunar revolution period. So, you could not tell the angle of illumination simply by knowing the Earth season - but you could use a lunar almanac, chart, or astronomy software to calculate this. Don't misunderstand - the angle is not "random," it's just dependent on periodicities that few outside of lunar-watchers bother to track. Nimur (talk) 15:16, 17 December 2011 (UTC)

Wouldn't it change throughout the night, ie. throughout the moon's course across the sky?. Or am I totally muddled here? IBE (talk) 15:21, 17 December 2011 (UTC)

The most important factor out of all the ones mentioned above is of course the latitude of the location of the observer which has nothing to do with the moon's orbital parameters. Dauto (talk) 16:47, 17 December 2011 (UTC)

Does that mean I am wrong about it changing throughout the night? I would have thought it could be horizontal at the horizon, and near vertical when at its zenith. Of course, if it is directly overhead, then there can be no such thing as horizontal - just turn around and it will go through every orientation (unless my brain is really out to lunch). IBE (talk) 17:46, 17 December 2011 (UTC)

You're probably confusing yourself because the angle of the moon's solar terminator with respect to the Earth's horizon is poorly defined. The horizon is a plane; the terminator is, technically, also defined by a plane; technically, the angle between two planes can be defined as the dot product of each normal vector. But that's probably not the geometry you're thinking about: you're probably imagining the projection of the terminator on to the visible disc of the moon as observed from your location; and at moonrise, or moonset, trying to figure the angle that makes to the apparent horizon (again, a projection of the horizon plane onto the small region of the sky that you're looking at). You might start at Horizontal coordinate system to see some of the geometric transforms you need to work in a more general coordinate system. Compound this with the fact that the moon's solar terminator is changing, slowly, and you actually have a quite complicated time-varying function to define this "illumination angle."

Assuming spherical earth and moon, the solar terminator is defined strictly by the vector between Sun and Moon. Your local horizon plane is determined strictly by your latitude and longitude. The angle between these two vectors varies based on the moon's current position in space - determined by its orbital parameters and the current time. Moon's position in space varies slowly enough that it is reasonable to consider its position "fixed" over a short period of observation. The other parameter is the Earth's rotation relative to the sun - this rotates at 15 degrees per hour - so it's very unsuitable to assume it is "fixed" for even the most rudimentary astronomical observation). Nimur (talk) 18:57, 17 December 2011 (UTC)

Galactic collison

What will happen when Andromeda collides with the Milky Way? --108.225.115.211 (talk) 16:19, 17 December 2011 (UTC)

See galactic collision. Bo Jacoby (talk) 16:35, 17 December 2011 (UTC).

There's an article on that: Andromeda–Milky_Way_collision. 79.148.65.247 (talk) 16:34, 17 December 2011 (UTC)

DIY antenna, starting from a USB adapter

Starting with a USB Wi-Fi adapter (which has an SMA connector), how can you make an antenna for it? BTW, commercial antennas would cost something like $30, so it must be something cheaper. Which is a good source of DIY projects for such things? Would connect a long cable on the adapter work as an antenna? 79.148.65.247 (talk) 16:33, 17 December 2011 (UTC)

There are people making all kinds of wi-fi antennas. Google for something like make wifi antenna for lots of instructions. Although I don't know if you'll be saving a lot of money; people tend to make antennas to get directionality or other efficiency, rather than to save money. $30 might not be the best deal you can make; shop around, search the web. 88.112.59.31 (talk) 17:07, 17 December 2011 (UTC)

I've found this site to be helpful when I've been fiddling with Wi-Fi http://www.usbwifi.orconhosting.net.nz/ --TrogWoolley (talk) 18:17, 17 December 2011 (UTC)

Physiology of getting warm

So: a clear winter's day, spend time outside, get cold, come in to a normal heated building. Have a nice cup of tea, and feel the warmth immediately, as far away from the esophagus as the legs. (The same effect can be noticed with alcohol; I am not sure if that has a separate physiological explanation.) What's going on? Is it a kind of learned reaction? The body saying "I know I was cold, and am cold, but from past experience I know I am going to be warm soon?" Also, what is the muscular reaction to warmth called -- the small involuntary contractions more discrete than continuous shivering? "Shudder" redirects there, though I think of them as distinct. BrainyBabe (talk) 17:11, 17 December 2011 (UTC)

Vasodilation, the expansion of blood vessels to change circulation, has both a voluntary and involuntary component. Nimur (talk) 19:05, 17 December 2011 (UTC)

For the opposite, see vasoconstriction. ~AH1 ^(discuss!) 03:14, 18 December 2011 (UTC)

Yes, I do think your body anticipates when it's warming or cooling at a rate that will make it too hot or too cold soon, and reacts accordingly. StuRat (talk) 05:27, 18 December 2011 (UTC)

Can an EMP shut down a diesel engine?

I understand that an EMP can shut down a gasoline powered engine, but I'm guessing it's because it uses spark plugs to ignite the fuel air mixture. A diesel engine does not have this, so will a diesel engine be unaffected by an EMP? ScienceApe (talk) 18:08, 17 December 2011 (UTC)

The electromagnetic pulse generated by, say, a nuclear weapon, can supposedly shut down a modern gasoline engine because it fries the microelectronics in the engine control unit; with the ECU dead there's nothing to fire the spark plugs, so the car stops. I'd imagine an old car with a distributor (and no delicate ECU) should survive okay. Diesel cars don't need the ECU for spark timing, but modern diesels still have ECUs which are fitted to all kinds of sensor and actuators. I don't know how modern diesels are designed to run when their ECU is totally dead; they may have a "run rough" failsafe, but I wouldn't be surprised if "don't run at all" is the fail safe mode they've chosen. -- Finlay McWalterჷTalk 20:03, 17 December 2011 (UTC)

There is a government report here on the potential effects of EMP. The section on automobiles and trucks is on page 115 (PDF page 131) with some prior lead-in discussion. I found another article here that includes some commentary based on the first reference. In summary, both automobiles and trucks would be affected to some degree due to increased use of electronic controllers, but the report seems to indicate that the effect would be much less than some would expect. Traditional coil and distributor (non-electronic) ignition systems would be less vulnerable. I suspect my '47 Chevy pickup truck would survive, but the headlights might take a hit. -- 24.254.222.77 (talk) 20:48, 17 December 2011 (UTC)

Thanks, that's a really excellent source. So, not as bad as everyone thought; come friendly bombs and fall on Slough, then. -- Finlay McWalterჷTalk 02:11, 18 December 2011 (UTC)

Angular momentum of the observed universe

Has anybody tried to actually calculate the Angular momentum of the Observable universe? If so, was there any net bias in the spin axis of distant galaxies or perhaps the polarization of the Cosmic microwave background radiation? If there was, what might this say about the the total size of the universe to get this number down to zero? Hcobb (talk) 22:20, 17 December 2011 (UTC)

I'm curious as to how you would have enough valid data to even start with such a calculation? For example, looking at a star that's a thousand lights year away, you're seeing where it was a thousand years ago, as opposed to where it is "now". Likewise if you were near that star, looking at our sun. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:07, 17 December 2011 (UTC)

This paper suggests that a universe with non-zero momentum is impossible (from a general cosmological viewpoint, this makes sense - the universe we believe to be isotropic, which would be impossible if there was any large scale rotation). That said, the fact are understanding of theory forbids it is no reason we shouldn't look. Galaxy Zoo, although a very simple crowdsourced experiment, looked at the spin directions of galaxies. They thought they found a small bias towards anti-clockwise galaxy rotations at first, but they now think that was just an interesting psychological error on the part of the volunteers and that there is actually no bias in galaxy spin. Smurrayinchester 00:56, 18 December 2011 (UTC)

The shape of the universe might determine the results. How would you calculate spin for an open non-spherical infinite universe of which only an infinitesimal portion is observable? ~AH1 ^(discuss!) 03:13, 18 December 2011 (UTC)

What if all we can see is an eddy? We'd see a net spin and that would give us some sense of how large the local flow would have to be, even if we couldn't see most of it. Hcobb (talk) 04:13, 18 December 2011 (UTC)

The OP specifically asked about the observable universe, so it's a perfectly well-defined question. I think the OP's idea was that we could draw conclusions about the size of the entire universe based on the theoretical requirement that the entire universe be isotropic (and therefore have zero angular momentum). If the observable universe had some spin by random chance then the size of that spin would allow us to estimate the size of the entire universe (the larger the universe, the less significant the bit we can see would be, so the larger its spin could be). I'm not sure if that idea would actually work, but it's moot anyway since the evidence we have is that the observable universe has no discernible angular momentum. --Tango (talk) 05:18, 18 December 2011 (UTC)

I'd disagree that the evidence that the universe has no discernible angular momentum. At this stage, it would seem perfectly reasonable to even assume the universe may have a minuscule net angular momentum. There are a lot of subtle processes that go on in the first microseconds of the Big Bang that have broken most symmetries that we might have otherwise assumed went unbroken. So for now I think it's a safe assumption that there's some net angular momentum left over. Is it measurable? As everyone has said so far, it's probably too subtle for current astronomy to confirm or deny. On the scale of fundamental particles, however, I have no idea, but I'm sure there's theories out there that break that symmetry. From what I understand, though, symmetries that we take for granted in the universe seem to be broken more often than not. SamuelRiv (talk) 07:45, 18 December 2011 (UTC)

From the point of view of classical mechanics the contents of the universe could rotate relatively to absolute space, but from the point of view of general relativity there is no absolute space. An inertial frame of reference is unrotating with respect to distant galaxies. So the univers has no angular momentum relative to an inertial frame of reference. Bo Jacoby (talk) 15:34, 18 December 2011 (UTC).

How much leaf-area does it take to support a human being?

How much leaf-area does it take to support a human being? It takes a certain plant biomass -- some edible by humans, some edible by their prey, some not -- to give a human and his/her prey enough food to eat. On average, how much would the total area of the photosynthesizing organs -- the leaves -- of those plants have to be, at the leafiest time of year, to support one average human sustainably? Eldin raigmore (talk) 22:26, 17 December 2011 (UTC)

The problem with that is it would depend on if those leaves are facing the Sun or at an angle, and if they get direct sunlight or not. To get around this, a certain amount of land area is found in the calculations, rather than leaf area. Another problem is that this calculation is highly dependent on the diet of the human. A vegetarian diet takes many times less land area than an all meat diet. The location also matters, as a place on the equator with good weather can grow far more food. StuRat (talk) 05:18, 18 December 2011 (UTC)

Partial answer with rough data: A human requires very roughly the amount of energy intake that the sun shines on 1 m² (about 150 W). Photosynthesis has an efficiency of roughly 1%. So that would mean 100 m² of (human foodcrop) farmland, or rather more since, as you say, we don't eat all the parts of the plant, so maybe 200 m². Plus some if we want to eat meat, as Stu pointed out. DirkvdM (talk) 09:37, 19 December 2011 (UTC)

Violating the Heisenberg Uncertainty Principle

Would it be possible to determine simultaneously both the position and velocity of an electron, thus violating the Heisenberg uncertainty principle, by bouncing both a photon and a negative photon, with equal but opposite energies, off the electron at the same time, so the electron is located without disturbing it? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:11, 17 December 2011 (UTC)

Photons are their own anti-particles; there aren't distinct anti-photons, I don't think. And in any case, wouldn't this require knowing, ahead of time, the position of the electron to a level of precision beyond that allowable by the UP? That is, doesn't this beg the question of how you knew where the electron was to begin with? --Mr.98 (talk) 23:30, 17 December 2011 (UTC)

An anti-photon would merely have the opposite CHARGE to a photon. A negative photon would have negative everything - negative energy, negative spin, negative wavelength... see negative mass.

And as for the knowing-ahead-of-time-where-the-electron-is, just keep firing photons and negative photons through the vacuum until an electron just happens to pass exactly through the midpoint between the photon and negative photon generators... Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:34, 17 December 2011 (UTC)

The Uncertainty principle is NOT based on the fact that it is impossible to detect an electron without disturbing it. On the contrary, the fact that it is impossible to detect an electron is based on the uncertainty principle (That's why it is called a principle - it comes first). The uncertainty principle is based on the fact that an electron (or any other particle) really doesn't simultaneously have an entirely defined position and momentum. Dauto (talk) 23:44, 17 December 2011 (UTC)

(Edit conflict) It seems a bit meaningless to ask about the properties of a "negative photon" in this case. One might as well ask whether we could determine an electron's position and momentum by measuring changes in the luminiferous aether. Anyway, I think UP would pose other, slightly better hidden problems that would mess up your result anyway. For instance, you'd need to know the precise locations that each photon was emitted from (impossible), and they'd need to be lined up perfectly to know the position of the electron perfectly. Uncertainty forbids us from knowing the position of the emitters precisely enough. We also don't know anyway of producing a stream of photons with exactly the same wavelength - even the best lasers will have a tiny bit of variation. Nor can you perfectly know the timing of the release. Plus, though I must admit I'm hazy about how this machine is meant to detect an electron, I'm pretty sure that, if it works as I'm imagining it (electron absorbs light, re-releases it) when the electron interacts with the photon there will be an essentially unknowable time lag between absorption and emission. All of this contributes to the uncertainty of the measurement.

In short, you can never know a precise position, time or momentum of the photons you release, so you can't know the precise position of the electron either. This part of what makes the uncertainty principle so powerful - as Dauto says, because every particle is subject to the principle, any piece of fantastic machinery you invent to circumvent the limit must itself be limited by the principle. You can't know precisely where the sensor is, so you can't know precisely where the sensee is.

(Oh, and if your plan is for an electron to absorb the positive and negative electrons at the same time, and their energies and momenta cancel perfectly, I'm not sure I see any reason for the electron to ever release them. The state of an electron + photon + negative photon = the state of an electron, and we never observe electrons in the lab spitting out "negative photons" (... or do we?).) Smurrayinchester 00:30, 18 December 2011 (UTC)

There are no negative photons, or at least, the photon is the negative photon. Also, a photon is chargeless, unlike as is implied above; moreover, antiparticles do not have opposite mass, they have equal mass. As for the actual question, no, it would fail, for exactly the reasons already given. Phoenixia1177 (talk) 04:55, 18 December 2011 (UTC)

I don't quite understand the question either, except that it seems to involve knowing both the energy of the photons and the time to infinite accuracy. That's impossible: UP also states that energy and time cannot be simultaneously known, just as it says that position and momentum can't be simultaneously known. --140.180.15.97 (talk) 19:27, 18 December 2011 (UTC)

December 18

Electricity from water

Hi. This 2003 invention is just one of many small-scale electricity generation mechanisms powered by water alone. Compared to water fuel cell claims, most of these seem legitimate. Do we have an article discussing water-powered electricity? Thanks. ~AH1 ^(discuss!) 03:09, 18 December 2011 (UTC)

The article says that pumping water through a gizmo can generate electricity. In no way did it indicate the efficiency of the process. It is by no means "powered by water alone," since energy is required to operate the pump that creates the pressure to force water through the gizmo. The energy output might be far less than the energy input. Edison (talk) 04:13, 18 December 2011 (UTC)

Seems like a turbine except with no moving parts, which I'm sure is a good thing. Is this the only article discussing the technology? If so, I would question whether it's legitimate or not. ScienceApe (talk) 04:52, 18 December 2011 (UTC)

"Do we have an article discussing water-powered electricity?" Yes: Hydroelectricity. Actually, the device described isn't so much generating electricity from water, as from water pressure and flow - like conventional hydro-power systems. While it is interesting, there is no evidence that it is useful... AndyTheGrump (talk) 04:59, 18 December 2011 (UTC)

Our Micro hydro and Pico hydro articles discuss hydroelectric power installations of less than 100 kW and 5 kw respectively, but this U of A invention is at a scale way below what is covered in those articles. Also, the 10 - 16 micron channels of the device would require the filtration of water if used in a "natural" (exposed reservoir) setting, which would impact efficiency. (Note that the physicsworld article linked by the OP doesn't imply any free lunch. Quoting the U of A team, "It allows for the direct conversion of energy of moving liquid to electricity with no moving parts and no pollution.”) -- ToE 06:35, 18 December 2011 (UTC)

"less than 5 kDa by molecular weight"

This is quoted from Wikipedia article Actovegin.

"According to Gulevsky, et al., Actovegin "is highly purified hemodialysate extracted from vealer blood by ultrafiltration."[1] There are less than 5 kDa by molecular weight of organic substances in Actovegin.[4]

"Actovegin has been shown to improve the transport of glucose over a plasma membrane and the uptake of oxygen by tissues.[1] This can lead to aerobic oxidation, which provides a cell with access to more energy and potentially enhances its function.[1] Actovegin has large amounts of superoxide dismutase enzymes and magnesium.[4]"

1) What does it mean to say "There are less than 5 kDa by molecular weight of organic substances in Actovegin."?

2) Does that sentence contradict "Actovegin has large amounts of superoxide dismutase enzymes"? Superoxide dismutase enzymes sound to be organic substances. Thanks, Wanderer57 (talk) 04:37, 18 December 2011 (UTC)

It sounds horribly worded, probably some sort of autotranslation perhaps? (What the heck is "vealer blood"? Do they mean fetal calf serum?). I think what is meant is that that take bovine serum and perform ultrafiltration on it with a 5 kilodalton molecular weight cutoff membrane. Superoxide dismutase is an organic compound, but one that is much greater than 5 kDa. However, reference 6 in the article indicates that Actovegin is protein-free, and injecting proteins like bovine superoxide dismutase into humans is a good way to induce an immune response, so I doubt it has superoxide dismutase in it. You may want to contact User:Tim1965 and ask him to clarify his edit [5] & references. -- 140.142.20.101 (talk) 20:46, 18 December 2011 (UTC)

Apparently "vealer" is a synonym for a young calf; one wonders at the prodigious vocabulary of the Russian scientists who dredged it up for their paper.... - Nunh-huh 00:13, 19 December 2011 (UTC)

Thank you both. I've raised the issue at Talk:Actovegin Wanderer57 (talk) 03:35, 19 December 2011 (UTC)

Quantum measurement problem

Hi, can anyone tell me if there is a particular flaw in the following argument, and if so, what?

Background: Currently, when a quantum measurement takes place, it is not known what exactly causes collapse. It appears from the mathematics that quantum particles exist in superpositions, but we never measure superpositions, only discrete outcomes. The simplest case I can think of is electron spin - typically, it can exist in a hybrid state, of spin-up/spin-down, but we never measure two different spins. (Spin-up and spin-down can be thought of as clockwise and anticlockwise for simplicity.) We do not know whether the electron should be thought of as fundamentally different from the measuring apparatus, or whether it is the same, and some sort of aggregation is responsible for destroying the superposition.

Now: Could the electron in fact be genuinely a spinning particle, and be unaware which way up the universe is? Then the particle itself is on much the same footing as the measuring apparatus - we do not know which way it is spinning (clockwise or anticlockwise about a given axis) and it does not know which way is up. Consequently, the confusion about orientation is reciprocal. That way spin is a genuine property, but it is relative to something. I'm willing to learn the maths needed to understand the issue, but it will take time, and my main interest is in resolving this question, so I want to know what the exact error is (if any) so I can map out the territory I need to cover. I have the Schaum's guide to QM, and have made a tentative start, but no more. Thanks in advance. IBE (talk) 06:13, 18 December 2011 (UTC)

Up and down have no intrinsic meaning. Left on their own the electrons' spin vector would be expected to be randomly oriented in space (all directions, not just up / down). However, an experiment to measure spin works because we introduce a preferred direction, usually by introducing a magnetic field. For example, in the Stern-Gerlach experiment, we pass a beam of electrons (presumably randomized) through the field, we find that half are deflected in the direction of the magnetic field and half are deflected in the opposite direction. Those that follow the field, we call spin up, and the others we call spin down, but the notion of up/down was imposed by our field. The first surprise is that the split is so binary. Classically, we would expect the deflection to be proportional to the z-component of the electron's spin vector, which for randomized classical particles would imply a smooth distribution from up to down. However, the electrons we observe are either completely up or completely down regardless of how random we thought they were originally. The uncertain spin is said to have collapsed into one of the two spin eigenstates. Something about the nature of measurement and quantum mechanics causes this selection process. Since we are discussing measurement, you might also want to think about the double slit experiment where the issue of up/down spin is replaced with a physical separation (i.e. left slit or right slit) which may help to clarify some of the ways that measurement is spooky. For example that experiment shows that individual photons, if not observed, must go through both slits and subsequently interfere with themselves on the other side, which requires a real superposition state (and not merely some hidden notion of left or right). Dragons flight (talk) 08:44, 18 December 2011 (UTC)

First, the electron is a fuzzball and not a point. If electrons where point particles then the Pauli exclusion principle would not work. What you take to be a definite measurement is simply the state of the observer mixed in with the apparatus. And since observers are huge critters (and getting more massive every year), the total system is almost exactly "classical". The wave function does not collapse, it just gets so tiny in the scale of everything else going on that it approaches zero uncertainty for the overall system. Hcobb (talk) 18:11, 18 December 2011 (UTC)

Patient-specific tumoral vaccines

Hi, I've been reading about patient-specific tumoral vaccines and they seem great. They harvest the patient's very own tumoral antigens, use them to load a vaccine, add an adjuvant and inject it back into the patient, who develops an immune response to the cancer and destroys it.

However, these vaccines seem to extend life by a few months, but rarely do they achieve complete remission. Why is that? This type of treatment is as targeted as it gets, since it uses tumoral antigens that are specific to the patient's very own tumour. Do these vaccines eventually fail because of problems with the antigens? Is it because the adjuvants used are not powerful enough? Or is it due to some other problem? Thanks!--109.14.102.187 (talk) 09:01, 18 December 2011 (UTC)

The best answer to your questions appears to be "yes". This is a complex topic, as illustrated by the complexity of a recent high-quality review article on the topic of cancer vaccines (PMID 21248270). Major challenges include overcoming tolerance to "self" antigens (as you say, selection and condition of antigen, and of adjuvant, may be key), the potential for autoimmunity, and the stimulation of the most effective T cells while avoiding stimulation of regulatory T cells (PMID 15286781). Clearly, there is much to be learned about the mechanisms underlying these challenges. Scray (talk) 05:28, 19 December 2011 (UTC)

The way I look at it, when somebody gets (a noticeable degree of) cancer, that means something is wrong with their immune system. In the above case it seems to be assumed that the problem with it is an inability to recognize the tumor cells. If so, then that treatment should help, but there may be other problems, like a weak or suppressed immune system overall. Also, any response that puts more pressure on the tumor will cause those cells which have mutated (so they are no longer recognized as tumor cells) to thrive. StuRat (talk) 06:03, 19 December 2011 (UTC)

Ethanol expiration date

Is there any reason for the expiration date on pharmacy alcohol (used for disinfection etc.)? Gil_mo (talk) 13:07, 18 December 2011 (UTC)

Many products which, by their nature, do not normally decay or degrade (like water or ethanol) are nevertheless given a "best before" date, because the manufacturer knows that the packaging that contains them is imperfect. Sometimes the containers are slightly gas-permeable, sometimes the product is degraded by heat or ultra-violet light, and sometimes there is some small amount of reaction between the container and the product. These expiration periods tend to be quite long, and even then the manufacturer is taking a particularly conservative stance - they're assuming you'll be keeping the product in difficult conditions. -- Finlay McWalterჷTalk 13:19, 18 December 2011 (UTC)

Pepper and salt mills

• http://www.williams-sonoma.com/products/cole-mason-oslo-salt-pepper-mills/

Summary

• Grinds salt and pepper using precision grinding mechanisms.
• Pepper mill has a long-wearing hardened-carbon-steel grinding mechanism.
• Salt mill employs a durable, noncorrosive ceramic grinding mechanism.

Use

• Do not use with rock salt or sea salt flakes.
• Use only black, white or mixed peppercorns in pepper mill; not suitable for green and pink peppercorns.

• In the Wikipedia article: Black_pepper

Green pepper

Green pepper, like black, is made from the unripe drupes. Dried green peppercorns are treated in a way that retains the green color, such as treatment with sulfur dioxide, canning or freeze-drying. Pickled peppercorns, also green, are unripe drupes preserved in brine or vinegar. Fresh, unpreserved green pepper drupes, largely unknown in the West, are used in some Asian cuisines, particularly Thai cuisine.[7] Their flavour has been described as piquant and fresh, with a bright aroma.[8] They decay quickly if not dried or preserved.

Orange pepper and red pepper

Orange pepper or red pepper usually consists of ripe red pepper drupes preserved in brine and vinegar. Ripe red peppercorns can also be dried using the same colour-preserving techniques used to produce green pepper.[9] Pink pepper from Piper nigrum is distinct from the more-common dried "pink peppercorns", which are actually the fruits of a plant from a different family, the Peruvian pepper tree, Schinus molle, or its relative the Brazilian pepper tree, Schinus terebinthifolius.

I am not going to buy them and I am not advertising these products. Rock salt or sea salt flakes are easier to understand. Rock salt can be too large for the grinder and salt flakes may clog it. I just wonder why the "long-wearing hardened-carbon-steel grinding mechanism" cannot take care of green and pink peppercorns? -- Toytoy (talk) 13:55, 18 December 2011 (UTC)

I expect because they have some acidity that would eventually corrode the metal. Looie496 (talk) 17:53, 18 December 2011 (UTC)

I wonder why the pepper mill doesn't employ a durable, noncorrosive ceramic grinding mechanism too. Perhaps the long-wearing hardened-carbon-steel grinding mechanism is cheaper. I have actually seen pepper mills on sale containing mixed kinds of peppercorn including green and pink: ironically, they were made of plastic, and disposable.  Card Zero  (talk) 21:26, 18 December 2011 (UTC)

The plastic disposable ones obviously don't have to be hard wearing, they're designed to be thrown out once they are empty. As well as the ceramic possibly being more expensive, another factor is that it's more brittle. I actually bought a set exactly like this a long time ago, the steel pepper grinder is still going strong while the ceramic one eventually cracked and we had to chuck it out. Vespine (talk) 00:22, 19 December 2011 (UTC)

Dying in an elevator

Why is it mostly impossible to open the door from a stuck elevator from within without tools? Couldn't that kill someone? 88.9.213.105 (talk) 15:06, 18 December 2011 (UTC)

The doors in modern elevators are pretty complex. Remember that when the "elevator door" opens, it's really the synchronization of two doors (the inner cabin door and the outer shaft door) working at the same time. Now presumably you could imagine there being some sort of simple crank mechanism on the inside that would work without reference to the outside, but I'm not sure what purpose that would serve. The possible dangers from abuse of it are probably higher than the odds of actually helping someone. I imagine that you're thinking that the elevator will be trapped between two floors or something, or maybe just a few feet down from a door, and get stuck, and someone will need to get out (maybe they are having a baby or something) and wouldn't it be nice if they could just open the inner and outer doors and squeeze through the gap? But in practice that is a pretty dangerous operation, is really not the sort of judgment call your average person trapped in an elevator should be making, and is also probably not that common. The danger from misuse of such a device probably outweighs any benefits one would get from it. --Mr.98 (talk) 15:23, 18 December 2011 (UTC)

And seeing that there are escape hatches in the top of the elevator anyway... the one way you can leave an elevator and not be killed if the cable suddenly snaps. I've heard of people who are half-in and half-out of a jammed elevator trying to crawl through half an opening as you suggest... when the cable snaps. And thus, they snap. S.G.^(GH) _ping! 17:30, 18 December 2011 (UTC)

The cable doesn't even need to snap. All that's needed is for the elevator to resume normal operations and start moving again, which would snap anyone trying to crawl out. --140.180.15.97 (talk) 19:23, 18 December 2011 (UTC)

Most elevators don't have the escape hatch anymore. At least, not one that you could open without tools. I don't know if it's true, but someone from Otis told me that they stopped because it encouraged heroics and people wound up killing themselves trying to climb the shaft. APL (talk) 23:40, 18 December 2011 (UTC)

Elevators aren't always safe HiLo48 (talk) 00:01, 19 December 2011 (UTC)

There are very few places where being sprayed with lighter fluid and then being set on fire would be safe. APL (talk) 01:53, 19 December 2011 (UTC)

It's fairly coincidental that this question should come up considering there is that news item plus the other woman in New York who died in another elevator incident last week. Dismas|^(talk) 02:54, 19 December 2011 (UTC)

It's worth noting that cable snapping accidents are so rare as to be essentially be discounted entirely when worrying about elevator safety. I think it has happened something like two or three times in the last 100 years and they were very unusual circumstances (planes running into buildings and severing the cables). As our elevator article points out, the most dangerous things regarding elevators involve maintenance malfunctions, or people doing dumb things relating to open doors and/or shafts. Adding a way to manually open the door from within by the common person seems to me like it would increase this sort of risk, not decrease it. --Mr.98 (talk) 02:56, 19 December 2011 (UTC)

And even if a cable snaps, isn't there a safety mechanism to stop it the lift? I once saw some footage of someone demonstrating just that with a model. The cable was cut and the lift got instantly stuck. I assume this is a very simple mechanism that is still used. DirkvdM (talk) 09:06, 19 December 2011 (UTC)

Yes. Elisha Otis himself did a very dramatic demonstration at the 1854 World's Fair. While he was riding one of his elevators he had an assistant cut the cable with a fire axe, a stunt that sold a lot of elevators. APL (talk) 11:23, 19 December 2011 (UTC)

Electromagnetic radiation and their relationship with electro magnetism

I'm trying to get a firm grasp on their exact relationship. So you have light which is electromagnetic radiation. But this light is not affected at all by electromagnetic fields under normal circumstances. Light will not create any electric or magnetic fields in a vacuum correct? Light possesses electric and magnetic fields and that simply causes the wave like nature of light. Is this fairly correct? ScienceApe (talk) 15:39, 18 December 2011 (UTC)

I don't think that Magnetic/Electric fields don't affect them "at all"...--81.17.23.103 (talk) 16:05, 18 December 2011 (UTC)

The normal electromagnetic theory is linear. That means the fields can be added and subtracted and still behave the same way. So that light waves can pass through light waves or fields. Things can get more complicated if you consider matter with non-linear optics or the photon nature such as ultra high energy gamma rays which cannot pass through a magnetic field intact. Graeme Bartlett (talk) 20:45, 18 December 2011 (UTC)

Electromagnetic radiation, including light, fundamentally involves oscillating electric and magnetic fields traveling through space. Equipment designed to measure these fields (provided it is sensitive and fast enough) will detect the passage of this electromagnetic radiation by seeing fluctuating electric and magnetic fields. Visible light is so high frequency that commonly available electrical equipment can't measure the fast fluctuations in the field, but lower frequency radiation such as radio waves are routinely measured with fairly simple electrical equipment (we call them radios). Dragons flight (talk) 20:38, 18 December 2011 (UTC)

Duality

Can the question of Cartesian Duality be addressed scientifically?--81.17.23.103 (talk) 16:00, 18 December 2011 (UTC)

In principle, yes. If information really flowed into the brain from a nonphysical res cogitans, in principle we would be able to see that happening. But in practice, our current understanding of brain function is far too limited for us to be able to see it. Looie496 (talk) 17:49, 18 December 2011 (UTC)

Not clear at all. The causal effect could be hidden inside quantum indeterminism. --Trovatore (talk) 00:31, 19 December 2011 (UTC)

what does non-physical mean? I never really understood it, I mean I don't deny it but... I also don't understand it...--Irrational number (talk) 17:52, 18 December 2011 (UTC)

Non-physical means interactions that do not obey the currently understood laws of physics or any simple modification of them. Looie496 (talk) 19:26, 18 December 2011 (UTC)

That is a question of metaphysics, it's not easy stuff. I decided to try to learn more about philosophy a couple of years ago and after reading and listening to a lot of material on the subject, it's still mind bending. I suppose the article which addresses this specific subject is Dualism. Vespine (talk) 00:05, 19 December 2011 (UTC)

It would be a complicated question for some versions of dualism, but for Descartes's rather straightforward version it is not so complicated -- he believed in what philosophers call substance dualism. Looie496 (talk) 00:27, 19 December 2011 (UTC)

Help finding source on Chicken vision

I am writing an article on chicken eyeglasses. (yes, chicken eyeglasses see, e.g., [6]). I am looking for a reliable, preferably scientific source, that says that chickens are not color blind, or that that they see in color. I have tried various searches without luck.--Fuhghettaboutit (talk) 16:43, 18 December 2011 (UTC)

This paper shows that chicken colour perception is, as we say in Scotland, pure gallus. -- Finlay McWalterჷTalk 17:00, 18 December 2011 (UTC)

Perfect. Thank you and so fast. If you want to see the silly article it will be at Chicken eyeglasses soon. Damn, damn, damn, damn, damn. It's a blue link. Looks like someone posted after I started writing this in November. Well my version is certainly a four times expansion so I'll be able to make DYK.--Fuhghettaboutit (talk) 17:13, 18 December 2011 (UTC)

Perhaps we need an animal eyewear article, as there's also Doggles and blinders, at least. -- Finlay McWalterჷTalk 17:24, 18 December 2011 (UTC)

I couldn't help but put the search term into Google Patents. I didn't, in my 5 seconds of looking, find the ones described in the article, but I did find this wonderful anti-pecking patent: [7]. Who knew that Kanye West's style was so derivative? --Mr.98 (talk) 17:52, 18 December 2011 (UTC)

The citation for the patent described in the article links to the patent. I uploaded the image from it to the commons a while back. I also found a patent infringement lawsuit between two inventors of chicken blinders; I think one of them is the patent you linked.--Fuhghettaboutit (talk) 18:09, 18 December 2011 (UTC)

Oh yes, I have seen that patent, now that I look at it again. I have an amusing book of wacky patents, and it is featured among them. This of course does not answer your question in any way, shape, or form... --Mr.98 (talk) 03:58, 19 December 2011 (UTC)

Ayds

How much benzocaine was in ayds per serving? --Shanedidona (talk) 18:10, 18 December 2011 (UTC)

5 mg.[8] Red Act (talk) 09:37, 19 December 2011 (UTC)

Manuka honey health claims - quackery?

I've only been dimly aware of people mentioning that manuka honey (article nearly unintelligible) allegedly has health benefits, both from the eating of the stuff and the smearing of it onto open wounds. Someone mentioned it above and it reminded me. So, is this just another 'miracle health food'/alternative medicine fad malarkey (along similar lines to the Acai berry fad or drinking colloidal silver solution), or is there really something to it? I had a Google around this afternoon but didn't manage to find anything definitive. --Kurt Shaped Box (talk) 20:57, 18 December 2011 (UTC)

Or indeed royal jelly. Remember when lots of people used to swallow capsules of that stuff every day, apparently because it supposedly did or prevented something that I forget now... :) --Kurt Shaped Box (talk) 20:59, 18 December 2011 (UTC)

I consider myself quite "quack aware" but i think there's definitely something to honey. Even a preliminary pubmed search of manuka honey yields some interesting reading. The problem is of course, that the interesting and beneficial effects which have been found get misreported and misrepresented by certain people who promote honey with all sorts of "quacky" claims. Acai berries on the other hand have been found to be no better or worse then most other common berries that can be bought for fractions of the cost of "exotic" Acai berries; it's pretty much ALL marketing, I've seen 1L of Acai berry juice selling for $80! Vespine (talk) 23:53, 18 December 2011 (UTC)

What must people in Brazil think of that? Probably find it quite amusing, in a 'those crazy foreigners with too much money' sense, I'd assume... --Kurt Shaped Box (talk) 09:04, 19 December 2011 (UTC)

Pretty much... except for the locals for whom Acai berries were one of their staple foods, who take an understandably dimmer view on Acai berry prices suddenly becoming so expensive they can barely afford them. Smurrayinchester 09:11, 19 December 2011 (UTC)

Honey in general is known to be antibacterial: honey#In_medicine. Manuka honey apparently is antibacterial, in one particular way, more than other honeys. So it might be a great thing to smear on wounds, but I'm not certain why you'd want to eat it. The pubmed results suggest maybe the idea is to keep your teeth clean, or fight bad breath? I'd be afraid it would kill off your gut flora and give you diarrhoea.  Card Zero  (talk) 06:54, 19 December 2011 (UTC)

Cheers for the answers - I did wonder, as I was expecting to find the typical situation where the sceptics and believers were raining fire upon each other over the internet over whether the stuff worked or not - and detailed entries on the usual debunking websites... but didn't. --Kurt Shaped Box (talk) 09:04, 19 December 2011 (UTC)

You may also be interested in Propolis#Medical_uses. Covers some of the quackery (essentially noted as such), but also gives several references for reputable studies on potential health benefits. SemanticMantis (talk) 13:37, 19 December 2011 (UTC)

Pauli exclusion principle and speed of light

In his televised lecture tonight on BBC, Dr Brian Cox stated that because no two electrons in the universe can have the same energy level (Pauli exclusion principle), then if you change the energy level of an electron here on earth, you must necessarily alter the energy levels of all other electrons in the universe. Fair enough. But he said that this happens instantaneously. How is this consistent with the finite value of c?--92.28.71.33 (talk) 23:36, 18 December 2011 (UTC)

Fixed your link for you. I'm no where near capable of actually understanding or explaining what you're talking about, but my interpretation is that the limit is imposed specifically on "information"; "changes" can occur faster then the speed of light, but those changes can not transmit information. It seems intuitive that if you can cause changes you can transmit information, but that is not the case... At which point I really have to defer to someone who knows what they're talking about. Vespine (talk) 00:00, 19 December 2011 (UTC)

I don't know about this particular claim/interpretation, but for your reading perusal there are other quantum mechanical effects that appear to happen faster than the speed of light (potentially instantly) — see e.g. quantum entanglement. The trick is, as Vespine says, no information is imparted in this fashion, so it doesn't violate special relativity. Einstein called this "spooky action at a distance" because this sort of thing appeared to happen without any obvious physical means transmitting these changes of state. --Mr.98 (talk) 02:51, 19 December 2011 (UTC)

Well, this sounds like nonsense to me. An instantaneous change would be detectable and could be used for faster-than-light communication, so you're right to complain about that, but the rest of it is wrong too. Ionizing an atom doesn't do anything to other atoms on distant planets separated from it by a vacuum, and the exclusion principle doesn't imply that it should. -- BenRG (talk) 07:23, 19 December 2011 (UTC)

I think (haven't seen the show yet) he's talking in terms of wavefunctions here. Every electron's wave function is spread throughout the universe, vanishingly small but not-quite-zero. An electron can be anywhere in the universe... except for in a state already occupied by another electron. Changing the probability of finding an electron in one state must change the probability of finding every other electron in the universe in that same state by an incredibly small degree. Smurrayinchester 09:02, 19 December 2011 (UTC)

Oops, and like Vespine says, this wouldn't violate the speed of light because it wouldn't transmit information. You can't see a wavefunction directly, you can only infer its shape from the distribution of electrons over thousands or millions of measurements. Because the only place where this change would be relevant would be at the point in space occupied by your electron, you couldn't use this to send information to another planet. Smurrayinchester 09:06, 19 December 2011 (UTC)

December 19

Oh, you scared me!

We've all experienced it. You turn a corner on a footpath or enter/leave a room or a building etc, and you meet another person coming in the opposite direction, who wasn't expecting anyone there and they get startled and they say "Oh, you frightened me!" or "Oh, you scared me!".

I've always wondered what goes through people's minds just before they utter these words. Taken literally, they mean you deliberately caused them fright, but if questioned, they would admit there was no intention on your part to do so. So, it's down to your mere unexpected presence being fright-inducing. That's understandable enough; anything that's unexpectedly somewhere can cause a shock. If I turned a corner on a footpath and found a huge 6-foot tall pile of gold there rather than other pedestrians, I'd be shocked too. Frightened? Not too sure about that. Even if I were frightened, I wouldn't think of the pile of gold as having "frightened me".

So why do people tend to "blame" humans for their fright in these sorts of situations, when they wouldn't blame anything else that elicited a similar fright response in them? How do psychologists explain this? -- Jack of Oz ^{[your turn]} 04:37, 19 December 2011 (UTC)

My initial reaction to anything that startles me by its sudden proximity is "jee..." or "sh...", and then, if it is a person, I feel the need to explain: "You scared me." I seldom explain things to inanimate objects, though, to be honest I could not always be certain with some of my lecture audiences. Bielle (talk) 04:47, 19 December 2011 (UTC)

I don't interpret any intent in "you scared me". You could just as easily say "a spider scared me", doesn't imply the spider did it deliberately. I think it is synonymous with "your presence scared me". Vespine (talk) 05:02, 19 December 2011 (UTC)

The term I would use is "startled", and I wouldn't say we're "blaming" the other person, just communicating with them. We could be startled by a loud noise or a creepy critter or most anything else, but telling a thunderclap or a spider, "You scared me!" would be kind of a waste of breath. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:48, 19 December 2011 (UTC)

Is "You scared me" simply an abbreviation of "Your sudden appearance startled me" which, being much less colloquial, we would be far less likely to say? HiLo48 (talk) 08:01, 19 December 2011 (UTC)

Similar case: If you enquire about someone's relative and hear they're dead, you'll likely say "I'm sorry", even though it's not your fault. (Presumably - that would make for an interesting argument in court; "He apologised, so effectively admitted he did it!" :) ) What matters in both cases is not what you say. Ignoring the event would be rude, so you have to say something. What it is you say is relatively unimportant because the other person understands what you mean. DirkvdM (talk) 08:55, 19 December 2011 (UTC)

Totally agree, it is a language issue, not a psychology issue. The verb scare has several meanings, including one that is for involuntary scaring of someone else or something. --Lgriot (talk) 10:08, 19 December 2011 (UTC)

Nice to see you back here, DirkvdM. It's been a while. -- Jack of Oz ^{[your turn]} 10:30, 19 December 2011 (UTC)

Just dropped in for something different, had a bit of a look around and couldn't restrain myself. :) But maybe you'll see more of me, depending on how busy I'll be. Just as long as it doesn't become an addiction again. :) DirkvdM (talk) 11:40, 19 December 2011 (UTC)

I'm not so sure it isn't a psych issue. A psychologist who subscribes to the view that humans remain responsible for their own experiences and their own feelings, and practises what he preaches, might, if startled in such a scenario, say "Oh, I felt slight fear when I saw you there unexpectedly", rather than "Oh, you frightened me". -- Jack of Oz ^{[your turn]} 10:37, 19 December 2011 (UTC)

I've heard someone say it to a cat that suddenly appeared. It probably depends on what sort of entities you tend to talk to. --Colapeninsula (talk) 10:40, 19 December 2011 (UTC)

Why do you believe that "you scared me" implies it was deliberate?

As a verb "scare" means "to fill, especially suddenly, with fear or terror; frighten; alarm." There's no mention of intent.

In fact, if you'll often hear people say "the storm scared me" or something similar. APL (talk) 11:15, 19 December 2011 (UTC)

Bumping your head

Why is it that if you walk underneath a low overhead obstacle, and manage to accidentally bump your head into it, that you always instictively glance at what you bumped into, knowing very well what it was? All though, it would look peculiar if you just keep on walking and just ignore the whole thing. Plasmic Physics (talk) 08:37, 19 December 2011 (UTC)

Or, why is it that when there are others around, and you bump your head, you always give a forceful overreaction, just to make sure that everyone notices your silly mistake? Plasmic Physics (talk) 08:39, 19 December 2011 (UTC)

Hmm, no I don't. --Lgriot (talk) 10:25, 19 December 2011 (UTC)

It would be evolutionarily advantageous, from the point of view of survival, for people or animals who are hit on the head to look in the direction from which they are hit. In times when low doorways were rare and it was more common to encounter predators, enemies, or falling rocks and branches, quickly assessing why you were hit would be useful. In such situations, an instinctive reaction would allow you to immediately orient on a potential threat without having to consciously think about it.

It may also be related to the well-known fact that if you tap someone on the shoulder they always turn round. --Colapeninsula (talk) 10:45, 19 December 2011 (UTC)

Could be that it also saves face a little if people are watching. Only an idiot would trip over or bang his head against something he knew was there. So, when you do exactly that, you pretend it wasn't your fault. APL (talk) 11:11, 19 December 2011 (UTC)

Dutch National Science Quiz 2011

I have translated the questions of the Dutch National Science Quiz 2011 and put them on a subpage of my user page, so the ref desk squad can sink their teeth into them. Nothing to win (anymore), just for fun. Enjoy. DirkvdM (talk) 08:41, 19 December 2011 (UTC)

Probability

Hello everyone. Let's imagine there's a betting house whose only objective is to break even, not to make a profit. Is it correct to say that it should offer odds of $4 per dollar bet for an event that only has a 25% probability of happening? Or have I calculated the odds incorrectly? Thanks. Leptictidium (mt) 09:29, 19 December 2011 (UTC)

That's correct. Red Act (talk) 09:44, 19 December 2011 (UTC)

As long as they don't return your original stake along with the $4 prize. --Colapeninsula (talk) 10:47, 19 December 2011 (UTC)

And if the same betting house were to offer odds of $2.20 per dollar bet for a given event, what would be the probability of that event happening? Would it be 45%? Leptictidium (mt) 11:04, 19 December 2011 (UTC)

does poop always have E. coli?

hi i would like to know if human poop always contains e. coli, or only sometimes. thanks.