Earth Mean Orbital Speed
| Value | 29,780 m/s |
| Status | Conventional / typical value |
| Source | NASA planetary fact sheet (mean orbital velocity) |
| Categories | Astronomical |
| millimeter per year | 939,785,330,000,000 mm/yr |
| millimeter per day | 2,572,992,000,000 mm/day |
| millimeter per hour | 107,208,000,000 mm/h |
| inch per day | 101,298,900,000 in/day |
| foot per day | 8,441,574,800 ft/d |
| inch per hour | 4,220,787,400 in/h |
| meter per day | 2,572,992,000 m/d |
| millimeter per minute | 1,786,800,000 mm/min |
| meter per hour | 107,208,000 m/h |
| inch per minute | 70,346,457 in/min |
| millimeter per second | 29,780,000 mm/s |
| foot per minute | 5,862,204.7 ft/min |
| centimeter per second | 2,978,000 cm/s |
| meter per minute | 1,786,800 m/min |
| inch per second | 1,172,440.9 in/s |
| kilometer per hour | 107,208 km/h |
| foot per second | 97,703.412 ft/s |
| mile per hour | 66,615.963 mph |
| knot | 57,887.689 kn |
| meter per second | 29,780 m/s |
| mach (sea level) | 87.512563 Ma |
| kilometer per second | 29.78 km/s |
| speed of light | 0.000099335388 c |
Learning zone
Take the orbit's circumference and divide by the year: about 940 million kilometres in 31.56 million seconds, near 29.8 km/s. Kepler's second law means it is not constant — Earth moves at 30.29 km/s at perihelion in early January and 29.29 km/s at aphelion in early July, which is why the northern summer half-year is a few days longer than the southern one.
The number has a distinguished experimental history. Bradley discovered stellar aberration in 1728 because starlight appears tilted by v/c ≈ 20.5 arcseconds as Earth swings around, giving the first direct proof of Earth's motion and an early value for the speed of light. A century and a half later Michelson and Morley looked for the effect of the same 30 km/s on the speed of light itself, found nothing, and set relativity in motion.