Wikipedia:Reference desk/Archives/Science/2006 September 8

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September 8

How large are the Mars rovers?

I'm curious to know the dimensions of the Opportunity and Spirit Mars rovers. I can't seem to find these specs on the Internet. Thanks!

Cruise vehicle dimensions: 2.65 meters (8.7 feet) diameter, 1.6 meters (5.2 feet) tall Rover dimensions: 1.5 meter (4.9 feet) high by 2.3 meters (7.5 feet) wide by 1.6 meter (5.2 feet) long

Weight: 1,062 kilograms (2,341 pounds) total at launch, consisting of 174-kilogram (384- pound) rover, 365-kilogram (805-pound) lander, 198-kilogram (436-pound) backshell and parachute, 90-kilogram (198-pound) heat shield and 183-kilogram (403-pound) cruise stage, plus 52 kilograms (115 pounds) of propellant

From mars tv. Also, check out Mars Exploration Rover ---Sluzzelin 06:51, 8 September 2006 (UTC)

One interesting dimension is that the cameras are mounted at 150 cm high, giving views of about human eye level. Rmhermen 16:21, 7 October 2006 (UTC)

Useful fictions inside of science

What are some useful fictions that have been created for calculational purposes similar to a center of mass/gravity? A center of gravity isn't an actual feature of matter, just something we impose upon matter in order to help make our calculations easier for a given system. Thanks--droptone 12:32, 8 September 2006 (UTC)

See WP's articles on mathematical models in physics, and on theory. ---Sluzzelin 12:48, 8 September 2006 (UTC)

That reminds me of a joke my boss once told me about calculating the surface area of a chicken. First you assume that it's a perfect sphere... – ClockworkSoul 12:53, 8 September 2006 (UTC)

I remember this book: Consider a spherical Cow was quite popular a while back.---Sluzzelin 13:05, 8 September 2006 (UTC)

Depends how broad you want to make you definition of fiction. You could say that energy and entropy are useful fictions, since you can't measure them directly - you have to infer them from other properties of an object or system. And temperature, pressure, density and viscosity are all average measures that only make sense for a large population of atoms or molecules, so you could argue that they are also fictions. Velocity depends on your frame of reference, so maybe that is a fiction too. In fact, the only properties that are truly "features" of elementary particles seem to be spin, charge and mass. Gandalf61 14:45, 8 September 2006 (UTC)

• Newtonian physics is technically wrong, in that it doesn't account for relativity, but still widely used for most calculations.

• The Dalton model of the atom, while useful for basic chemistry, is not as useful in particle physics.

• Planetary and lunar orbits are approximated as ellipses, while the true orbits must account for various perturbations.

• The "no air resistance" model of ballistics.

StuRat 19:35, 8 September 2006 (UTC)

Body Mass Index assumes every human has an identical body shape, but is effectively used to determine obesity. While it could be improved by using body shapes or even getting an extremely accurate BMI by weighing people in water, the difference between BMI and the highly accurate indexes is statistically insignificant for nearly all people. --Kainaw ^(talk) 20:12, 8 September 2006 (UTC)

By fictions do you mean specifically fictitious entities that we postulate in science, or just any (probably false) assumption made in a scientific theory? Lumping the two together, here are a few:

1. The perfect rationality assumption used in the Homo economicus model of human behavior is often defended as a useful fiction.
2. Infinite populations are often used in evolutionary game theory and population genetics models in biology, these are certainly false assumptions. (There's actually a list at replicator dynamics.)
3. The use of frictionless planes in physics. (Or really just about any calculation done in an intro physics class and most engineering classes.)
4. Point particles used in Newtonian mechanics, special relativity, and general relativity.
5. Fluid dynamics assumes that fluids are continuous, they're not.

I attended a talk recently about use of fictions in computer simulation modeling, the video is archived here (its the second talk). As I recall he makes a distinction between "fictions" and "modeling assumptions." But he has a bunch of interesting examples. --best, kevin [kzollman][talk] 22:00, 8 September 2006 (UTC)

Chicken? Cow? Feynmann always called it a horse. — [Mac Davis] (talk) (Desk|Help me improve)

Isn't any unit an abstraction and therefore fiction? An object doensn't have any metres in it, length is a quality we assign to it. In more practical terms, what is your height? One part of this is the issue of precision. Any measurement is an approximation and therefore not exact. So is it real? But there is also the definition of someone's length. Do you include the hair on your head (if any)? If so, is it combed? What about the length of a punk with a Mohawk hairstyle? Converrsely, the centre of gravity is just as real as the geometric centre and therefore the radius of a planet (another use of the quantity 'length'). DirkvdM 12:41, 9 September 2006 (UTC)

I'm not sure if this is what you're looking for, but consider the planet Earth. We've assigned it all sorts of "scientific fictions", such as its axis (there's no actual rod connecting the North and South Poles!) and the "imaginary line" we call the equator. Similarly, the "imaginary lines" we call the tropics of Cancer and Capricorn, the Arctic and Antarctic "circles", and pretty much every other "line" of longitude and latitude. I could go on, but as I said, I'm not sure if this is exactly what you're looking for. Loomis 22:23, 12 September 2006 (UTC)

Help to identify spider

Hello, can someone please tell me what spider this is? Or at least if it is poisonous? Sorry for the bad pic but I only had my cellphone camera available at the time. I live in Gauteng, South Africa. I am afraid for my children's safety. The spider is about as big as a toddler's hand. One enters our house every week or so. If I wave an object like a broom near it, it raises its front legs (?) towards the object. Is this a defensive or aggressive pose? Sandman30s 14:13, 8 September 2006 (UTC)

That picture really isn't very much to go on. I believe, in general, that when a spider raises its front legs it is generally an aggressive, "Look at my teeth" pose, but I only know about Australian spiders in that respect. This page contains pictures of some of the more "medically important" spiders of South Africa that you can compare it with. Apparently South Africa also has trapdoor spiders and baboon spiders, neither of which would be very fun to get bitten by. Again, I'm not a spider expert in any respect, though. If I had to guess by the picture alone, the long-legs, big-head would make me worry that it was a violin spider, which have poisonous (but not always deadly) bites. I would definitely try to kill it in any case—a shovel would be my method of dispatching it, personally. --Fastfission 14:43, 8 September 2006 (UTC)

Thanks very much for the detailed answer. My best guess from all those pictures is the lesser baboon spider (HARPACTIRELLA), it doesn't look like the violin spider due to a different colour, unless the violin is also dark brown with dark red and black legs. I will try to get a better pic the next time, sorry. Also if the spider is not poisonous, I would not like to affect the ecosystem around the house, as the spiders would reduce my overpopulation of crickets :)

I'd much rather have the crickets. :-) StuRat 19:21, 8 September 2006 (UTC)

Not to be too much of a pedant, but all spiders are venomous. I have no idea whether this particular spider is dangerous, however. --Ginkgo100 ^{talk · e@} 20:18, 8 September 2006 (UTC)

Are you sure? I remember that that was some sort of urban myth. I'd check Snopes if I had the time. - Mgm|^(talk) 20:45, 8 September 2006 (UTC)

Correction to the above from spider: there are a few species not able to inject venom. --Ginkgo100 ^{talk · e@} 20:23, 8 September 2006 (UTC)

Really, there are only a few, as in 14 or less if I recall correctly, and they all live in remote regions of the jungle. I created two articles, and some redirects a while ago, when a new species was discovered that did not have any venom. Instead, it traps prey in it's web, then bundles it up, tigtens the cords until the prey is broken to pieces. The spider proceeds on to regurgitate digestive juices, pour them onto the prey, wait, then feast. — [Mac Davis] (talk) (Desk|Help me improve)

Looks like a "jagspinnekop" (Palystes sp. - African hunting spider), especially as you mention the striped legs, and the very typical raising of the front legs when threatened. The raised legs are impressive, but only a show - it does not attack that way. It hunts at night, and has no web as such, just a nest which takes 2-3 days to build. Though one cannot judge size, it looks like a youngster you have there (inter alia it still has 8 legs!). Also called a "reënspinnekop", (rain spider) from it's alleged habit of appearing inside when rain threatens. This spiders's bite hurts like a bee-sting, but won't kill - unless you get a heart attack from fright. It normally runs away - very fast once it starts running - to a dark corner somewhere. If you have trees outside (or dense bushes or ivy on a wall) you may find its large fist-sized nest of leaves, twigs and silk hanging inside the denser growth - be cautious, the female guards the nest. I leave them be, they don't build nests inside your house, and I've watched them catch other goggas inside at night. They definitely eat crickets, but there is no way they will prevent the periodic "cricket epidemics". If you wish to catch it, it is legal to keep it, and you can handle it if you don't mind an occasional bee-sting-bad bite. Contact a museum to find the correct diet, etc. The site also gives advice on how to catch it and return it outside. I normally use a plastic shopping bag which I place over it and then coax it into the bag, trying not to hurt the legs, then leave the bag open in a tree. The "bobbejaanspinnekop" (Harpactira/ella you mentioned - Therasophidae - Baboonspider) is bulkier, legs relatively shorter and oriented differently, more hairy, does not show the clear markings you mention, does not typically show that same threatening stance, and is a protected species, because of a demand as "pets" in the first world countries. Searching the web for "rain spider" or "hunting spider" should give the best results if you want to know more. --Seejyb 20:55, 8 September 2006 (UTC)

Correction to the above - a rainspider dragged a leaf into my lavatory (I live in Centurion, Gauteng, South Africa), glued it to the ceiling, and built a nest around it. Apparently the gestation period is three weeks. I don't know if the spider is going to take her brood with her and leave, or if my domicile is going to have a hundred tiny spiders flocking all over it. Peter Wade, 11 December 2006

Still hard to identify but looks very much like the second pic on this page you talked about - the huntsman. These things become absolute monsters (size of adult hand) and don't seem infected by normal insecticide - will given it's not an insect :) Good to know it's not worse than a bee sting. Will definitely get a better pic next time to get a proper ID. And for the record - I freakin HATE CRICKETS! Their incessant ventriloquist chirping interferes with some frequency in my brain and I cannot sleep and cannot find the little buggers, in the day or night! GRRR. And to make it worse we get 'Parktown Prawns' (King Crickets) where I live - harmless but they have to be the ugliest darn things alive (good at hiding too). Ugh. Sandman30s 22:26, 8 September 2006 (UTC)

Cats are good at catching crickets. User:Zoe|(talk) 23:19, 8 September 2006 (UTC)

Sounds like a much better choice to me. StuRat 01:22, 9 September 2006 (UTC)

Yeah, I would say it's a huntsman. We have plenty of them in Australia. They tend not to be aggressive, as you can see from the article page. BenC7 09:06, 9 September 2006 (UTC)

Having lived in South Africa I think "seejyb" above is right on the money with the answer - though I have found that catching the spider is a simple task using a large glass and a sheet of paper - approach slowly and place the glass over the spider trapping it then slip the sheet of paper under the glass wait a while and the spider will crawl to the bottom of the glass hold the paper in place and take the spider in the glass outside and shake it out onto a bush or tree. The spider lives! and you are rid of it!Cycloneweaver 16:50, 12 September 2006 (UTC)

diabetes in cats

Can someone please advise what choices for cats are available? My vet is at a loss as to bringing down the insulin level. i've tried humulin u, humulin m, and nothing works. i'm getting pretty desperate.

Try feline diabetes and the wiki on pet diabetes for further links and references. Please understand that we can't give medical advice at the reference desk. Good luck and all the best to your feline friend. ---Sluzzelin 14:55, 8 September 2006 (UTC)

I have been using PZI with my cat with some success, my vet says she prefers it to humulin. In addition, putting them on a low carbohydrate diet is considered important and has resulted in a reversal of diabetes for some cats. My cat is on Hill's Prescription M/D. Of course, this is only one case, and I'm not a vet. --best, kevin [kzollman][talk] 21:39, 8 September 2006 (UTC)

ribose sugar

Is a ribose sugar a reducing sugar

Look at the structure of ribose and see if it contains the substructures or other features that are consistent with those of a reducing sugar. DMacks 15:10, 8 September 2006 (UTC)

Paraffin lanterns & alcohol

Would it be possible to safely run a paraffin lantern on alcohol if you haven't got any paraffin handy? If not what could you run it on that doesn't need to be obtained from hydrocarbons. AllanHainey 15:35, 8 September 2006 (UTC)

Paraffin is a solid hydrocarbon while ethanol is a liquid alcohol. Because it's not really the solid wax of paraffin that burns, but rather the resulting liquid/gas, if your lamp can accomodate a liquid fuel, it may be able to run properly.--Russoc4 17:47, 8 September 2006 (UTC)

In the UK, paraffin is a liquid fuel, and paraffin wax is a solid - the constituent of candles. --G N Frykman 17:54, 8 September 2006 (UTC)

Forgot about that...well, ethanol may or may not work properly. I found a very indepth page [1] describing and comparing many fuels that can be used in camping stoves. The same applies here, only the fuel has to travel through a wick. The only problem I can forsee with ethanol is that it boils relatively easily. It's also less efficient when comparing BTUs/lb. isopropyl rubbing alcohol is not recommended. --Russoc4 19:04, 8 September 2006 (UTC)

I'd tend to recommend strongly against the use of ethanol in a lantern. Ethanol burns with a hotter, bluer flame that doesn't generate much light and will be harder on your lamp hardware. In addition, it has a higher vapour pressure (meaning that heating it during lamp operation may result in various sorts of failure of your lamp, some quite dramatic) and lower flashpoint. TenOfAllTrades(talk) 21:15, 8 September 2006 (UTC)

I presume you are talking about a non-pressurised, wick-burning system. Alcohol, petrol, lighter fluid or any similar fuel will not be safe in a lantern designed for paraffin - you will create a fireball, if not an explosion. The machine is not designed to handle such highly volatile substances. In practice, a light vegetable oil does work, but it stinks. Turpentine should be a safe option, and also stinks. --Seejyb 22:01, 8 September 2006 (UTC)

Burn!!

It's my understanding that when you burn organics like wood, or sucrose, the impurities of water and smoke components are burned off leaving residual carbon behind. If this is true, why does this residue not continue to burn? Doesn't carbon oxidize to form CO2? --Russoc4 17:42, 8 September 2006 (UTC)

See charcoal--Light current 17:44, 8 September 2006 (UTC)

Many people confuse heating and burning. See destructive distillation. --G N Frykman 18:00, 8 September 2006 (UTC)

Soot – which is mostly carbon – is the result of incomplete combustion of organic matter. As long as the fire remains hot and well-supplied with oxygen, the carbon will burn off to form carbon dioxide. (Under conditions of inadequate heat or oxygen, you may instead end up with carbon monoxide.) TenOfAllTrades(talk) 18:09, 8 September 2006 (UTC)

So charcoal/coke is made by "heating" wood/coal, but not actually burning it completely in enough oxygen. I get that part. You didn't answer my question. What I don't get is that when wood burns completely, it creates ash, which glows for some time, but then dies out. Why does it not burn if it's mostly carbon? --Russoc4 18:51, 8 September 2006 (UTC)

IT'S NOT CARBON. I don't know about your ashes, but the stuff in my fireplace looks like white fluffy powder, plus a few lumps of charred unburned wood. A better question is: why do very tiny pieces of charcoal stop burning? Or this: what is "wood ash's" composition? Google searches say: calcium carbonate, potassium carbonate, aluminum oxide, magnesium oxide, and lots of other stuff. In other words, the ashes are the traces of minerals used by the tree. See: [2] --Wjbeaty 23:41, 8 September 2006 (UTC)

Burning an organic material oxidizes it, leaving oxides of its component elements, the most common elements in organics are carbon hydrgoen and oxygen. I there is insufficient oxygen, you will be left with unoxidized elements. So hydrogen and carbon, you are unlikely to notice any hydrogen, and carbon is in the form of soot. Carbon needs the heat from the fire to form new bonds with oxygen, so will not spontaneously oxidize once oxygen is sufficient, so it will be left. Philc _T^E_C^I 21:04, 8 September 2006 (UTC)

Oh... well, that does clear some things up. So essentially, a burnt up, blackened matchstick has no carbon, just other random impurities. --Russoc4 13:56, 9 September 2006 (UTC)

Er, no. A blackened matchstick will be black (primarily) because of the remaining unburnt carbon. (White residue is mostly mineral impurities.) Overall, the process of combustion releases energy; we see this as heat and light. However, the reaction – in this case, the combustion of carbon to form carbon dioxide – requires a small amount of energy to get started. Normally combustion is self-sustaining once started; a small amount of heat from the reaction is fed back in to the system to drive the oxidation of more fuel. This feedback loop breaks down, however, if too much heat is drawn away from the fuel. That's why you can blow out a match—your breath cools down the fuel (paper or wood) in the matchstick, ending further combustion.

This is also why charcoal is so difficult to light. You have add (and ignite) lighter fluid to charcoal to supply adequate intial heat to start the charcoal burning. Once ignited, however, charcoal will burn very hot. TenOfAllTrades(talk) 14:16, 9 September 2006 (UTC)

Ahh... ic now. Thanks! --Russoc4 16:53, 9 September 2006 (UTC)

Aldol Compound

Can anyone help me out on this one? I'm trying to figure out the name of this compound that results from an aldol reaction. It is a yellow solid with a molecular formula of C₁₈H₁₆O₃, and its experimental melting point is 167°C to 172°C. ChemFinder is no help either, unless I'm not looking in the right spot. --Russoc4 20:05, 8 September 2006 (UTC)

File:Aldol.PNG

• Try if you can get your hands on a book like the Handbook of Chemistry and Physics, BINAS or if you happen to be able to read Dutch the "Chemiekaarten". I would also recommend you draw up the different compounds that could result with that molecular formula and make a guess at which it is by determining whether long chains have a lower/higher melting point and how saturation affects it. - Mgm|^(talk) 20:51, 8 September 2006 (UTC)
• If you do the guessing well it will reduce the number of compounds you need to look up. - Mgm|^(talk) 20:53, 8 September 2006 (UTC)

I considered the Handbook. If I have to, I'll use it. Thanks though. --Russoc4 21:00, 8 September 2006 (UTC)

chemfinder won't be any help. break the compound down into its components, you've got the indanone, an (E)-configured exo alkene, and a dimethoxy substituted benzene ring. start combining the pieces into names, such as (E) 2-(3',4'-dimethoxystyrl)indanone. not iupac, but it'll fly. alternatively if you want to go iupac, start breaking down the functional groups even further. In the real world, software like chemdraw has automated the naming of such compounds, and you'll often see things referred back to structures (eg indanone 1) in order to make life easier. sing out if i've lost at some point, it's hard to gauge what level you're on. Xcomradex 22:56, 8 September 2006 (UTC)

I purposely made it hard to tell :P I'm only in my 1st of 3 sememsters of organic chem. We did this in our second lab, and though I'm not sure if we really need to identify the name, it can't hurt. We did this to practice recrystallization. I'm a chemistry major, as you might tell from my user page, which also lists my classes :D. No biggie if I can't get a good name though, but thanks for your help! --Russoc4 02:42, 9 September 2006 (UTC)

It can't have both "indan" and "styryl" in the name, since each of those substructures would include the α-carbon of the enone. If you like indanone as the parent structure, then the substituent is a benzylidine derivative. DMacks 06:03, 11 September 2006 (UTC)

i'd say they don't want you to name it in iupac terms, i'm up to six years (and counting) of org chem, and it still made me think. you'll pick up soon enough that iupac terms are just unwieldy for anything remotely complex. eg 2-[3,4-dihydroxy-2,5-bis(hydroxymethyl)tetrahydrofuran-2-yl]oxy-6-(hydroxymethyl)tetrahydropyran-3,4,5-triol is unrecognisable, and it only gets worse when include stereochemical descriptors. but tell any chemist 'sucrose' and they'll know what you're on about straight away. good on you for going the extra mile though, that'll get you good marks. Xcomradex 04:02, 9 September 2006 (UTC)

That's probably why ashes are so good for plants, being the rests of all the trace minerals? If the minerals were in the plant you burnt, they must be useful to the plant growth/maintainance.---Freebird- 14:29, 15 September 2006 (UTC)

American passenger rail profitability

Why is it that, despite the commercial viability of passenger railways in Europe and Japan, American passenger rail has never turned a net profit since 1930, four decades before the founding of Amtrak? C. M. Harris ^{Talk to me} 20:09, 8 September 2006 (UTC)

Gasoline is far cheaper in the U.S. than in every European country I've been to (Norway, Sweden, Denmark, U.K., France, Italy, and Turkey). I assume it is cheaper than all of the European countries. While we complain about $3/gallon gas, a friend of mine in Italy is complaining about $10/gallon gas. Since gas is so cheap, there is no incentive for people in the U.S. to use the railroad, which even with the cheap tickets is still not much cheaper than driving. So, if ticket prices were increased to allow the rail to profit, nobody would want to ride. --Kainaw ^(talk) 20:21, 8 September 2006 (UTC)

What does "commercial viability" mean? I thought most non-US rail systems were government-subsidized... DMacks 20:37, 8 September 2006 (UTC)

Most rail systems are subsidised, as a lot of countries recognize the rail service not as a gold digging source of income for the government, but as a service, which the government helps provide, in exchange for all the taxes etc. Philc _T^E_C^I 21:00, 8 September 2006 (UTC)

in NZ we privatised the railways, and if you ever wanted an example of why you don't privatise a natural monopoly, Tranz Rail is it (and NZ's privitised telecomunications service Telecom New Zealand too). Tranz rail ran the NZ railways into the ground, closing line after line due to poor maintanence, let alone the asset stripping. Xcomradex 23:03, 8 September 2006 (UTC)

In addition to all the above, consider the problem of distance. Railways in European countries and Japan don't have to cover particularly large areas. The United States, on the other hand, is gigantic, spreading across an entire continent. It costs a lot more to operate a train from New York to Los Angeles than it does to run one from London to Edinburgh. On top of that, the trip takes several days, which is unacceptable to most Americans when they can fly the same distance in five or six hours. (Not that anything operated by the government could ever attain profitability, but that's a separate issue.) --Aaron 23:16, 8 September 2006 (UTC)

High speed rail (such as maglev) could solve the time problem, especially between populus, close cities, like the Boston/New York/Wshington DC corridor. Of course, in these days of rampant terrorism, the high speed line would need to be well protected, as it would be a natural target. StuRat 05:06, 9 September 2006 (UTC)

Railways have to compete with other modes of transportation and those are subsidised, so the railways have to be subsidised too to keep the prices down. In the case of airplanes it's obvious - they don't have to pay tax over the fuel. And I have once heard that (in the Netherlands at least) car travel is also subsidised for about 50%. I just don't know any further details on this, but I suppose road building and maintenance with general public funds in stead of just taxes relatedc to car driving is an important aspect. I also once heard that if people had to pay the real cost of driving a car, no-one would. DirkvdM 13:49, 9 September 2006 (UTC)

Jet fuel is taxed in the U.S. with different cities having different rates. Rmhermen 23:28, 9 September 2006 (UTC)

Various economic booms in Japan really helped to boost the rail industry, allowing the national rail company (and later, numerous privatized rail companies) to extend, improve, and add numerous lines leading to remote areas of the country, as well as improve the Shinkansen (bullet train services). Now that the infrastructure has long been a staple of modern Japanese life, I doubt even a major depression could cause much harm to the rail industry. I also doubt that Japan would be able to achieve such a feat again if they had to start now. You can see effects of the rail industry "dealing" with recent economic pressure by the age of a lot of the trains (many of the trains run by private companies are very Art Nouveau).  freshofftheufoΓΛĿЌ  16:04, 9 September 2006 (UTC)

In the US, there were a number of relevant historical factors that occur around 1930 et seq. The '30s started with the Great Depression which showed a decrease in passenger and cargo traffic. Millions of cars were sold in the US between 1935 and 1940. (Q.v. Ford Model B (1932) which produced >4M units in 1932-34) There was a huge upsurge in rail traffic during World War II. Returning from the war, most people could drive, the rails had an economic fall-out from the sudden cessation of war-related traffic, and by 1956 the Interstate Highway System was started. The Interstate system was initially composed of state highways which had been around for some time, so the capacity for road travel was already present.

In the present, Intermodal transport is most common, where rail transport is used for freight and passenger traffic that happens to start and end at a rail hub (which are rather sparse in most of the US). Air transport is common for time-critical transport, or transport to otherwise infeasible destinations (e.g. the backwoods of Alaska). And the bulk of distribution from sea hubs and rail hubs is in the form of truck traffic. In a very real sense, containerization commoditized the packaging of freight, making transport methods more interchangable (and thereby reducing the inefficiencies of switching modes).

A more modern analogy is the last mile in telecommunications, where it is recognized that bulk data transport makes sense for links near the root of the distribution hierarchy and lower-capacity, parallelizable transport makes sense near the leaves of the hierarchy. This is especially evident in the package delivery companies, like Federal Express and UPS.

Finally, truck transport is also a way for a chain of companies to control exactly how their inventory moves. A company with its own trucks does not have to wait for rail transport or some other bulk transport to schedule a shipment. Thus, on-demand shipping becomes possible if you have your own trucks.

In the area of passenger transport, the two advantages of rail prior to the time you mention: faster and cheaper have been overcome by other technologies. If faster is the requirement, then air travel is superior (although increased processing times at airports are reducing this margin somewhat). If cheaper is the requirement, then the bus, or personal automotive transport is superior.

-- Fuzzyeric 01:00, 14 September 2006 (UTC)

grasshopper

how do you tell the difference between a grasshopper and a cricket?Kevinamccracke 22:22, 8 September 2006 (UTC)

Color ? Grasshoppers are typically brown or green, while crickets are usually black. StuRat 00:55, 9 September 2006 (UTC)

Follow StuRat's links and read that grasshoppers have short antennae and crickets have long ones. I used to mix the two up in the naming of my photographs until I read those articles. DirkvdM 13:50, 9 September 2006 (UTC)

Length of Time To Circumnavigate Globe

I did a Wikipedia and Google search, but to no avail.

If I utilized only:

• 1) Public Airports/Airplanes (No Private Jets)
• 2) Automobiles
• 3) Trains, Subways, Chunnel, etc.,
• 4) Boats, and
• 5) Human Powered Vechicles (Bicycle, etc.)

What is the absolute minimum time it would take to circumnavigate the globe?

Thanks, --69.138.61.168 23:28, 8 September 2006 (UTC)

It'll make a major different depending where you're starting from, and how much of a 'straight line' you want to do... if you take a boat in summer, you could circumnavigate around the north pole in five minutes... if you want to stick within ten miles of the equator at all times, it'll take significantly longer. --Mnemeson 23:34, 8 September 2006 (UTC)

Ha! I didn't even think about taking a boat around the North Pole. Good answer!

It will need to be a submarine or icebreaker, because the surface of the water at the North Pole is covered with ice. StuRat 00:52, 9 September 2006 (UTC)

probably 48 hours by plane. JFK - Narita - Heathrow - JFK--69.138.61.168 23:40, 8 September 2006 (UTC)

I agree with 48 hours, by plane. The only time you would need any other form of transport would be to get from terminal to terminal in the airports. StuRat 01:09, 9 September 2006 (UTC)

It took me 24-28 hours to get from Orlando International Airport to Bangkok International Airport. — [Mac Davis] (talk) (Desk|Help me improve)

Of course a plane would be fastest. If you are required to stick within a certain distance of the equator, you probably wouldn't find commercial flights to suit you. But if the requirements are less strict, an eastbound plane would be faster than a westward bound one because it could hitch a ride on the jet stream. On top of that, it would cross the international date line (as Phileas Fogg found out) and gain a day (or lose one, depending on how you look at it). DirkvdM 14:11, 9 September 2006 (UTC)

I would assume they want to know the actual elapsed time, so don't care about time zones or the date line. StuRat 00:34, 10 September 2006 (UTC)

A quick check with kayak.com shows that it's not unreasonable to do this in 44 hours or less by commercial flights; one sample itinerary I found was (all times local):

• Leave London Heathrow at 12:30 PM, Thurs. Sept. 28; arrive Bangkok at 6:05 AM, Friday. (Thai Airways, Flt 911)
• Leave Bangkok at 7:30 AM Friday, arrive Tokyo Narita at 3:40 PM Friday. (All Nippon, Flt 5696)
• Leave Narita at 4:55 PM Friday, cross date line, arrive LAX 10:52 AM Friday. (All Nippon, Flt 7018)
• Leave LAX at 1:08 PM Friday, arrive back in Heathrow at 7:40 AM Saturday. (United, Flt 948)

You'd be arriving 43 hours, 10 minutes after you left; you'd have spent 38h, 14m on aircraft, and the trip would cost $5459 economy. And your luggage would wind up in Cleveland. Interestingly, the LHR-NRT-LAX-LHR itinerary, without the Bangkok stop, takes less time in the air (31 hours) but due to the connections, takes longer total. (And is $1000 more, not that that really matters.) --ByeByeBaby 19:25, 10 September 2006 (UTC)