Wikipedia:Reference desk/Archives/Science/2014 June 21

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June 21

Has anybody ever seen an overweight redhead?

question asked and sufficiently answered
The following discussion has been closed. Please do not modify it.
Yep, this is my question. --AboutFace 22 (talk) 01:48, 21 June 2014 (UTC) Here's one: [1]. Here's another: [2]. :-) StuRat (talk) 01:59, 21 June 2014 (UTC) I don't think we need anymore of this. We have enough of an answer.--Jayron32 02:04, 21 June 2014 (UTC)

See POMC. Wnt (talk) 00:27, 27 June 2014 (UTC)

Movie stunt

In Goldeneye, when James Bond rides a motorbike off a cliff, how does he catch up to the plane? I mean, he's in freefall, but so is the plane -- AND the plane's engine thrust is also adding to its acceleration. So according to the laws of physics, the plane would either hold its lead, or more likely even pull further ahead -- right? 24.5.122.13 (talk) 02:21, 21 June 2014 (UTC)

See fiction and come back if there is something there if you don't understand. --Jayron32 02:25, 21 June 2014 (UTC)

Don't bite the newbies. It's perfectly valid to ask if science portrayed in a movie is realistic or not. That's what we're here for. If you don't like such Q's, don't reply to them. StuRat (talk) 02:31, 21 June 2014 (UTC)

With respect StuRat this poster is not a newbie and the framing of his question indicates s/he understands the impossibility of the situation. Richard Avery (talk) 07:31, 21 June 2014 (UTC)

Yes, and a motorcycle and rider are less aerodynamic than a plane, so you would expect them to be slowed down even more, due to air resistance. StuRat (talk) 02:27, 21 June 2014 (UTC)

Bond films tend to rely heavily on suspension of disbelief; in other words, "just sit back and enjoy the show —and don't think about it too much".  —71.20.250.51 (talk) 04:42, 21 June 2014 (UTC)

Well, if we do want to analyze it, it's actually rather complicated. First, the motorbike is in free fall and would follow a parabolic trajectory if air resistance (friction) was not significant, but the force of friction will act diagonally in the opposite direction to its motion, i.e. horizontally backward at first, but also upward as it begins to fall.

But as to the plane, it's not in free fall: it has wings. Normally the lift would be in an upward direction to counter the plane's weight, but if I remember the scene correctly, the plane tilts nose-down as soon as it goes off the cliff. This means that the lift will also be exerted diagonally, upward and somewhat forward. Like the motorbike, the plane experiences air resistance (friction or drag in a diagonal direction opposite its movement, i.e. upward and backward, since it's diving nose-down; but the engine's force is in the opposite direction, forward and downward.

Frankly, I have no idea of whether this means it's possible that a motorcycle moving sufficiently fast when it goes off the cliff could follow a trajectory that brings it next to a plan that goes into a dive under power... but I do say that it's not obviously impossible. I also say that it might well require an extremely high speed that in practice the motorcycle might not be able to reach in the time and space available, or maybe at all. --70.49.171.225 (talk) 05:08, 21 June 2014 (UTC)

In that case, the trajectories will diverge -- the plane will continue in its power-on dive until it impacts terrain several miles away, whereas 007 will fall to his death near the base of the cliff.  :-( 24.5.122.13 (talk) 05:59, 21 June 2014 (UTC)

• Not necessarily. If when the respective vehicles leave the clifftop the motorcycle's speed is higher than the plane's, or if the plane's nose-down attitude sets up a higher rate of descent, then the motorcycle's path is initially higher and it can cross the plane's path. --70.49.171.225 (talk) 03:23, 22 June 2014 (UTC)

Generally true, but not in this case -- in the shot taken when 007 goes over the edge on the bike, he's seen to be moving at the same speed as the plane. 24.5.122.13 (talk) 04:06, 22 June 2014 (UTC)

If James Bond knows he can't die, then he can take any risk he wants, with the full expectation of somehow surviving it intact. I'm reminded of at least a couple of other movie scenes. In Speed, the bus somehow jumps the gap between two sections of roadway despite those sections being on the same level. And in Indiana Jones and the Temple of Doom, a mine transport vehicle jumps a long (albeit downhill) gap in the rails, and not only lands safely, but squarely back onto the track and keeps going. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:28, 21 June 2014 (UTC)

• In Speed, when the bus actually gets close to the gap you see that it hits some construction materials that were piled up near the edge. This would deflect it upwards as required for the jump. The scene is still impossible because until that last moment you had a clear view of the road all the way to the gap and there was no such pile of stuff on it. (And also because in practice a pile of material not intended as a ramp would not be strong and cohesive enough to effectively form one.) --70.49.171.225 (talk) 03:23, 22 June 2014 (UTC)

• That's known as pulling a fast one on the audience and hoping they don't notice. Like in The Blues Brothers, where Elwood puts the car into reverse, stomps on the accelerator, flipping the car end over end without any kind of twist in the air, yet somehow lands facing the opposite direction. FYI, the way they actually made that scene in Speed was to drive a bus on flat pavement with a ramp somewhere, which they hit at high speed and vaulted into the air before landing with a big thud. Then they interwove that footage with film of an empty highway. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:31, 22 June 2014 (UTC)

Well, in a sense it's true that James Bond can't die -- there have been at least five secret agents with the alias "James Bond 007", and when one is KIA'd, presumably he'd be replaced in short order ;-) 24.5.122.13 (talk) 19:08, 21 June 2014 (UTC)

This article lists some evidence against the James-Bond-is-a-code-name theory. (And in favor of the it's-just-a-show-I-should-really-just-relax theory.) -- BenRG (talk) 05:12, 22 June 2014 (UTC)

With regard to the Bondmobile, it might be that in Casino Royale, he won it back after it was stolen from the MI6 motorpool by the KGB in 1997... (This would also explain why he had to use a series of BMW cars as replacement vehicles in the meantime.) ;-) 24.5.122.13 (talk) 09:20, 22 June 2014 (UTC)

Speaking of Bond, and questionable stunts, one of the more infamous occurred in one of the later Connery Bonds, possibly Diamonds are Forever, in which he's speeding through an alley which dead-ends into a narrow walkway. He hits some object which tilts the car enough to drive through it and emerge at the other end unscatched. Trouble is, those bits were filmed at different times, with the car tilted opposite ways. Oops! ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:35, 22 June 2014 (UTC)

It's actually a case of quantum tunneling which allows 007 to make the jump onto the plane, the mine car land on the tracks, Han Solo survive Star Wars etc.

OK, bullshit. It's based on conditional probability — with or without quantum flavor. If one knows that something very improbable has happened, it is not uncommon that that implies something improbable before. The thing about quantum tunneling is that it's possible but extremely improbable for large bodies; the "real magic" is the conditional probability. The plot dictates that the hero survived, and that implies that something improbable happened.

If "(Insert hero here) cannot die" is one of the fundamental laws, then no matter how improbable a stunt is, they will make them — usually via one of the methods which are "the least improbable". If there is no such method, something really bizarre can happen: the hero could disappear on one side of the wall and reappear on the other side. It doesn't have to be a wall; it could be a bullet , a vehicle, etc. However, a much less improbable explanation why Han Solo lives through Star Wars is that the Stormtroopers are utter crap when it comes to aiming, and simply miss. (And the fact that he shot first in the opening Space Bar scene.) It might be a once-in-a-lifetime coincidence that all the Stormtroopers he faces personally are bad shots, but still much more probable than solid-body tunneling. - ¡Ouch! (^{hurt me} / _{more pain}) 07:36, 23 June 2014 (UTC)

Maybe the Galactic Empire made the tragic mistake of outsourcing their military as a cost-cutting measure. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:31, 23 June 2014 (UTC)

I'm not that big in to the expanded universe or anything besides the movies but aren't Stormtroopers mostly GM clones of Jango Fett? (Our article suggests some non clones were allowed in but it's not clear how many or when.) If so, it's hardly surprising they were so incompetent, he probably used the same science team that he used for both Death Stars and was distracted when fortelling the future like he was when he missed the teddy bears. (To be fair, it may not have been entirely his fault. I suspect anyone mildly competent on the science team was remotely strangled by Vader at some stage.) Nil Einne (talk) 13:43, 23 June 2014 (UTC)

If you absolutely must have a reason - then consider it like this: 100,000,000 people try to outwit all of the storm-troopers...200 British agents try to take down the bad guys. Only by incredible luck does one of them succeed. Who do you make the movie about? One of the 99,999,999 people whom the storm-troopers managed to take down before they could shut down the shield generators or whatever? One of the 199 British agents who die trying desperately not to get chopped in half by the bad guy's laser? No...you make the movie about the one guy who pulls it off.

That doesn't just happen in fictional worlds. Consider WWII movies...our hero jumps onto an abandoned tank and uses its .50-caliber machine gun to hold the enemy at bay, even though the vehicle is on fire and may explode at any moment. He defends his retreating unit, leaping off of the vehicle and running away at the last moment. Is this a likely thing to happen? Hell no! It's astronomically unlikely. However, To Hell and Back (film), (from which this example comes) - tells the true story of Audie Murphy - who really did do that (and a bunch of other crazy things).

Why did they make that movie - rather than a movie about any of the unknown number of guys who tried equally dangerous things and died in the attempt? By cherry-picking only the very least probable stories from the 100 million people involved in the war who DIDN'T do anything remarkable - you get an incredibly skewed view of the kinds of things that happened. In WWII, the USA alone expended 47 billion rounds of small arms ammunition and 11 million tons of artillery ammunition - when you include what the other allies went through, the total is probably twice that. Germany lost around 5 million people in combat and Japan about 2 million - so it takes several tons of artillery shells and about 10,000 bullets to kill a single man. This means that most people in combat didn't kill a soul and had thousands of bullets and truckloads of bombs simply missing them. This doesn't make for good entertainment - so the glory goes to the very, very few who were very, very lucky (or very, very unlucky - depending on how you look at it).

Translate that to fictional worlds and you can justify James Bond (or Han Solo) as simply being the one who made it by sheer luck whom the story gets to be made about.

Or it's just fiction - so sit back, enjoy the movie - and try not to worry about it!

SteveBaker (talk) 17:07, 25 June 2014 (UTC)

Which is more acidic? SO2 or SO3

There is acidity constant for SO₂ in its article. But I could not find or estimate the acidity of SO₃. Please help me. And I have another problem. Which has high bond strength? H₂ or HCl?--G.Kiruthikan (talk) 08:12, 21 June 2014 (UTC)

Bond strength is inversely proportional to bond length (a corollary of Coulomb's law) so just find which of the two has a shorter bond length, and that one has a stronger bond. Or you could just find the bond dissociation energy of each! which is the standard measure of bond length. --Jayron32 14:10, 21 June 2014 (UTC)

As for acidity, SO₃ is the anhydride of H₂SO₄, whereas SO₂ is that of H₂SO₃ -- guess which is the stronger acid? 24.5.122.13 (talk) 19:12, 21 June 2014 (UTC)

Not everybody knows that H₂SO₄, sulfuric acid, is stronger than H₂SO₃, sulfurous acid. That is, sulfuric acid is stronger than sulfurous acid in the short run. As a pollutant in air, sulfurous acid, formed from hydration of sulfur dioxide, will eventually oxidize to sulfuric acid. Robert McClenon (talk) 21:12, 21 June 2014 (UTC)

As a matter of fact, the reason why there's no acidity constant for sulfur trioxide is because its acidity is so mind-bogglingly high that it converts to acid completely in aqueous solution: SO₃ + H₂O → H₂SO₄ → H⁺ + HSO₄^- (note no equilibrium arrows -- the reaction goes completely to the right). 24.5.122.13 (talk) 21:38, 21 June 2014 (UTC)

H₂SO₄ does have a pKa (–3 in water), meaning that second reaction is either just a very strongly directed equilibrium or the actual acid-forming reaction is more complicated than that equation suggests. Well, "and" not or most likely. DMacks (talk) 03:56, 22 June 2014 (UTC)

And the first reaction also has an equilibrium constant, but again a very forward-shifted one (doi:10.1021/ja00536a008). DMacks (talk) 04:00, 22 June 2014 (UTC)

Hang on. All these answers appear to assume aqueous solutions, in which case we are not dealing with SO₂ and SO₃. The acidity/basicity of a compound is a measure of its propensity to donate/capture a proton. Since these two compounds have no protons to donate, these compunds can surely not be acidic? Perhaps the OP can clarify the intended question in this light. —Quondum 05:35, 22 June 2014 (UTC)

SO₂ and SO₃ are Lewis acids: they accept a pair of electron from H₂O. Ruslik_Zero 07:07, 22 June 2014 (UTC)

They are also Arrhenius acids: meaning that dissolving them in water produces excess hydronium ion; they do this as hydroxide acceptors. One way to represent the reaction of SO₂ with water is SO₂ + H₂O -> HSO₃^- + H⁺; the Arrhenius definition of an acid is any substance that, when dissolved in water, produces H⁺ ions. What they are not is Bronsted-Lowry acids; however that's why we have three common acid base theories (Arrhenius, B-L, and Lewis). Each of the three theories compliments the others, and none by itself completely captures all acid-base behavior. You can get to the B-L behavior in 2 steps, however, by considering the reaction of of SO₂ with water a separate reaction producing H₂SO₃, and then considering the B-L reaction the second step. It's all a matter of perspective. --Jayron32 20:18, 22 June 2014 (UTC)

Even that seems to depend on the precise definition. According to the original definition given in Acid–base reaction, they are not acids, since they do not dissociate in water; they merely induce a dissociation of H₂O and bind with the hydroxyl ion. In all, it is clearly complicated, and more context is needed to frame the question sensibly. —Quondum 23:55, 22 June 2014 (UTC)

The simplest Arrhenius definition is based on pH... if substance + water = pH lower than 7 (at 25 deg C), then it is an acid; conversely if said pH is greater than 7 it is a base. Any first year college chemistry student should be able to calculate Ka based on pH and the dissolved amount of SO₂; the rest of the difference in "definition" is trivial. --Jayron32 03:02, 23 June 2014 (UTC)

You seem to be missing the point: the OP mentions SO₂ and SO₃; no mention of a solvent, nor of H₂SO₃ and H₂SO₄. Arrhenius's original definition, according to the article, refers to dissociation, and thus the substances only fit the definition upon having reacted with H₂O to produce the the latter compounds, whereupon they may dissociate when dissolved in accordance with the definition. If arbitrary intermediate reactions are permitted prior to the dissociation referred to in the definition, anything is possible. Example: 2Na + H₂O → 2NaOH + H₂. Does this make the metal into a base via this definition? The Arrhenius definition simply does not apply to the question as posed. —Quondum 03:33, 23 June 2014 (UTC)

Acid_dissociation_constant#Definitions discusses the calculation of Ka for substances that do not directly act as proton donors, and thus do not strictly "dissociate". See the last two examples for boric acid and complex metal ion hydrolysis. The boric acid example is a direct analogue for discussing SO₂ in this context. --Jayron32 03:39, 23 June 2014 (UTC)

Those are discussed under the Brønsted–Lowry generalization, not the Arrhenius definition. —Quondum 05:14, 23 June 2014 (UTC)

Well, the words Bronsted-Lowry appear literally in the text before those words, but they do not fit the Bronsted-Lowry model. There's no proton donation going on. They also, as you have already noted, do not fit the Arrhenius model all that well either. And yet, we can still calculate a Ka just fine. That's what's funny about actual reality compared to you trying to pigeonhole it all into the models you want to fit it in. Chemists the world over are just fine with working out the Ka of SO₂, and oddly enough, did it without having to consult you to find out they were doing it wrong. --Jayron32 05:58, 23 June 2014 (UTC)

My bad for using the article as reference. Acid–base_reaction#Solvent_system_definition seems to be the appropriate model here. We both understand the general chemistry, it's the communication that's the problem. Let's drop it. —Quondum 14:05, 23 June 2014 (UTC)

Other Mammals which reach Sexual Maturity after age 10?

Other than Human Beings which other mammals on average take more than 10 years to reach Sexual Maturity? (Yes, I know there are valid cases of sexual maturity in Humans occurring prior to age 10, but on average, I'm pretty sure it is after)Naraht (talk) 10:35, 21 June 2014 (UTC)

Gorilla, for one. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:20, 21 June 2014 (UTC)

It is often highly correlated in mammals to size so look to whales, elephants and so on. A Google search of <"do not reach sexual maturity until * years" mammals> indicates (after only looking at the first few result pages): Orcas at around 15; Dugongs at around 10; female elephants at around 10; male short-finned pilot whales at 12 or later.--Fuhghettaboutit (talk) 15:39, 21 June 2014 (UTC)

As Fuhgettaboutit says, sexual maturity, as well as longevity, are often correlated to size. Human late sexual maturity and longevity are a special case, having to do not with size (humans being smaller than gorillas but longer-lived) but with language and learning. Having elders as a community memory is extremely useful for humans, especially pre-literate humans (but also literate humans). Also, human females are the only apes that have menopause, which is probably (but I haven't looked for a source) related to longevity, so that older women don't die in childbirth. Robert McClenon (talk) 17:27, 21 June 2014 (UTC)

The more I research this, the more it comes back to r/K selection theory. Animals with high K-selection strategy seem to both live longer and mature later in that lifetime. So age of ssexual maturity seems like a single facet of this... Thanx!Naraht (talk) 17:54, 22 June 2014 (UTC)

@Naraht: See also parental investment, which is usually closely linked to age to maturity. Humans and some other slow-to-mature species also have some neotenous traits. SemanticMantis (talk) 18:02, 22 June 2014 (UTC)

• Shouldn't this be "who reach"? μηδείς (talk) 02:00, 23 June 2014 (UTC)

No. The relative pronoun "who" is reserved for human antecedants. I bow to the expert opinion of Fowler "If writers would agree to regard that as the defining [restrictive] relative pronoun, and which as the non-defining, there would be much gain both in lucidity and in ease." and I would reword the title as [Are there] other mammals that reach sexual maturity after age 10?. 84.209.89.214 (talk) 13:09, 23 June 2014 (UTC)

If you're going to speak Butter Ullshit you should at least dent improperly. So, the sentence, "The program, whose creators did not foresee its versatility, achieved consciousness unexpectedly" is not only improbable, it's ingrammatical in your alternate universe??

That's not a good test case. Whose is the possessive, not only of who, but also of that or which. So for example, it's perfectly correct to refer to "all minerals whose hardness exceeds 6 on the Mohs scale". On the other hand, "*all minerals who are harder than feldspar" richly deserves its asterisk. --Trovatore (talk) 00:33, 25 June 2014 (UTC)

The sentence within quotes in the unsigned post above Trovatore's post lacks only a Full stop at the end to be grammatically correct. Please sign your posts. 84.209.89.214 (talk) 00:12, 25 June 2014 (UTC)

Why do people wrap food in the oven with aluminum foil?

Aluminum foil is highly reflective, so wouldn't wrapping food in aluminum foil make it take longer to heat up? If so, why do people wrap their food in aluminum foil before putting it in the oven? 65.92.5.124 (talk) 23:35, 21 June 2014 (UTC)

It's also highly conductive, so it doesn't make much of a difference in heating time. 24.5.122.13 (talk) 23:48, 21 June 2014 (UTC)

Yes. Remember that heat can be transferred in various ways. Food in an oven is heated by radiation from the gas flame or electric heating element, and a reflector will block this. But the flame or element heats the air near it by conduction, which heats the air in other parts of the oven by convection and/or conduction. This hot air in turn heats the food by conduction. --70.49.171.225 (talk) 03:31, 22 June 2014 (UTC)

You do it if you want to keep the moisture in. Dmcq (talk) 23:50, 21 June 2014 (UTC)

Is suppose you put the shiny side pointing in as well so the reflectivity is minimised? — Preceding unsigned comment added by Seans Potato Business (talk • contribs) 02:02, 22 June 2014‎ (UTC)

Discussed at Aluminium foil#Properties DMacks (talk) 03:47, 22 June 2014 (UTC)

It also helps retain moisture within the food, and minimizes subsequent cleaning of the pans, trays, and oven.--Shantavira|^{feed me} 11:01, 22 June 2014 (UTC)

Note also that reducing the radiative heat transfer is not necessarily an unwanted thing. It may very mildly increase the time it takes to heat up a large object but as stated above probably not by much. Conversely it can be an advantage when baking a pie or cheese cake or cake of some sort in the oven to reduce excessive browning or burning of the top. Usually this will involve covering just the top rather than wrapping and also generally only half way in (clarification: to the cooking time) if necessary. Nil Einne (talk) 14:10, 22 June 2014 (UTC)

• There are two main reasons. First, as stated above, to keep moisture in. Second, there are many situations where slowing heat transfer is actually a good thing. If you are cooking something large and thick, it can easily burn on the outside before it even begins to heat up at the center. Aluminum foil greatly equalizes the distribution of heat inside. Looie496 (talk) 15:34, 22 June 2014 (UTC)

Thanks for all the answers. 65.92.5.124 (talk) 20:38, 22 June 2014 (UTC)

• If you've ever had a baked potato at an actual restaurant it is a brown idaho that's been scrubbed, blinded, and washed, stabbed at least twice, fatally, with a carving fork, been embalmed in vegetable oil, then wrapped in tinfoil and cooked at 450F for at least an hour. The longer the better. This is the Harkkonen recipe. It retains the water and the supplety of the skin while achieving maximal softness of the flesh. I believe there are a series of paintings done by H. R. Giger but they are the private property of Denny's, not for public distribution.