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125 Years of Longitude 0 0' 00" At Greenwich
An anonymous reader writes "This week marks the 125th anniversary of the International Meridian Conference, which determined that the prime meridian (i.e., longitude 0 0' 00") would travel through Greenwich, UK. One of the reasons that Greenwich was agreed upon 'was that 72% of the world's shipping already depended on sea charts that used Greenwich as the Prime Meridian.' Sandford Fleming's proposal of a single 24-hour clock for the entire world, located at the center of the Earth and not linked to any surface meridian, was rejected / not voted on, as it was felt to be outside the purview of the conference."
And don't forget the 180th meridian that came with it. When you cross the 180th meridian, you have to set your watch back/forward 23 hours !
Quite a few people are unaware of it ;-))
http://adsabs.harvard.edu/full/1919PA.....27..416F
Everything I write is lies, read between the lines.
It's a wonderful thing to live a phlegms breath away from such a staple part of our species everyday lives.
I wonder how much longer it will take for the US to catch up?
For example, we continue to teach date formatted in a completely nonsense format (MM/DD/YYYY) instead of either high to low (YYYY/MM/DD) or low to high (DD/MM/YYYY) like the rest of the world. Plus using AM/PM instead of 24 hour ("Military Time") again like the rest of the civilised world.
Don't even get me started on our lack of metric....
It is worth noting that in the coordinate system most used today (WGS84), this is no longer true.
See this explenation or check google maps.
I agree. At the same time you should abolish the whole "daylight savings" time. Just use UTC for everything, and then simply state that stores 3 hourse before local midday and close 8 hours after (for the 9am-8pm hours).
How many other Greenwich's are there at 0 longitude?
Moderation Total: -1 Troll, +3 Goat
It's called Riyadh Solar Time - look it up. It last one year year before they realised how much of a pain in the arse it was. Also, Japan used to have per-city time zones in five-minute increments, and that was a real pain for doing business, or calculating journey travel/arrival times. Discrete time zones for relatively large areas are just more practical in general.
Clearly you're not a woodworker. Small measurements are where the metric system shines... large measurements people just estimate anyway.
"Growing old is inevitable; growing up is optional."
nuff said.
I have tried finding a reference to this and can't. What does it mean by being located at center of the Earth and not linked to any surface meridian? Time zones are linked to surface meridian's right? So how would a system work that was not linked to anyplace on the surface?
stores [open] 3 hours before local midday
You imply that the entire population can consistently and correctly subtract 3 from a number.
And as always, I think grandpa Simpson's classic comment really sums up the attitude behind why so many Americans are reluctant to switching; “My car gets forty rods to the hogshead, and that's the way I likes it!”
/Mikael
Homer himself would say: Greenwich... mmmm.. pizza!
Set your phasers on "funky"!
Many people forget to deal with, or at least poorly handle time zones in software. I think it would be much easier to just adapt to using a single time for the entire planet ... they're just numbers. Who cares if you need to wake up at 23:00?
One of my favourite Jeff Atwood quotes is "All you UKers who live in UTC+0 are a bunch of dirty, filthy, stinking time zone *cheaters*".
Quickly, convert from 1234 kiloinch to miles! The beauty of the metric system is that there is one unit for distance, which is a meter. All others are just prefixes. A kilometer is just a kilo meters, so 1000 meters. All you have to do is move the decimal point. With the imperial system, going from the small distance unit (inch) to the large one (miles) requires a lot of conversion. And then you have a third, medium unit called the feet, just to make it a little more unwieldy.
Anybody wondering why it's doesn't run through Paris? Take a look here
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
It's what makes time travel POSSIBLE!
You forgot yards.
Feet should be abolished. You would say "He is 1 yard and 35 inches tall". Or "I wouldn't touch it with a 3 yard pole".
Then the conversion to meters would be easy (not for heights, though, because 9% error is too much).
Quickly, convert from 1234 kiloinch to miles!
$ time units -v '1234 kiloinch' miles
1234 kiloinch = 19.47601 miles
1234 kiloinch = (1 / 0.051345219) miles
real 0m0.046s
user 0m0.040s
sys 0m0.008s
That didn't take to long at all!
Seriously, the metric system has a lot going for it in some ways, but is harder in others. For example, while 10 is a great multiplier (since we tend to think in base 10), it doesn't have a lot of factors. For example, dividing by 3 doesn't work so well. Sure, you and I know that 1/3 meter is 33.33333 cm, but that's not as easy as 1/3 foot being 4 inches. 5280 (the number of feet in a mile) is divisible by 2, 3, 4, 5, 6, 8, 10, 11, 12, 15 and a lot more. Not that a 15th of a mile comes up a lot, but if it does, you can be assured that it's exactly 352 feet!
The metric system units are also more calibrated to scientific use than everyday use. The meter is too long and the gram is too light (the liter is about right). Other things, like degrees Celsius are too big (not to mention as arbitrary as Fahrenheit). And metric time never really took off -- you still have seconds, minutes, hours, etc.
All in all, the metric system is optimized for scientific work where conversions between units happen more often, and knowing that 100 million micrograms is .1 kilograms is useful. But it doesn't work so well for common, human scale use.
"Save the whales, feed the hungry, free the mallocs" -- author unknown
The reason is that this kept the 90 degree west meridian in the same place the the original. Guess where that is...
Tells you where the power and money was when the GPS system was set up.
First, the article you linked says nothing about why it was moved other than GPS was more accurate. Care to cite a source on your claim? There's someone in the comments saying it, but that's also not sourced.
Also, I love that you say that but ignore this, from the article you linked. This is about selecting Greenwich as the prime meridian back in the day:
Rival 1: Washington was a key competitor, but the US threw its weight behind Greenwich, taking it out of the race.
Any chance to bash the US, eh?
When I go, I'm flying Air Bizarre. It's a good airline. You buy a one way round trip ticket. You leave any Monday, and they bring you back the previous Friday... That way you still have the weekend.
I'm trying to figure out what you are referring to.
Ridgeway, WI?
this guy's house in Belleville, IL?
Memphis, TN?
New Orleans, LA?
The Galapagos Islands?
You are aware that the US built the GPS system right? We designed it. We paid for it. We launched it. We still pay for it to operate and be maintained.
Since the system gains it's "zero" from a ground based reference it only makes sense that it's based on a location in the US since we are the ones that built the system. It's nothing short of amazing that the Prime Meridian only moved 100m. That's a testament to the skill of those that came before.
Keep in mind that my tax dollars fund this and it's open for the whole world to use, so quit yer bitchin.
Actually I would say that we should be permanently in daylight savings time year round, making that the new standard time.
Tesla was a genius. Edison however was a overrated hack who liked to torture puppies.
In my younger days I was pretty damn good with wood, and working with sixteenths of an inch (or a thirty-second of an inch, or tighter, with a wood that sawed and sanded clean), was cake. So was sliding between an eighth and five thirty-seconds in my head. Approximations were something along the lines of 'a fat eighth.' It was all easy. On the other hand, people who can read perl like it was a second grade textbook frighten me. Although I'm sure it's cake for them.
As for estimations, what is your value for 'large'?
All cities used to have their own local time. The railroads were the first to push for standardized time-zones.
I used to leave near New Orleans.
My bet is "this guy's house in Belleville, IL"
Leap seconds.
The ONLY problem with that is that you need your time aware product to be updatable for leap seconds and that adds a few cents to your $100 GPS locator.
But missing out on leap seconds means the stars change location faster and we have to update all the astronomy books and astronomy software and astronomy hardware.
The costs are about equal.
It's the gadget manufacturers trying to offload a cost onto someone else.
Not just gadget manufacturers. There must be lots of software that has to care about leap seconds, and they are a pain. Especially for distributed software that relies on systems being in sync with each other. This is largely because of a lack of foresight on OS writers. Most systems use some kind of Unix style timestamps that have no concept of leap seconds, so either the time has to jump, or the length of a second has to be adjusted for a short while to bring systems back in line with UTC after a leap second. This makes timestamps a little unreliable after a leap second and software that depends on them (e.g. by rejecting updates with timestamps in the future) can fail. Where I work we have 24hr operations on a world-wide basis, but these are reduced as much as possible whenever a leap second is due, to minimize the damage from a leap second induced software bug.
There are basically three time standards:
o GMT: Based on the rotation of the Earth.
o IAT: Based on atomic clocks (or whatever the latest best clocks are).
o UTC: Adjusted to be an integer number of seconds offset from IAT, to bring it within a second of GMT (hence leap seconds).
Most of the world uses UTC (with a plus/minus for timezones). There is a US proposal to drop UTC all together, and live off of IAT. So what if midday at Greenwich starts to drift a little from 12:00:00, and ends up at at 12:01:00 in a hundred years or so? If you want to know what time a star will rise, or where exactly to point your telescope, then use GMT. Everyone one else can use IAT. UTC is a standard based on an affection for GMT but a desire for accuracy that causes more problems that it solves. Get rid of it.
Also, as far as I know there has never been a leap second removed instead of added, but it is possible. How much software is going to fail when that happens? Probably not much on a global basis, but it could include critical systems.
Foot. Plural is feet, singular is foot.
,furlongs for longer distances, rods, poles, yards, feet for medium distances and inches and parts thereof for small measurements. There is no need to calculate 1,234,000 inches, ever, unless you want to know how many of your penis lengths are in 19.48 miles (411,333.3). And you start by converting inches to yards after just 36 of them. Metric is good for digital measurements, imperial is good for analogue measurements like half, quarter, third. But fractions seem to be a mystery to people these days.
And you very rarely need to convert imperial measures within the same system. It was designed and implemented around specific tasks, so you use miles, leagues
You guys wanna get anal about this stuff? We should have 13 months of 28 days (364 days) and a tack-on day, since there's 13 lunar cycles a year. Instead, we had some nutcase priest named Greg or something that decided back in the Crusading days. We should have a clock that does not change. Instead, we have Ben Franklin's BS. Congress in 2007 spent $150M studying DST, and found it was actually a net loss in energy. We should not have time zones. We should have a set UTC, and businesses and people adjust to that clock. We should have a day system similar to Internet Time a la Swatch. It may not have gone anywhere, but it's actually as clear as can be. It would be a great system to adopt. And finally, the reason that the metric system never caught on in Imperial areas is because while it makes sense, people have a tendency to handle smaller numbers better. Feet are often used in everyday measurements because they have actual feet on their body. We don't have meters on our body. If we could come up with something in the Metric system, maybe call it a "Third", you could convert people. 30 centimeters is user-unfriendly. So is 450ml when you can have a pint, though that's less a problem. People don't have to be adjusted into these new distance schemes. Just make gas be sold by liter, and put all road signs with km (mi), and tell detroit that all cars have to be km friendly. It's really not hard; we just don't have the spine politically to move the needle on something that is truly important, but often overlooked at trivial.
And lie in bed while the sun shines at midnight. Yeah right.
Most people who use SI units in their everyday lives are perfectly content to either express fractions as fractions or settle for 0.25, 0.33..., 0.166... and so on. It's more a matter of what you're used to.
As for the meter being too long, well most people here in Sweden don't seem to have any trouble "just knowing" how long a meter is, and there's also the decimeter (0.1 m), centimeter (0.01 m) and millimeter (0.001 m).
As for grams, there are also hectograms (100 g), kilograms (1,000 g) and tons (1,000,000 g) that are all in common use.
Celsius makes a lot more sense to me, 0 C = water freezes, 100 C = water boils (and it's "compatible" with the Kelvin scale). What was it fahrenheit was measured by? 32 F = water freezes, 100 F = body temperature, 212 F = water boils?
Admittedly I have some bias as I am more accustomed to SI units but I find them easier to work with in practically all situations (including everyday situations like cooking where the main problem tends to be with recipes where someone's thrown in some random "add n ounces/cups/hogsheads").
/Mikael
Greylisting is to SMTP as NAT is to IPv4
For example, while 10 is a great multiplier (since we tend to think in base 10), it doesn't have a lot of factors.
Irrelevant. A yard being 36 inches is only useful because you do some calculation and then need to convert "quarter-yards" into inches. Outside forced examples (or generous approximation), you end up with some ugly fraction anyway.
If you really need lots of factors then use multiples of 96mm (or something). For example, pre-made kitchen furniture comes in multiples of 300mm (for cupboards etc).
The metric system units are also more calibrated to scientific use than everyday use. The meter is too long
Too long for what? It's 7.5km from my home to work, that's an easy number. I ride a bike which is definitely human-sized. The frame size is 46cm, the wheels are 70cm diameter, the nuts and bolts holding it all together are typically 6, 8 or 13mm (IIRC). The bike lanes are 1.5m wide, the car lanes 3m wide, the road markings (I guess) 10cm wide. If the metre "too long" for any of this, should I be using the yard, foot, inch or mille? And a chain, furlong, mile, or league for the distance to work?
and the gram is too light
Then use ten, a hundred, a thousand, or a million of them, as appropriate.
All in all, the metric system is optimized for scientific work where conversions between units happen more often
Perhaps they'd happen more often if it were easier.
Sure, you and I know that 1/3 meter is 33.33333 cm, but that's not as easy as 1/3 foot being 4 inches.
Sure. How much is 1/5 foot again? There are problematic numbers in every system, but this strawman seems to jump up every time.
5280 (the number of feet in a mile) is divisible by 2, 3, 4, 5, 6, 8, 10, 11, 12, 15 and a lot more. Not that a 15th of a mile comes up a lot, but if it does, you can be assured that it's exactly 352 feet!
At least for me, remembering numbers like 5280 doesn't sound any easier than knowing that for example 100/8 is 12.5.
The metric system units are also more calibrated to scientific use than everyday use. The meter is too long and the gram is too light (the liter is about right). Other things, like degrees Celsius are too big (not to mention as arbitrary as Fahrenheit). And metric time never really took off -- you still have seconds, minutes, hours, etc.
All in all, the metric system is optimized for scientific work where conversions between units happen more often, and knowing that 100 million micrograms is .1 kilograms is useful. But it doesn't work so well for common, human scale use.
Which is just why we have the prefixes, like kilo- centi- etc. Normally for instance kilograms are used instead of grams (unless the amount is under 1 kilogram), centimeters are used instead of meters if the length is under 1 meter etc. Just as easy as feet or pounds, just lot less to remember. And the mathematics of it, we use base 10 mathematics anyway, so you do have to learn your math in any case. Whereas having to know how many feet are there in a mile is knowledge only needed because of those units. All in all, I happen to think that people feel the system they've used to is easier only because theyve learned it since childhood.
Well, when Fahrenheit created his temperature scale, he made 0 degrees F the temperature that salt water (think the ocean) froze at. He used 100 degrees as the body temperature of a person. (Alas, he calibrated the temperature on himself, and I read that his metabolism was high...most people are 98.6 F)
I can think well using both units, so I don't care, but it wasn't like his numbers were completely random..
Doh!
Seriously, standards have often been used to lock out competition.
What was it fahrenheit was measured by? 32 F = water freezes, 100 F = body temperature, 212 F = water boils?
For reference, 0F is when salt water freezes, 32F is when fresh water freezes, and 100F is human body temperature (or at least that of Dan Fahrenheit.) The boiling point of water was not taken into account for creating the scale, it was just placed upon the scale later on.
I will grant that your point remains intact however.
One neat detail about the Celsius scale making more sense: Originally it was reversed, as in 0C was the boiling point of water, and 100C was the freezing point. It was only 'reversed' years later and against his will (Well, I believe he was dead by then, but still.)
It should also be kept in mind that both Fahrenheit and Celsius scales were created before 'temperature' was really understood. At that point in history, heat and cold were both forces that were believed to exist separately. Today we know there is only heat and lack of heat, but at the time it was believed there wasn't really an upper OR lower bound on temperature, and the scales were made accordingly.
Once the concept of heat as energy was realized, and there was a lower bound (absolute zero) but still no real upper bound, a new scale for scientific purposes was made to match, called Kelvin.
It's even more absurd when you look at other units. Inches/feet are the only unit with this convenient factoring relationship, others have less convenient relationships like 8, 14, 16 and 20.
- Video. The PAL standard is better quality than NTSC (Never The Same Color), so why did the Americas adopt an inferior option?
That's sort of like asking why we adopted the clearly inferior analog STDV standard instead of digital HDTV. NTSC was standardized in 1953, PAL was not standardized until 1963. Naturally, PAL was the superior standard...it was based around technology that was ten years more advanced.
So how much does a gallon of water weigh? How about that 2 gallon/10l gas can, how much will that weigh when it's full? In metric it's easy since 1l of water = 1 kg Gasoline has a relative density of 0.71-0.77 (lets call it 0.75) so in metric 10l of gasoline is 7.5kg All without a calculator or writing anything down, lets see if you can do that in pounds and inches. Yes you might have to deal with learning to use 1.25 1.6 and 2.5 more often but it's no less work then learning how many feet are in a mile or fluid oz in a pint etc. Not to mention that the UK and US numbers are often different.
You're right on one thing: the metric system is base-10, but definitely should have been based on base-12, which is the basis of the ratio between some imperial units. In case of base-12 dividing by 3 would've been straightforward.
It's very impractical to have a unit system which uses base different from your general number system. There is certainly a good argument for using base-12, but if we do so, it must be done everywhere, and not just for measurements; otherwise you create more problems than you solve.
You miss the point. The advantage of using the same base across all measurements is not merely that it goes well with the digits we use, but it means different type of measurements work well together. A cubic meter works out to exactly a thousand liters, which when filled with water would weigh 1 metric tonne, which is 1 thousand kilograms. The pressure of 10 metres of water works out to 1 atmosphere, which is approximately 100,000 Pascal, which is 100,000 Newtons per square meter. At sea level the acceleration due to gravity is approximately 10 M/s so 1kg is roughly 10 newtons worth of weight. If you have a force of 1 Newton over 1 meter , you get 1 joule worth of energy, which is the energy drawn per second by 1 ampere of electric current at an electric potential of 1 volt.
Now, lets say you have a pool of water that is 10 feet deep and 10x20 yards by the sides. You want an electric engine operating at 230V to drive a pump that can empty the pool through a pipe that has a diameter of 3inches. The drain is at ground level. You don't want to leave it on unsupervised at night so you want it to take no more than 2 hours. How many amperes of current will your engine draw? What's the total amount of energy necessary to empty the pool? How much pressure does the pump have to handle?
I would STRONGLY suggest you convert to SI units before trying to solve that problem.
All in all, the metric system is optimized for scientific work where conversions between units happen more often, and knowing that 100 million micrograms is .1 kilograms is useful. But it doesn't work so well for common, human scale use.
I would disagree. People will adapt to any unit system they know. Really the proof of this is the system we use in america. It is quite possibly the worst collection of units I could think of, with there being NO consistency in conversions. While you say that the gram is too light, I doubt that people that use it think so. Mainly because they know the system. I know I would much rather use a system where the units make sense.
the metric system is optimized for scientific work where conversions between units happen more often
No it isn't. Scientific work almost always uses scientific notation with SI base units. Prefixes are often skipped entirely.
Prefix notation is most useful for technology trade and everyday usage.
and knowing that 100 million micrograms is .1 kilograms is useful. But it doesn't work so well for common, human scale use.
What a red herring. It works perfectly well in any case.
Micrograms might not be an everyday example, but looking at the nutritional information on food I can tell you e.g. the salt equivalent on your plate.
I live in the US, and I really, really wish we went to metric. The whole base 10 thing is cool, but metric is just elegant, because all of the units are related. For example, 1 liter of water always weighs 1 kilogram (yeah I know kilogram is a measure of mass). A cubic centimeter (cc) of water always weighs 1 gram. Tell me off the top of your head how much a cubic inch of water weighs, I'll wait for you to get out your calculator.
Celsius is not as arbitrary as Fahrenheit, 0 = freezing point of H2O, 100 = boiling point of H20. Do you know the boiling point of water in Fahrenheit without having to look it up?
...a single 24-hour clock for the entire world, located at the center of the Earth Wouldn't that be a bit difficult to read, what with all the molten lava and such?
I've abandoned my search for truth; now I'm just looking for some useful delusions.
In your original post, you use the sentence "Tells you where the power and money was when the GPS system was set up." to get in a free bit of US-bashing, as another poster said. The parent to which you replied attempted to explain why things to you using Objectivity, which you conveniently ignored.
As GP to this post stated, the GPS system was design, built, and paid for by the US. The US is still paying for this system. I suppose you can interpret that to mean that money and power were located in the US when the system was launched. It also means there was a hell of a lot of Smart and Reasonable as well. Tell me, can non-USians use the system? Indeed they can. Do they pay for it? Nope. Do I personally mind? Not a bit.
But you make it sound like GPS was some "Free Gift From God" that was wrenched away from whatever your favorite country happens to be. It wouldn't exist for anyone to use if it hadn't been built and paid for by someone. The US happened to do it. Big Fucking Deal if the Prime Meridian moved 100m. If you've got that much of an anti-US agenda, by all means, go about your business assuming the non-WGS94 standard. Just make sure you avoid anything that supports it and, by your logic, supports an unfair US takeover of the Prime Meridian. So that means no telecommunications, air or sea travel, commerce that wasn't produced/manufactured locally, etc.
Oh, GPS is incredibly fucking useful for modern life? Huh. How 'bout that. The Prime Meridian getting moved 100 meters doesn't seem like such a big deal in comparison now, does it?
Rival 1: Washington was a key competitor, but the US threw its weight behind Greenwich, taking it out of the race.
Any chance to bash the US, eh?
How's that bashing the US? All it says is that the Prime Meridian may well have been Washington had the US government not supported Greenwich. It's a fact, not a bash.
If I have nothing to hide, you have no reason to search me
right handed versus left handed traffic. solution best decided by vanuatu:
http://upload.wikimedia.org/wikipedia/en/9/9b/Vanuatu_driving.png
rail gauge. there's european and chinese, standard, but russia uses a broad gauge, which is a serious problem for economic development:
http://www.chinapost.com.tw/business/2008/01/11/138592/Beijing-to.htm
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
A clock that works thanks to a nuclear reaction ? Call me old fashioned (and it won't be the first time), but I will use my Galilean Pendulum, thank you.
Using the same base across all measurements is really convenient - parent is correct about that.
But GP is also correct in that it is super convenient for your measurement base to have many factors. A unit comprising 10 smaller units can be smoothly divided in half, but not in thirds or fourths. For that purpose, 12 is a much more useful number than 10. You guys are debating the orthogonal advantages of two different systems: both are correct.
So the ideal would be a base 12 metric system, with all units scaling by twelves and grosses, ideally paired with a base-12 arithmetic system.
Sadly, that's a pipe dream. The cultural inertia of base 10 is so strong we don't even think about it --- it makes the "strong" US attachment to imperial units look weak.
I stole this sig from someone cleverer than me.
No one would empty that pool with an electric engine operating at 230V. Clearly it would run on 120V.
That didn't take to long at all!
You need to count the time it takes for you to switch to a terminal session and type the command in.
All I want is a secure system where it's easy to do anything I want. Is that too much to ask ~~ Randall Munroe
All in all, the metric system is optimized for scientific work where conversions between units happen more often, and knowing that 100 million micrograms is .1 kilograms is useful. But it doesn't work so well for common, human scale use.
You know, I think you are right. I've been traveling around a bit and every place on the planet, I hear people say things like "Gosh I hate those weather reports! I can't tell if it is cold enough to wear a sweater!" and "It is so hard to estimate my height because the meter is so big and the centimeter is so small!" and "I hate grocery shopping because a kilo of apples is too much!"
The most common thing I hear people say, day-in and day-out is "I wish we had done what the USA did and used pounds, feet, inches, miles and degrees F!". I have never heard anyone say "Those Americans are idiots, aren't they?"
Sarcasm aside, using two systems is a royal pain in the ass. Even if there were some benefits to wide use of the non-SI units, the US has lost this battle. The rest of the world is not going to switch away from SI - the six billion plus people using SI are eventually going to make it economically impossible for the US to continue to try to maintain a separate bunch of weights and measures.
I think we lost this one. We would be best off going cold turkey and switching overnight sooner rather than later, but I suspect we will continue to drag along for another fifty years or so until someone finally drags us kicking and screaming into the nineteenth century.
I dimly remember before UK currency went metric (I was very small). The sense of joy when I could suddenly understand money! Wheee!
Eric Baird
No, I'm not going to do your homework for you again. Stop asking.
That's the case with a lot of the things discussed in the GP... they were developed one place, then independently developed somewhere else at a later time. But by then, there was already an installed base in the first place, and you couldn't switch to the newer standard, even if it was better, because it was too expensive to scrap your existing investment. Then there's the tendency to have vendor lockin for a lot of stuff. So those are some of the reasons for the great thing about standards (there are so many to choose from!).
What about the people in Antarctica, you insensitive clod!?!?!?
I think Pi/3 is better.
1.047 ...
If you inscribe a hexagon inside a circle, it's the difference in ratio between the curved and straight-line distances between two adjacent points, and as "one-point-somethingsmall", it has a nice fundamental look to it.
Nice and easy to visualise. You know that the perimeter of a circle is six-point-something times the radius, because the inscribed hexagon has six sides.
And it gets rid of those one-third bits when you're dealing with spheres.
Far as I can tell, the reason for using the 3.14 ... number doesn't seem to do with logic or geoemtry, it seems to be a hangover of the tools that Greek stonemasons used to use when making pillars. It's the ratio between the caliper-width of a pillar, and the length of a piece of string wrapped around the pillar.
But geometrically, it's not sensible to be comparing the length of the flat base of a semicircle against the curved sections of //two// semicircles. It's not comparing like with like. You either compare radius with perimeter, as the earlier poster said (~6.28....), or you compare diameter with semiperimeter (~1.57 ... ), or you compare radius against arc (~1.047 ... )
Pi itself is a pretty stupid number. It's the mathematical equivalent of the human appendix, or the QUERTY keyboard. IMO it's one of the most damning indictments of human civilisation that we're still using it.
I feel ill whenever I hear SETI guys talking about broadcasting PI as a way of contacting alien civilisations. Yeah, right, broadcast to the whole universe how dumb we are, why don't you ... :-Z
If I was an alien, and I picked up a transmission of "pi", it'd tell me that the species was arrogant, technologically advanced but mentally a bit retarded, and unable to understand deep relationships or alternative perspectives. It'd tell me that the species considered themselves mathematicians, but had some fundamental inability to see their own mental shortcomings. It'd be a species that wouldn't deal well with cultural conflicts, becuase they'd be sure that their own way was right, and they'd not be able to see the possibility of other points of view.
It'd be a species that you wouldn't ever want to have to deal with. So you'd warn everyone to stay away, and you'd draw up a contingency plan for eliminating the nasty species should they ever start building interstellar spaceships.
So if there are intelligent lifeforms similar to us nearby, with decent technology, we might be looking at a global extinction event as first contact
Thanks for that, SETI
Eric Baird
As for the meter being too long, well most people here in Sweden don't seem to have any trouble "just knowing" how long a meter is, and there's also the decimeter (0.1 m), centimeter (0.01 m) and millimeter (0.001 m).
You've put your finger exactly on the problem. According to the SI system, these extra units shouldn't exist - there should be just the metre and the millimetre, with nothing in between. But as the previous poster said, the metre is too long and the millimetre is too short so we end up having to invent extra units which fit the actual scales on which we work. Describing something as being 342mm long isn't visualisable when you start from just knowing what a mm is. You need to translate it into something else (e.g. cm) and then you can start picturing it.
The inch is a much more comfortable natural size to work with then either the metre or the millimetre, but the arithmetic is a bit harder if you're not used to it.
PAL and NTSC were designed for countries in which the mains frequencies were different.
PAL is 25 frames per second because it was designed to be viewed in a country in which domestic electric lights flickered at 50Hz.
US TV standards were based on a refresh rate of 30 frames per second (later 29.97), because the official US mains frequency was 60Hz.
Both systems were designed to minimise aliasing effects between the refresh rate of the TV screen, and the flicker of local domestic electric lighting.
Eric Baird
Well, Yes. The US generously built the GPS system to map the entire world, so that it could be used to target US planes and missiles at any point on the globe. It would have been a bit silly if the system only enabled the US military to bomb sites within the US.
This would have somewhat limited the system's military usefulness (for the US, at least).
GPS was opened up for worldwide civilian use, for free, so that foreign aerospace companies wouldn't launch their own competing system that enemy countries could then use to target sites within the US, and US targets abroad, without the US government having an "off switch" or control over the spoiler systems. Companies within the US have legal restrictions that prevent them from certain sorts of satellite or mapping activities that relate to US territory. Making GPS free for civilian use was supposed to eliminate the business model of any competing civilian geolocation satellite systems, including those outside US legal jurisdiction, because it's difficult to come up with a business model that competes with "free".
The EU is now finally putting up the Galileo system regardless (rollout commencing 2010), but throughout the project planning stages, the US has let it be known that it regards Galileo as an "unfriendly" system, and it's been made known that if there was ever any serious chance of hostilities breaking out between the US and another country, that seemed likely to result in the US being attacked, one of the first things that would be likely to happen would be the US shooting down the Galileo system's satellites.
So I think it's fair to say that the US has been quite keen for there not to be any other competing GPS-type system.
GPS is great, wonderful, marvellous, incredible. But let's not pretend that it was originally part of a great humanitarian plan, or that something like Galileo wouldn't have been launched years earlier if it wasn't for political considerations, Europe not wanting to antagonise the US, and European private industry not being able to create a business model for launching commercial geolocation satellites while GPS use was being given away for free, specifically to undercut them. Europeans have benefitted from free access to GPS for years (yippee!), but the price has been the lack of a system more closely tailored to local needs. In the end, we've decided that we really have to pay to put up our own system anyway.
In an ideal world, there'd be a reciprocal arrangement whereby American citizens would also be able to make use of Galileo if they wanted to, but I suppose there's a chance that the US Government might not want Galileo access generally available within their borders, and might take steps to prevent that happening.
Eric Baird
To be fair to GPS's accuracy, it was never intended to be a system that would allow locals to dial up locations that corresponded to their local street maps, or to help them find their parking places or the local restaurant. It's numbers don't have to agree with the "proper" latitude and longitude numbers for a site that appear on official local maps.
Its system was designed to produce a persistent numerical overlay that linked the position of a receiver with coordinates specified on US military satellite imagery. It doesn't matter for GPS that it puts Greenwich Observatory's nominal position "out" by 100 metres, as long as the US satellite imagery also offsets the observatory's nominal position by the same amount, so that if the US ever needs to aim a cruise missile down Greenwich's main telescope, that missile's going to get to the right place.
In that hypothetical, the missile wouldn't care that the observatory's nominal position doesn't agree with it's official position on official UK Ordanance Survey maps. GPS is designed to work with US military maps, calibrated to a convenient reference point in US territory rather than to Greenwich, UK. The US military has to have their own independent mapping system, because they can't afford to be reliant on foreign countries doing the job properly for them, and being 100% truthful about where their military installations are.
If you want to turn the dodgy GPS figures into "proper" survey numbers (eg, for archaeological reference work), you either use a different system, or you survey the place yourself, or you use an overlay mesh that converts GPS locations into "proper" locations. Assuming that Galileo comes online as planned, and they haven't buggered it up, and it hasn't been sabotaged technically or politically, there'll soon be an alternative consumer system anyway. What's important is that we keep the GPS coordinate for locations separate from other numerical descriptions of those locations, and don't mix up the different coordinate systems. Which is easy enough to do, I guess we just stick a "GPS" prefix on the front of a GPS location, "Gal" (or similar) on the front of a Galileo location, "OS" on the front of a UK Ordanance Survey location, or come up with some other handy set of abbreviations. As long as we all know that there are differences, and don't mix up the different sets of numbers (like Wikipedia coordinates and GPS coordinates) we should be okay.
Eric Baird
For a while, the US was seriously considering using the Washington Meridian as its "zero" reference for all US mapping. Similarly, at one point they were considering having a brand new unit of length, defined as the length of a pendulum that swung in exactly one second when dangled at sea level at latitude 45 degrees (which would have been similar to, but not quite the same as, the metre).
In the end they set aside the idea of having their own independent system, and went with what was already popular.
The reason why Greenwich Time was so popular wasn't especially political, it was just that Greenwich as a long-standing, reliable, well-funded, high-profile observatory that was practically on the Thames, really near to where all the international shipping came in to park to use the docks. An agreed time-base was critical for navigation, and Greenwich tried to provide one. In the 1830's they also instituted the Greenwich Time Ball", which was a visual signal that passing shipping could use to calibrate their clocks. Some places used cannons, but the speed of sound meant that if you were a way away, your timing would be off. Greenwich's light-signal was better, provided that you had your telescope pointed in the right direction at the right time.
Because it was near the docks, ships didn't have to worry about passing at exactly the right time - chances are, they'd be holed up there anyway. So "Greenwich Time" was a free, easy international timebase for shipping that let captains calculate longitude, lots of ship's captains carried Greenwich Time around with them to the rest of the world, and it was a natural reference for mapping.
It also didn't hurt when England standardised on Greenwich time nationally, so that in theory, you could get Greenwich Time at any English port.
By contrast, Washington Time wouldn't tie into to the same existing nautical map-base, there probably wasn't a huge amount of international shipping parked within view of the Washignton Monument, and since the US had trouble even insisting that US maps were drawn up with reference to the Washington Meridian and Washington time, they probably did the right thing by dropping the idea, and using the existing standard. It's easy to carry Greenwich Time around the whole UK and coastal Europe by boat, with very sensitive mechanical clocks, it wouldn't have been so easy to take Washington time to both US coasts via shipping. Things got easier with the railroads and telegraphs, but for US shippng to be redrawing all the existing sea-maps specifically for a new reference system that they didn't really need ... it probably wasn't a brilliant idea.
Eric Baird
simply state that stores 3 hourse before local midday and close 8 hours after (for the 9am-8pm hours).
All the stores already post their hours, because some close at 10pm local time, and other close at 2am local time. So just post in UTC. 14:00 - 04:00, instead of 6:00am to 10:00pm.
One pint of water is one pound. Eight pints in a gallon.
Done.
Celsius makes a lot more sense to me, 0 C = water freezes, 100 C = water boils (and it's "compatible" with the Kelvin scale). What was it fahrenheit was measured by? 32 F = water freezes, 100 F = body temperature, 212 F = water boils?
The boiling point of water is a really lousy datum for a temperature scale. Two problems, first it isn't well defined given a specified pressure, secondly atmospheric pressure depends on both altitude and weather condition.
FWIW, Fahrenheit is compatible with the Rankine scale. For any kind of calculation regarding temperature, one will need to use a look-up table anyway, so Kelvin doesn't have that much of an advantage over Rankine. If you want a rational temperature scale, use electron-volts.
A Shadeless room is a brighter room.
Not completley random, just completley arbitary and unrelated in any meaningful way.
72% of the world's shipping already depended on sea charts
With this kind of usage share, one may reasonably expect Internet Explorer to also stick around for another century and a quarter.
Know your pads. One time pad: good for cryptography. Two timing pad: where to take your mistress.
A pint is 568 ml and a pound is 453 grams.Water's different round your place??
Wanted : A Signature.
I'm sorry, you are wrong. According to the SI, the millimeter does not exist as a separate unit. It's just like the centimeter or the kilometer, a prefix to the unit of a meter. Using SI prefixes to SI units is SI accepted, so these extra "units" should and do exist.
No, you don't have the need to calculate how many times a small unit goes into a big one. Other people do. Also, why should I start with yet another conversion I can screw up?
Also, fractions of 10 are not very hard either. 4 is 2,5. 3 is 3,33 repeating. Imperial does not really have an advantage here, as you have to memorize the fractions for both.
Also, out of your head, how much does 7,5 gallon of water weigh in pounds and ounces? I can tell you the weight of 7,5 liter of water instantly. It's 7,5 kilogram.
You miss the point. The SI system originally called for prefixes which go up and down in factors of 10^3. Micro, milli, kilo, mega, etc. This was found to be unworkable, particularly because of the metre being a difficult size, and so centi was introduced. It is still a second class citizen though - we don't talk about centi-grams, centi-ohms, centi-litres etc. If the metre were a more useful size we wouldn't need centimetres either.
HTH
John
Actually, from what I've seen in countries that actually use SI/metric units (I'm not counting Britain, Canada and other "converts") centiliters, decimeters and other similar uses of prefixes are very common. I have a soda bottle next to my laptop right now that has "50 cl" printed on it.
/Mikael
Greylisting is to SMTP as NAT is to IPv4
Beercan in the fridge. It says 33 CL. Small water bottle: 30 CL. Recipies often talk about adding a deciliter of something.
In the defense of meters, if feet were a useful size we wouldn't need inches or fractions of inches. Don't drill-bits come in 1/16th inch increments in the States? If inches were a useful size, we wouldn't have miles. Whatever size you pick a unit length to be, there will always be a need for a different unit length. If set the meter to be as long as an inch or a foot and remove the centimeter from common use, we would still need a unit for, for example, Earth-Sun distances. So in the end it all boils down to which system is easier to do math with. And SI wins that game, in my opinion.
It's much more difficult to change existing infrastructures; when they exist for longer times than to create a new infrastructure.
Still, to create a full new network of 230V the costs would be enorm for supplier and users. All devices have to be adapted.
We had a few years ago the adaption of 220V to 230V because of our (over)usage of raw power and power drops. That even took it's toll for many...
It has happened before from POTS to fiber; so; maybe it should be tought about to create a new, secondary network; but; for which reason exactly?
A device at 230V which takes 10A will be 21A at 110V. Safety wise, 230V would be safer, because the load required would be less.
For me they are damn right, since they got their born right of taking their stand at it. This doesn't mean I approve all actions of the/a same government....
I don't even know we got a standard office here in Europe which brings the plentoria of filters back to managable states; next to that car parts which are so freaking expensive, for a rubber often got asked 20 euro, while I'm not that stupid to be able to accept the production proces of that rubber; really; costs 10 euro to produce, to even give them 50% profit.
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
Either I wasn't clear or you misread it. I was giving an example of the US supporting a non-US solution, since the AC seemed to think the US always wanted its own way. The "bash the US" comment was aimed at the AC.
The UK is supposed to be replacing all its "height and width" signs on UK bridges etc with metric distances, because of the number of foreign lorry drivers who don't know the exact height of their articulated lorry in feet and inches, and keep hitting things. In fact, low bridges in the UK keep getting hit by UK residents in large vehicles, because even =we= can't work out height conversions on the spot in imperial!
I have a happy memory of once seeing someone try to drive an empty double decker bus under a bridge that was about eight inches too low. The resulting explosion of glass was one of the prettiest things I've ever seen (sigh).
That bridge was always getting things stuck under it. Once I even saw an army tank transporter firmly wedged under it.
"Miles per gallon" still seems to be lingering in the UK, but IMO it'll have to go, if only for the fact that there's not a single international standard for how big a "gallon" is supposed to be. AFAIK, US land-miles are now supposed to be the same as UK land-miles (they used to be slightly different thanks to the "old" US inch being different to the "old" imperial inch), but US liquid gallons and UK liquid gallons are still significantly different - the US gallon is based on the old abandoned UK "wine gallon", of 128 fl oz, whereas the later "imperial" gallon used in the UK is based on the "ale gallon" of 160 fl.oz. The US and UK fluid ounces are also supposed to be slightly different. Pints, too. So presumably the same car can have different local MPG ratings in the US and UK. If someone published MPG ratings in the UK, they'll presumably be wrong for a reader in the US, and vice versa.
Eric Baird
Bigger pints! More beer! Yaaay!
I've never heard anyone complain about fizzy drinks or fruit juices being sold in the UK by the litre, or about cans of drink coming in 330ml cans. It's only when it comes to milk that people seem to get funny about it.
Some years back, UK supermarkets changed some of their packaging and started selling milk in litres and whole fractions of a litre, and I thought it was really neat. And then, once I'd gotten used to it, someone must have complained, and they went back to selling them in pint-equivalents. I was really pissed off about that.
Eric Baird
Either I wasn't clear or you misread it. I was giving an example of the US supporting a non-US solution, since the AC seemed to think the US always wanted its own way. The "bash the US" comment was aimed at the AC.
Right, fair enough, I misread it as you aiming the "bash the US" comment at the article the AC linked to. Sorry.
If I have nothing to hide, you have no reason to search me
But if you're saying that the choice allowed manufacturers to use the mains frequency as a timebase, and omit a load of timing circuitry from their TV sets, then that sounds like a much more convincing reason.
PS, while you're here, since you seem to know a bit about this - is it true that the US and UK tv standards defined different colour responses for screens and cameras, and defined different phospor "recipes"? I once read in a really ancient computer graphics textbook that because the phosphors were different, computer graphics people were advised that their animations' colours might look wrong if they showed their pieces abroad. I never really knew whether to believe that one or not (although there was a time when US imports shown on UK tv always seemed to make all the people look orangey).
Eric Baird