Wikipedia:Reference desk/Archives/Science/2015 March 2

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March 2

Why are my coffee mugs too hot?

I often reheat plunger coffee that's gone cold by putting it in a mug in the microwave. I long ago worked out that 3 minutes on High works best. By that time the coffee is the right temperature for drinking, and the mug is comfortably warm. This system has worked dandily for at least 8 years. But over the past few weeks, the mug has been coming out way too hot, and I need a protective cloth to hold it. And the coffee is boiling, which is not what I want. I want hot, not boiling. I have an eclectic selection of mugs, some as old as the microwave (about 12 years), others acquired more recently. But it doesn't seem to matter which vintage or variety of mug I use, it always comes out too hot now, when it never did before. I haven't changed the microwave, the settings or the time. I could just reduce the time, but I want to understand what's suddenly changed. Is this overheating perhaps a symptom of impending microwaval menopause, or even failure/death? Has it become unsafe? Or would I need a technician to pull it apart to be sure? -- Jack of Oz ^{[pleasantries]} 08:47, 2 March 2015 (UTC)

I'd agree that it was the microwave oven, except that, in my experience, old microwaves become less efficient, so you would get cooler coffee. Could it be that the voltage delivered to your house from the mains has gone up ? I'm not positive that this would make the microwave run hotter, but it certainly does make incandescent light bulbs burn hotter and brighter. My aunt had this problem. I noticed that her incandescent bulbs burnt out very quickly and in some cases scorched the fixtures, so I put a monitor device on an outlet and found her voltage was indeed running way above spec. If you have any incandescent bulbs left in your house, do they seem brighter ? StuRat (talk) 08:59, 2 March 2015 (UTC)

We replaced them all last year, Stu. If it's relevant, we live in an area where blackouts are a way of life. Mostly they last only a few seconds, but sometimes they're many hours long. Also, our broadband connection goes down too often for my liking, often preceding rainy or stormy weather. Our TV reception is mainly good, but occasionally not. But we've never had any particular problems with our general electricity supply and I'm not aware of any fluctuations in power. -- Jack of Oz ^{[pleasantries]} 09:13, 2 March 2015 (UTC)

If you can dig up an old incandescent light, that might be worth a test. Of course, the power company won't accept that as proof that voltage is too high. For that you will need a device like this: [1]. That one is for the US market, though, and you will want one for Australian outlets. Your local home improvement store might have one.

Note that excess voltage could indeed be dangerous, potentially causing a fire. Basically, every wire carrying an excess voltage will be a bit hotter than normal, and, depending on your initial margin of safety, that just might make something hot enough to catch fire.

More likely, some of your smart appliances may refuse to turn on with a voltage out of spec, while others might shut down after a few minutes, due to an over-temperature reading (some will turn back on as soon as they cool down, while others require hitting a reset button).

Those numerous short power outages you mentioned also fit the pattern of poor maintenance, which could lead to an over-voltage situation. The system is doing some type of automatic switching to get your power back after each, but it may not verify the voltage range, as a human repairman hopefully would. StuRat (talk) 09:23, 2 March 2015 (UTC)

I'd recommend getting a plug-in voltage/power meter, such as the Kill-A-Watt (other manufacturers' devices are available, such as the Floureon TA-836A), and check what the voltage of your mains power supply is. If you are in the United States, then the voltage should be 120V, and the frequency 60Hz. I'm not sure what the tolerance is, but it's probably within 5%. LongHairedFop (talk) 16:24, 2 March 2015 (UTC)

This all makes a great deal of sense, and I'm very glad I asked. Thanks, Stu. I'll be calling someone tomorrow. -- Jack of Oz ^{[pleasantries]} 10:05, 2 March 2015 (UTC)

If you mean you will call the power company, they certainly wouldn't do anything here unless I had better evidence than "my coffee is too hot". If you mean an electrician, then they could indeed measure your voltage, probably using the same type of devices we mentioned. However, they are likely to charge far more than the $20 for the device. (If you're worried that you need to be an electrician to use such a device, don't be, just plug it in and read the numbers.) StuRat (talk) 16:56, 2 March 2015 (UTC)

I remember that some older models used mechanical timers to turn off after the chosen time. If you're relying on one of these, is it still accurate? Bazza (talk) 11:18, 2 March 2015 (UTC)

Are you placing the mug in a different place inside the oven? (See recent what if). If the oven has a rotating plate, is it rotating normally - gunk in the works or something? 88.112.50.121 (talk) 13:17, 2 March 2015 (UTC)

Oh dear, MICROWAVING coffee? This is a cardinal sin against this noble beverage. I'm afraid a trouting is in order. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 11 Adar 5775 17:10, 2 March 2015 (UTC)

Seconded. And remember to microwave the trout first. - ¡Ouch! (^{hurt me} / _{more pain}) 13:16, 4 March 2015 (UTC)

I don't think there's any way we can rule out some degeneration in the electronics regulating the power consumed by an unknown microwave that could lead to an increase in the microwave output. On the other hand, could more ions in your coffee make it more conductive? (like if some salt gets in from a new water softener or something?) Sure it might have to do with house voltage but I'm really skeptical. I don't think you'll get a trustworthy answer here. Wnt (talk) 19:15, 2 March 2015 (UTC)

• I tend to microwave X in one container, then decant it into another room-temperature container. Does that solve the problem? μηδείς (talk) 22:59, 2 March 2015 (UTC)

Not really. It doesn't address why the mug historically never got too hot while now it always does, under exactly the same conditions. -- Jack of Oz ^{[pleasantries]} 21:32, 3 March 2015 (UTC)

If the machine has a clockwork timer like my ancient microwave, then possibly it is sticking, as Bazza suggested above, but perhaps you've checked that it still takes no longer than three minutes when set to three? Dbfirs 21:49, 3 March 2015 (UTC)

I have to agree with Wnt and others that it seems a bit hard to believe this is mostly due to overvoltage, primarily because I think there's a good chance you would have noticed other problems if it's sufficient to cause a big difference to the microwave heating. For starters, most fans will go fast. You're in Australia and it's summer (okay technically may be autumn under some definitions now), do you have no fans that you would have likely noticed if going faster? Also since you're in Australia so the voltage is probably nominally 230V, and if you're noticing a significant difference the mains voltage is likely a fair amount higher than the upper limit of 264V. I think many devices with power supplies, possibly including any compact fluourescent lights, are going to start having noticable problems. (In the US, it's probably a lot more resonable you won't notice, because many devices nowadays are 100-240V, so even if the voltage is significantly above tolerances, for anything not using the 240V double live outlets, it'll have to be very high before devices should have problems, theoretically at least.) Nil Einne (talk) 11:40, 4 March 2015 (UTC)

Is it safety to enter a dog or cat into the emergency room or hospital?

I'm looking for scientific articles about. Thanks 149.78.32.22 (talk) 14:04, 2 March 2015 (UTC)

Well, dogs are sometimes brought into hospitals to make elderly and other patients happy. I doubt if they would be allowed into emergency rooms though. http://www.petsastherapy.org/

217.158.236.14 (talk) 14:16, 2 March 2015 (UTC)

• There's also the question of the difference between the emergency room entrance and lobby and the actual treatment area. Presumably a blind person with a broken hand who walked in would be allowed access to the lobby and the staff would follow protocol on how to deal with the dog (contact a guardian/emergency contact, presumably) and put the patient in a wheelchair so she didn't need the dog to go with her in the treatment area. I would suggest calling a hospital main directory, and asking. μηδείς (talk) 17:18, 2 March 2015 (UTC)

Yes, in certain circumstances - see: APIC State-of-the-art Report: The implications of service animals in health care settings and Animal-assisted activity and infection control implications in a healthcare setting. This policy has been developed using those two papers. Richerman (talk) 17:54, 2 March 2015 (UTC)

Total eclipse and light levels

Does a solar eclipse make the sky noticeably darker? — Preceding unsigned comment added by 194.66.246.88 (talk) 14:20, 2 March 2015 (UTC)

It certainly does! http://www.eclipse2017.org/2017/what_you_see.htm 217.158.236.14 (talk) 14:22, 2 March 2015 (UTC)

The more the sun's disk is covered by the moon, the darker things get. It's not like cloud cover. It's like the sun is on a dimmer-switch. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:25, 2 March 2015 (UTC)

Exact date of previous total eclipse visible from the North Pole on the first day the Sun appeared above the Horizon after the end of the Polar Winter

Exactly such an eclipse will happen on March 20 this year. What was the previous date this has happened? Count Iblis (talk) 15:36, 2 March 2015 (UTC)

An interesting question that I cannot answer. Looking at Fred Espenak's eclipse pages on the NASA web site, under this page there is an atlas of total and annular solar eclipse tracks covering the 5,000 years from −1999 (i.e. 2000 BC) to 3000, in the form of 250 GIF files each covering a 20-year period. I used wget to download the entire set and looked at each one. Because they are Mercator projection maps, they cannot show the North Pole itself, but they go up to about latitude 85°N. So I looked for all eclipse tracks sometime in the month of March that ran off the north edge of the map and therefore might reasonably reach the Pole.

Now, I was doing this by eye, so it's possible that I missed a few, but it's a fairly easy thing to look for. It's also possible that there were solar eclipses with such a short track that they were only visible in the immediate area of the Pole and did not come onto the map at all—but not very likely. It's also possible that I miscopied some dates.

Be that as it may, these are the only ones I found. (The longitudes given on each line are my estimate of where the track's centerline runs off the north edge of the map.)

• March 28, −1056: total, 65°W
• March 21, −428: annular, 50°E
• March 14, −189: total, 45°E
• March 24, −171: total, 0°
• March 23, 228: total, 70°E
• March 27, 480: annular, 20°W (?—see note)
• March 15, 1382: annular, 150°W
• March 17, 1616: total, 90°W
• March 20, 2015: total, 25°E
• March 26, 2267: annular, 55°W
• March 23, 2536: total, 80°E
• March 29, 2788: annular, 135°E

Note: Two tracks run off the top of the same map near this position and the labels are so placed that it's hard to tell which one goes with the date in March.

I have not attempted to determine the dates of sunrise at the North Pole in these years, but if any other events of the type being asked about occurred or will occur in the 5,000-year period, it would seem that they should be on one or more of these dates. Perhaps there is astronomy software available that will allow the specifics of these eclipses to be explored. --70.49.169.244 (talk) 19:13, 2 March 2015 (UTC)

User:Count Iblis are you sure that 20 March is the first day of sun at the North Pole? Both the US Navy (form B) and the Canadian Research Council (Choose location by longitude and latitude) using 90N 0W and UTC time show the first sun as 18 March.

Denoising cine film

Many times when watching old b/w film clips on the tv, I wonder whether it is possible to remove all the scratches and other noise electronically ( maybe by spectral subtraction). If it is possible, how long to repair 1 hour of b/w film? --86.190.191.136 (talk) 15:39, 2 March 2015 (UTC)

Have you read our article on noise reduction? It covers several classes of techniques. The first step would be to digitize the old footage, so that it can be processed via digital signal processing. Here's a discussion of how to denoise old film using a filter and the program handbrake -[2]. SemanticMantis (talk) 15:46, 2 March 2015 (UTC)

Professional film restoration is labor-intensive even if done digitally. I think it can take man-months per hour of film. Automated noise reduction, which is all that the noise reduction article seems to cover, can't reliably tell scratches and noise from detail that should be there. -- BenRG (talk) 01:51, 3 March 2015 (UTC)

Why no exact date for the Toba eruption?

According to our article the eruption ccurred 69,000 to 77,000 years ago. Why can't we tell the exact date from the Greenland ice cores? Count Iblis (talk) 15:42, 2 March 2015 (UTC)

This Nature paper gives 73,500 years ago [3]. You'd probably have to read the full paper and perhaps some of the cited work if you want to work out methods they used to calculate or the estimated error. Probably this figure could be added to the article. The older Nature paper cited in the article is from 1978 and only gives "~75,000". SemanticMantis (talk) 15:51, 2 March 2015 (UTC)

As for the second question, you'll never get an exact date from an ice core. Our article ice core discusses some of the sources of error. My understanding is that a modern specialist could probably give a much smaller range, but nobody will ever seriously claim the data shows that the eruption occurred e.g. 9:32 AM local time on some Thursday in March... SemanticMantis (talk) 15:55, 2 March 2015 (UTC)

According to [4] the current best dates come from Ar-Ar radioactive dating of the debris and are 73.88 ± 0.32 ka BP and 75.0 ± 0.9 ka (1-sigma uncertainty). The paper also says that so far no one has definitively identified the Toba eruption in either Greenland or Antarctic ice. That's not to say that evidence of the eruption isn't there, it is more likely that it is there but no one knows which volcanic layer belongs to Toba. The paper then goes on to discuss 9 different volcanic layers in ice cores as possible Toba candidates during a 2 thousand years interval. Toba was an equatorial eruption, and even the very largest equatorial eruptions will leave smaller traces in ice cores than moderate eruptions that came from volcanoes near the ice sheet. So even though Toba was massive, you can't simply look for the largest ice core spike and call it a day, one has to carefully figure out which layer belonged to Toba, and apparently no one is sure of that yet. Dragons flight (talk) 16:36, 2 March 2015 (UTC)

• Does the fact that this happened prehistorically, about 70ka before writing, an order of magnitude per annum, answer the question? μηδείς (talk) 22:57, 2 March 2015 (UTC)

I think I know what order of magnitude means, and what per annum means, but not how they go together here. —Tamfang (talk) 03:10, 3 March 2015 (UTC)

I believe this usage traces its etymology to dog Latin. Nimur (talk) 15:00, 3 March 2015 (UTC)

• Looks like some folks here might be barking up the wrong tree. The full-length reference given at Toba catastrophe theory is giving me a 404, but the locked-up version at [5] at least gives an abstract that the 1000-year period is dated +- 5000 years. So it would seem like GISP2 is not well correlated to the actual date, as of 2012? Maybe there are unconformity(ies) in the ice? Wnt (talk) 02:11, 3 March 2015 (UTC)

Double slit observation

In our grade 12 physics class, our teacher taught us about the matter-wave duality by discussing the double-slit experiment using electrons, light, and small forms of matter, which all produced interference patterns on a screen. He also brought up how, interestingly enough, if one tried to observe which slit the electron/photon/particle goes through, the pattern collapses and one simply sees two bands on the screen. I would like to know: what did my teacher mean by "observing"? Does he mean scientists simply stared at the slits and the pattern collapsed? Does he mean they tried to detect it using a device? If so, what device? Thanks for your help. 74.15.7.133 (talk) 17:35, 2 March 2015 (UTC)

In a typical experiment you set up a fluorescent detector behind the slits, which emits a flash of light whenever a particle strikes it, and you use a camera to capture the flashes. Looie496 (talk) 17:40, 2 March 2015 (UTC)

We have a "double-slit experiment" article that includes lots of details (at various academic levels). In particular, there are some sections about the effects of trying to detect which "which way" the wave/photon goes. Regarding your actual question, I think you mean you would not see the two-slit pattern if the pattern collapses? Presumably you would only see the pattern from the one slit through which a particular photon goes rather than two-slit interference? There are some interesting experiments discussed in the article that speak against the strict claim that it's completely unobservable. DMacks (talk) 17:49, 2 March 2015 (UTC)

He said instead of seeing an interference pattern, one would simply see two bright bands (I've corrected it in my original question), which is why I was wondering through what means would cause this to happen. And thanks, I will read up on it. 74.15.7.133 (talk) 17:56, 2 March 2015 (UTC)

Your teacher was wrong when he said that you'd see two bright bands on the screen. If that were true, there would never be interference in the first place.

The rule in quantum mechanics is that you get interference between different "histories" that lead to the same final state. That's the same final state of everything, not just the particle going through the slit. So if the particle leaves any record of which slit it passed through, there's no interference, because although the particle itself may end up in the same place on the screen, the record of which way it went is different.

If the particles going through each slit end up in different areas of the screen—which is the only way you'd get two discrete bands on the screen—then there will be no interference between the slits in any case because there are no histories involving both slits where even the particle itself ends up in the same place, never mind the rest of the universe.

Looking at the slits won't do anything. Your eye can't reach out into the world and measure anything at the slit; it can only detect light that passes through the pupil of the eye. If that light contains information about which slit the particle went through, then the existence of that information means there will be no interference pattern, whether or not your eye is there. If it doesn't contain that information, then you won't be able to see which slit the particle went through. -- BenRG (talk) 17:12, 3 March 2015 (UTC)

Can sexual arousal cause a penis fracture in a fully clothed man?

If a man is sexually stimulated by some visual or auditory stimulus, and then he gets aroused, will his penis become erect and make him feel uncomfortable while having a layer of clothes on him that prevents penis movement? At this point, is this the reason why the man would intentionally disrobe in order to allow some movement for the erecting penis? 66.213.29.17 (talk) 17:44, 2 March 2015 (UTC)

You may be interested in reading our article on chastity belts. SemanticMantis (talk) 19:29, 2 March 2015 (UTC)

Does that mean that a man can actually control an erection, if he were just wearing pants? 66.213.29.17 (talk) 19:54, 2 March 2015 (UTC)

It means that experiencing penile fracture due to arousal with concurrent spatial restrictions is (ETA: PROBABLY) unlikely. (ETA: Note that we do not give medical advice here, and this comment shall not be construed as such by any reasonable party. Especially because no details of any case are given, and all discussion is purely hypothetical in nature. SM claims no medical expertise, and no warranty is provided, expressed, or implied, for the accuracy or correctness of any comments made by SM. See here [6] for more info.) Discomfort is another issue, and highly subjective. If you are a man, I suggest you do some WP:OR. If you are not a man, you might find one who is willing to help you learn and experiment or at least discuss (provided that you both consent and you are above the age of majority in your jurisdiction). SemanticMantis (talk) 20:05, 2 March 2015 (UTC)

And for that gratuitous comment, I have not only begun an ANI complaint against SemanticMantis, I have vowed to WP:STALK his every edit for the next year. Ha. Ha. Ha? μηδείς (talk) 22:49, 2 March 2015 (UTC)

What? I've updated my response to make it clear that I am not giving any medical advice. If you disagree or think my comment violates some rules or guidelines, feel free to delete it. SemanticMantis (talk) 23:57, 2 March 2015 (UTC)

Thanks. I asked this question, because I read a news article about people having sex in a public office. I figured that the woman might have triggered sexual arousal, which made the man's penis erect, and then the erection led to disrobing semi-consciously, and then that led to sexual intercourse. I mean, disrobing in a public place with huge windows even when you think that no one is watching doesn't sound very instinctive. Though, that case just shows that people can have sex anywhere. 66.213.29.17 (talk) 20:32, 2 March 2015 (UTC)

See Peyronie's disease (NSFW) for our article, incidentally. Tevildo (talk) 22:45, 2 March 2015 (UTC)

Awareness of erect penis

When a man is sexually aroused and his penis becomes erect, is he aware that the penis is erect without seeing it? 66.213.29.17 (talk) 21:38, 2 March 2015 (UTC)

Very much so, yes. --Stephan Schulz (talk) 22:55, 2 March 2015 (UTC)

It's actually not unusual for males to sometimes get erections even without becoming at all aroused, sometimes from sitting down for a long time, sometimes just after waking up. Especially for young males, some of my most embarassing memories are from my youth having erections at inconvenient times.. In any case, whatever the cause, it's usually quite obvious to the user because of several different sensations, not just one. Firstly you can feel the blood engorging, you can feel the swelling, you can feel pressure against your clothes, if you are wearing them, if it is due to arousal there is usually several other associated sensations in the general "nether regions", like a low down butterflies sensation. It's all quite hard to miss. Having said that, i wonder if there's some proprioception disorder which would make it possible to have an erection while being completely unaware of it. Vespine (talk) 23:18, 2 March 2015 (UTC)

Wouldn't that be priapoception??? - ¡Ouch! (^{hurt me} / _{more pain}) 13:17, 4 March 2015 (UTC)

Livestock breeding, estrus cycles, and artificial insemination

While horses tend to breed during spring or summer and rarely in late fall or winter, they may have a more limiting breeding season than cows. Also, horses are allowed to reproduce with stallions, but cows - which can reproduce year-round - must be artificially inseminated with collected semen from a bull to produce milk? Why aren't commercial cows allowed to breed with bulls? 66.213.29.17 (talk) 22:26, 2 March 2015 (UTC)

See Dairy cattle#Reproduction. Artificial insemination is the most common method, but a small number of dairy farms still keep a bull for this purpose. Tevildo (talk) 22:52, 2 March 2015 (UTC)

There's no real use for dairy bulls, apart from siring. Beef bulls can be farmed, but they are dangerously unpredictable, and their meat is tougher. Stallions can be ridden, and thus are worth keeping. Thus its cheaper to use one bull to inseminate several herds of cows, and artificial insemination is easier than transporting the bull around the herds. LongHairedFop (talk) 16:14, 3 March 2015 (UTC)