Revision as of 15:45, 29 April 2017

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

• WP:RD/S

Main page: Help searching Misplaced Pages

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

How do I answer a question?

Main page: Misplaced Pages:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

• Teahouse
• Help desk
• Village pump
• Help manual

April 25

Why??

How many water molecules are attached in Blue Vitriol and in White Vitriol ?How its number is decided? — Preceding unsigned comment added by Achyut Prashad Paudel (talk • contribs) 09:30, 25 April 2017 (UTC)

Metal aquo complex covers some of it, as does Coordination complex. --Jayron32 10:50, 25 April 2017 (UTC)

Is there a deeper rail canyon (compare street canyon) in the world than the Chicago El?

Where in Chicago is the rail canyon the deepest? It's probably in the Loop or one of the els right before the Loop but I don't know where. Sagittarian Milky Way (talk) 14:27, 25 April 2017 (UTC)

Also, is there less prestige or desire to build, buy or rent on the outer side of a Loop street compared to the other side of the street or do they just not care? I would guess not it's but hey, maybe if you're a billionaire or the most prestigious law firm in the city or something being able to say you're in the Loop matters. Sagittarian Milky Way (talk) 14:38, 25 April 2017 (UTC)

• Not sure how this stacks up worldwide, but I'd see Liverpool as a contender here. Liverpool is a coastal port, with a large ridge behind the main city centre. This ridge of Edge Hill is made of sandstone which is an excellent material for tunnelling, both easy to tunnel and yet self-supporting.

The first Liverpool station was at Edge Hill, in a cutting 40 feet (12 m) deep with the boilers and engine sheds cut into the walls of the cutting (they're still there). The line then ran outwards to Manchester, through another deep cutting of 80 feet (24 m) - its depth was four times its original width, making it a rather famous sightseeing destination of this new 'steam age'. Lines extended through tunnels to stations nearer the town centre and docks. When Lime Street station was built this too was tunnelled through the sandstone, but after a landslip this was mostly opened up into more deep cuttings.

A wholly separate line, came into Liverpool from the South West along the river, first as the Garston and Liverpool Railway to Brunswick at the edge of the city, then extended as the Liverpool Central Station Railway through Liverpool St James in a deep cutting (maybe anoother 40'?) alongside the cathedral to a surface station at Liverpool Central, entered through a tunnel. These tunnels and cuttings, along with the Mersey Railway beneath the river, now form the basis of the modern Merseyrail underground/overground system.

Further lines, the Waterloo Goods branch and the Canada Dock Branch, came from Edge Hill to the northern docks, again through tunnels and cuttings although these were less deep than the others. Andy Dingley (talk) 15:28, 25 April 2017 (UTC)

• The article Elevated railway may help you research your question. --Jayron32 15:32, 25 April 2017 (UTC)

• I havent found an exact measurement, but at 168th Street (New York City Subway) one takes an elevator to transfer between the A line and the 1 line. I have seen a figure of 15 storeys and recall that the 1 line is 200ft below the surface. I am not sure if this answers your question, but it is surely deeper than 24 meters. μηδείς (talk) 17:19, 25 April 2017 (UTC)

The Gotthard Base Tunnel is 1.5 miles below the surface. That's the world record. It'd be 115°F at that depth if the HVAC broke. I had in mind canyons of buildings like but rock canyons are also welcome. Sagittarian Milky Way (talk) 19:34, 25 April 2017 (UTC)

In terms of natural canyons, the Royal Gorge Railroad at 1,250 ft (380 m) deep and not much wider than a city street probably wins. For artificial canyons, the buildings around Docklands Light Railway at Canary Wharf in London possibly equal those on the Loop (although the canyon formed isn't nearly as long), and Tokyo's Yamanote Line runs at surface level through some very built up areas. Smurrayinchester 07:19, 26 April 2017 (UTC)

(Oh, and Hong Kong Tramways are also probably worth a look - they run along Des Voeux Road, one of the most densely built-up parts of Hong Kong). Smurrayinchester 07:35, 26 April 2017 (UTC)

Clinton station (CTA Blue Line) and an adjacent tunnel are the lowest points of the Chicago "L" at a depth of 66ft according to this article. --Modocc (talk) 11:50, 26 April 2017 (UTC)

April 26

Intermodal container

For ocean shipping of Intermodal containers, does the shipping cost depend on the weight of the filled container or not? ECS LIVA Z (talk) 00:51, 26 April 2017 (UTC)

It appears not. A couple of sites that provide information on international container shipping do not mention weight as part of the cost , and two sites I found to get shipping rates don't include "weight" as a line to fill in, although one will have such a line if you selecting anything but a shipping container as your package . However, I do notice that some sites give a fixed weight to every size container. I wonder if shipping companies would refuse to take something over that weight. Someguy1221 (talk) 01:33, 26 April 2017 (UTC)

Rather old OP, I'm afraid, but back in the mid-1980's I was involved in ordering periodical shipments of manufactured items from my employers' factory in South Africa to their warehouse in Hampshire, UK. The quantity of goods could vary significantly from shipment to shipment, and were always sent in a standard shipping container, whose cost of delivery was the same regardless of how full it was. {The poster formerly known as 87.81.230.185} 90.217.249.244 (talk) 14:25, 26 April 2017 (UTC)

In my experience about a decade ago, there was no weight limit on the container for the ship-bound portion of the transit. However, unless you have a deep-sea dock in your backyard, something else is going to be required to get the container to your DC. I do not know about the rail portion, but trucking companies will have upper limits to what they're legally allowed to haul and probably also limits on what they'll haul without extra charge. Matt Deres (talk) 01:04, 29 April 2017 (UTC)

Installing a new thermostat on a 240V household heater

I have an old baseboard heater in a bedroom. It has no markings or ratings on it as far as I can tell, nothing written inside the unscrewable panels on each end. All I know is it's on the 240V household power (3 live wires plus a ground wire) and a 20-amp circuit breaker. I live in the United States.

When the heater is on, my clamp meter shows 6.2 amps on each of the three live wires going into the heater. If I understand the 3-phase AC article correctly, the total current going through the heater isn't 18.6 amps (3 × 6.2), but would actually be 6.2 amps.

I just bought a new programmable thermostat (heater only, no cooling) rated for a maximum load of 14.6 amps at 240V, which is a good margin for the heater.

So I want to know, before I install this thermostat, is my assumption correct that this heater is actually drawing 6.2 amps and is a safe load for the thermostat?

It's challenging to find a programmable heater-only thermostat rated for 20 amps at a decent price ($50-ish). ~Anachronist (talk) 05:31, 26 April 2017 (UTC)

You almost certainly do not have three-phase service. If you're in the U.S., you probably have split-phase. Do not mess around with electricity if you don't know what you're doing. Call a HVAC servicer. --47.138.161.183 (talk) 06:10, 26 April 2017 (UTC)

I've done a lot of work around the house with the single phase wiring. Even helped rewire the whole kitchen during a remodel and the city building inspector approved it. Whether the 240V is 3-phase or split-phase, the question still stands regarding the current I measured versus the load rating on the thermostat. ~Anachronist (talk) 06:23, 26 April 2017 (UTC)

The fact that you're asking the question about the current indicates that you don't know what you're doing and shouldn't be installing the thermostat. Seek expert advice from a qualified electrician. Any wiring mistake that you make that results in a fire could have serious consequences for your household and contents insurance policy. Akld guy (talk) 08:07, 26 April 2017 (UTC)

Is it on a 2-pole or 3-pole circuit-breaker? DMacks (talk) 12:34, 26 April 2017 (UTC)

If you are not skilled in electrical testing and wiring, there is too high a likelihood of injury or property damage to be messing with 240 volt wiring. Installing an inappropriate thermostat would be bad, if you wound up switching a neutral, for instance. Check with an electrician. Also, what kind of electrical device has NO NAMEPLATE? If I were working on the heater, I would have checked the voltage from each of the "live wires" to ground and to each other. Then I would know if there were two wires each with 120 volts to ground and with 240 volts between them, as is commonly seen in US household wiring, and a neutral wire with only a small or no voltage to ground, and 120 volts to it from each of the other two "live wires." If the wires are wye or delta connected, or high-leg delta, other voltage patterns would be seen. Edison 16:13, 26 April 2017 (UTC)

@DMacks: normal 2-pole 20 amp breaker. It's actually a pair of 20-amp breakers with the toggles connected together, so that both will always flip at the same time. They're on a circuit dedicated to two baseboard heaters, one in each bedroom.

Two poles means it's two hots (presumably split-phase at 180°, each 120V for 240V total, as Edison says) and the third current-carrying conductor is neutral. "Three-phase" (three hots at 120°) would require three poles of circuit-breaker. DMacks (talk) 19:09, 26 April 2017 (UTC)

@Akld guy: I've installed thermostats before, we have other baseboard thermostats in the house but those thermostats are mechanical ones rated at 22 amps. Electricians check my work — and I may call one anyway in this case. The fact that I'm asking a question doesn't indicate I don't know what I'm doing, it indicates that I am reluctant to cut off the heater wires to measure the voltage (they aren't connected with screw-off caps, but the crimp kind). But I did manage to measure the voltages by shoving the probe down into the back of the caps, see below. The clamp meter was an easy non-contact way to compare the current in the heater with the current rating of the breaker and the thermostat. If I were replacing the mechanical thermostat with a new 22 amp one, there would be no need to ask questions. But I want a digital programmable one in one particular room, and those don't seem to be available higher than about 15 amps. What gave me pause is that the rating on the thermostat is less than the circuit breaker (I can replace the circuit breaker with a 15 amp one if needed).

@Edison: Right, there is NO NAMEPLATE. Maybe if I pulled it off the wall (I see very large nails fastening them at the back, so I might damage the heater pulling it off) there might be a plate on the back. These baseboard heaters here are nearly 50 years old. So I have to resort to measurements to figure out its specs.

The voltages between the wires are: white-red: 210V; white-black: 8V; red-black: 12V; ground-red: 120V, ground-black and ground-white: 1V. Those low voltages fluctuated as the heater warmed up. But seeing that gave me the idea to put the clamp meter around the red and black wires together, and it read 12.5A or 0A, depending on the relative direction each wire passed through the clamp loop. That indicates that the red and black are in phase, and the heater is likely drawing 12.5A. Is that a reasonable deduction? If so, I'm reluctant to put a 15A thermostat on this thing; it's a bit too close for comfort. ~Anachronist (talk) 19:02, 26 April 2017 (UTC)

• Your unit is a 220 VAC 6.2 Amp resistive heater. Red and black are on the opposite sides of your single-phase (i.e., split-phase) service. This is just like any other big 220VAC appliance. If you have a thermostat that can handle 220 VAC at 6.2 Amp, you can in theory use it as a switch in either the red wire or the black wire, but I think this is a really bad idea, unless you are sure that the unit is designed to work that way. If you are replacing an existing thermostat, how is it wired? Does it interrupt just red, or just black, or is it DPST and interrupts both? How is your digital thermostat powered? If it expects 120 VAC and is designed to interrupt 120VAC, it is likely to to fail in the 220VAC system even if its internal relay can handle 6.2 A. If it were me I'd replace the entire unit. If this is infeasible, I would use a DPST 20A relay and use a 24 VAC thermostat to actuate the relay. I'd also think twice before accepting advice from random people on the Internet. -Arch dude (talk) 05:12, 27 April 2017 (UTC)

  @Arch dude: Thank you. I'm not following advice, just gathering information. In this case, the existing thermostat (a mechanical 22 amp thing similar to this) has been failing to keep the room at a constant temperature anymore; the room alternates between too hot and too cold, so I want to replace it, preferably with a digital programmable one. The one I bought is a 240V thermostat (this one) rated at about 15 amps, can be used in either a 2- or 4-wire installation. Thanks for confirming my heater is 6.2 amps, but still, I found myself uncomfortable with putting a 15 amp device on a 20 amp circuit (I don't want the thermostat to be the weakest point in the circuit), so I returned it to Home Depot today. I wonder why the only 22-amp heater thermostats I can find are mechanical? ~Anachronist (talk) 06:25, 27 April 2017 (UTC)

Cargo spacecraft visiting the ISS

Why do cargo spacecraft other than the Progress (i.e. the Dragon, Cygnus, H-II Transfer Vehicle, etc.) require the use of the Canadarm instead of using automated docking like the Progress? Given that the Progress, and previously the ATV, had automated docking capabilities, why weren't these just used for the other cargo spacecraft? Narutolovehinata5 07:37, 26 April 2017 (UTC)

International Space Station#Docking discusses the advantages and disadvantages of automatic vs. manual docking. --Jayron32 10:51, 26 April 2017 (UTC)

• This is because they use different ports. Progress and ATV use(d) the Russian SSVP docking system, the rest use the American Common Berthing Mechanism. The latter is a bigger hatch, easier for supplies, but is not suited for automated docking, due to different acceleration requirements at contact. Nitpick, when using Canadarm to place these VVs on a CMB, the term is berthing (as the name suggests), they don't dock. Fgf10 (talk) 07:54, 27 April 2017 (UTC)

Stowaway on a trip to space

The International Space Station is serviced by a variety of unmanned cargo drops. Supposing that someone could sneak onto one of those cargo flights without being noticed, would such a flight be survivable? Are the cargo modules pressurized, kept at a reasonable temperature, etc.? And would the additional weight be sufficiently within the safety margins that the rocket could reach its destination without running out of fuel (assuming no cargo was removed)? Dragons flight (talk) 14:20, 26 April 2017 (UTC)

Could a human survive? Sure, if you don't care about comfort, safety, or permanent health harm, and accepted very tiny margins of confidence. For example, Progress is not functionally very different from Soyuz, a manned Soviet spacecraft. In principle, they are the same vehicle, but engineered to different standards of safety, comfort, and confidence.

Would you be comfortable berthing in a vehicle that is essentially a fifty-year-old Soviet design, only built for carrying cargo with tolerances that are relaxed below the standards originally set for cosmonaut safety and comfort?

So if the question really is whether the journey might be livable, I think we can say yes. This obviously glosses over some of the practical difficulties. How would the stow-away crew get in? How long would they have to hide inside the module before the launch? How much kit could they bring with them - food, water - among other biological needs? Could they bring a spaceflight-safe seat or harness? Do they care about comfort and safety in even the slightest fashion? What rate of probable mortality or morbidity would be acceptable?

Nimur (talk) 16:21, 26 April 2017 (UTC)

Here is a short-course, from 2015, whose lecture notes are published on NTRS: ISS Payload Thermal Environments, taught originally by a team from NASA and Boeing to help train engineers who intend to deliver cargo payloads to ISS.

As always, if you learn to search NTRS, you'll find almost everything you need to know, in full-form.

Nimur (talk) 16:24, 26 April 2017 (UTC)

• Two obvious questions would be temperatures and also CO₂ buildup. Although the payloads (well, half of them) are pressurised with a breathable atmosphere, this doesn't include the life support needed for a payload that's also breathing. Andy Dingley (talk) 16:57, 26 April 2017 (UTC)

Another issue might be the accelleration of the rocket, which is usually kept down to an human sustainable level - not the most efficient way to put a mass into orbit with a rocket. Also these cargovessels have no heat shield. So anything goes wrong up there - you are toast. Also they would have to provide one extra seat for you to come back, in a vessel with an heat shield.

Anyway, if you think they let you sneak near one of these or even sneak something or someone in, you have probably seen to many James Bond or Jackie Chan-Movies. --Kharon (talk) 01:21, 27 April 2017 (UTC)

@Kharon: James Bond might only do that in a fictional scenario, but if Megan Rice were to try I would put money on her to win. The more sure everyone is that a place must have great security, the more vulnerable it is to people who don't believe in security. Wnt (talk) 00:25, 28 April 2017 (UTC)

Well, the Dragon capsule made by SpaceX certainly has a heat shield and full environmental systems on board. It has been used to take live animals to the ISS. The weight difference that one person would make can certainly be negated by the launch vehicle. I think it would be possible, from what I know of the Dragon capsule. The real question would be whether there was space that a human could fit in, as they are packed pretty tightly with supplies, and if the CO2 build-up was being controlled by the atmospheric system. The maximum journey time would be three or four days, so you would need to have enough water with you to survive that time. This is assuming the mission contained live animals. I don't know if they keep the environment sustained to the same levels when it is a mission that is not taking live animals to the ISS. Whatever the circumstances, I don't think it would be very comfortable, and I highly doubt that SpaceX would not notice a person on board. Zzubnik (talk) 03:26, 27 April 2017 (UTC)

video

How does this work?

I thought that buoyancy only depended on 1. the object's weight and 2. the amount of fluid the object displaces. My (admittedly poor) understand is that how that weight is distributed within the object has nothing to do with the buoyancy force. ECS LIVA Z (talk) 20:43, 26 April 2017 (UTC)

Is Buoyancy#Stability helpful? In non-uniform systems, mass distribution can affect the practical implications of buoyancy even if the magnitude of buoyancy force isn't affected by such things. — Lomn 20:54, 26 April 2017 (UTC)

The center of gravity doesn't change in this case though. The hourglass stays rotationally symmetrical throughout the video so its center of gravity stays in the center. ECS LIVA Z (talk) 22:46, 26 April 2017 (UTC)

I suspect the video is fake. The hourglass seems to be staying put on the bottom after the tube is flipped over, then there's an obvious edit in the video, after which it starts to rise. They probably just subbed in a lighter hourglass in a tube and resumed filming. StuRat (talk) 21:18, 26 April 2017 (UTC)

The floating hourglass paradox is a well known physics puzzle. You can buy these things in the right kind of novelty stores, and they behave exactly like this. There would be no point to faking the video. ApLundell (talk) 14:53, 27 April 2017 (UTC)

• I would expect that there is the usual buoyancy on the hourglass within the tube, but if that's quite close fitting then viscosity through the narrow gap between glass and tube will limit the speed it can float upwards at. Andy Dingley (talk) 21:44, 26 April 2017 (UTC)

This doesn't seem impossible, but I don't know if it is genuine. The key would be to have a flexible membrane at the bottom of the hourglass. As the sand in the hourglass lands on the membrane, it may reach a point where its weight can effectively counter the pressure of the liquid and push the membrane outward (or reduce the degree to which it bulges inward). This would increase the volume of the hourglass and make it buoyant. The classic demonstration of this type is the Cartesian diver, but in that case an external source delivers the pressure. Wnt (talk) 22:11, 26 April 2017 (UTC)

I suspect this is just a one-element version of the Galileo thermometer. The obvious cut may conceal an interval while the overall apparatus (or the water) is warmed so that the float rises, and the hourglass sand inside the latter is a deliberate red herring. {The poster formerly known as 87.81.230.195} 90.217.249.244 (talk) 05:20, 27 April 2017 (UTC)

This is a valid explanation. I was already somewhat suspicious that the liquid was not water (something about the refraction... it's hard to say); a liquid other than water likely has a much lower heat capacity or may change volume to a greater degree. The liquid would need to start off at an elevated temperature, making it less dense, and the hourglass would rise as it cooled off. My gut feeling is that the obvious cut here does not conceal chicanery, if only because that would make the riddle too easy. ;) Wnt (talk) 12:23, 27 April 2017 (UTC)

The floating hourglass puzzle can be immediately turned upside down to perform again after it has performed.

And you can make it yourself with a tube, some ordinary water, and an hourglass (Or rather, an egg timer. An actual hour glass would be unwieldy for this kind of demonstration.). You may need to add weight to the hourglass. It should be buoyant, but not very buoyant. ApLundell (talk) 14:58, 27 April 2017 (UTC)

@ApLundell: What's your source for that? I think my solution with the membrane could meet this specification, assuming there are flexible membranes on both the top and the bottom of the hourglass. Wnt (talk) 02:40, 28 April 2017 (UTC)

I'm sure there are lots of ways it could be gimmicked, but you don't need to. The physics puzzle famously works with an ordinary hourglass.

It was apparently first introduced by Martin Gardner in a 1966 article in Scientific American, but I don't have the issue so I can't confirm. It was very popular, zillions of people wrote in about it. He included it in his book Mathematical Carnival.

There's no shortage of examples of this device. (Search for "Floating Hourglass" or "Rising Hourglass") Here's a video of one constructed with a wider tube, so the explanation of the trick is more obvious .

ApLundell (talk) 04:03, 28 April 2017 (UTC)

@ApLundell: I'll grant that looks very similar .... but there's a key difference. The hourglass in that video does not sink on its own! It simply stays in place at first when the whole tube is flipped. So no matter what it looks like, I don't think it works the same way at all. Wnt (talk) 09:45, 28 April 2017 (UTC)

@Wnt: I don't know what to tell you except to encourage you to rewatch the video that started this thread. In it, the video begins with the hourglass floating at the top of the tube until a hand manually rotates the entire assembly. Exactly as in the classic rising hourglass demonstration.

By the way, The tubes can be made with an hourglass of positive or negative buoyancy. (That is, once the static friction is released, they will either sink of rise.) Here's a video where there's one of each. One that performs like the classic rising hourglass as seen in the video that started this thread, and one exactly opposite. In either case, the fascinating part is that the hourglass refuses to move until its center of gravity has lowered a bit. ApLundell (talk) 13:59, 28 April 2017 (UTC)

Wow... I totally misremembered what I'd seen happen. OK, so none of my fancy hocus-pocus is actually needed. Although the membrane thing actually *would* help anyway (the hourglass would float once the sand was down against the membrane, and refloat later) this is indeed just as you said, a simple matter of friction from an unstable center of gravity. Wnt (talk) 01:01, 29 April 2017 (UTC)

It is possible that when the sand is at the top of the hourglass, it's exerting a slight pressure on the air in the lower chamber, compressing it slightly, and as the air flows to the top of the hourglass it decompresses. But this would work only if the volume of the hourglass somehow changed with this difference in pressure, maybe using a membrane as Wnt suggests above. Another explanation: Notice that you never see the hourglass rising with the rounded end on the bottom? The flat end is starting out at the bottom. So that flat end may be 'stuck' momentarily to the end of the cylinder, and its own buoyancy pulls it up.... in which case the sand is just misdirection. ~Anachronist (talk) 06:51, 27 April 2017 (UTC)

The centre of mass (CM) of the hourglass stays on the axis of symmetry, but it does move down. Just after the thing is inverted, the CM is in the upper half, but when some of the sand has fallen, the CM moves to the lower half. The centre of buoyancy (CB) always remains at the exact centre of the hourglass. When the CM is above the CB, the hourglass is unstable and tries to rotate, thereby wedging itself against the walls of the tube, so that friction can overcome the force of buoyancy. When the CM gets below the CB, the hourglass is stable and gets free of the walls.

There is an additional effect, which I didn't completely calculate here. Because the CM of the hourglass not only moves, but even accelerates, the effective weight of a running hourglass is variable and different from the weight of the same hourglass when all sand is stationary at the bottom. It may depend a bit on the exact shape of the hourglass. If you wish to calculate, there are four components: the mass of the sand in the upper half, which is a cone (or maybe not exactly a cone) of shrinking mass, accelerating down; the mass of the sand in the lower half, which is a cone of increasing mass, accelerating down; the sand currently falling, which is in free fall and therefore does not contribute to the weight of the hourglass; and the sand hitting the lower pile, which rapidly accelerates up, slightly overcompensating for the sand in free fall, because the length of the free fall changes. PiusImpavidus (talk) 11:04, 27 April 2017 (UTC)

• The standard answer to this puzzle is the static friction caused by the top-heavy hourglass trying to rotate, and therefore pressing firmly against the side of the tube .

ApLundell (talk) 14:53, 27 April 2017 (UTC)

• I think that Martin Gardner covered this in Scientific American decades ago. It has to do with the friction of the hourglass against the wall changing as the sand goes down. See this. The Martin Gardner article was reprinted in the book Mathematical Carnival, in chapter 14 titled "The Rising Hourglass and other Physics Puzzles". Hardback: Knopf, 1975; softcover: Vintige, 1977. Bubba73 14:40, 29 April 2017 (UTC)

CO2 nose tingling

While drinking Pepsi from the bottle, the carbon dioxide I inhaled had a tingling effect on my nostrils. Why is that? I thought tingling only occurs in dissolved form. 212.180.235.46 (talk) 20:51, 26 April 2017 (UTC)

I notice little bits of soda or champagne splashing out the glass as bubbles near the surface burst. I suspect that some of these land in your nose. StuRat (talk) 21:51, 26 April 2017 (UTC)

@StuRat: you can get the tingling effect even when the bottle is away from your mouth. I have always had two tiny holes in the hard palate behind the upper two front teeth; linking the mouth to the nasal cavity (they're mostly blocked but on some days I can suck air through them). I think carbonated water can go up these holes, still bubbling, and give the nose a tingling sensation. ~Anachronist (talk) 07:04, 27 April 2017 (UTC)

If carbon dioxide dissolves in water, some of it gets converted to carbonic acid. Your respiratory tract is moist, so this happens. This is the same mechanism by which things like chlorine gas have their deadly effects: the molecules dissolve into the secretions lining your eyes and respiratory tract, forming acids, which then attack the tissue. --47.138.161.183 (talk) 21:58, 26 April 2017 (UTC)

AC Transformer Ratings

My power supply (built from a kit) says that it needs a 2x9VAC transformer to output 5V DC: is this the same as 18 VA? Can I use an 18 V transformer that outputs 1 A? I don't understand why they list the specifications as 2x9 instead of 18, when all the transformers I find for sale just say 18. OldTimeNESter (talk) 23:19, 26 April 2017 (UTC)

Your kit should have some kind of circuit diagram to show how things connect I suspect it needs more than two connections to the power supply, and that you have to connect them correctly, not at random. Your circuit may need a centre tap, where the two 9V windings are connected in series. Some transformers can also be connected in parallel (in phase) to double the current output. Graeme Bartlett (talk) 23:50, 26 April 2017 (UTC)

No, 2x9VAC is not the same as 18 VA. The reason why the kit manufacturer has specified a transformer with two secondary windings of 9V each depends on several factors, and it's impossible to say why they have done so without seeing the circuit design. It may help to understand that when AC is rectified in a four-diode diode bridge, the DC voltage that results is very close to 1.4 times the AC voltage supplied by the secondary. Similarly, when using a two-diode full-wave rectifier circuit with center-tapped transformer, the DC voltage that results is very close to 1.4 times the AC voltage supplied by half of the transformer secondary. Here are some configurations, from which we can make some deductions:

• 1. Two 9V windings in series (18VAC) applied to a diode bridge result in 25.2 VDC, far more than required.
• 2. Two 9V windings connected in series (forming a common center tap) to a half-wave rectifier result in 12.6 VDC, about right for deriving 5VDC via a regulator device.
• 3. Two 9V windings in parallel (in phase!!!) connected to a diode bridge result in 12.6 VDC, about right for deriving 5VDC via a regulator device, and able to deliver nearly twice the current as that of configuration 2.

We can almost certainly discount configuration 1, leaving either of the other two options. Therefore your 18 V transformer is almost certainly not suitable. It will definitely not be suitable if the kit uses option 2's half wave rectifier, unless your transformer has a center tap (you didn't mention one). The kit should describe how to connect the two 9VAC windings, from which you could deduce what type of rectifier is employed. Or you could just count the diodes. Akld guy (talk) 06:54, 27 April 2017 (UTC)

Check whether the 2-diode circuit described at Rectifier#Full-wave rectification (B2U) is used in your power supply. The transformer in this circuit can be described as having an 18 V AC center-tapped output, which is the same as 2 x 9 V AC outputs connected in series. Please do not write "18 VA" unless you really mean "18 Volt-ampere". The 2-diode circuit can be replaced by the 4-diode circuit also shown at Rectifier#Full-wave rectification (B2U) which would allow a simpler transformer with 9 V AC output. Blooteuth (talk) 13:44, 27 April 2017 (UTC)

The circuit diagram has 4 diodes: it shows the transformer having four inputs from mains, labelled from left to right as Va, 0, 0, and Vb. The two "0" inputs are tied to ground, and each of the Va,Vb connects to two of the diodes. Both pairs of diodes are wired in parallel. I don't think it's a center tap, since the center output from the transformer is tied to ground. I actually haven't bought a transformer yet: I was just confused because I didn't see any of the listed at Jameco as 2x9, just 18. OldTimeNESter (talk) 14:03, 28 April 2017 (UTC)

That's a really confusing description, and I'm struggling to make sense of it. Akld guy (talk) 01:26, 29 April 2017 (UTC)

April 27

Portion control, food rationing, and economics

When it comes to portion control, so many sources suggest "using a smaller plate" or "using portion control containers" or "sharing the food with someone else" or "communal eating". However, I have found no one who suggests just buying expensive food intentionally while keeping the budget the same. What I mean is, the original food budget may be $50 a week per person. In order to make smaller portion sizes, that person may (1) reduce the food budget to $25 a week per person OR (2) buy expensive food (especially organic-brand food). Either way, the quantity of food is supposed to be reduced, because less money is used to buy food OR the same amount of money is used to buy expensive food; and certain low-nutrient foods (such as potato chips, soda, candy) are banned from the shopping list. So anyway, does economics-based food rationing work? Is there any research examining the effects of intentional food budget reduction OR the effects of swapping to expensive food? 50.4.236.254 (talk) 12:51, 27 April 2017 (UTC)

For most people, staying on a budget is difficult enough, but when pitted against the desire for food, it doesn't stand a chance. Not having enough food at home might lead to hitting the local burger joint, and blowing both the diet and budget at once. Also, many low cost foods, like potatoes, aren't a particularly good choice for losing weight. A variation on your idea I have heard of is the blackmail diet. Here you give a neutral party some of your money, with the idea that they will only give it back if you reach some goal, like a certain weight. If you fail, the money instead goes to some cause you hate. If you hate dogs, for example, it all goes to them.

You might also look at Maslow's hierarchy of needs, which shows that if a physiology need (in this case hunger) is not met, we would not think of any of the higher needs, like saving money for the future, until we satisfy the more basic need. StuRat (talk) 14:44, 27 April 2017 (UTC)

One of the things to note is that, counterintuitively, in developed countries, obesity is generally correlated with lower income, see here "In contrast to international trends, people in America who live in the most poverty-dense counties are those most prone to obesity" This is different than in lesser developed countries, where poor people are more likely to be underfed. That's because of the way that food economics works in the U.S. Convenience foods tend to be more economical because they have a longer shelf life and are easier to prepare (less time intensive), so in terms of long-term economics, poorer people in countries like the U.S. find it actually cheaper to subsist on energy-dense, nutrient-scarce foods because those are available, keep a long time, and are easier to prepare. For many of the same reasons, fresh foods may not even be readily available in poor regions of the U.S. (see Food desert); there's low demand, stores don't stock them as much, etc. In more affluent areas, people have time to shop more frequently, can afford higher wastage, and can spend more time preparing healthier meals. This fits well with Stu's reference to Maslow; hungry people don't have much time to worry about their figure or long term health prospects. --Jayron32 17:36, 27 April 2017 (UTC)

So, obesity-shaming in the United States is really a disguised version of poverty-shaming, and any discussion about poverty in the USA is bound to include class and race. And I've read in the recent news that Donald Trump has made huge tax cuts... for the rich. Awesome. Now, the rich is just going to get richer, and the poor is going to get poorer. Well, let's just hope that the people have some goodness and donate more money to charity and low-income gardens. With a weaker government and more powerful rich people, the only way to help the poor is to get the middle class to side with them.

I think if you're hungry, then you are very likely to think of the short-term costs. $1.00 for a pack of Ramen noodles may seem economical at the Dollar Tree, but just a few steps away, there are frozen vegetables and fruits. Though, you would have to account for cooking. So, you can look at foods that don't require cooking - like canned produce, even though they may be very soggy and bland. 50.4.236.254 (talk) 17:56, 27 April 2017 (UTC)

You've got really expensive ramen. I can generally find them for anywhere from 15 cents per pack to 33 cents depending on sales and the like... --Jayron32 10:51, 28 April 2017 (UTC)

I believe he meant a multi-pack, probably with 6 or 12 individual packages. StuRat (talk) 15:02, 28 April 2017 (UTC)

Trump proposed massive tax cuts for the rich, but that doesn't mean they will pass Congress. Many mainstream Republicans will oppose it because the deficit would skyrocket, and pretty much all Democrats will oppose it. As for Dollar Tree, I get 4 ounce frozen salmon fillets there, and 12 grain bread, so you can find healthy food even there. StuRat (talk) 04:04, 28 April 2017 (UTC)

Not an answer, but: the tradition of Lent seems of some relevance to this question. We have a notion of medieval times as being harsh, yet how did religious people of the era come up with a tradition of intentionally doing without food then? I would love to see something on the functional aspects of Lent traditions - do they combat obesity, and if so how? Was meat much more expensive relative to other foods in former times (as reflected by subsequent positions in the U.S. Catholic churches)? Did it make sense to avoid slaughtering animals at that time of the year, etc.? Wnt (talk) 00:35, 28 April 2017 (UTC)

People say that the Mediterranean diet is "healthy". Coincidentally, the Mediterranean countries are Catholic or Orthodox. Both religions do intermittent fasting. This video says that the rich did not eat fruits and vegetables, because they thought food from the ground was for the poor. Apparently, spices were not "from the ground". 50.4.236.254 (talk) 01:06, 28 April 2017 (UTC)

How are hard jelly sweets made?

How do Rowntree's Fruit Pastilles achieve their hard jelly consistency? Do they just use more gelatin than others or is there some other ingredient that gives the jelly a hard chewy consistency? — Preceding unsigned comment added by Nocontrolgorge (talk • contribs) 14:07, 27 April 2017 (UTC)

Not sure specifically on that brand, but generally candy hardness is determined by how long the candy is cooked. Candy making#Sugar stages covers the various stages of sugar hardness which is mostly based on the temperature you remove the cooked mixture from the heat at and the sugar concentration in the final mix. Making candy of any kind is basically sugar + water + flavors; to get a specific consistency you heat the mixture to a certain temperature, then cool it. The specific temperature it reaches is based on a colligative property called boiling point elevation. --Jayron32 14:41, 27 April 2017 (UTC)

And note that cooking it longer makes it harder by reducing the water content. StuRat (talk) 14:54, 27 April 2017 (UTC)

Can people still lose weight eating junk food?

Just a quick question; if someones basal metabolic rate is 1,600 calories a day can they still lose weight if they eat junk food like pizza and chocolate as long as it totals less than 1,600 calories a day? — Preceding unsigned comment added by Nocontrolgorge (talk • contribs) 14:08, 27 April 2017 (UTC)

It's possible. However:

1) It's quite unlikely they will feel full after that small amount of junk food, so actually do so is extremely difficult. It's quite easy to get 1600 calories from junk food in one meal, so that means no eating the rest of the day. See satiety.

2) They will still damage their health with unhealthy things (excessive trans fats, saturated fat, LDL cholesterol, sugar and sodium) and a lack of healthy nutrients (dietary fiber, HDL cholesterol, protein, vitamins, minerals, phytochemicals, antioxidants, etc.).

3) Their body may enter starvation mode due to a lack of healthy nutrients, and the basal metabolic rate may subsequently drop. Reducing the amount of junk food further may then only push them deeper into starvation mode, in a vicious cycle, leading to serious malnutrition.

4) Your 2 examples, pizza and chocolate, are two things that can be part of a healthy diet, provided it's a veggie pizza (with big chunks of veggies, not token diced bits), and dark chocolate, like 85%, and you don't have too much of either. Some other junk food, like soda, is unredeemable, as even using artificial sweeteners doesn't make it healthy. StuRat (talk) 14:36, 27 April 2017 (UTC)

Weight loss has a rather checkered reputation, but "starvation mode" isn't entirely a bad thing. Bear in mind that for many obese people, "starvation mode" doesn't literally mean an emergency breakdown of vital proteins, but simply a decrease in insulin resistance! If a diet fails at a weight loss goal but improves blood sugar levels, that is still a useful thing. Wnt (talk) 00:40, 28 April 2017 (UTC)

• Not only they can, but they will; the first law of thermodynamics is hard to beat, and energy can come only from "burning" the solid body mass with atmospheric oxygen and releasing it as CO2, losing one carbon atom in the process and its associated weight. (Unless that "someone" is capable of photosynthesis or other means of energy storage that do not involve the enthalpy of the food they eat, or you cheat with a technicality.)

Obviously, this does not imply anything about whether such a diet can be kept to from a mental point of view, and anyways human health is not summarized by one variable of weight, as hinted to by the above answer. Tigraan 14:35, 27 April 2017 (UTC)

• The definition of junk food is generally food that is low in nutrient density. Nutrient density is simply the ratio of micronutrients to food energy. This has nothing to do with whether or not you lose weight; weight loss is mostly a matter of using more energy than you get from your food. If you use more energy than your food provides, you lose weight. Junk food causes other health problems noted above due to the lack of necessary dietary nutrients, but strictly speaking if your manage your caloric intake, you can lose weight on a junk-food only diet. The documentary Fat Head, the film maker lost weight on an all-McDonalds diet for example. --Jayron32 14:48, 27 April 2017 (UTC)

The asteriod impact that wiped out the dinosaurs

This has been bothering me about the aftermath of the impact. Given the global-scale devastation and blackout conditions that persisted for years afterward, how was it possible for absolutely any living thing at all to actually survive the disaster? Just exactly how dark and how cold did the earth actually become, and how long did it last? If it really literally was as bad as is often shown on tv, there is simply no way that anything dependent on photosynthesis could have survived at all - and consequently also nothing higher up the food chain. It simply could logically not have been really as bad as the "popular" media portray it. Roger (Dodger67) (talk) 18:40, 27 April 2017 (UTC)

I have never seen any popular media portrayal of the years following the impact, so it would help if you pointed us to some of the ones you're thinking of. Henry 19:13, 27 April 2017 (UTC)

It depends (mostly) on how long (and cold and dark) the popular media are portraying it – I don't know myself because I avoid portrayals that are likely to be grossly inaccurate. Given that some life did survive, by definition the actual conditions must have permitted it, so we need to assess the conditions against that known fact. Bear in mind that plant seeds can survive for years before germinating when the right conditions return, and larger woody plants can also survive, alive but not growing, for lengthy periods. The terrestrial animals such as mammals and avian dinosaurs (aka "birds") that did survive were all small (I've read "cat-sized or smaller"), and may have subsisted mainly on carrion and plant seeds. ("Roast chestnuts. anyone?" "No, pass me some of the T. rex jerky.") Even most members of most surviving species would have died, but it only takes a few surviving pairs (or individual plants), to make it through and start repopulating (and evolving into all those suddenly vacated niches). Its harder to know what was going on in the oceans, but obviously something was. I presume you've already read Cretaceous–Paleogene extinction event and any relevant links and references. {The poster formerly known as 87.81.230.195} 90.217.249.244 (talk) 19:21, 27 April 2017 (UTC)

This Misplaced Pages article says: "Omnivores, insectivores and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. No purely herbivorous or carnivorous mammals seem to have survived. Rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on dead plant and animal matter. Scientists hypothesize that these organisms survived the collapse of plant-based food chains because they fed on detritus (non-living organic material)" --AboutFace 22 (talk) 22:36, 27 April 2017 (UTC)

Another factor is torpor (hibernation, estivation etc.) I looked for confirmation and found things like this. A fun thing I have in mind is that a human ship emerging from suspended animation is perhaps likely to really freak the natives of some other planet, where life didn't pass through this bottleneck and the emerging humans seem like mythical undead... Wnt (talk) 00:03, 28 April 2017 (UTC)

Our article on the Chicxulub crater mentions the Earth is estimated to have been shrouded in darkness for "several years, possibly a decade". Since many seeds can persist for decades, and some even over a century, while staying viable, it's totally plausible that some species survived the event. Now, it would certainly be devastating, and our article on the extinction event mentions that the majority of terrestrial plant species went extinct around this time. Someguy1221 (talk) 00:11, 28 April 2017 (UTC)

April 28

Girls having more moles on arms

This is a question I'm wandering about. Do you think on average girls have more moles on their arms than on guy's arms, focussing on teens and twenties? When wearing short sleeve shirts with arms exposed, I know girls tend to show more moles on their arms because girls tend to wear shorter sleeves than that of guys' as well as wearing sleeveless shirts more frequently. Asking a side question: do you think girls have greater average number of moles on their right arm than on the left; I can judge that based on the internet pictures I've seen. PlanetStar 02:18, 28 April 2017 (UTC)

@PlanetStar: Do you perhaps mean freckles, rather than moles? I ask this because your question suggests to me a relatively large number. Moles (nevus or melanocytic nevus) are normally small in number, as far as I'm aware. Due to the potential for malignancy, a large number of moles would likely be of significant medical concern. As for numbers relative to gender, age, demographics, etc — I don't know. Murph9000 (talk) 02:47, 28 April 2017 (UTC)

No I mean moles. Moles are usually benign and are not usually of medical concern. But if moles suddenly appearing and are rapidly changing would be a concern. Moles are part of development. See a picture of moles on teenage girl's arm here. PlanetStar 04:43, 28 April 2017 (UTC)

FWIW (not much), I'm a guy, and I have a similar density of moles on my arms/body. I think any casual personal observations are likely to be subject to confirmation bias, so we really need scientific sources to confirm or deny the hypothesis. This 1985 paper found in their survey (in New Zealand) no sexual differentiation in overall numbers, but that women have more on the arms, face and neck, while men have more on the back. From glances at other sources, there seems to be some correlation between mole development and sun exposure (though some moles are congenital) so this might reflect clothing and lifestyle habits in New Zealand (which might not apply elsewhere). {The poster formerly known as 87.81.230.195} 90.217.249.244 (talk) 05:15, 28 April 2017 (UTC)

remember also in New Zealand in the period before 1985, so it might not even apply in NZ any more. Nil Einne (talk) 06:51, 28 April 2017 (UTC)

Wind rose

Just for fun, I decided to look up the Wind rose for Portland, OR. But I got wildly different result from different sites. Which one is more correct? ECS LIVA Z (talk) 10:08, 28 April 2017 (UTC)

Are you sure they are in the same location in Portland? --Jayron32 10:38, 28 April 2017 (UTC)

Here's current data for KPDX (Portland International Airport): KPDX. At the top of that page is a link to "past weather..." including Frequency of Wind DIRECTION, based on Time of Day. These data are compiled by the National Weather Service, and all the raw records are available at no cost.

A lot of internet websites will try to commercially package and re-sell these free government services, but you can always go directly to www.weather.gov or www.noaa.gov to browse for what you seek, directly from its source.

If you put that data into a wind rose (for example, using your favorite spreadsheet charting and plotting tool), you can see that there are many options for plotting the result - do you want to average all winds or only winds during specific hours (e.g. only during daytime)? Do you want to consider all months, or produce a wind rose for a specific month? ... and so on. So, you can imagine that a few variations on the final chart may occur, depending on the kind of analysis you care to conduct.

Looking at prevailing wind is not only fun, it's useful: for example, here's Planning and Design of Airports, which has a whole chapter on wind speed and direction as they apply to the ... planning and design of airports.

Nimur (talk) 19:24, 28 April 2017 (UTC)

The first site listed by the OP says that it uses observations, while the second site listed by the OP uses fairly coarse-resolution (30 km) model output (look at "General information" near the bottom of the page). Model output will always differ from observations. Shock Brigade Harvester Boris (talk) 00:41, 29 April 2017 (UTC)

Is "queen ant" or "queen bee" accurate or anthropomorphizing bees and ants?

The term "queen" sounds like a lofty title. Why not just call these queens "baby producers"? 50.4.236.254 (talk) 11:59, 28 April 2017 (UTC)

Because we use the word "queen". Language is neither logical nor precise, nor is the language use of millions of people subject to the momentary whims of someone such as yourself. The word has been "queen" has been used in this context for a long time, in English since 1807. You aren't going to change it because you don't like it. --Jayron32 12:13, 28 April 2017 (UTC)

Doesn't every bee or ant in the respective colonies serve the queen bee or ant? If so, the term "queen" seems totally logical. "Baby producers" seems inadequate. ←Baseball Bugs carrots→ 12:24, 28 April 2017 (UTC)

That's assuming a one-way function. You can also assume the reverse: that the "queen" is serving the workers and replenishing the population, but not directly telling them what to do. 50.4.236.254 (talk) 12:32, 28 April 2017 (UTC)

That's true of proper royalty too. I mean, they theoretically serve a purpose that benefits the citizens of their domain. ApLundell (talk) 14:14, 28 April 2017 (UTC)

User:Baseball Bugs. It's complicated. Bumblebees are basically beaten into submission by the queen, and if she stops beating them for whatever reason, the strongest daughter will become fertile, start laying eggs, and start beating her sisters. Sometimes, in transition, there are multiple proto-queens, all fighting amongst themselves. Unlike human queendoms, ant colonies of many species have multiple fertile queens. Sometimes colonies established by multiple fertile queens. See Ant_colony#Organizational_terminology for some of the different ways they do it. Finally, though there are no true solitary ants, there are many solitary bees who "serve" no queen. SemanticMantis (talk) 19:13, 28 April 2017 (UTC)

The not-quite-aptness of the terminology is discussed in the article Queen ant.

On the other hand, they do form the center of their community, and they have servants that wait on them hand and foot. (Mandible and antenna?) So it's not entirely spurious.

In some species the queen has at least some small decision-making capabilities. In Honey Bees she has some control over the swarming behavior. (Although, surprisingly enough, the new hive construction site is chosen democratically. Swarming_(honey_bee)#Nest_site_selection)

ApLundell (talk) 14:14, 28 April 2017 (UTC)

The term "queen" better matches the modern role of the Queen of England. That is, she is well taken care of, but doesn't have much real power. StuRat (talk) 15:06, 28 April 2017 (UTC)

Don't use the term if you don't like it. "Queen ant" is technically informal, but plenty of myrmecologists use the term, even formal in scholarly writing e.g. (here ).

If you want to avoid anthropomorphic language, use gyne; that is the formal term for a queen ant, bee, or termite. See e.g. here for usage in the scholarly literature.

There are also terms gynergate and ergatogyne that describe various intermediate forms between workers (erg) and queens (gyne). We also have gamergate and ergatoid. SemanticMantis (talk) 19:21, 28 April 2017 (UTC)

The term "Queen" is also use for the vertebrate naked mole-rat and the Damaraland mole-rat. Interestingly, these are the only two eusocial mammals we know of, so they have a lifestyle and reproductive system similar to some of the ants and bees discussed above. DrChrissy 19:33, 28 April 2017 (UTC)

Hey @DrChrissy:. Not all authors consider those mole rates to be eusocial. Our NMR article gives this ref which says they are "arguably" eusocial. As you may know, there are (still) competing definitions, even in this decade. Here is an article that clearly considers them NOT to be eusocial, but instead semisocial, and also gives further refs on that. I'm wondering if this merits a more careful treatment in our article? SemanticMantis (talk) 20:23, 28 April 2017 (UTC)

So, humans aren't eusocial, because they do not divide individuals into reproductive and non-reproductive categories? What kind of social organization do humans have then? Homosexual humans do not reproduce. Do they make humans eusocial? 50.4.236.254 (talk) 19:53, 28 April 2017 (UTC)

No. It's when a species has most individuals non-reproductive that it becomes eusocial, as then the non-reproductive members have no purpose of their own, and only act like cells for the larger super-organism. I don't believe gay, infertile, or otherwise childless people in our society would say they have no purpose in life other than to serve the collective. StuRat (talk) 20:03, 28 April 2017 (UTC)

Eusocial has a definition. Some people might argue that some human societies may have counted as such, but in general we don't have obligate non-reproductive adults. Even gay people often reproduce, they're not sterile. Here's a nice article on evolution of sterility in honey bees. The generally accepted reason that eusociality is so rare outside of Hymenoptera is because they have haplodiploid sex determination, and this messes with the evolutionary pressures, relative to diploids like us. Male bees don't have fathers and can't have sons, and sister bees are more related to each other than they are to their parents or potential offspring! This is the short version of why we think sterility evolved in those clades. See Haplodiploidy#Relatedness_ratios_in_haplodiploidy for more info. SemanticMantis (talk) 20:10, 28 April 2017 (UTC)

Quite an attachment?

The idea came to me while using the Dremel.

If a tool resembling the one in the picture along exists, it would be a very capable way of making a neat hole in wood or plastic etc. Is an attachment like this there? Jon Ascton  (talk) 15:13, 28 April 2017 (UTC)

You're looking for a Hole saw. They exist for dremels. Notice that unlike the one you drew, they often(but not always) have a pilot bit in the center to guide them in. Otherwise they would skitter all over your work piece. ApLundell (talk) 15:18, 28 April 2017 (UTC)

Also notice the slots in the side of the saw pictured above. Some, but not all hole saws have these. The purpose is to allow you to insert a screwdriver or other tool to pry out the plug of wood, which often gets stuck in the saw after completing the hole. CodeTalker (talk) 17:07, 28 April 2017 (UTC)

The OP's image drill looks suitable for sawing large holes in soft material such as wood but the tools for the Dremel are for grinding small holes (3 to 12mm) in hard material. This is a single conical step drill for my cordless drill that gives a choice of hole sizes, works in most non-brittle materials and leaves suitable holes for countersunk wood screws. It's even occasionally useful as a crude reamer. Blooteuth (talk) 18:39, 28 April 2017 (UTC)

Alien fungus?

A friend of mine showed me this link purporting that alien fungus is growing on space stations. It sounds bogus, but I'm curious how that fungus grew on those places in the first place. Would terrestrial fungus somehow hitch a ride on a ship and then grow in space? ScienceApe (talk) 18:27, 28 April 2017 (UTC)

First of all, this is really old news, even if the UFO websites are just hearing about it. Here's a NASA story on the topic from more than 15 years ago. Microscopic Stowaways on the ISS.

Secondly, this is something that the NASA manned space flight program has studied really hard for a really long time. The pests are from Earth, not from outer space - they are Earth-based life forms that got on to the ISS hardware and somehow managed to survive on the interior and exterior of the space station, especially in fabrics, despite everybody's best efforts to sterilize the material before launch, during launch, in flight, and so on. Most astonishingly, some of these life forms don't die even if they're stuck on the outside of the station, exposed to harsh vacuum, temperature, radiation, sunlight, and so on.

Nimur (talk) 18:59, 28 April 2017 (UTC)

Sure, why wouldn't a fungus flourish inside a space station? The environment there is not so different than places molds grow on earth. Here's another NASA page describing how they specifically brought fungus to space to study how it grows there . See research article and photos here .

For the *outside* of a space station, that's a little more impressive, but we have a long and growing list of organisms that can survive the vacuum of space. If tardigrades can survive out there, it's not so surprising that some fungi and bacteria can as well. SemanticMantis (talk) 19:05, 28 April 2017 (UTC)

More links:

• Preventing "Sick" Spaceships, from ten years ago - another science blog on the same topic
• NASAFacts: Environmental Control and Life Support System, the current "executive summary" of the NASA program that monitors that sort of thing

When in doubt, try searching for content from www.NASA.gov, or if you're seeking a little more technically-advanced content, visit NASA NTRS.

Nimur (talk) 19:08, 28 April 2017 (UTC)

Getting rid of it might be difficult. In my home, I would spray bleach on it then open a window to ventilate the area, but I understand they rather frown on opening windows on the ISS. :-) StuRat (talk) 19:21, 28 April 2017 (UTC)

So they can survive in space, but do they grow, and are they in some way edible? If so, maybe they could be farmed on the moon, Mars, etc. ←Baseball Bugs carrots→ 20:12, 28 April 2017 (UTC)

Fungi need organic material to grow, and you'd have to bring that with you to the moon. The link I give above discusses how at least one species grows, with growth medium, in space. SemanticMantis (talk) 20:25, 28 April 2017 (UTC)

The OP may be interested in Tersicoccus phoenicis, a bacteria found only in spacecraft assembly "cleanrooms", and interplanetary contamination. Matt Deres (talk) 01:20, 29 April 2017 (UTC)

Question about the Time Dialtion

Is the longer path traced out by a light pulse in the triangle of time dilation REAL or pseudo like fictitious force relative to the stationary observer if I am not missing something in the following?

Please refer to the Time Dilation Triangle diagram in the link or you can make your own

Both upper and lower mirrors of the light clock are firmly attached to the ceiling and floor respectively of the moving frame.

Let the base of the time dilation triangle is AA’=s=vt’ where t’ is dilated time

Relative to the stationary frame

• The velocity of the moving frame is v in time t where t is not dilated. This means mirrors also move at v in time t (where t is not dilated).

• Length contraction also affect the exact position of the mirrors inside the moving frame

• The spatial distance covered by the moving frame at any time t is s=vt (where t is not dilated). Thus

• The spatial distance covered by upper mirror of the moving frame from B to B’ is s=vt (where t is not dilated)

• The spatial distance covered by lower mirror of the moving frame from A to A’ is s=vt (where t is not dilated)

Since the aforementioned spatial distances covered in t and t’ (BB’= AA”= s = vt’ and s = vt) are not equal therefore what would be the real distance of upper and lower mirror (or any stationary object) inside the moving frame from its original position B and A respectively relative the stationary observer 2001:56A:7399:1200:131:8B26:E7B6:F63 (talk) 23:25, 28 April 2017 (UTC)eek

The "real" distance traveled, from the perspective of the stationary observer, is vt. You would never calculate it as vt', since that value for time belongs to a different observer. To your original question: yes, the path traced is real, it has to be. How else is the light to pass between the mirrors from the perspective of the stationary observer? It's not clear to me what you are missing. Someguy1221 (talk) 00:08, 29 April 2017 (UTC)

April 29

Perseid meteor shower and other meteor showers, could it be from the Earth/Moon breakup?

Hi, scientists studying the Earth/Moon breakup recently have favored a collision as the cause. It seems that would create lots of debris that not all of which would be gathered into either the Moon or Earth, and since it originated on some point along the earth's orbit, there would be a chance the debris could continue to intersect the Earth's orbit for billions of years. Is this possible/likely? thanks.Rich (talk) 02:54, 29 April 2017 (UTC)

Billions of years seems unlikely. Over that period is should all be cleared out, if it intercepted Earth's orbit. Also, wouldn't the particles which escaped head off in random directions, rather than all the same direction ? StuRat (talk) 03:23, 29 April 2017 (UTC)

As that article implies, and Comet Swift–Tuttle confirms (with a reference), the Perseids come from that comet. Matt Deres (talk) 03:35, 29 April 2017 (UTC)

The earth/moon breakup is discussed at Giant-impact hypothesis and it mentions that the time of the impact can be dated from "stony meteorites" and it is backed by a reference, but it doesn't specify which shower (if any) the meteorites came from. Unfortunately, the reference is behind a paywall. The abstract implies that the meteorites involved were from long ago. Matt Deres (talk) 03:41, 29 April 2017 (UTC)

The source you're referring to is available on one of the authors sites here. I only skimmed through it and only understand half the terminology anyway, but as far as I can tell, they aren't referring to meteorites hitting the moon (or earth), but rather meteorites from the moon/earth breakup hitting other things, particularly 4 Vesta without linking them to any particular shower. It does say at the end:

although the importance of GI ejecta returning to strike the Moon has yet to be quantitatively evaluated, the values computed here suggest that it could play an intriguing role in the earliest phase of lunar bombardment.

Nil Einne (talk) 04:06, 29 April 2017 (UTC)

It's a cool source. It also mentions in the supplement that the debris created by the impact was expected to be cleared relatively quickly, with 99% of the ejected fragments either landing on the moon, a planet, sun, or ejected from the solar system by 250 million years afterwards. The supplement also lists the sources of the meteors referenced for the study, which come from all over the place, and in no case is it immediately obvious when the meteor was deposited on Earth except for the Chelyabinsk meteor. Perhaps if you really dug through the references you could find out when these meteors arrived on Earth (on first pass, even the articles they reference don't mention that, so you'd have to go for references of references at least). Anyway, seems like the authors are interested only in the age of the meteors themselves (since last molten), and not how long they've been on Earth. They do mention that the only fragments of collision expected to survive more than a few hundred million years would be those in highly inclined orbits of the sun, which would fit the perseids, except that those come from a comet. Someguy1221 (talk) 04:07, 29 April 2017 (UTC)

BTW, since it's been more than a year, the article even on the Science (journal) is no longer behind a paywall. It's available here with free registration. You can also access the supplements if you register. Nil Einne (talk) 04:45, 29 April 2017 (UTC)

Thank you for that clarification. I think what's confusing me is that they seem to be using the aforesaid meteorites to date the proposed impact using a technique I know nothing about called "40 Ar- 39 Ar shock degassing". We have an article on degasification, but it doesn't seem to be the same thing. In any case, it implies that the meteorites were available to study. We've been to 4 Vesta, but that article doesn't say anything about "argon". There's probably something in the PDF, but I'm unfamiliar with a lot of the terminology, making it difficult to quickly parse the text. Matt Deres (talk) 13:48, 29 April 2017 (UTC)

The short answer: over time most of the stuff gets pulled onto a collision course with something. The gravity of the Solar System's planets and moons perturbs stuff. Very small debris also loses orbital energy due to the Poynting–Robertson effect. This is why you don't see stuff randomly distributed around the solar system. It's why there's an asteroid belt. I'm sure there's the odd bit of leftover stuff out there, but most of the debris from the Theia impact never even reached escape velocity (which we know because it fell back to Earth or coalesced into the Moon). --47.138.161.183 (talk) 05:20, 29 April 2017 (UTC)

Is there a name for this mental defect ?

Normally when we interpret speech, we must decide between different possible meanings. For example, if someone said "Be careful, it's hot" after handing you food, then that would apply to the food. But if they said that before you went outside on a hot day, it would apply to the air temperature. If somebody is unable to pick up on the context, is there a name for that disorder ? StuRat (talk) 03:36, 29 April 2017 (UTC)

Cold bouncy balls

In this video (link), a bouncy ball is placed in liquid nitrogen. Once it's good and cold, it's thrown against the ground, and it shatters with a sound similar to that of glass. I'm not surprised that the coldness affects the ball's Elasticity (physics) somehow, but I would have guessed that it would act like a piece of gravel, simply not bouncing much at all. Why does it become brittle and shatter? Nyttend (talk) 13:39, 29 April 2017 (UTC)

Firefly question

On April 22, while I was out photographing something else, I took the first photo - an 8-second exposure. You can see fireflies flashing up to five times in 8 seconds. I went back to the same location five days later, to get more photos of the fireflies, but now a firefly didn't appear to flash the same way. I tried longer and longer exposures. The second one is a 97-second exposure, but it doesn't show any trails. What is the reason for the difference? Could it be a different species? Bubba73 14:29, 29 April 2017 (UTC)

If jetliner pilots both die soon after giving autopilot the controls on a SYD(morning)-LAX nonstop?

• Misplaced Pages resources for researchers
• Misplaced Pages help forums
• Misplaced Pages reference desk