Circular Measure
| Radius of a circle in seconds of arc
|
=
|
206,264
|
.
|
8062
|
| Radius of a circle in minutes of arc
|
=
|
3437
|
.
|
74677
|
| Radius of a circle in degrees of arc
|
=
|
57
|
.
|
2957795
|
| Circumference of a circle (360°) in seconds
|
=
|
1,296,000
|
|
|
| Circumference of a circle in minutes =
|
=
|
21,600
|
|
|
| Ratio of circumference to diameter (2πR)
|
=
|
3
|
.
|
1415926536
|
Astronomical
| Calendar year
|
=
|
365 d, 5 h, 48 min, 46 sec.
|
| Sidereal year
|
=
|
365.2563578 days
|
| Sidereal day
|
=
|
23 h, 56 min, 41 sec
|
| Mean solar day in sidereal time
|
=
|
24 h, 03 min, 56.5 sec
|
| Mean distance of the earth from the sun
|
=
|
92,800,000 miles
|
Physical
| Velocity of light per second
|
=
|
186,337 miles
|
| Velocity of light per second
|
=
|
299,878 kilometers
|
| Velocity of sound per second in dry air at 0° C
|
=
|
 C feet
|
| Velocity of sound per second in dry air at 32° F
|
=
|
 F feet
|
The formula 
for Centigrade, and 
for Fahrenheit scales is practically the same. For all ordinary purposes the value 1110 ft per sec when the temperature of the air is 50° F (30° C) or 1148 ft per sec when the temperature is 86° F (30° C) will meet all requirements.
