Wikipedia:Reference desk/Archives/Science/2014 September 13

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September 13

Cellular coverage on the London Underground

Is there a technical reason the London Underground is still one of the only major metro systems in the world to have no cellular coverage underground? 90.192.105.196 (talk) 00:18, 13 September 2014 (UTC)

They haven't installed it yet. --Jayron32 00:19, 13 September 2014 (UTC)

Apparently, this "national disgrace" has something to do with Huawei and China’s Red Army (according to that link from GoMobile News).   —71.20.250.51 (talk) 02:05, 13 September 2014 (UTC)

According to one blogger, who offers no evidence in favor of that theory and acknowledges that it's contradicted by statements from the companies involved. The blog comments by Neil McGrath and Jeremy Andrews, listing technical obstacles, are also unsourced but sound a lot more plausible on their face. -- BenRG (talk) 04:06, 13 September 2014 (UTC)

The New York subway system has Wi-Fi, at least on some lines. Or maybe it's only guaranteed in the stations (i.e. no antennas in the tunnels), though I've seen it work over a tenth of a mile past the tunnel-mouth. Typical station separation is half a mile, station length is a tenth of a mile, so that's up to 75% coverage when not crossing a river, and more by time.

Complete, cellular, coverage is coming in a few years, which means that you can then talk like an asshole for your entire commute. Sagittarian Milky Way (talk) 03:38, 13 September 2014 (UTC)

WiFi and Mobile Phone coverage are two different systems (at least in the UK). Dbfirs 08:17, 13 September 2014 (UTC)

For what it's worth, a Transportation for London spokesman said in early 2013 that "Given the financial pressures on TfL’s budgets, any solution would have to have been funded through mobile operators, with no cost to fare- or tax-payers. The parties were not able to agree a viable proposal and the project is not being progressed at this time." ([1]). -- BenRG (talk) 04:06, 13 September 2014 (UTC

So is Wifi and cellular the same thing in the us? 90.192.105.196 (talk) 10:23, 13 September 2014 (UTC)

No. WiFi and cellular mobile are completely different systems.--Phil Holmes (talk) 14:41, 13 September 2014 (UTC)

I don't remember, but maybe the speech data will use Wi-Fi technology until it gets outside. This seems to be better, as you don't need several sets of antennas (up to 4 for 4 companies?) in a tight space. To tell the truth, I don't remember to what degree antennas in tunnels is planned. Most lines become elevated railways as close as a half mile from CBDs, so the longer your commute is the more likely you'll be able to use Internet. (London doesn't have as many non-underground portions (I think)) Nonetheless, if the OP didn't already know it, New York is probably one of his few others, which shows that the two great English-speaking peoples suck. Sagittarian Milky Way (talk) 18:06, 13 September 2014 (UTC)

So if I use the underground I don't have to listen to someone shouting "I'm on a train" down their mobile - what's not to like? Richerman (talk) 19:08, 13 September 2014 (UTC)

The problem is mostly extroverts, not coverage. Their insensitive brains unwind with.. loud parties, lol and trying to get the attention of one with sub-vacuum cleaner loudness is like throwing a baby dust mite eye at a monkey. Sagittarian Milky Way (talk) 01:26, 14 September 2014 (UTC)

I've been told in New York it's the same project. Wi-Fi and 4G are being installed side by side. However, I've been in places where I got Wi-Fi but no Gees, umm bars. In most underground parts, even in the majority of stations, nothing. When the F train climbs to Smith–Ninth Streets (IND Culver Line) scads of phones come out for a few minutes to say, "Meet me at the station in x minutes". Jim.henderson (talk) 19:24, 13 September 2014 (UTC)

The first batch of Wi-Fi had stations on 6th and 7th Avenue lines south of Midtown. I don't know how far below 14th Street the first batch reached (if at all). It was extended northwards, the western L line was added, the Broadway line was added (I think, that line shares many stations with the previous three). Anything else? IDK. That explains your experience. I think the 1 might've gotten it all the way up in Harlem/Washington Heights a year ago, lol. Before Grand Central Station? Sagittarian Milky Way (talk) 01:26, 14 September 2014 (UTC)

Not really my subject, but apparently Virgin Media has a workaround system that operates at 100 Underground stations.[2] Alansplodge (talk) 12:42, 14 September 2014 (UTC)

Isn't that WiFi coverage as a substitute for mobile phone coverage? Presumably they haven't solved the problem of providing even 2G coverage underground. Dbfirs 12:23, 15 September 2014 (UTC)

4g speeds

This is similar but a different question to the above so thought if start it as a new question. Why is it that 4g speeds are so much faster in places like Tokyo or Seoul. I could swear that in these cities, the 4g connection is faster than a home fibre optic connection in the uk even indoors or on the metro. And also, how do they even install 3G/4g coverage on a moving train underground? Are there masts at intervals inside the tunnel or is it cabled to the train? 90.192.105.196 (talk) 10:23, 13 September 2014 (UTC)

Cabled to a moving train ? How could that possibly work ? I'd say they have antennas on the train and masts at intervals along the tracks. From inside the train they could then have you plug in or use a wireless method. They could also have you use the masts directly, but then they couldn't bill individual users as easily as if you must plug in, and would need closer masts, since the antenna on your device will be much smaller than one on the train. Also, if they are anything like US companies, they want to nickel and dime you to death any way they can, like charging you to plug in. StuRat (talk) 12:04, 13 September 2014 (UTC)

Well it could use track circuitry. But I suppose track circuitry wouldn't have enough bandwidth for 3G, let alone 4g. — Preceding unsigned comment added by 90.192.105.196 (talk) 12:49, 13 September 2014 (UTC)

The problem with "4G" is that it's not one single standard - or even one single specification for speed. When the service providers tried to agree on the next thing after 3G, they basically didn't agree - so everyone went off and labelled any small improvement that they could think of as "4G" - and the gullible public just assumed it would be some massive technological leap over 3G. So in some places, 4G is no faster than 3G and in others it's dramatically faster. Basically the term carries no meaning other than "Something made after the 3G standard". SteveBaker (talk) 14:47, 13 September 2014 (UTC)

What technology is it that gives Tokyo or Seoul it's 100mbps 4g then? It can't be lte can it? Uk lte only seems to get about 10mpbs at most. — Preceding unsigned comment added by 90.192.105.196 (talk) 21:02, 13 September 2014 (UTC)

LTE-Advanced.[3] Nanonic (talk) 21:13, 13 September 2014 (UTC)

Why might some NSaids cause "Sudden Weight gain" for some Human individuals?

I've heard this in relation to Etodolac. Why is it? Ben. Ben-Natan (talk) 12:01, 13 September 2014 (UTC)

I could think of some possible mechanisms:

1) Water retention. If this was the method, I'd expect them to say so explicitly.

2) Increased appetite.

3) Decreased metabolic rate. This could either be decreased basal metabolic rate, or a decrease in activity level, say if the med causes drowsiness. StuRat (talk) 12:08, 13 September 2014 (UTC)

I would have thought that "sudden" weight gain would pretty much have to be water retention. You have to increase your calorie intake, or decrease your activity level really drastically to put on weight rapidly...but water retention can happen very quickly. Fortunately, if it's the latter, then the additional weight is relatively easy to lose again. Of course a lot depends on what they mean by "sudden". SteveBaker (talk) 14:42, 13 September 2014 (UTC)

Can dog sense electrocuted water?

A recent news is being discussed in several Indian newspapers— dog sacrifices life to save passengers ALT1). Undoubtedly, it is a surprising news. We know about Dog intelligence, but is Dog so intelligent that it can sense electrocuted water a) of course she did not jump there before, b) the passengers did not notice the wire? --Tito☸Dutta 16:47, 13 September 2014 (UTC)

Comprehension of impending death aside, electricity does have a distinct smell and buzz. Dogs smell and hear better than humans do. It might have bothered her. Though just from reading that, it seems she didn't so much make an altruistic decision to let actions speak louder than words, rather was shooed into it by the group of busy people. In near-death experiences, humans tend to look for deeper meaning as to why they lived, and confuse correlation with causation in their rush. InedibleHulk (talk) 17:08, 13 September 2014 (UTC)

• That is an excellent point. Thank you. --Tito☸Dutta 17:20, 13 September 2014 (UTC)

InedibleHunk is wrong. Electricity is the movement of electrons - it doesn't have a smell. What electricity does to the medium it flows through might create a smell. So when you pass electricity through the air, it can cause the formation of ozone which has a very distinctive smell which people associate with electricity because small sparks smell of ozone. However, unless the water is unbelievably pure (which it clearly wasn't here), it's a much better conductor of electricity than the air. So if there is electricity passing through water, it won't be passing through the air - so no ozone smell. The only effect electricity has on water is (possibly) to electrolize it into hydrogen and oxygen - or to boil it into steam. Oxygen is already present in the air we breath all day long, so it doesn't smell. Hydrogen is ordorless (at least to humans), so it seems unlikely that the dog would have smelled anything whatever, steam would have condensed back into water vapor before it ever reached the dog. So I doubt there were any distinctive smells for the dog to pick up on - I don't see how it could have known that there was an electrocution hazard here.

But even if it did smell something - how would it know that there is danger involved with electricity in water? It couldn't possibly have learned it from anything it had seen in the past - and for sure it wouldn't have some kind of evolved 'instinct' to see danger in this situation.

I just don't buy this story. Dog barks incessantly...no surprise there...dogs do that. Dog stupidly jumps into the water, not realizing the danger and dies...no surprise there either. By pure luck (for the humans), this happens before the people get into the water. I don't think the dog deserves any particular credit here. SteveBaker (talk) 21:58, 13 September 2014 (UTC)

I'd figured someone would point out my too-general use of the word "electricity". Thanks for clarifying. And yeah, you're right that water doesn't spark. Overlooked that, somehow. InedibleHulk (talk) 17:58, 14 September 2014 (UTC)

Incidentally, the correct term is "electrified" water, not "electrocuted". StuRat (talk) 22:12, 13 September 2014 (UTC)

The water is dead, ain't it? —Tamfang (talk) 03:56, 14 September 2014 (UTC)

I realize you're joking, but this is the science desk - no, the water is not dead; it's non-living. Matt Deres (talk) 14:15, 14 September 2014 (UTC)

Of course, even though the water itself is nonliving, it contains many living micro-organisms, or perhaps dead organisms, depending on the electrical charge. I would guess that such life forms are rather resilient against electrocution, however. StuRat (talk) 16:02, 14 September 2014 (UTC)

Not sure if puddle animals are more resilient, but there's allegedly a man who is. As luck would have it, he's also Indian. InedibleHulk (talk) 18:03, 14 September 2014 (UTC)

Species id

Species?

Can some one identify the species? Thanks in advance. Nikhil (talk) 16:56, 13 September 2014 (UTC)

From the leaves I'd say gardenia but I can't say the flower is typical.--TammyMoet (talk) 20:06, 13 September 2014 (UTC)

The are 140 species of Gardenia, not to mention varieties. I agree with TammyMoet. μηδείς (talk) 22:36, 13 September 2014 (UTC)

Please help me in balancing the following redox reaction

Please help me in balancing the following redox reaction:

Cu + HNO₃ --> Cu(NO₃)₂ + NO + NO₂ + H₂O

(By the way, this question has been asked in PMT 1994) What are the coefficients of Cu and HNO₃ respectively? Options:

A) 2, 3 B) 2, 6 C) 1, 3 D) 3, 8

I tried to balance this redox by half reaction method, but after solving it half, the nitrogen atoms remain (or become) unbalanced. So, I cannot solve this at all.

I thought that the coefficient of HNO₃ must divisible by 2, as it gives 2NO₃^-, NO and NO₂. So the answer must be (2,6) or (3,8), but after doing that I could do nothing but put options into the reaction, which yields that (2, 6) is the correct answer. I just want to solve this by proper (step-by-step) method.

Important note: When I tried to get balanced this equation with Wolfram-alpha (click here), it gave the answer as below.

5Cu + 16HNO₃ --> 5Cu(NO₃)₂ + 2NO + 4NO₂ + 8H₂O

Yours faithfully,

Ravishankar Joshi — Preceding unsigned comment added by Ravijoshi99 (talk • contribs) 18:30, 13 September 2014 (UTC)

After looking at this reaction for some time I balanced it the following way:

2Cu + 6HNO₃ --> 2Cu(NO₃)₂ + NO + NO₂ + 3H₂O

so, the correct answer is B. The step by step: every Cu requires two HNO3 to produce one Copper(II)_nitrate and also produces one H2. On the other hand NO+NO2 requires two HNO3, which also gives three O atoms, which require three H2 to produce three molecules of water. So, we need two Cu and total 6 HNO3. Ruslik_Zero 19:22, 13 September 2014 (UTC)

You can use the algebraic method:

a Cu + b HNO₃ --> c Cu(NO₃)₂ + d NO + e NO₂ + f H₂O

Cu: a=c (1)

H: b=2f (2)

N: b=2c+d+e (3)

O: 3b=6c+d+2e+f (4)

to simplify the last one you can replace b in (4) by (3): 6c+3d+3e=6c+d+2e+f or 2d+e=f

you have 6 unknowns, 4 equations, meaning there are an infinite number of solutions. Then the best way to start is probably looking for the smallest coefficients and assign them values. b=2f so b>f and f=2d+e so f>d and f>e. so d and e are smaller than the rest.

Give d and e the smallest value: d=1, e=1; then f=3, b=6, c=2 and a=2; all numbers are integers, so it fits: 2Cu + 6HNO₃ --> 2Cu(NO₃)₂ + NO + NO₂ + 3H₂O

if you try d=1 e=2 you get c=2.5, so double the values: d=2, e=4 f=8, b=16, c=5, a=5: 5Cu + 16HNO₃ --> 5Cu(NO₃)₂ + 2NO + 4NO₂ + 8H₂O

if you try d=1 e=3: f=5, b=10, c=3, a=3: 3Cu + 10HNO₃ --> 3Cu(NO₃)₂ + NO + 3NO₂ + 5H₂O

d=3 e=1: f=7, b=14, c=5, a=5: 5Cu + 14HNO₃ --> 5Cu(NO₃)₂ + 3NO + NO₂ + 7H₂O

and so on... Ssscienccce (talk) 22:38, 13 September 2014 (UTC)