Wikipedia:Reference desk/Archives/Science/2016 November 25

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November 25

Charger question

If a charger is plugged in to a source of electricity but nothing is plugged into the charger, does it use electricity? Bubba73 ^{You talkin' to me?} 04:34, 25 November 2016 (UTC)

Some of them do, unfortunately. See wall wart#Efficiency (historical). StuRat (talk) 04:54, 25 November 2016 (UTC)

Thanks. I used to leave my car GPS on all of the time, but a couple of months ago my battery ran down. Since then I've been unplugging the GPS, but I wondered if it was sufficient to unplug it from the charger or if the charger needs to be unplugged. Bubba73 ^{You talkin' to me?} 05:03, 25 November 2016 (UTC)

It will take longer to fully discharge the battery with just the charger plugged in, but it still could happen. StuRat (talk) 05:25, 25 November 2016 (UTC)

Depends on the charger. My inverter has an energy saving mode that kicks in if the power draw is less than 7W. A typical USB charger is enough to kick the inverter into action. My 12V battery chargers also. This is with nothing plugged in to the chargers. However the charger for my electric toothbrush is not enough to switch the inverter on. In a car your cigarette lighter sockets are /probably/ switched off when you remove the key. Greglocock (talk) 11:46, 25 November 2016 (UTC)

Yes, they do use some energy. But the amount is very low - they are what's called a switched-mode power supply (see also here) and this uses very little energy until a phone is plugged in. xkcd provides a neat rule of thumb: since the energy has to go somewhere, you can tell if a power supply is wasting (much) energy if it feels warm. Blythwood (talk) 20:02, 25 November 2016 (UTC)

Testing pipelines

Is it an actual procedure to pressure-test an oil pipeline before use by pumping seawater into it? If done improperly, could it create a seismic hazard? (Question inspired by A View to a Kill, where this was done to purposely cause an earthquake.) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:52, 25 November 2016 (UTC)

Halliburton provides pipeline testing services by water flooding. Pipeline test pressure is typically held for a period of 8 to 24 hr with calibrated instrumentation recording both pressure and temperature throughout the test period. James Bond's opponent Max Zorin however planned to detonate explosives under the Hayward and San Andreas faults to cause seawater to submerge Silicon Valley. Blooteuth (talk) 13:28, 25 November 2016 (UTC)

So I take it as a "yes"? Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 01:59, 26 November 2016 (UTC)

"Yes" to the first, "No" to the second. There is a lesson to learn from the need for Destructive testing of the burst pressure of aviation tires. Using air would cause a dangerous explosion as the energy accumulated in compressing the air is suddenly released. Therefore this test is done using water that is virtually incompressible and only a little energy is released when the tire ruptures and contracts. Blooteuth (talk) 15:21, 26 November 2016 (UTC)

Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 01:33, 27 November 2016 (UTC)

Ticking time - bomb?

I own an Indesit gas cooker. The model is not identified but it is either KD3G2/G, KD3G2S/IR, KD3G21/G or KD3G21S/IR. It has electronic ignition which makes a clicking noise when the ignition button is pushed. The clicking is now continuous and the burners ignite without the ignition button being pushed. The normal method of enabling and disabling the flow of gas to the burners by depressing and rotating the control is unaffected. This is not one of the faults described in the manual. Should I be worried about this? 86.147.228.21 (talk) 14:18, 25 November 2016 (UTC)

If you think this could be a matter of concern you should contact a qualified repair person to inspect your cooker. Advice from a bunch of random people on the internet thousands of miles from your kitchen could do more harm than good. Shock Brigade Harvester Boris (talk) 14:24, 25 November 2016 (UTC)

Hear, hear! Tigraan^{Click here to contact me} 16:52, 25 November 2016 (UTC)

• The igniter is electric. There are a few forms of these: Piezo ignition makes one spark for each button press (so it isn't that), battery ignition has a battery, usually a D cell, and sparks continuously. It has the advantage of not needing an electric supply. More recent gas cookers have mains electricity supplies for lights, clocks, fans or electric elements and these ignite without a battery.

If it concerns you, remove the battery. If it's mains, then turn off the mains supply (and lose the clock etc.). Then repair it at leisure. Andy Dingley (talk) 14:43, 25 November 2016 (UTC)

The ignitor button can stick down on some gas cookers. You could try turning of the power, and then gently prying up the button. However, if you aren't confident about doing this, then contact a Gas safe registered repair person. LongHairedFop (talk) 16:38, 25 November 2016 (UTC)

Seriously, the Refdesk does not give advice - that's actually one of the rules. We can give you citations, we can even give you ideas, but we cannot tell you what you should do, because that's a value judgment. That said, your description gives me the impression the button might be stuck or the circuit that it closes might be otherwise shorted. I don't know if those igniters can wear out with overuse or not, potentially leaving you prone to unignited gas going off after an unexpected period of time as the igniter stops working reliably. Wnt (talk) 22:46, 25 November 2016 (UTC)

I would be quite surprised if an igniter, operating continuously, would not wear out eventually. StuRat (talk) 18:16, 27 November 2016 (UTC)

Note that in the UK it is illegal to carry out some kinds of repairs on a gas appliance unless one is a qualified engineer: this fault may well fall into that category. {The poster formerly known as 87.81.230.195} 176.248.159.54 (talk) 06:16, 26 November 2016 (UTC)

Your link suggests that a low-voltage electrical accessory would not fall into that category since it is not part of the gas supply, but I agree that, if in doubt, leave it to the experts. The replacement part might be [here], but if it is mains-operated ignition then it might be wiser to leave the replacement to someone who knows what precautions to take. Dbfirs 09:45, 26 November 2016 (UTC)

That link is incorrect and misrepresents the relevant law. Which I would note it doesn't even cite. Andy Dingley (talk) 23:13, 26 November 2016 (UTC)

Can female Guppys reproduce via parthenogenesis?

Two and a half years ago I was given two female Guppys. They lived without incident until around 3 months ago when one of them became bloated in the belly area for a few weeks and then disappeared. I have yet to find the body as the tank is very overgrown with algae, but I am certain it has died. Shortly after this I noticed a tiny baby guppy swimming about. It is rapidly growing and it is now clear that it is another female. While I do not know if the two original females had contact with any males before I got them, I know for certain they lived with me for two and a half years without any male contact. So where has this baby come from? Can the females reproduce via parthenogenesis? 103.193.118.31 (talk) 22:08, 25 November 2016 (UTC)

I don't know if this can happen specifically in Guppies, but some fish can change sex - see Sex change. One of your fish could have become a male and mated with the remaining guppy.DrChrissy ^(talk) 22:14, 25 November 2016 (UTC)

Having said the above, a search on Google Scholar reveals reports of apparent parthenogenesis in guppies here.[1] DrChrissy ^(talk) 22:36, 25 November 2016 (UTC)

I think it's possible, but there is a much more likely explanation than that. Guppies are members of the livebearer family, Poeciliidae. In these fish, the male deposits sperm in the female and the sperm can remain in the female a remarkably long time before resulting in pregnancy. Thus, it is entirely possible, and in this case probable, that one of your females had been fertilized more than two and a half years ago and, remarkably, stored the sperm all of that time. Aquarium enthusiasts who keep and breed livebearers see this sort of thing very often. (Your fish who died could have been pregnant, or could have had fish dropsy.) --Tryptofish (talk) 23:46, 25 November 2016 (UTC)

Wow! Great answer. I knew many animals could store sperm but I did not know they could do it for that long. I have just found this (Mittwoch, U. (1978). Parthenogenesis. Journal of Medical Genetics, 15(3), 165.) which throws hermaphrodism in a guppy into the mixture of a possible explanation. DrChrissy ^(talk) 23:53, 25 November 2016 (UTC)

This reference shows that female guppies can store sperm for at least 10 months. DrChrissy ^(talk) 00:49, 26 November 2016 (UTC)

Here's a link to that study, giving a value of at least 10 months: [2]. I found anecdotal statements of storage for around a year: [3]. I haven't found any source that says that they have established a definitive amount of time as being the upper limit. --Tryptofish (talk) 01:04, 26 November 2016 (UTC)

I was thinking about this last night. I suspect this lack of a defined upper limit is because of the way that science is (not) funded. Although it is of interest, I doubt it is of sufficient interest to pay someone to mate some guppies and then watch their tank for over a year! DrChrissy ^(talk) 18:54, 26 November 2016 (UTC)

I agree. One tends not to get tenure by waiting three-plus years for a fish to give birth. --Tryptofish (talk) 22:25, 26 November 2016 (UTC)

Is "plausibility" built into spacecraft?

I find this news to be very weird. Mars is not exactly a magic object - it doesn't have holes that let vacuum go all the way down to the surface or hands that reach out and grab spacecraft, so how did that Schiaparelli lander not have some kind of time delay built in where it had to fall for something within, oh, 50%, even 80% of the expected time before believing a "maximal" reading? For that matter, why wasn't the "maximal" reading an error, if it indicated an altitude on or below the ground before landing had commenced? Do other spacecraft have such things - is there a name for this kind of feature? Wnt (talk) 22:58, 25 November 2016 (UTC)

I guess they didn't put this part of the system through a rigorous stress test. There is only a limited amount of time available to wrap up the entire project, you can only do so some given number of tests, not every aspect of the system gets tested, so there may be problems that are not detected and fixed. Count Iblis (talk) 00:52, 26 November 2016 (UTC)

Very few things that work beautifully on paper survive a contact with objective reality. Working with IMUs you very quickly get to appreciate how well they are supposed to work in theory, and how poorly they work IRL. Even high-end IMUs are prone to many types of errors, some of which are covered in our IMU article (offset, drift, scaling, misalignment, noise, crosstalk) and some of which are not (finite sampling rate, underflow and rounding error cumulation, nonlinearity, saturation, overflow, data corrution due to environmental influences, and so on). I won't speculate what caused the Schiaparelli IMU to spew a second's worth of crap, or what logic was or should have been in place to allow Schiaparelli to ignore the said crap. However -- trust me on this one -- no matter how good the engineering is and how rigorous the testing is in the lab, nothing can fully simulate the Real Life and its infinite propensity for mayhem. Dr Dima (talk) 04:43, 26 November 2016 (UTC)

Mars is not exactly a magic object...or is it? --47.138.163.230 (talk) 10:07, 26 November 2016 (UTC)