Science desk
< November 18	<< Oct \| November \| Dec >>	November 20 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 19

Onset of function of prostate and testes

At puberty in male humans, does the function of the testes generally begin before that of the prostate?

I'm curious because I recently remembered that it appeared to be that way for me. I'd been masturbating to orgasm for quite a while before puberty; when at the age of about eleven I started ejàculating it was viscous and stringy and so sticky I had to pull it off me, and it was several weeks before it became at all like a liquid. The other day I remembered this and it occurred to me that it could have been caused by a time difference in onset of function.

(Regular contributor here, using a throwaway account for privacy.) Throwaway1131 (talk) 01:41, 19 November 2015 (UTC)[reply]

Prostate#Development doesn't seem to contain much, but indicates that the prostate itself develops at around 9 weeks as an embryo. Wikipedia doesn't seem to have much to answer your questions, but perhaps if you researched more of the details of Gonadarche (the changes to gonads that occur during the early stages of puberty) you may find more about the mechanics necessary to answer your questions. --Jayron 32 02:46, 19 November 2015 (UTC)[reply]

I think so, although not substantially so. Puberty begins when the brain, through the pituitary gland, signals the gonads to ramp up production of sex hormones. The elevated level of sex hormones then triggers all the other stuff. The article on the prostate notes that its function depends on levels of testosterone and its metabolite DHT. So it's not inconceivable that the prostate could be delayed in "turning on". Note that most of semen by volume is produced by the seminal vesicle, not the prostate or the testes. An important part of the prostate's secretions are enzymes that break down other components of the semen to make it flow more freely. My guess is that you're largely right, and your semen had a low level of prostate components, which meant it stayed viscous. --71.119.131.184 (talk) 19:47, 19 November 2015 (UTC)[reply]

Earth's magnetic poles

How many times in Earth's 4.5-billion-year history did its magnetic poles switch places? When in the future will this happen again? GeoffreyT2000 (talk) 04:05, 19 November 2015 (UTC)[reply]

See Geomagnetic reversal. --Jayron 32 04:08, 19 November 2015 (UTC)[reply]

How do I make my own Nutrition Facts label?

Nutrition Facts is the label that comes with many packaged comestible items. What tools and knowledge do I need to compute the amount of nutrients by myself? Besides a calorimeter, what other tools do I need? How do I figure out the amount of sodium or sugars or vitamins or minerals? 140.254.70.25 (talk) 15:45, 19 November 2015 (UTC)[reply]

There are a number of different techniques for this, ranging from titrations, spectrophotometeric, atomic absorption spectroscopy, etc. It all depends on what specifically you are testing and what for. --OuroborosCobra (talk) 15:50, 19 November 2015 (UTC)[reply]

So, how do I make my own Nutrition Facts label? 140.254.70.25 (talk) 16:05, 19 November 2015 (UTC)[reply]

I agree with OuroborosCobra, with the addition that most food manufacturers just ask their suppliers for the nutritional facts of their ingredients, and then just use the weighted average of the ingredients that goes into one serving, or look it up from a database reference. Sending out samples to outside labs for a complete analysis is usually prohibitively expensive, especially for small companies. shoy (reactions) 16:07, 19 November 2015 (UTC)[reply]

Are you also asking about software and printers capable of printing an adhesive label ? StuRat (talk) 18:38, 19 November 2015 (UTC)[reply]

if the crab supernova had planet

• I LOVE SUPER NOVAE FOR THEIR BEAUTIFUL LIGHT CELEBRATING WHEN THEY ARE APPEARING BRIGHTER AND THEIR SENDING OR OUR LIFE MATERIALS AND SPECIALLY THEIR PALPITATING PULSAR AS OUR HEARTSBold text

We know the black hole can not destroy its planet (as i approved last). But the supernova is different , what was happened for earth size and distance planet when the star was exploding even due at 1054 ?--Akbarmohammadzade (talk) 16:17, 19 November 2015 (UTC)[reply]

Any inner planets should be destroyed, but planets farther out (~hundreds of AU) could be ejected or find a new orbit around the remnant. [1] --Amble (talk) 16:39, 19 November 2015 (UTC)[reply]

So let's get some facts straight here. Firstly, it's called "The Crab Nebula" - but it was once a star that exploded into a supernova about 7,500 years ago. But because it's around 6,500 light years away, the light from the explosion didn't reach Earth until about 1,000 years ago - which is when Chinese and Islamic astronomers wrote about it. That explosion would have had to be incredibly violent. Even now, the debris from it is moving outwards at nearly 1,000 miles per second - or about three and a half million miles per hour! With all of that energy thrown out from the original star, it had insufficient energy left to hold it's massive weight against it's own gravity, and the core collapsed to become an incredibly dense neutron star - which is still out there.

OK - so what about planets. Firstly, not all stars have planets - so perhaps there weren't any. If there were, then the ones closest to the star would undoubtedly have been utterly destroyed by the initial explosion. In the vacuum of space, the material from the star would continue to move outwards in an expanding ball at millions of miles per hour - but as the size of that ball increased, the amount of material being thrown against any outer planets would rapidly diminish. But even a relatively low density gas moving at that incredible speed would rip away atmospheres of rocky planets and tear away at the surface of gas-giants. That initial pulse of energy would push on each planet and nudge them out of orbit somewhat.

Knowing exactly what would happen to each planet is a complicated thing. The size of the original star and the exact distance, mass and composition of each planet would factor into what happened - some might be torn to shreds, others pushed out of their natural near-circular orbits into crazy elliptical patterns that would send them out further and then have them fall back closer to the supernova's core. It's possible for a planet to wind up in a new, stable, orbit further out from the neutron star. I suppose it's also possible that enough force might be exerted on a planet for it gain escape velocity and to travel outwards with the debris cloud forever - but it could never go fast enough to avoid being continually bombarded with radiation and high speed particles from the star - so it's fate is never going to be good! For sure, any planet with an atmosphere would lose it instantly as the shock-wave passed it.

SteveBaker (talk) 15:53, 22 November 2015 (UTC)[reply]

Does keeping plants inside the house have any meaningful impact on the oxygen concentration in the home?

^Topic ScienceApe (talk) 17:10, 19 November 2015 (UTC)[reply]

Only if your house is hermetically sealed (plants in a Controlled ecological life support system would have a measurable impact); your body is putting out an order of magnitude more carbon dioxide than a houseplant excretes oxygen, and you don't asphyxiate yourself by breathing. The Air changes per hour rate in a reasonably ventilated building is much higher than most people think. ‑ iridescent 17:17, 19 November 2015 (UTC)[reply]

Though they may some impact on the CO2 concentration. Ruslik_Zero 20:34, 19 November 2015 (UTC)[reply]

It takes roughly 20 trees to match the O₂ needs of one person [2]. So unless you are keeping a forest in your house, you probably aren't making much of a difference. Dragons flight (talk) 20:43, 19 November 2015 (UTC)[reply]

Electric Dimmer

Does an 'electric dimmer' help reducing the cost of electric bill? -- Space Ghost (talk) 18:26, 19 November 2015 (UTC)[reply]

Incrementally, maybe. But your average major appliance is going to pull way more juice than that. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:31, 19 November 2015 (UTC)[reply]

If you use it at a dimmer setting than you otherwise would, then yes. Some caveats:

1) You should have CFL or LED bulbs to save energy, and only certain ones work with a dimmer.

2) You could also just put a lower wattage bulb in, if you never need full brightness.

3) There were some very old dimmers that just wasted the "unused" electricity while generating heat. I doubt if you have any of those.

4) Dimmers often have rather limited wattage they can handle. Probably not an issue unless you are using halogen lights.

5) Dimmers tend to wear out more quickly than regular light switches. StuRat (talk) 18:35, 19 November 2015 (UTC)[reply]

Points noted, but, I was watching a programme made by a guy who hosted Top Gear show, he was showing/proving disturbances occurring when using dimmers. Basically, if you use dimmers than it disturbs the flow of electricity, and apparently, its not good to use one... Anyway, I'll bear both of your statements and the Top Gear guy's information in mind, I hope you guys do too, recall before fiddling with electrical stuff. Thank you. -- Space Ghost (talk) 18:53, 19 November 2015 (UTC)[reply]

I can think of few people whose opinions I'd take less seriously on electrical engineering than Jeremy Clarkson; every electrical appliance will "disturb the flow of electricity", since converting electric flow into light, heat or motion is the entire point. Of course a dimmer switch is going to "disturb the flow of electricity", since that's the entire point of a TRIAC; while (very) old dimmer switches worked by resistance, which as StuRat correctly points out just dissipated "spare" energy as heat, the thyristor in a modern dimmer switch works by partially interrupting the alternating current (in effect interrupting the flow of electricity hundreds of times per second to cut down the flow to the bulb). As Baseball Bugs says, the energy saved will be minimal as a lightbulb really doesn't use much power to begin with unless you're running an anti-aircraft searchlight; your best ways to save power around the home is to turn down the heating/air conditioning, and replace your washing machine. ‑ iridescent 21:24, 19 November 2015 (UTC)[reply]

(adding) What you don't want to do with a dimmer is use it on fluorescent bulb (usually marketed as "low energy bulbs" or Compact fluorescent lamp bulbs) that isn't explicitly marked as safe to use with them, unless you have a particular desire to see your house go up in flames. ‑ iridescent 21:36, 19 November 2015 (UTC)[reply]

iridescent, I think it was probably James May, not Jeremy Clarkson. Rojomoke (talk) 21:38, 19 November 2015 (UTC)[reply]

A bad TRIAC can leak noise into the power line, much to the chagrin of guitar players (especially those with noise-sensitive single coil guitar pickups). Here's pickup maker Seymore Duncan's thoughts on mitigations for that: [3] (although there are several other causes for hum on single-coil pickups). If I understand the mechanism properly, the noisy TRIAC leaks junk into the building wiring, which acts as an antenna broadcasting that, which the single-coil pickup receives (single-coil pickups are great at detecting all kinds of RF and magnetic garbage, including radios, phones, and CRT TVs) - the active parts of a guitar amp (which are coupled to the pickup coil) are magnetically isolated from the mains (by a transformer), so I think that the dimmer hum doesn't get in through the amp's mains connection. Guitars with humbuckers are much less sensitive to dimmer noise. -- Finlay McWalterᚠTalk 00:20, 20 November 2015 (UTC)[reply]

I understand what you all have stated, I do understand about the disturbance too, its just that it was shown in a way that it is completely bad to use dimmers... Thank you all. Regards. -- Space Ghost (talk) 19:10, 20 November 2015 (UTC)[reply]

The fancy term for these "disturbances" is harmonics. These are an issue in electrical power engineering, but if you're not being billed based on power factor (which you aren't if you're a standard residential customer) they're the power company's problem, not yours, unless as mentioned above you're an electric guitar player or doing something else sensitive to electrical noise. And anything that isn't a perfect linear load generates harmonics, including motors and the switched-mode power supplies that modern electronics use for mains power. As far as saving power goes, I personally don't see the point of using dimmers. Using CFLs or LED lights will save way more power so it's something you should be doing already. Aside from that, just turn off lights when you don't need them. As others mentioned, a typical home's energy use mostly goes to appliances and climate control, so focus on those to save energy. --71.119.131.184 (talk) 20:10, 20 November 2015 (UTC)[reply]

I understand. I'm environmental friendly too, except on/for some helpless lifestyle things. Regards

-- Space Ghost (talk) 05:43, 21 November 2015 (UTC)[reply]

Dimmers generate a duty cycle from the AC of the power grid. LEDs lamps, transformers and LED based bulbs connected to a dimmer required to be specified for this environment as "dimmable". These light-weight transformers athe switched-mode power supplies, couppling their reference output to the input and have recifiers installed that can handle the dimmers AC wave form. LEDs are also feed from current pulses substituting and adequate constant current to fit the LED's specification. Those pulsewidhs might interfer with the dimmer's output causing a permanent damage when components are not designed for such operation. Note dimmers may differ in cutting on or off the sine wave. Rectiviers tolerate the cut off more easyly, than the turn on to pte peak voltage to the AC which the inexpensive bulb dimmers do by their phase shifting circuit. --Hans Haase (有问题吗) 12:26, 21 November 2015 (UTC)[reply]

Peeps, I bought this pen size USB led light today, it consist of 10 led light or so, I also have a universal plug with a USB port, I wonder if I could/should plug it with the universal plug, use it instead of the fluorescent bulb that I have; it's powerful enough. I just need an assurance in, whether its better or not energy saving wise cause its connected with a plug into a socket. If not, then I'll use it with my PC port. -- Space Ghost (talk) 21:38, 21 November 2015 (UTC)[reply]

My guess is that if you need to have the PC on anyway, then plug the light into that - but if you have to turn on the PC just to power your light, then that's likely to be a collossal waste of energy. However, much depends on the computer's power supply...a desktop PC would offer different trade-offs than a laptop. But to be honest, the cost of running the LED light is so tiny compared to running (say) your refrigerator, it hardly matters. SteveBaker (talk) 03:57, 22 November 2015 (UTC)[reply]

Your pen-size USB LED shouldn't consume more than 2.5 watts (500 milliAmps at 5 volts) - because that's all that a USB 1.0 or 2.0 port is guaranteed to deliver - but I doubt that it uses even a fraction of that. A small PC will need at least 100 watts - probably much more if it's a powerful one with fancy graphics and a high speed multi-core CPU. My PC has an 800 watt supply.

So adding the LED light probably adds considerably less that 1% to the PC's power requirements.

SteveBaker (talk) 04:27, 22 November 2015 (UTC)[reply]

Thank you. -- Space Ghost (talk) 18:37, 22 November 2015 (UTC)[reply]