Equator one whose plane passes through the center of the globe. The plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator. In the cycle of Earth's seasons, the equatorial plane runs through the Sun twice per year: on the equinoxes in March and September. To a person on Earth, the Sun appears to travel above the Equator (or along the celestial equator) at these times. Light rays from the Sun's center are perpendicular to Earth's surface at the point of solar noon on the Equator. Locations on the Equator experience the shortest sunrises and sunsets
Nautical time maritime usage, GMT retains its historical meaning of UT1, the mean "solar" time at Greenwich. UTC, "atomic" time at Greenwich, is too inaccurate, differing by as much as 0.9 seconds from UT1, creating an error of of a minute of longitude at all latitudes and which is at the equator but less at higher latitudes, varying roughly by the cosine of the latitude. However, DUT can be added to UTC to correct it to within 50 milliseconds of UT1, reducing the error to only . In practice, nautical times are used only for radio communication, etc. Aboard the ship, e.g.