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NASA Will Go Metric On the Moon
An anonymous reader writes "Space.com is reporting that NASA has decided to use the metric system for its new lunar missions. NASA hopes that metrication will allow easier international participation and safer missions. The loss of the Mars Climate Orbiter was blamed on an error converting between English units and metric units. 'When we made the announcement at the meeting, the reps for the other space agencies all gave a little cheer,' said a NASA official."
Now if only American car companies will budge that extra 17/32" and finish going metric rather than forcing me to have 2 sets of tools for one car. Then I can "Compare Prices on Physics and Engineering" here at /.
This is a necessary, but difficult transition. Yes, difficult. Maybe it's pretty easy for the programmers, but for the mechanical guys out there (like myself), this introduces a huge relearning phase. Say, for example, I need some sheet metal to function as a structural piece. I can be pretty confident that my initial guess will be pretty close to the final thickness value if specified in imperial units. I also know what's typically readily available from suppliers (eg: 1/4" is far more common than 15/64"). Not only must I do a conversion from my ingrained inch units into "foreign" metric, but I must also look up which sizes are common.
With time, I would be just as good with metric as with imperial units. And I want to change to metric for its obvious advantages. It's just that my design confidence and productivity would falter through the transition. I'm quite sure I'm not alone on this.
IWARS.
People, in general, disappoint me. Politicians even more so.
There's nothing inherently inaccurate about the measurement system itself. You can measure down to the millionth of an inch if you want. If a contractor is going to be loose with their measurements, they could just as easily say "Eh, that's about two meters" as "Eh, that's about seven feet". You can't make people measure down the the millimeter just because it's available on their measuring tape.
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You use 3 significant figures in the imperial system when you say 7'11". Why do you feel you have to use 5 significant figures in the metric system? 2.13 m is good enough. It's not that hard really.
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Using the metric or imperial system would not matter one bit if all you're measuring is distance or volume. But as soon as you start converting distance into volume (quick question: how many cubic inches in a pint?), or thrust into velocity (quick: you apply a one-pound force to a one-pound object for one second. What's the resulting speed, measured in mph?), or torque into power, or energy into force or power, the beauty of the SI (metric) system really stands out. In the imperial system, the only way to get these calculations right is to insert all sorts of wacky numbers. Which you need to remember with potentially infinite precision.
Try this beauty: 1 Nm (Newton-meter) equals 1 J (Joule) equals 1 Ws (Watt-second). In the imperial system you'd have to insert all sorts of wacky numbers to go from pount-feet to calories to, strangely enough, Watt-seconds again. (Electricity, even in the US, is always measured in metric.)
Or more practical: Ever tried to convert the torque that your car engine delivers (measured in pound-feet) at a certain rpm (rounds per minute) to the horsepower (hp) that it delivers? In SI, it's a simple multiplication: Power (measured in W, or more commonly kW) = 2 * pi * torque (measured in Nm) * rotation speed (measured in 1/s). No wacky, imprecise numbers. Just 2 * pi due to the rotation and that's it.
The SI system and all the calculations you do with them are completely void of wacky numbers, with only a few exceptions:
- 2 times pi for anything that involves rotation.
- Natures constants like c (lightspeed), g (gravitational accelleration), e (elementry electric charge) and a few others, about half an A4 page full of them.
- Natural properties (like density) of materials that you use.
Since NASA does *a lot* of these calculations (how much force do you need to accelerate/decelerate the lunar lander, what's the effect of gravity?) I can understand why they switch to metric.
Yeah, right, so that would make it 1000 days in a year? And PI==10.0, I guess. The problem with imperial unit apologists is that they make such unreasonable arguments to try to justify an unreasonable system.
Now, let's get this straight, write it down carefully: the International System unit of time is the second. Minutes, hours, days, weeks, and months are ***NOT*** metric units
We have such weird units of time partly because neither the lunar month nor the solar day are exact divisors of the year and partly because of an old tradition on dividing the day. But, no matter how hours and minutes are counted, these are not part of the International System. You may buy eggs and beer cans by the dozen, but a kilogram is still a thousand grams.
You do realize, of course, that using metric units in no way stops you from using fractions rather than decimal whenever it is convenient?
You may use 3/4 cups of something; I'll use 1 1/2 dl. And one pint is a fairly good size for a beer, but then, so is 40cl, the normal size in Sweden. But of course we don't call it "40cl"; it's a "large beer".
If I estimate people's height, I'll just estimate to the nearest 5cm. That is a pretty convenient scale; fine enough to get close, and rough enough for me to have a good chance of being right.
Pretty much none of your arguments have anything to do with the units used, but with how you use them - and you can do it equally with either measurement system. As a guess, you have not had to use metric very much so you just have never built up a collection of mental tools equal to the one's you use for inches and stuff, and so you see it as clumsy and ill-fitting.
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