Wikipedia:Reference desk/Archives/Science/2010 December 10

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December 10

Dear New Yorkers, why haven't I seen buildings built ABOVE your streets?

Manhattanhenge. ~AH1^(TCU) 03:25, 11 December 2010 (UTC)

The City of New York is in an EPIC land crunch, yet there is so much valuable real estate floating above your wide avenues. Apparently, there are just a few structures built above streets, but why aren't there more? Since parking is extra tough in your beloved city, why shouldn't parking garages be built above your streets?

Then there are the waterways. Hudson and East River could have buildings built on supports (that would have to be like the ones seen on arch bridges in order to provide clearance for boat traffic.)

So despite the land crunch, why doesn't New York see more of these?: http://forum.skyscraperpage.com/showthread.php?t=151423 --129.130.99.68 (talk) 21:29, 9 December 2010 (UTC)

New York isn't really in an epic land crunch. The population density of the outer boroughs is much lower than Manhattan; there are large areas of Queens and Staten Island that are essentially suburban in character. Also, there's not really a huge demand for new office towers in Manhattan itself. Some, but not so much as you imply, that demand is somehow drastically ahead of the ability to keep up with it. --Jayron32 21:36, 9 December 2010 (UTC)

ec. I can not speak for the city of New York, but there would be some engineering challenges if you want to build buildings that cover the city streets. First, you need to be able to support the building with a large tunnel going through its base. Not impossible, but it does create greater construction expenses. Second, if you are going to close off the sky above the streets, you are going to have to install adequate ventilation systems to prevent a buildup of vehicle fumes, specifically nasty things like carbon monoxide. Third, the streets are owned by the city of New York, which will add a lot of red tape to anyone wanting to build there. I am sure there are other complications, but I think that the conclusion is that we do not have much in the way of over-street buildings because the point where the engineering and bureaucratic challenges being less then the costs of simply building elsewhere has not been passed. Googlemeister (talk) 21:39, 9 December 2010 (UTC)

The simple answer is that the 1916 Zoning Resolution ensures that even the bum in the gutter can look up and see the stars above – and be so reminded, that this is the land of opportunity where a man can achieve anything he wants to.--Aspro (talk) 23:49, 9 December 2010 (UTC)

I love this answer! However, in 1916 they were unable to project planetarum displays to the underside of tunnels and therefore the resolution must be updated. Also, air quality control. Ginger Conspiracy (talk) 05:40, 11 December 2010 (UTC)

There's also the psychological aspect. Some of us enjoy the idea of having at least some feeble connection with nature, rather than being entirely surrounded by man-made structures the entire day. An outdoor walk between the office and the train station on a nice day can provide a little of that. If the sun's shining, you can help stave off seasonal affective disorder, and even synthesize some vitamin D while you're at it. Red Act (talk) 00:03, 10 December 2010 (UTC)

You'll find a few of them in Boston. For example, the Floating Hospital for Children. Paul (Stansifer) 04:32, 10 December 2010 (UTC)

Besides, it's already been done. The MetLife Building, the Helmsley Building and other buildings on the Park Avenue axis are built above the extensive rail yards north of Grand Central Terminal. Madison Square Garden's built over the late lamented Pennsylvania Station (New York City).Acroterion _(talk) 04:38, 10 December 2010 (UTC)

Also, the very page you linked to, original poster, contains a number of examples from New York City. As for the East River and Hudson River, a significant portion of the Manhattan shoreline is landfill. Instead of building into the water "on supports", they simply filled the water in, especially in the downtown area. Further, both waterways are very deep and impractical to build over completely without resorting to suspension bridges and the like. Also, as others have said, there's is not currently a land crunch. Pfly (talk) 04:47, 10 December 2010 (UTC)

Syd Mead had a good idea related to this in his plan for replacing the World Trade Center. Comet Tuttle (talk) 18:12, 10 December 2010 (UTC)

Physics trouble

I'm having trouble solving a physics problem:

A 2kg weight is hanging in a rope inside a car accelerating at 4 m/s^2, what is the angle on the rope?

Just a pointer to what formula I should use is most appreciated since I'm at a total loss at the moment. 95.80.22.142 (talk) 10:45, 10 December 2010 (UTC)

F = ma ;) Intuition should tell you that the rope will be at an angle from the vertical, hanging backwards. Now solve for the force of the rope on the weight – because it is at an angle, there will be two components which sum to the gravitation force on the weight. The horizontal componant has to be 2 kg × 4 m/s² = 8 N to accelerate the weight at the same rate as the rest of the car, so calculate the angle for which the horizontal component is 8 N. Physchim62 (talk) 11:13, 10 December 2010 (UTC)

You don't need a formula, you just need to understand what you're doing. This is, I guess, why you don't have a specific formula in your notes. Start by drawing a diagram and marking on all your forces. Okay, you need an equation that links force and mass, but I'm pretty sure you know one ;) Then let us know if you need more pointers, when you've done that. Don't just use something someone gives you, because then you'll be lost on the next question! 86.161.208.185 (talk) 11:16, 10 December 2010 (UTC)

When you are satisfied you have worked out the correct method, and have the correct answer, it will be very revealing to contemplate what the angle on the rope will be if the object at the end of the rope is not 2kg, but 3kg. Dolphin (t) 11:42, 10 December 2010 (UTC)

... and also the angle when the acceleration of the car is equal to the acceleration due to gravity ! :-) - WikiCheng | Talk 12:43, 10 December 2010 (UTC)

Another fun experiment is to see just how close to horizontal you can possibly get the rope by accelerating it faster in the horizontal direction. In cartoon physics, you often see a 90-degree angle when a road-runner or something starts accelerating really fast, dragging a rope behind them or whatnot. In practice, this is not possible - there will always be some vertical displacement (unless another, different force exists to counteract the effect of gravity). Nimur (talk) 18:33, 10 December 2010 (UTC)

How can this not be {{homework}}? Ginger Conspiracy (talk) 05:42, 11 December 2010 (UTC)

Of course it's homework. Have you read our guidelines on homework? This section mostly conforms nicely. Not much to moan about here. 86.161.208.185 (talk) 11:59, 11 December 2010 (UTC)

You're right. I'm not complaining about it. I try to help with homework, too. I just wish everyone, whether asking or answering, was better about saying which questions are homework. Ginger Conspiracy (talk) 00:07, 12 December 2010 (UTC)

Why would they need to? We only bother if it's skirting our guidelines, which this in no way does. 86.161.208.185 (talk) 01:45, 12 December 2010 (UTC)

Turbocharging in motorcycles..

I want to know as we use turbochargers in diesel engines... can we do the same in powerful bikes to improve it's performance..? —Preceding unsigned comment added by 220.225.96.217 (talk) 13:25, 10 December 2010 (UTC)

Typing "Turbo motorcycle engine" into Google confirms that motorcycle engines can be (and are) turbocharged. --Jayron32 13:33, 10 December 2010 (UTC)

ofcourse... but are they useful.. and why do we not turbocharge every motorbike..? —Preceding unsigned comment added by 220.225.96.217 (talk) 13:41, 10 December 2010 (UTC)

Turbocharging is rarer on motorcycles for a number of reasons. Motorcycles are much lighter than cars and can get away with a less powerful engine with less low end torque. Too much power and the bike becomes very difficult to ride. Sports bikes rarely have much more than 200 hp for even the most powerful superbike (With the exception of weird specials like the Dodge Tomahawk. This can be achieved with high revving normally aspirated engines. Since creating a surplus of power on a bike is easier than in a car, the disadvantages of turbocharging quickly become an issue. Turbos take up space, which is at a premium on sports bikes. They create uneven power delivery which makes the bike hard to ride. They also get very hot which can be an issue when the turbo is just inches from your body. The only place where turbo bikes are common AFAIK is on the dragstrip. --Leivick (talk) 15:42, 10 December 2010 (UTC)

Turbocharging a bike can easily result in over 300bhp, on a motorbike that is insane. For an example of a turbocharged bike, watch this. http://www.youtube.com/watch?v=r3IxSjuMUCE 81.145.247.90 (talk) 16:52, 10 December 2010 (UTC)

Two other comments to add to the points above:

1) Both turbochargers and superchargers are also used to get the same power out of a smaller engine, and you might wonder why this approach isn't also used on motorcycles. In the case of cars, a standard aspiration V8 might be replaced with a turbo 4 cylinder. However, there are limits to how small, and how few cylinders, you can put in an engine, without creating problems. While a single cylinder engine does exist, it's not ideal.

2) Turbo lag is perhaps more of limitation on a motorcycle, where low-end acceleration is more desired. Superchargers lack this problem, but have their own issues. StuRat (talk) 16:51, 10 December 2010 (UTC)

Wankel Bikes?

I can see why no turbos, but why aren't all bikes wankels? i know some bikes have been wankels, but why haven't they displaced the piston engine? smooth, compact... i doubt gas mileage is a factor. for that matter, who decided that the V-twin was the archetypical bike engine? (i know, mr. harley and mr. davidson, but....) with it's mandatory short stroke and resulting bad performance at low rpm? Gzuckier (talk) 21:17, 14 December 2010 (UTC)

Transporting Gases....

I have seen, while transportig gases instead of using a single tank sometimes many cylinders interconnected are used.. why do they do so...? I saw it on mini truck it was assembly of near about 40 cylinders and all of them were connected with metal pipes.. are there some special kind of gases which need this type of transporting..? —Preceding unsigned comment added by 220.225.96.217 (talk) 13:31, 10 December 2010 (UTC)

A standard high pressure gas cyclinder is 50 litres in capacity and is pressurized to 200 bar when full, giving approximately 10,000 litres of gas. If you want more gas than that (but not hugh industrial quantities) you use more cylinders, because it's cheaper than constructing a larger pressure tank and then having it certified for safety. Physchim62 (talk) 14:07, 10 December 2010 (UTC)

Something like that [1] ?--Stone (talk) 15:00, 10 December 2010 (UTC)

Multi-element gas containers (MEGC) are missing from the articles on gas_cylinders and storage tanks and the effect that these tanks have on standardizing the licensing for storage and transportation of hazardous gases. It really could do with being added. The image of the MEGC battery truck shows a hazchem number for hydrogen. --Aspro (talk) 16:00, 10 December 2010 (UTC)

MEGC are constructed in a way that you can unload the whole package, while a battery vehicle like in the image above has a fixed connection and the gas containers stay on the truck al the time. [2] .--Stone (talk) 19:43, 10 December 2010 (UTC)

If the individual tanks can be disconnected and used individually, then this provides an additional flexibility. Yes, smaller tanks could be filled from a larger tank, but this takes time and labor, will lower the pressure, incur a risk of leaks, etc. Compare this with gallons of milk you buy at the store. The store could get a 10,000 gallon tank and fill the one gallon containers individually, but that method isn't as practical. StuRat (talk) 16:31, 10 December 2010 (UTC)

Volume, volume, volume. Ginger Conspiracy (talk) 05:43, 11 December 2010 (UTC)

what percent of people are using 3G technology.....in world..

i wanto to know this because i am going to purchase a mobile with 3G technology and i live in india.. i am curious that buying it would be worthful in next 2 years or not... —Preceding unsigned comment added by 220.225.96.217 (talk) 13:39, 10 December 2010 (UTC)

Not sure, but they're been selling "4G" in the U.S. for a while now. If you go with a prepaid phone (the type where you buy cards to extend them) instead of a contract, then you can more easily abandon your current phone/plan should better or cheaper ones become available.

One general comment on mobile phones, though, you need to look over the coverage map very carefully to see if the areas where you live, work, etc., are covered, especially if you are far from a major city. If you aren't covered by any of the major carriers, you might consider a satellite phone instead of cellular, although they do tend to be more expensive. StuRat (talk) 16:24, 10 December 2010 (UTC)

I don't think that the number of users has much bearing on whether 3G is worth it. Perhaps a larger number of users will lead to more coverage, but that's a loose connection. Paul (Stansifer) 00:50, 11 December 2010 (UTC)

It also depends on what you count as "worthful". What do you think the advantage will be to you of using 3G? Here in the UK there's wide 3G coverage (this gives links to maps but they don't appear to work) but 2G usage is very wide indeed. Tonywalton ^Talk 01:04, 11 December 2010 (UTC)

Hawking Radiation and negative mass

So a negative mass (or energy?) particle causes a blackhole to lose mass correct? But I was under the impression that negative mass should be repelled against gravity. Shouldn't the negative mass particle be deflected away from the black hole... Unless it's able to quantum tunnel through it... My second question is, why don't these negative mass particles destroy us or our planet? Shouldn't they be appearing all around us? Wouldn't they slowly eat away at our mass too? Or maybe even quickly... I believe a 228ton blackhole only lasts around 1 second. ScienceApe (talk) 16:42, 10 December 2010 (UTC)

There is no negative mass. What happens in Hawking radiation is that an antiparticle (which still has a positive mass!) falls into a black-hole and anihilates some small part of the black hole, while the "virtual pair" of the antiparticle escapes, resulting in a net loss of mass by the black hole. The mass lost is equal to the mass of the escaping particle, and the energy from the anihilation results in the black hole getting warmer. --Jayron32 17:00, 10 December 2010 (UTC)

I don't believe that is correct. An antiparticle annihilating inside a black hole would still add energy to it, not subtract it. The "virtual" particle is the one that falls in the black hole, while the real one escapes. This virtual particle is not a real particle, it's more of a mathematical concept. The thing with virtual particles is that they can't exist in the first place, unless the math works out. Which is why it falls in - that's the only way it can exist. And that's why even if they appear around us (which they sort of do), they can't do anything, because that would violate various laws of physics. And yes, I know this is a very fuzzy answer. Presumably the math works out, but since we have never observed it we don't really know what happens. Ariel. (talk) 18:29, 10 December 2010 (UTC)

I think you're taking the virtual-particle picture of black hole evaporation too literally. I've never entirely understood Hawking radiation, but John Baez, who is pretty knowledgeable about these things, mentions here that it was not originally derived based on virtual particles, and questions whether there even exists a correct derivation of it based on virtual particles. Virtual particles are just a funny way of doing calculations in quantum field theory, and they don't always give correct answers even in the absence of gravity. -- BenRG (talk) 18:45, 10 December 2010 (UTC)

Maybe I should have posted this video first. http://www.youtube.com/watch?v=S6srN4idq1E This is where I got the whole negative mass thing from. So it's wrong? ScienceApe (talk) 23:31, 10 December 2010 (UTC)

I only watched the first 60 seconds, but I disagreed strongly with almost every sentence uttered by the narrator in that time. The last thing he said before I gave up was that Hawking's goal was to reconcile the quantum prediction that the vacuum is full of particles with the GR prediction that "nothing exists at the edge of a black hole". This is utter nonsense. It's so random that I don't even think it's a misinterpretation of something from a reliable source. More likely it was invented out of nowhere by a scriptwriter in an attempt to make a coherent narrative out of something that he/she didn't understand at all. This particular scriptwriter doesn't even seem to understand the difference between atoms and subatomic particles. Awful, just awful. The overhead photography was kind of neat, though. -- BenRG (talk) 01:12, 11 December 2010 (UTC)

Hawking radiation occurs when particle decay/creation splits across an event horizon, or through a naked singularity. Can neutron stars evaporate this way too when at least one of the particles is a lepton? Ginger Conspiracy (talk) 05:46, 11 December 2010 (UTC)

Hawking radiation has nothing to do with singularities, naked or clothed. I think that there is no Hawking radiation without an event horizon, i.e. ordinary gravitating bodies don't Hawking-radiate at all, but I'm not at all sure about that. Of course, ordinary gravitating bodies emit blackbody radiation in the ordinary way. If you're wondering whether a virtual electron-positron pair can appear in the vacuum with the positron annihilating with a nearby object and the electron escaping to infinity, with a corresponding loss of mass from the object, the answer is yes, but this is just an ordinary electron-emission event described in a complicated way. -- BenRG (talk) 06:43, 11 December 2010 (UTC)

A naked singularity is its event horizon. Ginger Conspiracy (talk) 18:57, 11 December 2010 (UTC)

No. There's no physics of singularities, naked or clothed. They don't have event horizons or anything. They're bugs in the theory. -- BenRG (talk) 22:02, 11 December 2010 (UTC)

Agreed and stricken. Ginger Conspiracy (talk) 23:58, 11 December 2010 (UTC)

La Nina

When does it end?Accdude92 (talk) 20:16, 10 December 2010 (UTC)

The La Niña‎ article lists this reference for the end of the current one. The article only says Early 2011, though.Vchimpanzee · talk · contributions · 21:05, 10 December 2010 (UTC)

This slide presentation, updated weekly, tells you everything you could possibly want to know about the current and predicted future state of La Niña. Looie496 (talk) 21:40, 10 December 2010 (UTC)

A quarter of ENSO forecast models predict El Niño by summer 2011, and the average prediction calls for an end to La Niña by spring 2011[3]. ~AH1^(TCU) 03:17, 11 December 2010 (UTC)

I am not convinced that there are any weather patterns at this level of atmospheric CO₂ which people are able to predict. We need vastly negative atmospheric carbon concentration growth -- perhaps using http://windfuels.com -- before we will be able to predict the relative stability of tropical storm and flood magnitude conditions again. Ginger Conspiracy (talk) 05:49, 11 December 2010 (UTC)

airplanes that run on car fuel

Do we have some kind of list of airplanes that will fly just as well on the gas you put into your car as the av gas that is 2x as expensive? Googlemeister (talk) 20:22, 10 December 2010 (UTC)

It depends on what sort of engine is running the airplane. There's nothing inherantly wrong with running a prop plane on gasoline. The gas you put in planes may be twice as expensive merely because you are buying it in an airport. Location has a lot to do with price. --Jayron32 20:26, 10 December 2010 (UTC)

That is a bit of an over simplification. We have an article on Avgas which give a bit more info.--Aspro (talk) 20:34, 10 December 2010 (UTC)

I assume the OP is referring to piston driven planes not jets (as they will run on just about any flammable liquid). It is not safe or legal to fuel a piston plane designed for specialized avgas on automotive pump gas. Avgas is special high octane fuel and putting lower octane fuel in an engine designed for it can cause detonation (a bumber in a car, but a potential disaster in a plane). There are however conversion kits available to convert avgas engines to run on automotive pump fuel (probably at the expense of some performance). As for the question about a list, I don't think it exists. --Leivick (talk) 20:37, 10 December 2010 (UTC)

Here is a list of the popular planes that can run on mogas. Red Act (talk) 20:42, 10 December 2010 (UTC)

Excellent Red Act. Does anyone know if the RV-9 is cleared to run on car fuel? Googlemeister (talk) 21:08, 10 December 2010 (UTC)

Gasoline can be refined into kerosene with the excess hydrocarbons being used to run the still, with energy and/or fuel left over. Ginger Conspiracy (talk) 05:51, 11 December 2010 (UTC)

It is incorrect to talk about certain airplanes being suited to automotive gasoline and certain other airplanes not being suited. It is the ENGINE that is either suited or not suited to automotive gasoline. Instead of Googlemeister asking whether the RV-9 is cleared to run on car fuel he should be telling us what engine is installed in the airplane, and asking if that engine is suited to car fuel. The RV series are amateur-built airplanes and so they don't all have exactly the same engine. Different amateur builders choose to install different engines in the same airplane type. Dolphin (t) 12:18, 11 December 2010 (UTC)

back in my Chevrolet Corvair days, a lot of their engines ended up in airplanes; they were obviously pump gas. Gzuckier (talk) 21:21, 14 December 2010 (UTC)

What should I do with this jelly?

It's in a Mason jar with a Ball lid. In the eleven years I've lived alone, no one has given me one of these, so it must have been given to my father before that.Vchimpanzee · talk · contributions · 21:00, 10 December 2010 (UTC)

Unlike a tin-can, it will not have absorbed any iron or tin etc. Cannot think of anything else to be concerned about. A really good port is often much older. You could auction it on eBay. --Aspro (talk) 21:25, 10 December 2010 (UTC)

To clarify, Aspro points out that it will likely be as edible now as it was 10 years ago, and I agree. However, if it was canned improperly, there may still be a risk of botulism. SemanticMantis (talk) 21:30, 10 December 2010 (UTC)

(edit conflict) Homebrewed preserves are also more likely to have been incorrectly prepared. Your idea is good, but it should be noted that Grandma's kitchen is unlikely to have the quality control measures in place to make certain that this particular jar of preserves was prepared in a way to survive till today uncontaminated. --Jayron32 21:33, 10 December 2010 (UTC)

I can't believe that a Mason jar lid could maintain a good seal for 11 years. If the lid is still sucked on after that time (indicating a good seal), I suppose it would be edible, but I am skeptical that that would happen -- the rubber is too porous -- and if the seal is not intact, you obviously should not eat it. Looie496 (talk) 21:35, 10 December 2010 (UTC)

Thanks. I didn't expect to able to use it. I wonder if I can even open it.Vchimpanzee · talk · contributions · 21:51, 10 December 2010 (UTC)

What has the rubbers sealing capacity got to do with it? In the days before tine-cans and things, our grannies used pig bladder etc. Also: Google “egyptian tombs edible honey”. Botulism spores are a theoretical danger but a healthy immune system will cope with these (otherwise this common spore would have resulted in all of our deaths by now). --Aspro (talk) 22:31, 10 December 2010 (UTC)

Botulism poisoning is the result of the secreted botulinum toxin, which can be generated in an improperly-sealed can. A healthy immune system successfully eradicating the surviving bacteria (if any) does nothing about the already-accumulated toxin. TenOfAllTrades(talk) 22:56, 10 December 2010 (UTC)

So that's OK then, as botulism pores are only preserved in high sugar environments, rather than acting as healthy growing environments for the little wiggly things themselves. Hence, the habit developed, for using sugars for preservation! I almost feel like bidding for this blast-from-the-past myself.--Aspro (talk) 23:09, 10 December 2010 (UTC)

Responding to Aspro's previous question, to understand what the rubber has to do with it, you have to understand how home canning works. When you can something, you heat it to nearly boiling, then put the lid on it, and as the contents cool, the air inside contracts, creating a negative air pressure that holds the lid down tightly enough to create a seal. If the rubber leaks, you eventually lose the negative air pressure inside, and end up with a lid that is just sitting loosely on the jar. Once that happens, many bad things can follow. Looie496 (talk) 00:56, 11 December 2010 (UTC)

The Egyptian honey is a red herring. Honey has antibacterial properties. Jam does not. APL (talk) 05:00, 11 December 2010 (UTC)

Concentrated sugar is itself antibacterial, if I recall correctly. The explanation I've heard is that it dehydrates cells via osmosis. I would have thought that the main antibacterial effect of honey was simply its concentration of sugar; is that not so? --Trovatore (talk) 22:07, 11 December 2010 (UTC)

Virginia Cooperative Extension says "although most jams and jellies can be stored safely for at least a year, they lose their flavor and color during storage" and "Home canned foods can be stored safely for up to 1 year. Do not eat foods stored longer than 1 year."[4] The University of Maine Cooperative Extension says "Jellies, jams, and spreads are best if eaten within a year. They are safe as long as the lids remain vacuum-sealed."[5] Red Act (talk) 06:25, 11 December 2010 (UTC)

Try a few milligrams first, and if you don't die in a week... BZZT! PSSHT! I'm sorry, you may not ask the Reference Desk for medical advice. Please share your jelly with a licensed physician or veterinarian. Ginger Conspiracy (talk) 05:55, 11 December 2010 (UTC)

I had several times jam which was ten to 15 years old. The taste was bad of one so I threw it away. If you are healthy an it is not meat with botulism there are only a very few things which would be capable to harm you if you try a small portion.

You may not die or even get any symptoms of illness, it doesn't mean you aren't harmed. There are plenty of toxins, particularly mycotoxins which are carcinogenic or have other cumulative/chronic exposure effects which you probably don't want and there's often no real guarantee you will taste them. Jam probably isn't so bad but I would be worried about peanut butter for example. (So yes this is somewhat OT but I strongly dislike the common but misleading claim 'if it taste's okay and you don't get sick in a few days it isn't harmful') Nil Einne (talk) 10:36, 11 December 2010 (UTC)

I agree, I understand some mycotoxins cause pernament irreversable damage to your liver or kidneys. 92.28.245.105 (talk) 00:57, 14 December 2010 (UTC)

um, just throw it out, why take ANY risk?

I've had a lot of success since I've adopted a variation of Murphy's law, the original of which reads: "If it can go wrong, it will." I just assume it will go wrong regardless of whether it can. So, quit worrying if it can do you harm, assume it will, and throw that shit out. 82.234.207.120 (talk) 12:11, 12 December 2010 (UTC)

I agree. You can buy a pint of jam for like $5. Googlemeister (talk) 15:15, 13 December 2010 (UTC)

Expensive. I've just bought a pound (454g) of strawberry jam for 38p, which is about 60 cents. 92.28.245.105 (talk) 00:54, 14 December 2010 (UTC)

Plateosaurus and bipedal walking

So, we all know by now that Plateosaurus couldn't pronate its hands and had to have walked bipedally. The problem is that a lot of reconstructions of Plateosaurus I've seen walking this way look pretty goofy. If you look at that image (the hands still look weird, but that's not what I'm talking about), you'll see that the tail acts like a third leg to support the dinosaur's weight. That would be fine when standing, I'm pretty sure, but dinosaurs didn't drag their tails while walking. To walk bipedally that way with tail in the air just doesn't look right. There must be some sort of explanation to this (as they certaintly walked that way), so what is it? Crimsonraptor (talk) 22:58, 10 December 2010 (UTC)

I don't see a problem, personally. Presumably they made continual adjustments to their balance, in part by tail movements, just as their relatives the birds did and do. 87.81.230.195 (talk) 00:57, 11 December 2010 (UTC)

Maybe. It's just that a 2000 lb plus animal standing on two regular feet would probably have difficulty in some way. Not going into the whole diplodocoid-rearing-up debate, I've seen elephants go up on two legs, which sort of compares to the proportions. But that really isn't a good comparison, as they're built a lot differently. Crimsonraptor (talk) 01:07, 11 December 2010 (UTC)

The usual idea is that they walk with the head balancing the tail, pretty much horizontal, like in the silhouette picture in the Plateosaurus article. 81.131.51.70 (talk) 05:39, 11 December 2010 (UTC)

OK, the silhouette looks reasonable. A more upright stance than that, though, would likely be problematic. Crimsonraptor (talk) 14:03, 11 December 2010 (UTC)

Any chance that they used a similar approach to this Australian traffic hazard with a weighty tail? HiLo48 (talk) 06:38, 11 December 2010 (UTC)

A hopping plateosaur? A weird image comes to mind... but yeah, that could work! Crimsonraptor (talk) 14:03, 11 December 2010 (UTC)