Speed of gravity
| Exact values | |
|---|---|
| metres per second | 299792458 |
| Approximate values (to three significant digits) | |
| kilometres per hour | 1080000000 |
| miles per second | 186000 |
| miles per hour | 671000000 |
| astronomical units per day | 173 |
| parsecs per year | 0.307 |
| Approximate light signal travel times | |
| Distance | Time |
| one foot | 1.0 ns |
| one metre | 3.3 ns |
| from geostationary orbit to Earth | 119 ms |
| the length of Earth's equator | 134 ms |
| from Moon to Earth | 1.3 s |
| from Sun to Earth (1 AU) | 8.3 min |
| one light year | 1.0 year |
| one parsec | 3.26 years |
| from nearest star to Sun (1.3 pc) | 4.2 years |
| from the nearest galaxy (the Canis Major Dwarf Galaxy) to Earth | 25000 years |
| across the Milky Way | 100000 years |
| from the Andromeda Galaxy to Earth | 2.5 million years |
| General relativity |
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|
In classical theories of gravitation, the changes in a gravitational field propagate. A change in the distribution of energy and momentum of matter results in subsequent alteration, at a distance, of the gravitational field which it produces. In the relativistic sense, the "speed of gravity" refers to the speed of a gravitational wave, which, as predicted by general relativity and confirmed by observation of the GW170817 neutron star merger, is equal to the speed of light (c).