Australia completed this change in the 70’s very successfully without any of the problems you are claiming. Educating the public about the changeover and the new speeds is part of the process. Also, do you think that anyone from the UK who takes their car across to France or Ireland has trouble adapting to the speeds? All modern cars have km/h speeds indicated, even if only as a secondary scale.
Centimetres should never, ever be used in engineering. Millimetres are far more suitable for working with wood. They completely eliminate the need to work with any decimal points or fractions. When Australia converted to metric, the building industry very intelligently decided that mm is to be used exclusively and cm are not allowed.
Actually, in my experience, most sites do allow good passwords. I have a little over 200 sites stored in my password manager, and of those, about 90% of them use long randomly generated passwords with letters, numbers and symbols. About 5% are still long, but imposed some restriction on either length or the use of symbols and the remaining 5% are crap due to really bad password restrictions limiting lengths to below 12 characters or less.
The article said 600 MB/s, not "Mbps". There is a difference. The former is megabytes per second, the latter is megabits per second. And, yes, it does.
3840*2160 = 8294400 px/frame
Colour depth is 24 bits per pixel
And either 24, 25 or 30 frames per second, depening on whether it's native film rate, or adjusted for PAL or NTSC. In either case, the calculation is:
3840*2160 px/frame * 24 bit/px * 24 frame/s = 4,777,574,400 bits/s = 4.78 Gb/s or around 597.2 MB/s
The mass of such things has only been determined experimentally with a relatively significant margin of error. It's also not a definition that would lend itself to the development of practical realisations of the kilogram as what's called a transfer standard, nor a scale with which to test them.
It needs to be possible for weights to be produced, and then tested. The results from these tests would identify a given weight as being 1 kg plus or minus a measured error range. This then becomes a transfer standard, that can be used to calibrate other scales, and forms part of the traceability chain for certification. With a new definition, the current IPK would then become just another transfer standard along with all the other official copies.
I commented about this elsewhere in the thread, but basically, the density of water is dependent on pressure and temprature. Pressure is dependent on force and area. Force is dependent on mass and acceleration, which creates a cycilical definition. Also, the level of precision and accuracy that water can be measured is not high enough.
If that were ever found to be the case, then we could just redefine the second to something that is even more accurate than its current definition to resolve the problem. The new definition would define a new value that is within an acceptably small margin of error (probably on the order of a few femtoseconds or less), such that the new definition doesn't significantly alter the definition of any other units linked with it, at least within any measurable precision.
The density of water is dependent on temperature and pressure. Pressure is defined as a unit of force per unit area (Newtons per square metre). Force is subsequently defined in terms of mass times acceleration (1 N = 1 kg * 1 m/s^2). Congratulations, you have just created a definition of mass that is dependent on itself. Also, the ability to purify water and measure its volume to a high enough accuracy and precision is extremely difficult.
Wow, you fail. If the US had some miraculous metal that could maintain a very constant mass, with greater accuracy than the IPK, then such a thing could also be used for the kilogram. But you are wrong, and they don't. Any artifacts the US does use for mass calibration, which includes at least their official copy of the kilogram, are also subject to the same kind of fluctation in mass that the international prototype kilogram is for many of the same reasons, if not more because it's handled far more frequently than the IPK is.
That was the original definition, but it's not precise enough. It's extremely difficult to get water with an exact isotopic composition. VSMOW is used, but even that is not reliably reproducible to the necessary level of precision.
Also, the density of water is very much related to the temperature and air pressure. Pressure is measured as a unit of force per unit area. Typically, Newtons per squre metre (the Pascal unit). Force, is then in turn defined as a unit of mass times acceleration, with the Newton being 1 kg * 1 ms-2, which obviously results in a cyclically dependent definition, because it would be defined as 1 kg of pure water at a specific temperature and pressure measured in:
Pa = N/m^2 = kg/m*s^2
To get around this problem, you would need to define the Newton in terms of its relationship to other units, ultimately ending up linked to a fundamental constant of nature. The Watt balance approach is trying to do this, by linking the definition with the Ampere. That would reverse the relationship of the Ampere, which is currently defined in relation to the kilogram.
That would then gives a direct way to link those units with the kilogram, and there is no need to precisely measure 1 cubic decimetre of water. You just develop an extremely precise scale that can measure any test mass very precisely and accurately based on the new definition. The difficulty is actually putting that into practice and eliminating as much measurement error as possible. NIST and other laboratories around the world are trying. The problem is, the margin of error in the measurements are still higher than desired.
With a well managed, rapid changeover, you too would get used to the new system in no time. A lot of people over estimate the difficulty in switching because they don't understand how a well managed changeover works.
The best way to switch is to do it quickly. Eliminate as many non-metric units as possible. Get rulers, scales, and whatever else that measure exclusively in metric, and start actually using it.
The most basic things you could do in your own home are to set your kitchen and bathroom scales to metric, get rulers and/or tape measures that are labelled in mm-only. Learn your own height in cm. Learn the size of things around your home in metres (such as the height of a door, the length of your table, the distance from your couch to your TV, etc.) Get thermometers that are labelled in Celsius (or cover up any Fahrenheit labels) and use websites for weather forecast that let you set your preferences to Celsius and either km/h or m/s for wind speed. Find recipes that specify all ingredients primarily in grams or millilitres (A lot of UK recipes do this) and avoid recipes that specify measurements primarily in cups and spoons.
If you were to consciously make the decision to switch your own life to metric (which I would strongly recommend), and did so by removing any and all temptation to revert to the old system, then you would adjust in no time.
Many other people your age and older have done it in many other countries. There's nothing preventing you from doing it too, except your own willpower.
There are many reasons to convert that aren't simply because everyone else is.
The US is effectively in a state of operating with dual measurement systems, and that is costing your economy significantly. Various industries need to keep and maintain two different sets of tools with different measurements, many industries use a confusing mix of both units. e.g. The electronics industry is a big mess, with internationally acquired components being specified in metric, while PCB design and manufaction in the US is done in imperial. Internationally, everything is done in metric.
Your roads are designed in Ramsden's chain (100 US survey feet), with long distance measurements being done with GPS in metres and then converted.
NASA has fucked up so many times, by living in a hybrid world of both systems, rather than actually properly committing to change.
Your continued use of non-metric units in the health industry risks lives due to doing calculations with the wrong units. e.g. calculating how much medication to prescribe and accidentally using lbs instead of kg. Or using non-standard symbols for metric units, such as MG for milligram (which should be mg) and MCG for microgram,which should be ug (slashdot won't let me enter the proper micro sign) More info on these problems here. http://themetricmaven.com/?p=67
Ultimately, this hybrid system costs your economy more because you cannot effectively work the the same set of tools that everyone else can. It affects your education system because kids must learn two systems, and yet when learning metric, have very little reinforcement in the home due to many consumer products being labelled in USC or both systems, with comparitively few labelled in exclusively metric. I think wine bottles are one of the few products that aren't labelled in both systems.
Things like road signs are also up to the individual states, and given that most of them are bankrupt, it would be hard to convince them to add that to their budget.
"The Congress shall have Power To... fix the Standard of Weights and Measures" - US Constitution.
That gives the federal government the power to state what is and is not a legal unit of measure. Make miles, feet and yards illegal for trade, and set a proper deadline for conversion, and the states will have to comply. As a bonus, it would also create thousands of jobs around the country, with jobs including manufacturing road signs, printing temporary replacement signs to be used for a rapid changeover, and employing workers to actually go out and install the new signs.
With proper planning and management, the whole thing could be organised and completed within 1 to 2 years, with an effective rapid changeover date around the end of that period, and with ongoing maintenance taking care of the removal of old signs with new permanent signs.
The mandate wasn't strong enough. NASA's Constellation project was being developed in USC units, up until it got cancelled in 2009. They had been granted an exception to the metric requirement due to short sighted perceived costs for the changeover, and yet still ended up going way over budget, which ultimately led to its cancellation. There should have been absolutely no exception granted for any new projects. Now, though, new companies like SpaceX are doing their entire development in metric, and the ISS is to be decommissioned in a few years, so hopefully NASA won't have any real excuse for continuing to use USC measurements for any new developments.
No, only in America is PCB design done in mils. Every other country uses mm. More information about the problems that has caused and continues to cause here. http://themetricmaven.com/?p=454
You just perfectly illustrated the problem with conversion strategies that involve keeping both units around. Even though you have the superior metric measurements available, you stick with what you're comfortable with, despite admitting that it also causes many problems with calculations.
If you actually did decide to switch to metric and not use imperial for any measurements, then you would very quickly get used to the mm-markings on a tape measure. It's also significantly easier if you get yourself a tape measure that is marked in mm, not cm. That is, one labelled 10, 20, 30, , 100, , and not 1, 2, 3, , 10,
Your work would speed up significantly because:
1. Using mm, all measurements and calculations would be done in whole numbers. You would never again have to do calculations with fractions, like 7 5/8.
2. Millimetre precision is sufficient for wood working, you very rarely need to use decmal fractions of a millimetre.
3. You would not need to memorise complicated fraction to decimal conversions, and vice versa.e.g. You wouldn't need to know that 0.4375 is 7/16ths or work out that 0.90625 is 29/32.
4. The kerf of metric circular saw blades are typically specified in mm to at most 1 decimal place. e.g. 1.5 or 2.0 mm. In imperial, that is usually specified as a decimal fraction of an inch to 3 decimal places. When you want to cut a piece of wood multiple times, accounting for this lost length is much easier than trying to do the same in inches. In metric, you can measure and mark multiple points to cut, precisely accounting for the kerf of the blade, and then cut all of them in one go. In inches. it's extremely difficult to measure, for example, 0.078" (a real value I just looked up). That particular blade is most likely exactly 2.0mm, as 2mm in inches is 0.0787 inches. Instead, you would have to cut, measure the next bit, cut again, and repeat.
There are probably more benefits too that I've missed. All of these benefits would more than make up for any lost time from trying to read a metric tape measure, which you would get used to very quickly, after which you would wonder why you didn't switch earlier.
When I see a distance of a multiple of 60 one can quickly determine how many hours it will take to get there when driving.:-)
In km, when you see a distance that is a multiple of 100, you can also very quickly determine how many hours it will take, at least on a highway, freeway or country road with limited traffic, when you assume an average speed of 100 km/h.
Also, it is much easier to instantly recognise a multiple of 100 than it is to recognise a multiple of 60, and also much easier to divide by 100 than by 60.
e.g. How many hours would it take you to drive each of these distances at 60 mph (assume distances stated in miles)?
a) 1020 b) 880 c) 900 d) 440 e) 1200
Now assume those are distances in km, repeat the same for driving at 100 km/h. The answers are much easier in km/h, because you simply divide by 100 and round to the nearest hour or half-hour.
There is no reason BOTH systems couldn't be kept on the signage.
Don't duel with dual. That was the motto adopted by the Australian building industry when they did the conversion, and for very good reason. Conversion strategies that involve using both units together consistently and continually fail to work. I challenge you to find a single, completely successful conversion program anywhere in the world that has succeeded by using and maintaining dual units. You won't find one.
The most successful conversion strategies are those that transitioned relatively quickly, where the old units were completely removed when the new units were put into effect. Pat Naughtin has written significantly about this effect, having been involved in the building industry and subsequently being involved with metrication processes around the world over the last 40 or so years. Read about it all on his website http://metricationmatters.com./
So, yes, there is a huge reason to not have a transition strategy that publishes both km and miles on speed and distance signs simultaneously. It won't work and will only serve to slow the transition process. If you simply specify a date, or at least a very short period of a few days, in which all signs will be changed over from miles to km, then the changeover will be much more successful. There are strategies to do this very quickly, if it is well planned. Australia did it, and the US could do it too.
The modern strategy would likely involve stick on replacement labels that go on to the existing signage, and the gradual replacement with more permanent fixtures as needed for general maintenance. Other strategies involve deploying new signage that is covered up until the changeover date, then subsequently covering and removing old signage. Australia did the latter over 40 years ago very successfully.
For weather, the scale is arbitrary and there is no technical benefit to having Fahrenheit over Celsius, or vice versa. People like myself who grew up with Celsius find Fahrenheight to be crazy and difficult to work with. People like yourself find the opposite.
However, having a temperature scale which, at one end, roughly approximates the core body temperature of a human, and at the other, being the coldest attainable temperature of ice water and salt mixture really has no benefit whatsoever. I've heard the argument about F being "more precise" than C because the magnitude of 1 F in nearly half that of 1 C. But it's bogus for several reasons.
1. It completely ignores how well the human body senses temperature.
We can roughly feel a change in temperature of about 1 C, and so for weather, having a scale more precise than that isn't really that useful. But even so, many modern digital thermostats support increments of 0.1 C anyway, which is more than enough precision.
2. It ignores how weather reports determine and report temperature
The temperature can change by several degrees between where you are and where the weather station recorded or estimated the temperature. Weather reports usually give relatively large temperature ranges for a given period, usually a day, or when stating only a single value, they state an approximate extreme for each region.
3. The "degrees of frost" measurement sometimes used in the US is based on the concept of degrees below freezing point of water, 32 F. That is a completely unnecessary concept when using Celsius because the freezing point is simply 0.
There are many applications in which the relationship to water is useful. Cooking, for one. Water is used a lot and having the temperature at which you cook things relate to water is extremely useful. If you want something cooked at 100C, then putting it in boiling water is fine. Other times, if you want something at, say 80 or 90 C, then you know that if it starts to boil, it's too hot. On the opposite end of the spectrum, you know you don't want things in your fridge to be frozen, so you want to ensure that it doesn't go below zero.
As a convenience, the temperature at which people can stand to touch relatively comfortably is around about half way up the scale, somewhere around 50C, give or take a few degrees. Hotter than that starts to get really uncomfortable and over 60C starts to burn quite quickly.
Another clear advantage is that if the entire world was using a single, common temperature scale for everyday use, regardless of which that was, it would mean far less need for conversion when communicating internationally. As an Australian, it is really annoying when searching for various things in English, only to find that so many sources are aimed at Americans with any stated temperatures published in Fahrenheit, which I then need to convert. Sometimes, it's not even clear what scale that's being used and I have to figure it out based on other information. Conversely, if an American finds some temperature they need to know published in Celsius, they would also likely want to convert it too, which annoying and time consuming.
As an example, looking up information about how to temper chocolate. A lot of the information is published with values in F. You need to know 3 separate temperatures for the process, and having to convert them to C and remember the new values is very time consuming and confusing.
In everyday applications, it does absolutely give a very useful approximation that is good enough. For cooking with ingredients that are specified in mL, it's often possible to simply put your mixing bowl on a scale and pour them in. The 1 g/mL approximation is close enough, and will probably still get you closer than if you tried to measure the ingredient volumetrically with typical kitchen jugs or measuring cups.
For large scale applications, such as building something that contains a lot of water (e.g. a large aquarium), determining the volume of the aquarium in cubic metres tells you how heavy all that water is going to be to a near enough approximation, which then lets you calculate how thick you need to make the glass viewing window to support it all, or how strong you need to make your building foundations. For such applications, an order of magnitude estimate in tonnes is enough it won't matter if you're out by even a few hundred kg, as you'd likely want to be able to support several tonnes over your estimate anyway.
No, 16 US fl oz is 473 mL, but 16 oz or 1 lbs is 453.5g. They are not the same.
16 UK fl oz of water, however, is equal to 16 oz at 62 deg F and 1 atm of pressure. This is based on the definition of the Imperial gallon as 10 lbs of water at that temperature and pressure, and there being 160 fluid ounces in an Imperial gallon, as opposed to the 128 fl oz in a US gallon.
Also, the Imperial and USC ounces are not different because the reference temperatures are different. They are different because the definitions of the gallon is different. The US gallon is exactly 231 cubic inches.
Easy unit conversions is not the only benefit of the metric system. The ability to work entirely, or almost entirely, with whole numbers and only a single unit for each measurement, regardless of your application, is another huge benefit. It makes calculations significantly easier than working multiple units and fractions.
In construction and most other engineering, working entirely with mm allows you to use whole numbers for everything, as you usually never want more than mm level precision for such projects. You can use a single unit for all measurements in a plan. For a house, everyone from the architect to the brick layer to the carpenter and carpet layer and whoever else do everything exclusively in mm, and rarely, if ever, use any decimal places for anything and absolutely never use fractions.
When working with feet and inches, you often have 2 separate units - feet and inches, sometimes with an added fraction - all mixed into a plan. Some people would work just with inches, such as those tradesman working on the small scale stuff, whereas the overall floor plan is done predominately in feet. It's all just a confusing mess.
Don't forget that the feet used in the construction of roads, where miles are relevant distances, are ever so slightly different from ordinary feet. Road construction in the US is done in chains of 100 US survey feet, which for long distances, are measured with GPS in metres before being converted for planning.
Slashdot Mirror
Australia completed this change in the 70’s very successfully without any of the problems you are claiming. Educating the public about the changeover and the new speeds is part of the process. Also, do you think that anyone from the UK who takes their car across to France or Ireland has trouble adapting to the speeds? All modern cars have km/h speeds indicated, even if only as a secondary scale.
Centimetres should never, ever be used in engineering. Millimetres are far more suitable for working with wood. They completely eliminate the need to work with any decimal points or fractions. When Australia converted to metric, the building industry very intelligently decided that mm is to be used exclusively and cm are not allowed.
Actually, in my experience, most sites do allow good passwords. I have a little over 200 sites stored in my password manager, and of those, about 90% of them use long randomly generated passwords with letters, numbers and symbols. About 5% are still long, but imposed some restriction on either length or the use of symbols and the remaining 5% are crap due to really bad password restrictions limiting lengths to below 12 characters or less.
That's U+002D HYPHEN-MINUS, which is in ASCII. But U+2212 MINUS SIGN, assuming that's what he tried to use, is not in ASCII.
He was presumably talking about the degrees symbol (U+00B0).
The article said 600 MB/s, not "Mbps". There is a difference. The former is megabytes per second, the latter is megabits per second. And, yes, it does.
3840*2160 = 8294400 px/frame
Colour depth is 24 bits per pixel
And either 24, 25 or 30 frames per second, depening on whether it's native film rate, or adjusted for PAL or NTSC. In either case, the calculation is:
3840*2160 px/frame * 24 bit/px * 24 frame/s = 4,777,574,400 bits/s = 4.78 Gb/s or around 597.2 MB/s
It's obviously more for the higher frame rates.
The mass of such things has only been determined experimentally with a relatively significant margin of error. It's also not a definition that would lend itself to the development of practical realisations of the kilogram as what's called a transfer standard, nor a scale with which to test them.
It needs to be possible for weights to be produced, and then tested. The results from these tests would identify a given weight as being 1 kg plus or minus a measured error range. This then becomes a transfer standard, that can be used to calibrate other scales, and forms part of the traceability chain for certification. With a new definition, the current IPK would then become just another transfer standard along with all the other official copies.
I commented about this elsewhere in the thread, but basically, the density of water is dependent on pressure and temprature. Pressure is dependent on force and area. Force is dependent on mass and acceleration, which creates a cycilical definition. Also, the level of precision and accuracy that water can be measured is not high enough.
If that were ever found to be the case, then we could just redefine the second to something that is even more accurate than its current definition to resolve the problem. The new definition would define a new value that is within an acceptably small margin of error (probably on the order of a few femtoseconds or less), such that the new definition doesn't significantly alter the definition of any other units linked with it, at least within any measurable precision.
The density of water is dependent on temperature and pressure. Pressure is defined as a unit of force per unit area (Newtons per square metre). Force is subsequently defined in terms of mass times acceleration (1 N = 1 kg * 1 m/s^2). Congratulations, you have just created a definition of mass that is dependent on itself. Also, the ability to purify water and measure its volume to a high enough accuracy and precision is extremely difficult.
Wow, you fail. If the US had some miraculous metal that could maintain a very constant mass, with greater accuracy than the IPK, then such a thing could also be used for the kilogram. But you are wrong, and they don't. Any artifacts the US does use for mass calibration, which includes at least their official copy of the kilogram, are also subject to the same kind of fluctation in mass that the international prototype kilogram is for many of the same reasons, if not more because it's handled far more frequently than the IPK is.
That was the original definition, but it's not precise enough. It's extremely difficult to get water with an exact isotopic composition. VSMOW is used, but even that is not reliably reproducible to the necessary level of precision.
http://en.wikipedia.org/wiki/Vienna_Standard_Mean_Ocean_Water
Also, the density of water is very much related to the temperature and air pressure. Pressure is measured as a unit of force per unit area. Typically, Newtons per squre metre (the Pascal unit). Force, is then in turn defined as a unit of mass times acceleration, with the Newton being 1 kg * 1 ms-2, which obviously results in a cyclically dependent definition, because it would be defined as 1 kg of pure water at a specific temperature and pressure measured in:
Pa = N/m^2 = kg/m*s^2
To get around this problem, you would need to define the Newton in terms of its relationship to other units, ultimately ending up linked to a fundamental constant of nature. The Watt balance approach is trying to do this, by linking the definition with the Ampere. That would reverse the relationship of the Ampere, which is currently defined in relation to the kilogram.
That would then gives a direct way to link those units with the kilogram, and there is no need to precisely measure 1 cubic decimetre of water. You just develop an extremely precise scale that can measure any test mass very precisely and accurately based on the new definition. The difficulty is actually putting that into practice and eliminating as much measurement error as possible. NIST and other laboratories around the world are trying. The problem is, the margin of error in the measurements are still higher than desired.
With a well managed, rapid changeover, you too would get used to the new system in no time. A lot of people over estimate the difficulty in switching because they don't understand how a well managed changeover works.
The best way to switch is to do it quickly. Eliminate as many non-metric units as possible. Get rulers, scales, and whatever else that measure exclusively in metric, and start actually using it.
The most basic things you could do in your own home are to set your kitchen and bathroom scales to metric, get rulers and/or tape measures that are labelled in mm-only. Learn your own height in cm. Learn the size of things around your home in metres (such as the height of a door, the length of your table, the distance from your couch to your TV, etc.) Get thermometers that are labelled in Celsius (or cover up any Fahrenheit labels) and use websites for weather forecast that let you set your preferences to Celsius and either km/h or m/s for wind speed. Find recipes that specify all ingredients primarily in grams or millilitres (A lot of UK recipes do this) and avoid recipes that specify measurements primarily in cups and spoons.
If you were to consciously make the decision to switch your own life to metric (which I would strongly recommend), and did so by removing any and all temptation to revert to the old system, then you would adjust in no time.
Many other people your age and older have done it in many other countries. There's nothing preventing you from doing it too, except your own willpower.
There are many reasons to convert that aren't simply because everyone else is.
The US is effectively in a state of operating with dual measurement systems, and that is costing your economy significantly. Various industries need to keep and maintain two different sets of tools with different measurements, many industries use a confusing mix of both units. e.g. The electronics industry is a big mess, with internationally acquired components being specified in metric, while PCB design and manufaction in the US is done in imperial. Internationally, everything is done in metric.
Your roads are designed in Ramsden's chain (100 US survey feet), with long distance measurements being done with GPS in metres and then converted.
NASA has fucked up so many times, by living in a hybrid world of both systems, rather than actually properly committing to change.
Your continued use of non-metric units in the health industry risks lives due to doing calculations with the wrong units. e.g. calculating how much medication to prescribe and accidentally using lbs instead of kg. Or using non-standard symbols for metric units, such as MG for milligram (which should be mg) and MCG for microgram,which should be ug (slashdot won't let me enter the proper micro sign) More info on these problems here. http://themetricmaven.com/?p=67
Ultimately, this hybrid system costs your economy more because you cannot effectively work the the same set of tools that everyone else can. It affects your education system because kids must learn two systems, and yet when learning metric, have very little reinforcement in the home due to many consumer products being labelled in USC or both systems, with comparitively few labelled in exclusively metric. I think wine bottles are one of the few products that aren't labelled in both systems.
Things like road signs are also up to the individual states, and given that most of them are bankrupt, it would be hard to convince them to add that to their budget.
"The Congress shall have Power To ... fix the Standard of Weights and Measures" - US Constitution.
That gives the federal government the power to state what is and is not a legal unit of measure. Make miles, feet and yards illegal for trade, and set a proper deadline for conversion, and the states will have to comply. As a bonus, it would also create thousands of jobs around the country, with jobs including manufacturing road signs, printing temporary replacement signs to be used for a rapid changeover, and employing workers to actually go out and install the new signs.
With proper planning and management, the whole thing could be organised and completed within 1 to 2 years, with an effective rapid changeover date around the end of that period, and with ongoing maintenance taking care of the removal of old signs with new permanent signs.
The mandate wasn't strong enough. NASA's Constellation project was being developed in USC units, up until it got cancelled in 2009. They had been granted an exception to the metric requirement due to short sighted perceived costs for the changeover, and yet still ended up going way over budget, which ultimately led to its cancellation. There should have been absolutely no exception granted for any new projects. Now, though, new companies like SpaceX are doing their entire development in metric, and the ISS is to be decommissioned in a few years, so hopefully NASA won't have any real excuse for continuing to use USC measurements for any new developments.
No, only in America is PCB design done in mils. Every other country uses mm. More information about the problems that has caused and continues to cause here. http://themetricmaven.com/?p=454
You just perfectly illustrated the problem with conversion strategies that involve keeping both units around. Even though you have the superior metric measurements available, you stick with what you're comfortable with, despite admitting that it also causes many problems with calculations.
If you actually did decide to switch to metric and not use imperial for any measurements, then you would very quickly get used to the mm-markings on a tape measure. It's also significantly easier if you get yourself a tape measure that is marked in mm, not cm. That is, one labelled 10, 20, 30, , 100, , and not 1, 2, 3, , 10,
Your work would speed up significantly because:
1. Using mm, all measurements and calculations would be done in whole numbers. You would never again have to do calculations with fractions, like 7 5/8.
2. Millimetre precision is sufficient for wood working, you very rarely need to use decmal fractions of a millimetre.
3. You would not need to memorise complicated fraction to decimal conversions, and vice versa.e.g. You wouldn't need to know that 0.4375 is 7/16ths or work out that 0.90625 is 29/32.
4. The kerf of metric circular saw blades are typically specified in mm to at most 1 decimal place. e.g. 1.5 or 2.0 mm. In imperial, that is usually specified as a decimal fraction of an inch to 3 decimal places. When you want to cut a piece of wood multiple times, accounting for this lost length is much easier than trying to do the same in inches. In metric, you can measure and mark multiple points to cut, precisely accounting for the kerf of the blade, and then cut all of them in one go. In inches. it's extremely difficult to measure, for example, 0.078" (a real value I just looked up). That particular blade is most likely exactly 2.0mm, as 2mm in inches is 0.0787 inches. Instead, you would have to cut, measure the next bit, cut again, and repeat.
There are probably more benefits too that I've missed. All of these benefits would more than make up for any lost time from trying to read a metric tape measure, which you would get used to very quickly, after which you would wonder why you didn't switch earlier.
When I see a distance of a multiple of 60 one can quickly determine how many hours it will take to get there when driving. :-)
In km, when you see a distance that is a multiple of 100, you can also very quickly determine how many hours it will take, at least on a highway, freeway or country road with limited traffic, when you assume an average speed of 100 km/h.
Also, it is much easier to instantly recognise a multiple of 100 than it is to recognise a multiple of 60, and also much easier to divide by 100 than by 60.
e.g. How many hours would it take you to drive each of these distances at 60 mph (assume distances stated in miles)?
a) 1020
b) 880
c) 900
d) 440
e) 1200
Now assume those are distances in km, repeat the same for driving at 100 km/h. The answers are much easier in km/h, because you simply divide by 100 and round to the nearest hour or half-hour.
There is no reason BOTH systems couldn't be kept on the signage.
Don't duel with dual. That was the motto adopted by the Australian building industry when they did the conversion, and for very good reason. Conversion strategies that involve using both units together consistently and continually fail to work. I challenge you to find a single, completely successful conversion program anywhere in the world that has succeeded by using and maintaining dual units. You won't find one.
The most successful conversion strategies are those that transitioned relatively quickly, where the old units were completely removed when the new units were put into effect. Pat Naughtin has written significantly about this effect, having been involved in the building industry and subsequently being involved with metrication processes around the world over the last 40 or so years. Read about it all on his website http://metricationmatters.com./
So, yes, there is a huge reason to not have a transition strategy that publishes both km and miles on speed and distance signs simultaneously. It won't work and will only serve to slow the transition process. If you simply specify a date, or at least a very short period of a few days, in which all signs will be changed over from miles to km, then the changeover will be much more successful. There are strategies to do this very quickly, if it is well planned. Australia did it, and the US could do it too.
The modern strategy would likely involve stick on replacement labels that go on to the existing signage, and the gradual replacement with more permanent fixtures as needed for general maintenance. Other strategies involve deploying new signage that is covered up until the changeover date, then subsequently covering and removing old signage. Australia did the latter over 40 years ago very successfully.
For weather, the scale is arbitrary and there is no technical benefit to having Fahrenheit over Celsius, or vice versa. People like myself who grew up with Celsius find Fahrenheight to be crazy and difficult to work with. People like yourself find the opposite.
However, having a temperature scale which, at one end, roughly approximates the core body temperature of a human, and at the other, being the coldest attainable temperature of ice water and salt mixture really has no benefit whatsoever. I've heard the argument about F being "more precise" than C because the magnitude of 1 F in nearly half that of 1 C. But it's bogus for several reasons.
1. It completely ignores how well the human body senses temperature.
We can roughly feel a change in temperature of about 1 C, and so for weather, having a scale more precise than that isn't really that useful. But even so, many modern digital thermostats support increments of 0.1 C anyway, which is more than enough precision.
2. It ignores how weather reports determine and report temperature
The temperature can change by several degrees between where you are and where the weather station recorded or estimated the temperature. Weather reports usually give relatively large temperature ranges for a given period, usually a day, or when stating only a single value, they state an approximate extreme for each region.
3. The "degrees of frost" measurement sometimes used in the US is based on the concept of degrees below freezing point of water, 32 F. That is a completely unnecessary concept when using Celsius because the freezing point is simply 0.
There are many applications in which the relationship to water is useful. Cooking, for one. Water is used a lot and having the temperature at which you cook things relate to water is extremely useful. If you want something cooked at 100C, then putting it in boiling water is fine. Other times, if you want something at, say 80 or 90 C, then you know that if it starts to boil, it's too hot. On the opposite end of the spectrum, you know you don't want things in your fridge to be frozen, so you want to ensure that it doesn't go below zero.
As a convenience, the temperature at which people can stand to touch relatively comfortably is around about half way up the scale, somewhere around 50C, give or take a few degrees. Hotter than that starts to get really uncomfortable and over 60C starts to burn quite quickly.
Another clear advantage is that if the entire world was using a single, common temperature scale for everyday use, regardless of which that was, it would mean far less need for conversion when communicating internationally. As an Australian, it is really annoying when searching for various things in English, only to find that so many sources are aimed at Americans with any stated temperatures published in Fahrenheit, which I then need to convert. Sometimes, it's not even clear what scale that's being used and I have to figure it out based on other information. Conversely, if an American finds some temperature they need to know published in Celsius, they would also likely want to convert it too, which annoying and time consuming.
As an example, looking up information about how to temper chocolate. A lot of the information is published with values in F. You need to know 3 separate temperatures for the process, and having to convert them to C and remember the new values is very time consuming and confusing.
Just to add to my comment, 100 cubic metres of sea water weighs about 103 tonnes, which is not far off from an approximation of 1 t/m^3.
In everyday applications, it does absolutely give a very useful approximation that is good enough. For cooking with ingredients that are specified in mL, it's often possible to simply put your mixing bowl on a scale and pour them in. The 1 g/mL approximation is close enough, and will probably still get you closer than if you tried to measure the ingredient volumetrically with typical kitchen jugs or measuring cups.
For large scale applications, such as building something that contains a lot of water (e.g. a large aquarium), determining the volume of the aquarium in cubic metres tells you how heavy all that water is going to be to a near enough approximation, which then lets you calculate how thick you need to make the glass viewing window to support it all, or how strong you need to make your building foundations. For such applications, an order of magnitude estimate in tonnes is enough it won't matter if you're out by even a few hundred kg, as you'd likely want to be able to support several tonnes over your estimate anyway.
No, 16 US fl oz is 473 mL, but 16 oz or 1 lbs is 453.5g. They are not the same.
16 UK fl oz of water, however, is equal to 16 oz at 62 deg F and 1 atm of pressure. This is based on the definition of the Imperial gallon as 10 lbs of water at that temperature and pressure, and there being 160 fluid ounces in an Imperial gallon, as opposed to the 128 fl oz in a US gallon.
Also, the Imperial and USC ounces are not different because the reference temperatures are different. They are different because the definitions of the gallon is different. The US gallon is exactly 231 cubic inches.
Easy unit conversions is not the only benefit of the metric system. The ability to work entirely, or almost entirely, with whole numbers and only a single unit for each measurement, regardless of your application, is another huge benefit. It makes calculations significantly easier than working multiple units and fractions.
In construction and most other engineering, working entirely with mm allows you to use whole numbers for everything, as you usually never want more than mm level precision for such projects. You can use a single unit for all measurements in a plan. For a house, everyone from the architect to the brick layer to the carpenter and carpet layer and whoever else do everything exclusively in mm, and rarely, if ever, use any decimal places for anything and absolutely never use fractions.
When working with feet and inches, you often have 2 separate units - feet and inches, sometimes with an added fraction - all mixed into a plan. Some people would work just with inches, such as those tradesman working on the small scale stuff, whereas the overall floor plan is done predominately in feet. It's all just a confusing mess.
Don't forget that the feet used in the construction of roads, where miles are relevant distances, are ever so slightly different from ordinary feet. Road construction in the US is done in chains of 100 US survey feet, which for long distances, are measured with GPS in metres before being converted for planning.