Wikipedia:Reference desk/Archives/Science/2015 August 1

= August 1 =

Evolution of the universe and multiverse
In string theory, there are different physical laws in different universes. I want to see how universe will evolve if there are different physical laws. I can't find any website which has a simulation where I can add different values and see the result. Some scientists are saying that there is only one way to know that we are in a multiverse, i.e, finding the gravitational waves which are formed when our universe collides with another universe. Is there any other way to know that? Supdiop ( Talk 🔹 Contribs ) 01:17, 1 August 2015 (UTC)
 * I doubt that any website will show how the Universe evolves with different physical laws, as it takes supercomputers many months of calculation to make these models . Dja1979 (talk) 02:03, 1 August 2015 (UTC)
 * Thanks Supdiop ( Talk 🔹 Contribs ) 17:49, 3 August 2015 (UTC)

Pain in shrimps
There is a product that consists of sealed small aquariums which contain shrimps, algae, and bacteria among other living beings living in equilibrium in a closed eco-system. Ecosphere seems to be the most famous brand, but there are alternatives.

How can we know that whether the shrimps living in this bubble experience pain or something similar to it? If we wanted to analyze it rationally, how whould we proceed?--Scicurious (talk) 07:57, 1 August 2015 (UTC)
 * Pain in invertebrates is the relevant article. Tevildo (talk) 08:21, 1 August 2015 (UTC)


 * The shrimp have no predators inside the sphere - limited (or zero) exposure to disease - if it truly does provide for all of their needs, they never want for food.  They might well be happier there...if a shrimp can be "happy".
 * Incidentally, these spheres are not really self-perpetuating - the shrimps rarely survive more than a couple of years, then everything goes to hell. SteveBaker (talk) 18:21, 1 August 2015 (UTC)


 * I have not heard of these before. Interesting concept.  Presumably the only energy input is sunlight, and I find it difficult to believe they can get the balance of the biota right to prevent algal blooms while creating sufficient energy for the shrimp to survive in any long-term way. Along with Pain in invertebrates you might also look at Pain in crustaceans. DrChrissy (talk) 19:08, 1 August 2015 (UTC)
 * We have an article Ecosphere (aquarium). It gives a time frame of 2-3 years for the shrimp, but this is from the manufacturer. The most useful looking ref there seems to be this old one from Carl Sagan (it's on the manufacturer's site but was published in a magazine), but other then being old, it doesn't seem to actually say how long it was owned. Nil Einne (talk) 21:33, 1 August 2015 (UTC)


 * I would think that the shrimps end their days suffocating in a marine equivalent of Xingtai  like smog. Metabolism create many complex hydrocarbons. There appears not to be any activated charcoals included to help to absorb these. The (dead) coral will also increase the calcium content of the water (dissolved by the acids formed from metabolism). Planet Earth has a troposphere, stratosphere and ionosphere  where these  hydrocarbons get broken down again (by UV, mono-atomic oxygen etc.),  into gases that are useful to biological life forms(the other spheres are nether here nor there in this). So I can’t imagine these shrimps end their days as very happy shrimps in such foul water and so probably experience great distress. --Aspro (talk) 22:39, 1 August 2015 (UTC)

Can I use a battery-powered electric toothbrush in the shower?
I just bought a brand-new battery-powered electric toothbrush. I was just about to use it, but then it dawned on me. Can I use this in the shower? (In other words, brush my teeth while I am in the shower.) I read the package, and it said nothing at all about contact with water. And, of course, it is probably assumed that a toothbrush will have contact with water (whether in the bathroom sink, or shower, or wherever). But, still, it seemed like something that is maybe not a good idea? I was not sure. Any thoughts? And, if it is safe/OK to use in the shower, how can that be, seeing that it is electric and has a battery? Thanks. Sorry if the question sounds stupid. 2602:252:D13:6D70:CDE5:E7AB:66FA:70CE (talk) 19:12, 1 August 2015 (UTC)
 * According to Philips, yes. Other brands of electric toothbrushes are available, but I'd have thought that one you couldn't use in the shower would be at a bit of a marketing disadvantage. Tevildo (talk) 21:07, 1 August 2015 (UTC)


 * Mine has a battery, but no charger. It's just a stand-alone variety, not like the one in the link you provided.  So, back to my second question:  if indeed it is safe/OK to use in the shower (as seems to be the case), how can that be, seeing that it is electric and has a battery?   2602:252:D13:6D70:CDE5:E7AB:66FA:70CE (talk) 22:40, 1 August 2015 (UTC)
 * To start with, you should check the manufacturer's website (or the instructions) for confirmation that it is safe to use. As a consumer product, it's very likely to have a electrical safety certificate from the appropriate authority (such as Underwriters Laboratories).  As the voltage will be low, there's no risk of electrocution - the main risk is a short-circuit causing the battery to overheat.  This will have been addressed by the designer - if it uses disposable batteries, it might have a "Do not use NICAD batteries" warning, as these have a low internal resistance and are more likely to overheat than other types.  As a device intended for use in wet conditions, the electrical components will be in a watertight compartment - see IP rating for the various standards applicable. Tevildo (talk) 22:59, 1 August 2015 (UTC)


 * Chances are it uses two or three AA cells, which if you go and chuck them into a cup of tap water do remarkably little- even if you connect them in series (well how do you think I know that?). The voltage, up to 4.5 V, is not sufficient to endanger life and limb unless you manage to surgically insert them into your body. So don't do that. http://msgboard.snopes.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=104;t=000779;p=1 discusses 9V batteries and tongues. On balance it seems that even 9V is extremely unlikely to hurt you, given that you hold the device in your hand and the bit in your mouth is a plastic (ie insulating) wand. Also " The lowest voltage for fatal electrocution I found in literature is 46 volts (in Patel & Lo, Stroke (1993), vol. 24 pp. 903-905), five times higher than the voltage in question. " - when discussing 9V batteries. If the device is not designed for use in damp or wet environments then it was designed by an idiot, and will probably corrode and fail. But it won't hurt you unless you drop it on your toe. Greglocock (talk) 02:22, 2 August 2015 (UTC)
 * I have an electric toothbrush. Its battery is rechargeable and is sealed inside the hand-piece. I agree with User:Tevildo - there is no risk of electrocution of the user if it is taken into the shower or a bath or swimming pool. The worst that could happen is rapid and premature discharge of the battery, necessitating recharging before further use; but even that is highly unlikely. Any electrical item that is likely to be used in the vicinity of moisture is either designed to be fully immersed in water; or it carries a large warning label saying "Do not use this appliance when wet or near water". Dolphin  ( t ) 06:37, 2 August 2015 (UTC)


 * Why would you use a toothbrush in the shower? ←Baseball Bugs What's up, Doc? carrots→ 07:02, 2 August 2015 (UTC)


 * I brush my teeth while I take a shower. Don't lots of people do that?   2602:252:D13:6D70:CDE5:E7AB:66FA:70CE (talk) 07:48, 2 August 2015 (UTC)
 * Rinsing your mouth with warm water? ←Baseball Bugs What's up, Doc? carrots→ 11:22, 2 August 2015 (UTC)


 * Huh? I don't understand what you are asking.  In my shower (up on the top of the shower metal door), I have a toothbrush and a tube of toothpaste.  When I am taking a shower, I shampoo my hair, soap my body, wash my face, etc.  And I also brush my teeth.  Don't lots of people do this?  I don't understand your question about "rinsing your mouth with warm water".  I rinse my mouth with whatever water is flowing from the shower head.  The temperature of which can be controlled or adjusted.  Sometimes, yes, it's warm.  But, so what?  It's not boiling hot.  I am standing in that water for a shower, so it's appropriate temperature for my body to endure. 2602:252:D13:6D70:C7:1BA9:2BBB:41C5 (talk) 20:52, 2 August 2015 (UTC)


 * Don't worry about Baseball Bugs, he's not from planet earth, he's just collecting data for his alien overlords. Yes there's nothing wrong with brushing your teeth in the shower with hot water, My wife and I do it all the time too. Vespine (talk) 23:07, 2 August 2015 (UTC)


 * I don't brush my teeth on the shower, but I do shave my face there, having previously gotten hair, shaving cream, and blood all over, when trying to shave over the sink. Clean-up is far easier in the shower. StuRat (talk) 23:21, 2 August 2015 (UTC)


 * Never in all my born days (all of which are earth-bound) have I heard of someone brushing teeth in the shower - until this section. Shaving, I could see. But it seems like a terrible waste of water to brush your teeth there. And warm water? Yuch. Most of us would use the spigot on the sink, the cold water spigot to be exact. Much less water usage, and much more palatable. ←Baseball Bugs What's up, Doc? carrots→ 23:27, 2 August 2015 (UTC)


 * Wow, I am incredulous that you have never heard of this. From reading your last post, however, I think that you are not "getting" the concept.  I don't go into the shower in order to brush my teeth.  While I am (already) in the shower, I also brush my teeth while there.  In other words, if I have to brush my teeth at another point in time in the day, I don't step into the shower to do it.  I just use the bathroom sink water spigot.  2602:252:D13:6D70:E5F9:B511:1547:7BC9 (talk) 02:31, 3 August 2015 (UTC)


 * This has veered off topic, but I have to say, I'm surprised by Bugs' anti-warm water bias. My personal feeling has been that warm water encourages bleeding (i.e. preventing vasoconstriction), making any gum issues on flossing or brushing easier to see, and my personal perception has been that bleeding flushes out a wound.  Web searching I found some dentist  advising "warm to hot" water in a Water Pik for rinsing, but he doesn't say why there and my search terms imposed a bias. Wnt (talk) 03:26, 3 August 2015 (UTC)


 * I'm with Bugs on this one. Brushing your teeth in the shower ain't nat'ral. And I, for one, welcome our new alien overlords. Gandalf61 (talk) 12:24, 3 August 2015 (UTC)
 * Brushing your teeth in the shower is completely normal. From now on, just to spite Bugs, I will step into the shower every time I wish to brush my teeth - with my electric toothbrush, which is three times a day. At least I will smell of my Old Spice body shampoo constantly and will have the very comfortable experience of warm water cascading onto my arthritic bones. KägeTorä - (影虎)  ( もしもし！ ) 19:28, 3 August 2015 (UTC)


 * I could imagine early electric toothbrushes having a removable brush, which is designed to get wet, inserted into a motor unit, which is not designed to get wet (or perhaps you could say the brush is waterproof, while the motor is only water resistant). Air vents for the heat would be the main issue.  But, since a brush is only intended to be used a couple minutes at time, it could also just shut off when it gets too hot, in which case you could use it again when it cools.  (I suppose you could put metal cooling fins on the motor, too, if you don't mind a retro 50's look.) StuRat (talk) 23:21, 2 August 2015 (UTC)


 * Cordless charging might support such, but keep the charger far away from water. The bearing and fittings to the motor might not support such application like this amount of water, water under pressure or dip into fluid. -- Hans Haase (有问题吗) 12:48, 3 August 2015 (UTC)