Earth and the Universe Eric Angat Teacher PMHS

Earth Rotation and Revolution The term Earth rotation refers to the spinning of the Earth on its axis. One rotation takes 24 hours and is called a mean (average) solar day. The orbit of the Earth around the sun is called Earth revolution. This celestial motion takes 365 1/4 days to complete one cycle. Further, the Earth's orbit around the sun is not circular, but elliptical. An elliptical orbit causes the Earth's distance from the sun to vary at different times of the year.

93 million miles

93.43 million miles 147 million km+ 152 million km÷ million km÷1.6

In astronomy, axial precession is a gravity-induced, slow and continuous change in the orientation of an astronomical body's rotational axis. In particular, it refers to the gradual shift in the orientation of Earth's axis of rotation, which, like a wobbling top, traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years (called a Great or Platonic Year in astrology). The term "precession" typically refers only to this largest secular motion; other changes in the alignment of Earth's axis - nutation and polar motion - are much smaller in magnitude.

The nutation of the axis of the Earth was discovered already in the twenties, eighteen century by J Bradley, but this nutation was not explained in detail until 20 years later.Because the dynamic motions of the planets are so well-known, their nutations can be calculated to within arcseconds over periods of many decades..Values of nutations are usually divided into components parallel and perpendicular to the ecliptic. The component wich works along the ecliptic is known as the nutation in longitude. The component perpendicular to the ecliptic is known as the nutation in obliquity. Celestial coordinate systems are based on an "equator" and "equinox," which means a great circle in the sky wich is the projection of the Earth's equator outwards, and a line, the Vernal equinox intersecting that circle, which determines the starting point for measurement of right ascension. These items are affected both by precession of the equinoxes and nutation, and thus depend on the theories applied to precession and nutation, and on the date used as a reference date for the coordinate system.

The Coriolis force Wind curves to right in the northern hemisphere and left in southern hemisphere.

Earth’s Magnetic field protecting us from cosmic radiation.