light-time

light-time

The time taken for light, radio waves, or other electromagnetic radiation to travel at the speed of light (3 × 105 km s–1) between two points. The light-time along the mean distance between Sun and Earth is 499 seconds. More precisely, the light-time for unit distance is a constant, τA, equal to 499.004 78 seconds. Since the light-time between celestial bodies and Earth varies as the Earth revolves in its orbit, a correction – the equation of light – must be made to calculations involving measurements of time. Light-time produces a delay between transmission and reception of command signals and data between Earth and a spacecraft.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
And since there was no right light-time, all light-time was right.
Among the topics are gravitational wave foreground radiation from neutron star-dwarf binaries, the chromospheric activity of late-type stars of the different rotational periods, spectrophotometry and model atmosphere flux fitting, the light-time effect and tertiary companions in close binary stars, the age of the local interstellar bubble, and the current status and outreach activities of radio astronomy in Malaysia.
This led them to hypothesise the presence of two giant planets whose gravitational effect would cause the stars' orbit to wobble and consequently slightly alter the measured time between eclipses due to the light-time effect.
Our geocentric predictions below include this light-time correction.--R.
Multiply the light-time from M31 by another thousand --into the future now--and when does it bring us?

Full browser ?