why 360 degrees?
why 360 degrees?
(OP)
Considering radians vs degrees, we engineers know the many advantages of radians. Degrees has the advantage of representing many common angles as round numbers. But how did they come up with 360 degrees in a circle?
There are some eerie overlaps with time. The number 60 playing a role. 60 seconds in a minute and 60 minutes in an hour. 6 * 60 degrees in a circle. Minutes and hours show up as subdivisions of degree. I can't quite make the connection between time and degrees. Rotation of the earth would seem the logical tie, but doesn't seem to work. In one hour we should rotate 360 degrees/24 = 15 degrees. In on minute earth would rotate 15/60 = 1/4 degrees... not the same as one minute angle measure which is 1/60 degree.
So, who came up with 360 degrees in a circle and why?
There are some eerie overlaps with time. The number 60 playing a role. 60 seconds in a minute and 60 minutes in an hour. 6 * 60 degrees in a circle. Minutes and hours show up as subdivisions of degree. I can't quite make the connection between time and degrees. Rotation of the earth would seem the logical tie, but doesn't seem to work. In one hour we should rotate 360 degrees/24 = 15 degrees. In on minute earth would rotate 15/60 = 1/4 degrees... not the same as one minute angle measure which is 1/60 degree.
So, who came up with 360 degrees in a circle and why?
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RE: why 360 degrees?
360 can be handily divided by 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 30, 36, 40, 45, 60, 90, 120, 180. Pretty useful mathematical properties.
RE: why 360 degrees?
I thought the babylonians counted 360 days in a complete year, and used this fact to divide the circle into 360 equal parts. But I may be mistaken. I found the following link with answers:
http://m
RE: why 360 degrees?
Supposing there was an ancient astronomer, with a slight fixation on the number 60.
If he was to look up overhead half way between sunset and sunrise every day, after 360 days (roughly) he'd see the same star field, in the same place relative to his surroundings. Every night the star field would rotate by approximately 1/360 of a circle.
Only problem with that is that obviously 360 <> 366.25 (or is it 364.25?), so our observant astronomer is going to see a quite noticeable error in his lifetime, or even 5 years.
Cheers
Greg Locock
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RE: why 360 degrees?
Maybe the guy thought it was easier to round the number to 360 rather than 365 to make his calculations...
Cyril Guichard
Mechanical Engineer Consultant
France
RE: why 360 degrees?
http://www.dozenalsociety.org.uk/
RE: why 360 degrees?
corus
RE: why 360 degrees?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: why 360 degrees?
Took a history of math course as an undergrad. It was aimed at teachers but since it was a 300 level math class, it counted as a technical elective. It was that or advanced thermo.
RE: why 360 degrees?
RE: why 360 degrees?
RE: why 360 degrees?
The teachers of the ancient Babylonians were aliens with six fingers on each hand, that's where the 60's came from.....
Larry
RE: why 360 degrees?
Leap years are every year that is divisible by 4, except years that are divisible by 100 are NOT leap years (1900 was not a leap year), except years that are divisible by 400 ARE leap years (2000 was a leap year).
Recently the world has gone off the astronomical clock so time is now determined only by physics via atomic clocks. Good bye leap-seconds, which were used to reconcile astronomically determined time with time determined by the vibrations of cesium atoms.
RE: why 360 degrees?
http://tycho.usno.navy.mil/leapsec.html
http://www.bipm.fr/en/scientific/tai/
Hg
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RE: why 360 degrees?
Cyril Guichard
Mechanical Engineer Consultant
France
RE: why 360 degrees?
Another interesting (at least to me) tidbit, is why there are 180 Fahrenheit degrees between 0 and 100 Celsius degrees. (180 being 360/2, so this is at most half off topic). According to Wikipedia, there are several different stories.
The one I originally heard was that Fahrenheit's original scale was zero for the freezing point of a saturated salt water solution, and 100 degrees for normal human body temperature. These were fairly constant and readily available reference points. Another interesting point being that it was based on a nice metric-like difference of 100 degrees.
The Celsius scale originally had zero represent the boiling point of water, and 100 as the freezing point, but Carl Linnaeus suggested reversing it, which was much more popular. The Farhrenheit scale was later adjusted to even up with the Celsius scale at the 180 to 100 degree ratio, necessitating the change of normal body temperature to the familiar (to Americans, anyway) 98.6 degrees.
RE: why 360 degrees?
Just imagine Joe Public being told that new cars' speedometers will now record speed in SI units!
RE: why 360 degrees?
As in 16.67 meters per second instead of 60 kilometers per hour?
Respectfully
RE: why 360 degrees?
RE: why 360 degrees?
RE: why 360 degrees?
In a very strict technical sense, the SI system is MKS, standing for meters, kilograms and seconds. Waross is right. :)
JHG
RE: why 360 degrees?
http://www.unc.edu/~rowlett/units/sifundam.html
and probably many other sites. Meters, kg, and seconds are fundamental SI units.
Larry
RE: why 360 degrees?
http://
RE: why 360 degrees?
A.
RE: why 360 degrees?
We needn't worry, in the short span of some 113 million years in the future, considering the slowering of earth rotation, the year length would be just about 360 days.
RE: why 360 degrees?
RE: why 360 degrees?
RE: why 360 degrees?
If it takes 113 million years to get rid of 5 days per year, then I guess in 113/5 ~ 23 million years from now we will have one less day per year. And in 23/4 ~ 6 million year we will have 1/4 less day per year. No more leap year?
Then after that we'll have to start subtracting days. Do we keep taking them out of February (delete Feb 27 next?), or do we try to even out the months by going taking it out of a 31-day month (I never liked January anyway).
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RE: why 360 degrees?
Yes, but don't forget days will become less but longer with more daylight and starlight for work or leisure.
RE: why 360 degrees?
If I recall correctly, 6400 military millirads make a circle (not 6200). The approximation was made to make mental arithmetic easier for calculations of range in the battlefield. Close enough for government work.
RE: why 360 degrees?
The nice thing about mils is that if your first salvo falls ten metres left of a target at one km range, you just need to traverse right ten mil to get the next salvo onto the spot just vacated by the target.
Correction (in mils) = Miss Distance across range (in m) divided by range (in km)
A.