When was the metric system declared “base” system for Astronomic Mathematics?

I've been trying to fiend some information on this for a school project but all my searches have, sadly, come up empty.
So I’m hoping someone here could help me? It would be much appreciated.

-SpaceMelon

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There's a lot of info on this site about SI
http://www.bipm.org/en/home/

The International Union of Pure and Applied Physics is here
http://www.iupap.org/

And the International Astronomical Union is here
http://www.iau.org/

Between them you may find out what you're looking for.

(I suspect that SI was adopted by various scientific disciplines at about the same time as it adopted by the General Conference on Weights and Measures back in 1960, but as you're looking for something a bit more authoritative you may need to do a bit more digging. )

Welcome, SpaceMelon.

Unfortunatly, not everyone always realised that metric WAS the standard. Remember the Mars Climate Orbiter?

Astronomers normally use the metric system for a variety of reasons.

The Meter was origionally designed by an astonomer based on 1 arc minute of distance, which equates to a 40000km Circumfrance of earth. It has since been redefined to be the distance light travels in 1/299,792,458 of a second, or for ease, light travels 29.97 meters in a micro second.

The history of this standard is varied, and the only hold out not using it is the Unitied States. Even though the US was instrumental in getting it established as the International Standard.

As to when it was designed in 1670 by a french astronomer.

for details...http://lamar.colostate.edu/~hillger/origin.htm

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The mistake with the MCO totally mystifies me. As a child in the US in the sixties I learned metric. When I hung out with my father at the Lawrence Rad Lab they always used metric. In his science classes he always used metric. The fact that a computer program was written to use feet per second units baffles me.

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When I am done here I think I will go create something from metal.

In molecular biology metric has always been standard. Any time you have to deal with quantities that vary over several orders of magnitude (such as solute concentrations) this only makes sense. Also, international standards make a lot of sense in science. (For the same reason English is the de facto language of science.)

Engineers don't often have to go from feet to nano-feet, so the advantages of metric are not so obvious. Also, My understanding is that standards for engineering practices are defined on a national (or state) level, so the international concordance is not so important.

Still, you'd think the Lockheed engineers would at least realize that OTHER people use metric!

True, but there have always been hold outs out there. For example pilots still work in knots, and I can remember using diffraction gratings that were specified in lines per inch. (IIRC the shuttle uses knots and nautical miles, which alledgedly led to a cockup with a shuttle based experiment in the '80s, thoughh I could have this completely wrong. )

I believe tha's 0.2997 meters/nanosecond!

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T. Anderson

GAK,

sorry it's 29.97 Metters per microsecond. I stand corrected.

__________________
There is no problem that cannot be solved by a suitable application of high explosives - US Army Demolitions School

I just saw Hayley's comet, she waved, Said "why you always running in place? Even the man in the moon disappeared, Somewhere in the stratosphere" - Shinedown

http://worldsofothersuns.home.comcast.net/

SI isn't the standard in astronomy. They confound us with cgs units, after having drilled SI's mks units into our heads all our lives. And if you're not lucky, whoever is teaching your astronomy lectures will not understand that you have no freaking clue what an erg is.

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No, it is 299.7 meters per microsecond.

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When I am done here I think I will go create something from metal.

There are also 2-digit years and non-Unicode character sets in new programs. At least they stopped using 32-bit numbers for the size of a file and/or free space on a disk, once the problem became widespread enough in the mainstream.

--John

Heh. I thought this metric stuff was supposed to make things easier!

~ .9836 feet per nanosecond.

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0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...

A foot with clipped toenails, close enough for gummit work.

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Just a nit pick. The Metric system is outdated, and is no longer (formally) used. The SI (Le Systemme International D'Unites) replaced it many decades ago. Both systems use similar units, but many archaic Metric Units (calorie, centimeter, etc) have no place in SI.

???

Centi is an SI prefix and meter is the SI unit of length therfor centimeter is a legitimate SI unit.

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When I am done here I think I will go create something from metal.

Ok, I checked and I was wrong about cm. We engineers think in powers of 10 evenly divisible by 3. I forgot the rest of the world still used the less convienient prefixes. ops:

However SI does exclude derived units based on cgs such as ergs and dynes.

Liberia and Myanmar are also recognized as "holdouts", although they (and the U.S.) have joined all other nations in official adoption of the metric system. Formal declaration and mainstream incorporation are two different beasts, however.

"centimeter" is used extremely much in Europe. Only in engineering calculations we say .10^-2 m. All our rulers (how do you call all these things) geometric devices, etcetc, well anything that measures lengths between 10 m and 5 cm is divided into centimeters (and millimeters). People don't thing of it as "centi-meter" it is just a word in daily use, it is so common to us.

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I heard a story, but I've forgotten the details. It was something like this:

It was proposed to use the metric system in Europe. Russia made all their planes in metric system (double readouts), to be allowed to fly in Europe. Only, the proposal never came through. Now the Russians are the only ones flying with a metric system.

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To the regular visitor of internet bulletin boards it is clear that it's an excellent idea your parents get to choose your real name.

European countries used to have a mixture of units used in aviation. At least Germany was fully metric, France I think also was or at least was mostly metric, UK used miles per hour for speed I think and so on. Well, Germany lost WW2 and German aviation was shut down in the aftermath, and the allied forces taking over were rather unmetric. The Soviets on the other hand didn't lose and kept their metric aviation.

After the ICAO was founded and standardized on what most aviation used now, the Soviets of course didn't enthusiastically follow those old-fashioned imperialist units. :wink: I think the ICAO states requires that all commercial aviation follows their standards, so I guess Aeroflot planes travelling to those (most of Europe, for example) need double instrumentation to be allowed there.

And the Russians aren't the only ones metric. After sailplane flying was allowed in Germany again, they didn't follow the commercial aviation world, so thankfully gliders are still fully metric here. (Not only in Germany of course.)

Canada has been officially metric since 1975. There are some odd results that were not fully anticipated. For instance, nearly all building materials are still made in imperial units such as a 4' x 8' sheet of plywood or a 2"x4" piece of lumber. However, roofing shingles switched over soon after metrification which means you cannot repair an old roof. I smell a plot by the roofing industry.

All food products are sold by metric weight/volume which I find much easier for price comparison shopping. Hiways signs, weather, distances are all metric. The younger generation such as my grandchildren have no clue what an inch or a yard is. Oddly enough although I prefer metric I still use the imperial system a lot. That is because I have a machine shop at home and all my equipment is inch based as certain items like my lathe was made in 1937. Also, although metric hardware is available it is still much easier to find UNC and UNF hardware (imperial units).

It will be a long time before the changeover is anything close to complete and I am sure that certain things will never change. For example every country in the world uses socket handles that have 3/8" and 1/2" square drives regardless of what socket goes on it metric or not.

The odd thing about machining is that even though all of my equipment is SAE I do everything in decimal fractions. All measurements are in thousandths, hundreths and tenths etc. That has been the case for a very long time. It's a bit funny sometimes. I hang out on a machinist BBS and if you really want to see the fur fly just start a topic about metric vs imperial.

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When I am done here I think I will go create something from metal.

Which is of course, a perfectly logical 1.5 x 3.5 inches in actual dimensions!

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When I am done here I think I will go create something from metal.

Actually it's 2x4 less the width of the saw cut on both sides (approx 1/8") for rough sawn timber (UK) so it's about 1+7/8 x 3+7/8 after conversion.

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I just wished they had fudged the meter a bit to make g=10m/s.s, of course that only applies on earth, but that happens to be where I live! I don't think Bar is officially SI, but seems more intuitive to use compared to kPa. And, is the 2X4 measured prior to being dried?

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Just a nit pick of my own. The mass of the sun is measured in grams, the AU is defined in relation to the centimetre, and solar flux is measured in ergs/cm^2*Hz. Spectral lines are commonly measured in angstroms, and the jansky doesn't appear in the SI listings anywhere.

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"I'm making wheatloaf. It's like meatloaf, only with wheat"
"Isn't that just...bread?"

Which is no big deal, since dividing by 10 gives nanometers.

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T. Anderson

You mean multiplying by 10... 10 angstroms in 1 nm. 8)