Geocentric Coordinate Time Geocentric Coordinate Time Geocentric Coordinate Time (TCG - Temps-coordonnée géocentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to precession, nutation, the Moon, and artificial satellites of the Earth. It is equivalent to the proper time experienced by a clock at rest in a coordinate frame co-moving with the center of the Earth: that is, a clock that performs exactly the same movements as the Earth but is outside the Earth's gravity well. It is therefore not influenced by the gravitational time dilation caused by the Earth. TCG was
Iron Mountain Central Historic District Iron Mountain Central Historic District The Iron Mountain Central Historic District is a historic district, broadly located between Fleshiem and C Streets and between Iron Mountain and Stockbridge Avenues in Iron Mountain, Michigan. The district covers the city's central business district and adjacent areas. It is primarily commercial, but also contains the historic county courthouse complex, and school, library, and church buildings. It was listed on the National Register of Historic Places in 2013. Lake Superior Iron Ranges]] A major iron ore deposit was discovered near what is now Iron Mountain in 1878/79; the first ore from the first area