Yeah, tell that to the folks at NASA-- I can’t remember which, but wasn’t there a recent Mars probe that went dead because two teams were using different units?
Scientists and engineers almost universally use metric units. Angtsroms are metric, they’re just not in engineering notation. Swithching between British units and metrics is a PITA.
Snort. As ** Johm Mace** said, try telling that toNASA and Lockheed-Martin.
Hey guys, I never said that using Imperial AND Metric at the same time was sensible! Hell NO! Clearly it’s much, MUCH easier to use metric in scientific work. My point was that American scientists (in particular) learn at an early age to mingle between the two in a way that many other scientists in the rest of the world don’t - and I have the greatest respect for such people, in the context of their fellow Americans who trash the metric system out of ignorance.
Sorry if I didn’t get that across properly in my first post.
Oh, by the way, David? In your link there a moment ago regarding the NASA v Lockheed mixup, I see that the Lockheed people were specifying thruster boost in measurements of pounds, while NASA were expecting those measurement in terms of Newtons.
A slight hi-jack here but is it not the case that Newtons are a measure of force (regardless of gravitational pull) wheras pounds are a measurement of mass? It seems that they had two areas of miscommunication - namely, the units being used, the the logic behind those units.
I think that when you talk about a “pound” of force, it means the force exerted by gravity on a pound on earth, ie 9.8N/kg * 1lb.
There are both pounds force and pounds mass. In various engineering classes I took, however, we always used pounds force for force and slugs (1 pound = 1 slug times 1 foot per second squared) for mass, so as to avoid having to convert everything in terms of gravity. Pounds mass were generally considered some sort of bastard step-child to be avoided. One slug equals about 32.2 pounds mass.
No we don’t. I’ve been working in the physical sciences since my early days in college, and can’t remember any time that I used the British measurement system.
You might be thinking of US auto mechanics-- if any profession needs to work with both systems, it’s them.
A Google search shows:
Results 1 - 10 of about 1,390,000 for angstroms
vs.
Results 1 - 10 of about 2,120,000 for nanometers
+
Results 1 - 10 of about 350,000 for nanometres
So nanometers/nanometres is used nearly twice as often as angstroms on the web.
I’d assume nanometers|nanometres are much more prevalent than that (relatively) compared to angstroms as this Google test shows because in a professional (as opposed to popularized) context you’d typically write nm. Like in scientific/professional context you’d write 4 μA, 230 kV, 50 ns, 200 MW rather than 4 microamperes, 230,000 volts, 50 nanoseconds, 200 megawatts, respectively.
Of course Googling doesn’t work well either for nm (most hits will be for nautical miles or New Mexico) or for Å (expanded to AA by Google).
As for the question why Å has fallen out of favour: the most plausible explanation in my opinion is that the unit (1 Å = 0.1 nm) doesn’t fit in with the standard SI/scientific usage of working with powers-of-ten-divisible-by-three. Anecdotical: we got taught in school physics class in the 1970s that the Å was obsolete for that reason.
Wow. In high school physics here, we were taught that the angstrom is still used. Even in astrophysical research, angstroms are still used in reference to wavelengths of various spectral lines.
When I was studying Quantum (for which the Angstrom was introduced, according to the above) we usually used metric units. When I started in optics, we used Angstroms. Visible light was in the thousands of Angstroms (about 3500 to 7000), and that, aside from UV and near IR wavelengths, were the only places they were used. I’m still used to giving laser wavelengths in angstroms – 6328 for HeNe, 6471 for krypton, etc. But somewhere along the line they started using nm and microns, and I suspect the growing use of near IR lasers got them using nm because it was easier to change between nm and microns because the factor was a neat 1000, rather than the confusing 100. So the laser wavelengths started geting expressed as 632.8 and 647.1 or even 0.633 and -6.47, to go with 1.064 and other IR wavelengths. Now I don’t see angstroms very much, it’s true.
Until 4 years ago, I taught general chemistry. I’ve seen just about every general chemistry book on the market, including Chang (and Brady; Zumdahl; Brown and Lemay; Ebbing; Silberberg; etc.)
From my copy of Chemistry, Matter and Its Changes by Brady, Russell, and Holum (2000), it states:
Elsewhere in the book, where the wavelength of atomic spectra is discussed, nanometers are used exclusively.
I didn’t teach from Chang, and I don’t have a copy handy, but I still recall that most of the general chemistry textbooks I seen over the last decade do not tend to use angstroms.
BTW, I also used to teach physics. Angstroms aren’t typically used in introductory college physics textbooks, either. SI units are exclusively used.
In the semiconductor industry, Angstroms are still very much in use - more so as time goes by.
Nitpicking!
According to my back of the envelope calculations, the wavelength of 104.3MHz is 288 x 10[sup]8[/sup] Angstroms.
Really? I work in the chip business all I every see now is nm down from um a few years ago.
I’m an engineer. Pretty much all of us here do our calculations in metric. If necessary, the results can be converted to American units afterwards. These days, a computer can do the coversion instantaniously. Heck, my TI-85 calculator can do this with only a trivial extra step on my part.
As waterj2 wrote, in engineering pounds are force and slugs are mass. There is a unit system where pounds are mass and poundals are force but nobody uses it, or ever did to any great extent.
And I should add that I’ve been out of work for 23 years so I’m not current on today’s units but I expect much engineering work is now done in metric.
That’s not true. The U.S. Customary System (USCS) is still used by most engineers in the U.S. In this system, the unit for force is the pound-force (lbf) and the unit for mass is the pound-mass (lbm). I’ve never seen slugs used in engineering.
It’s a complete pain in the neck. To make calculations work, the correction factor g[sub]c[/sub] is constantly introduced into expressions to make the units work, where g[sub]c[/sub] = 32.174 lbm-ft/(lbf-s[sup]2[/sup]).
The NCEES (National Council of Examiners for Engineering and Surveying), which administers the examinations for Professional Engineers, is gradually switching to metric, but many problems still use USCS units.
I wish that were true. I just had a drafter spend an hour converting a state highway department detail from metric to USCS units to match the rest of our plans for a road reconstruction job. :rolleyes: The typical construction contractor wouldn’t know what to do with metric units. It’s simply never used.
Out of curiosity, what kind of engineer are you?
My point of view is primarily that of civil/environmental engineering.
I should note that my firm also does environmental site assessments. All of our sampling plans are laid out in feet and inches. Sampling results, however, are exclusively metric (e.g. mg/L, mg/kg, etc.). It’s pretty bastardized, I guess…
For what it’s worth, when I was in the Navy, all of the gauges were in USCS units.