when is the earth said to be at perihelion
Perihelion and aphelion Earth is about 147.1 million kilometers (91.4 million miles) from the Sun at perihelion around January 3, in contrast to about 152.1 million kilometers (94.5 million miles) at aphelion around July 4 â€” a difference of about 5.0 million kilometers (3.1 million miles). (These dates change over time due to precession and other orbital factors, which follow cyclical patterns known as Milankovitch cycles. For a table of these dates for various years, see Apsis.)
Apollo 13 April 17, 1970, 18:07:41 UTC (142:54:47 Ground Elapsed Time). Crew was on board the USS Iwo Jima 45 minutes later.
Moon landing To date, the United States is the only country to have successfully conducted manned missions to the Moon, with the last departing the lunar surface in December 1972.
Pierre-Simon Laplace The equilibrium theory, based on the gravitational gradient from the Sun and Moon but ignoring the Earth's rotation, the effects of continents, and other important effects, could not explain the real ocean tides.[30][31][32][28][33][34][35][36][37]