Wikipedia:Reference desk/Archives/Science/2013 November 29

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November 29

Polar opposites on the globe

If two geographic locations are exactly opposite each other on the globe, are they referred to as "polar opposites"? Or is that term strictly limited to the actual poles (North Pole and South Pole)? If "polar opposite" is not the correct word to describe the locations, what is the correct term? Also, is there a web site at which one can enter a specific geographic location, and its precise "polar opposite" would be identified? For example, what is the polar opposite of New York City ... or of Rome ... etc.? Thanks. Joseph A. Spadaro (talk) 00:35, 29 November 2013 (UTC)

See Antipodes. Red Act (talk) 00:48, 29 November 2013 (UTC)

A-ha, perfect. Thanks! Joseph A. Spadaro (talk) 04:53, 29 November 2013 (UTC)

There's various consequences of the Borsuk–Ulam theorem like for instance there is always a pair of antipodal points with exactly the same temperature and pressure. Dmcq (talk) 12:43, 29 November 2013 (UTC)

For example, the American Midwest is chilly, and the Indian Ocean is likewise experiencing a cold snap. Or are they? ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:14, 29 November 2013 (UTC)

The theorem, of course, knows nor cares nothing about the physics of the Earth's weather. But it's an interesting thought — where would you expect to find two such points? I'd probably start looking near the Equator, because there the antipodal points are at the same latitude, and near the terminator, because there you have one point at sunset and one at sunrise. Except, sunrise is probably colder than sunset, other things being equal, because it takes things a while to warm up and it takes them a while to cool down. So actually you want to be a little (maybe half an hour?) after sunrise/sunset at each of the points, which unless I've made a minus-sign mistake, means you want to be maybe 5-10 degrees east of the terminator. No guarantees, but if I had to start looking, 5-10 degrees east of the terminator on the Equator is where I'd probably start. --Trovatore (talk) 06:00, 1 December 2013 (UTC)

And the earth's weather, of course, knows nor cares nothing about some guy's theorem. I'm sure there are plenty of places on earth whose weather happens to match some other place or places, and it's always possible one such pair of points could be antipodes - likely near the equator, as you say, although the north and south poles might also be similar, on or near an equinox. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:05, 1 December 2013 (UTC)

Well, mathematics trumps physics — the theorem constrains the weather, not vice versa. --Trovatore (talk) 07:07, 1 December 2013 (UTC)

Yeah, right. Like the mathematicians who proved the bumblebee can't fly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:10, 1 December 2013 (UTC)

Who would those be, exactly? --Trovatore (talk) 07:17, 1 December 2013 (UTC)

Some character named Antoine Magnan. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:21, 1 December 2013 (UTC)

A search-engine-optimization consultant in Bangkok? --Trovatore (talk) 07:46, 1 December 2013 (UTC)

Except he later recognized he made a mistake in his analysis and retracted that claim. DMacks (talk) 13:00, 3 December 2013 (UTC)

So, if I read that article (antipodes) correctly, there are absolutely no parts of the USA that have a land-based antipodes opposite them ... correct? The antipodes for all locations in the USA is in the water/ocean somewhere. Joseph A. Spadaro (talk) 14:49, 29 November 2013 (UTC)

Just about. There's an island that's antipodal to a small portion of the US-Canada border; there's a slice of Alaska that's antipodal to a slice of Antarctica; and the Hawaiian islands are antipodes of various points in southern Africa. Aside from those, it's ocean. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:40, 29 November 2013 (UTC)

I think there may be a few more islands: the Crozet Islands seem to be antipodal to a spot in southeastern Washington, for example. Ile St.-Paul and Ile Amsterdam match up with two spots in Eastern Colorado. If you count US territories there could be more. --Amble (talk) 16:02, 29 November 2013 (UTC)

Thanks, all. Very helpful. Joseph A. Spadaro (talk) 13:49, 30 November 2013 (UTC)

Here's a truly wonderful map tool for exactly this purpose: Tunnel to the Other Side of the Earth]. --Amble (talk) 17:36, 30 November 2013 (UTC)

See Geography of the United States#Antipodes, Geography of Colorado#Antipodes, Montana#Antipodes, Geography of Alaska#Antipodes, and Hawaii#Antipodes. — kwami (talk) 07:50, 1 December 2013 (UTC)

Checking the helpful articles Kwami linked, I find that I miscalculated on the Crozet Islands. Their antipodal point is a bit off the coast of Washington. --Amble (talk) 03:00, 2 December 2013 (UTC)

Dreams

When I sleep with my electric blanket on, I think that I remember my dreams better than if I slept with it off. Am I just imaging things, or is there a reason for this? Seattle (talk) 02:15, 29 November 2013 (UTC)

Are you, by any chance, dreaming about being fried on a griddle? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:35, 29 November 2013 (UTC)

Do you, by any chance, wake up suddenly when you get too hot ? If so, this could explain it. When you wake up slowly the brain has time to purge your dreams, but waking suddenly prevents that. They do tend to then quickly fade, unless you concentrate on them or write them down, though. StuRat (talk) 09:25, 29 November 2013 (UTC)

Our article on sleep says that the brains oxygen consumption during REM sleep is higher than when we are awake. Studies in children have shown total oxygen consumption increasing when they switched from NREM to REM sleep. Dreams occur mostly during REM sleep and dream recall is more likely when waking up during a dream. So it could become too warm during REM sleep and wake him up, but that explanation won't work if he simply wakes up whenever his alarm clock goes off... Ssscienccce (talk) 15:48, 1 December 2013 (UTC)

I have experienced the same thing, not only remembering dreams but having particularly strange dreams too. Vespine (talk) 23:02, 1 December 2013 (UTC)

All sorts of changes in sleeping conditions, length of time, time of day, comfort and depth of sleep, mouth breathing or sleeping on sore limbs, displaced clothing, changes in light, temperature or sound during sleep, and so forth, can account for dreams of greater or lesser vividness and changes in their character. As I have aged, I have noticed my body has improved at interpreting signals. If I have a cold and mouth breath I will dream my teeth are covered in rubber or ash, or have fallen out. Just the other night I dreamt I went to work naked, and woke to find my undergarments riding low, in the same position I felt in the dream. My dreams will be unpleasant if I eat spicy food, and very vivid when I get good sleep after a period of bad sleep. I have no sources for this, since it is usually treated as anecdote (OR) by most sources. But I think most old-wives' tales are true. μηδείς (talk) 05:53, 2 December 2013 (UTC)

I must understand in simple words

How this amazing Google In-Street navigation technique works ! It amazed me ! Please explain this to me in the simplest way you could. How could it be that i navigate there so easily? Ben-Natan (talk) 02:41, 29 November 2013 (UTC)

Hulk no explain. Hulk wonder. Wonder why link to Flash Player storage settings, but dressed as amazing navigation technique? Hulk suspect plan, but miss point. InedibleHulk (talk) 02:52, 29 November 2013 (UTC)

Hulk make nobody laugh. μηδείς (talk) 04:44, 29 November 2013 (UTC)

Can't give away my good stuff for free. The important thing is the question (if it is a question) needs clarity or the right link. InedibleHulk (talk) 05:42, 29 November 2013 (UTC)

In the meantime, nosh on a Hulkaburger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:52, 29 November 2013 (UTC)

can't you guys explain how Google has the ability to shot in such an informative way? Ben-Natan (talk) 14:02, 29 November 2013 (UTC)

I assume you mean "shoot"? And it would take someone who's in-the-know about Google. Someone like that may turn up here, but there's no guarantee. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:12, 29 November 2013 (UTC)

Are you asking about Google Street View? Does that article give you the information you want?--Shantavira|^{feed me} 16:46, 29 November 2013 (UTC)

Steiner Route? --DHeyward (talk) 03:51, 4 December 2013 (UTC)

Ben, I can't actually tell what you're asking. You linked to a webpage about flashplayer settings. Could you describe what you want an explanation for? I thought it may be Google Street view as well, which Shantavira linked above, but I wasn't sure. Someguy1221 (talk) 04:01, 4 December 2013 (UTC)

Heaven's Gate cult

I just read this section about how Heaven's Gate began, and began getting very curious. I googled Chuck Shramek, the amateur astronomer whose CCD photo led to the cult, and saw many links denouncing Shramek's claims. However, I couldn't find out exactly what Shramek's claims were. Our article implies that he simply took a photo, didn't recognize the bright object as a star because of a software error, and asked people what the object was. If that's all he did, what was he denounced for? If he made additional claims, can someone with better Google skills help me find them? Thanks. --Bowlhover (talk) 06:20, 29 November 2013 (UTC)

As I recall, Shramek's only contributions to the whole episode were his photograph and his comments that he observed a "Saturn-like object" that appeared next to the comet in his photograph. After checking some star charts, he couldn't identify what that object was and appeared on the Art Bell radio show to ask listeners if they had any idea what that object could be. As far as I know, he never made any claims about what it was, just raised questions. Art Bell and his listeners took up the issue and ran with it and it grew from there. As the "hysteria" spread, the claims that the object was a UFO were wrongly attributed to Shramek. A quick google search found articles such as this one that seem to agree with what I remember from the time.--William Thweatt ^TalkContribs 06:32, 29 November 2013 (UTC)

That being said, Shramek turning to Art Bell and his fringe/conspiracy theory-themed Coast to Coast AM radio show for "answers" instead of professional academics or astronomers speaks volumes about his beliefs and/or motives.--William Thweatt ^TalkContribs 06:39, 29 November 2013 (UTC)

Ahh, thanks, I didn't know that Coast to Coast was a fringe-themed station. Now I'm even more puzzled. I'm an amateur astronomer too, and apparently, Shramek was a very competent amateur--competent enough to take a CCD photo through a telescope (which is much harder than it sounds). Yet he didn't know how to set the limiting magnitude on his star chart program, didn't know what stars looked like through his own telescope, and never thought to take another CCD image a few hours later to see if the mystery object moved and/or changed brightness. (I'm assuming that our article is accurate and that he claimed the Saturn-like object was following the comet, not just close to the comet.) I never thought an astrophotographer could be this ignorant. --Bowlhover (talk) 07:28, 29 November 2013 (UTC)

Because so many of the original pages have been removed it's hard to be sure, but it seems like Shramek might be getting an unfair rap in our article. In any case, he should no more be blamed for the suicide than the truck driver who transported Oswald's rifle to the post office should be blamed for the Kennedy assassination. Wnt (talk) 21:56, 1 December 2013 (UTC)

Mechanisms of gene regulation

What are mechanism of gene control in prokaryote?74.14.28.186 (talk) 07:50, 29 November 2013 (UTC)

Maybe this link helps. Ssscienccce (talk) 15:57, 1 December 2013 (UTC)

Read operon and follow the links from it. That isn't everything but it's a lot of the fundamentals. Wnt (talk) 23:41, 1 December 2013 (UTC)

Chargers and mobile phone

I am trying to understand what Common External Power Supply practically means. Can I charge any mobile phone with compatible socket with any charger that fits into the socket? I understand the voltage is fixed to around 5 V, but how about the current? Is there a danger of damaging the phone using the wrong charger or could it happen that the phone is just not charging? bamse (talk) 10:19, 29 November 2013 (UTC)

Provided the phone and the charger both properly implement the standard (and for anything coming from a big company, this can be assumed), they will be interchangeable. It's worth noting that this only applies to phone charging with micro-USB connectors, plugging some other charger into some other socket has no such guarentee. Also worth noting that there have been proof-of-concept attacks using chargers with some computing power, which allowed the charger access to the phone memory (without notification on the phone) via the USB connection. Currently the only source I can find is for iPhone [1], but in principle it could be possible for other mobile devices. MChesterMC (talk) 10:36, 29 November 2013 (UTC)

Many tablets use a micro-USB connector, but charge poorly from a standard phone charger, because the tablet requires more current than the charger can deliver. They will charge slowly while asleep, but may not charge while in use. Otherwise, things should be compatible.--Srleffler (talk) 08:08, 1 December 2013 (UTC)

The science of bike puncture repair kits

I was wondering how a bicycle puncture repair kit works.

1. What's in the vulcanising solution?
2. Why does it need to dry before you apply the patch?
3. Can it get too dry (what would be the optimal window for applying the patch)?
4. How long does it take to reach maximum strength of repair?
5. Why do patches seem to have a black layer and an orange/red layer?
6. Can these layers degrade over time?

— Preceding unsigned comment added by 78.148.107.250 (talk) 11:46, 29 November 2013 (UTC)

For those not familiar with these kits, and their mysterious properties, there's a picture one of one at Outline_of_bicycles. AndrewWTaylor (talk) 12:28, 29 November 2013 (UTC)

• I don't know the specifics, but the basic story is that the vulcanizing solution dissolves the rubber of the tube and patch into a viscous liquid. After you apply the patch, the liquid solidifies, giving a single layer of rubber uniting the patch with the tube. The time it takes to solidify is quite variable -- it depends on the amount of solution you use, how wet it is when the patch is applied, temperature, and perhaps other factors. If you do it ideally, it only takes a minute or so.

People who ride road bikes with high-pressure tires rarely use those patch kits, because they are a huge pain in the ass and the result often fails anyway, either immediately or very quickly. It's much better to carry a spare tube, and perhaps a patch kit in case the spare tube fails. It's possible that people who use lower-pressure tires have better luck with them; I don't know. Looie496 (talk) 16:53, 29 November 2013 (UTC)

The OP specifically states that the patch is applied after the vulcanizing solution has dried, which suggests it is used as a contact adhesive. We do have an article on vulcanization but it only talks about vulcanizing rubber to make it usable, such as to manufacture the inner tube in the first place. I imagine that the cross-linking of the polymer chains is still applicable though, except that it now happens between the patch and the inner tube. Richerman (talk) 17:37, 29 November 2013 (UTC)

I don't think that's correct. The adhesive should be nearly dry, but still tacky. If you wait until it is completely dry it won't work. The trick is to get it into a state where it will solidify very rapidly after you make the join -- it's a tricky operation. (I've used those things a number of times, but I gave up on them years ago, so my memory might have faded a bit.) Looie496 (talk) 17:56, 29 November 2013 (UTC)

If you're right that answers point 3. I imagine that you need the solution partly cured to ensure the adhesive has bonded to both surfaces but you want enough uncured solution left to form new bonds when you bring them together. It's years since I used one of these kits too :) Richerman (talk) 18:18, 29 November 2013 (UTC)

Are tire repair kits intented to be long-lasting, or are they only intended to keep you going until you can get to the bike shop? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:46, 29 November 2013 (UTC)

I'm sure I remember them lasting a long time on standard road bike tyres when I used to cycle to work and back. Richerman (talk) 22:32, 29 November 2013 (UTC)

I've never seen the point of visiting a bike shop for a flat tire. Takes more time than patching it yourself, and I've definitely had patched tires last for years of regular use. - Lindert (talk) 22:51, 29 November 2013 (UTC)

The OP asked if the patch would wear out over time. Of course it will. How often do tires go flat due to wear, vs. punctures? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:09, 30 November 2013 (UTC)

From the way you say that, you're probably not aware that in a bicycle you have a soft inflatable tube inside a more or less rigid tire. If you inflate a tube that isn't encased by a tire, it will blow up like a balloon. Tires wear, but tubes do not -- unless the tire is worn all the way through, in which case the tube will fail almost instantly. A patch goes on a tube, not on a tire. To apply a patch, you have to take the tire off the rim, pull out the tube, apply the patch to the tube, inflate the tube a little bit and put it into the tire, put the tire back on the rim, then inflate to full pressure. It is a laborious process. When a patch fails, it isn't because of wear, it's because the patch isn't well sealed onto the tube. It typically takes thousands of miles for a tire to wear through -- it depends greatly on the quality of the tire -- but a tube can be punctured by any sharp thing that penetrates the tire, a thorn for example. A tube typically costs $5-10, but a high quality tire can cost $50 or more. Looie496 (talk) 02:51, 30 November 2013 (UTC)

I meant, do the patches degrade over time while unused. 78.148.107.9 (talk) 00:58, 1 December 2013 (UTC)

I knew they used to be that way, and it appears they still are. So it would make sense that the patch would last until or if it gets punctured along with the inner tube. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:33, 30 November 2013 (UTC)

In my experience, a well-set patch lasts as long as the tube. You are in trouble if there are new punctures close to the old ones (you cannot stack patches), but other than that, they work very well. However, I've moved to puncture-proof tires, and ever since had only one puncture in 10 years (with about 30000-50000 km on the bike). The single exception was due to a glass dagger that would have killed your average vampire... --Stephan Schulz (talk) 18:36, 30 November 2013 (UTC)

One puncture in 10 years? What tires are these? I managed two punctures in two years with Schwalbe Marathon Plus tires. 78.148.107.9 (talk) 01:02, 1 December 2013 (UTC)

Yeah, what are these "puncture-proof tires"? I haven't found anything that works in acacia scrub. Puncture-proof tires combined with double Toughies and puncture-resistant inner tubes, and if I ride over a caltrop I'm flat in under three seconds. And I'll get three or four flats a day if I don't go far. (But then, I don't think even automobiles can use pneumatic tires in that terrain.) — kwami (talk) 07:17, 1 December 2013 (UTC)

I'm using Schwalbe Marathon Plus with good results. But then I'm in Europe and cycling (mostly) on streets. --Stephan Schulz (talk) 16:20, 1 December 2013 (UTC)

I examined one of these patches: after stretching them they curl up with the orange layer on the outside. So I think the black patch is vulcanized rubber and the orange layer is unvulcanized rubber: vulcanized rubber will deform elastically so return to its original form after stretching, the unvulcanized will deform plastically and be longer after stretching. When you apply the patch with the vulcanizing solution, crosslinks will be formed between the polymer chains and maybe between the patch and the tire. I assume unvulcanized rubber is used precisely because it's plastic instead of elastic: it will take on the shape of the tire surface, and keep that shape after vulcanization. Ssscienccce (talk) 16:42, 1 December 2013 (UTC)

CCHR

if this has any clear meaning, it's a request for medical advice
The following discussion has been closed. Please do not modify it.
How can CCHR help me with my drug? Applies to the whole world, or just me, not sure. 78.156.109.166 (talk) 20:20, 29 November 2013 (UTC) I'm not certain what CCHR you mean. If you mean Citizens Commission on Human Rights that is a Scientology front preaching against proper psychiatry and promoting their quack cures. May I put the standard answer to you about drugs, if you have any questions queries, problems then go and see your doctor. We are not qualified to answer medical questions. Dmcq (talk) 22:04, 29 November 2013 (UTC) You might want to clarify your question, and then repost it. Please read Wikipedia:General_disclaimer as well as WP:DAB. μηδείς (talk) 22:09, 29 November 2013 (UTC) Scientology is not medicine (nobody on either side claims it is) and the right to refuse medical treatment under the Nuremberg Code and similar ideas is a political issue, so people should feel free to discuss these topics (the latter might delve into Humanities Desk territory, but it's a border case). We'd need more information to be sure what your question is, but I suspect MindFreedom International, Psychiatric survivors movement, Mad Pride, and other such interlinked articles might make an interesting read. Regarding Scientology itself, I cannot tell anyone else what to do, but I will mention this: interested by their statement that 'clear's enjoy perfect memory, I offered to join them if the person could repeat the first words of our conversation. It was no idle offer - I'd really have gone (but it was before the days of surveillancing everything, I wouldn't try it now). Needless to say, the 'clear' did not do his part to get me as a customer Perhaps he was a suppressive person pretending to be a clear.. :) Wnt (talk) 21:52, 1 December 2013 (UTC)