8 Planets: Earth

3. EARTH: OUR MOTHER

✪ The Earth is the third planet from the Sun and comes between the planet Venus and the planet Mars.

✪ Earth is the only planet in the solar system that has life.

EARTH PROFILE
Mass	5.98 x 1024 kg
Diameter	12756 km
Mean density	5520 kg/m3
Escape velocity	11200 m/s  (11.2 km/s)
Rotation period (length of day in Earth days)	1 (23.93 hours)
Revolution period (length of year in Earth days)	365.26
Obliquity (tilt of axis degrees)	23.4
Mean surface temperature	281 K (07.85°C)
Mean maximum surface temperature	310 K (36.85°C)
Mean minimum surface temperature	260 K (-13.15 °C)
Visual geometric albedo (reflectivity)	0.39
Highest point on surface	Mount Everest (over 8 km above sea-level)
Atmospheric components	78% nitrogen, 21% oxygen, 1% argon
Surface materials	Basaltic and granitic rock and altered materials
Credits: NASA Planet Profiles

✪ Earth is the only planet in the Solar System to have water in its three states of matter: as a solid (ice), a liquid (sea, rain, etc.) and as a gas (clouds). 

✪ Earth is the only planet that has an atmosphere containing 21 percent oxygen.

✪ Earth is the only planet in the Solar System not to be named after a mythical God.

✪ The Earth is the only inner planet (Mercury, Venus, Earth and Mars) after mars to have  satellite, the Moon.  Earth have the largest satellite (Moon) among these. Mars has tiny two -  Phobos and Deimos.

✪ Earth is the only planet in the Solar System known to be geologically active, with Earthquakes and volcanoes forming the landscape, replenishing carbon dioxide into the atmosphere and erasing impact craters from meteors. The craters have sunk down or been worn away by wind and rain over millions of years. 

✪ The Earth takes 365¼ days to complete its revolution round the Sun.  The Earth’s year is therefore 365 days long but the ¼ days are added up and every fourth year has one extra day, on the 29th of February.  This fourth year is called a Leap Year (366 days) and is always a year which can be divided exactly by 4 and 400 – 2000, 2004, 2008, 2012, 2016.

✪ As the Earth orbits round the Sun it rotates on its axis. It takes 24 hour to complete a rotation. The side of the Earth that faces the Sun has daytime and the side of the Earth that is turned away from the Sun has nighttime.

✪ As the Earth orbits round the Sun it tilts very slightly and so gives us the seasons.

✪ Hence formation of seasons is due to earth's revolution and formation of day-nights are because of it's rotation on its own axis.

✪ Distance of Earth from the Sun (about 150 million km = 1 AU): 1. Perihelion (closest): 147,098,291 km (91,402,640 miles); 2. Aphelion (farthest): 152,098,233 km (94,509,460 miles)

✪ The Earth’s diameter, the distance round its middle at the Equator, 12756 kilometers or 7926 miles.

✪ The Earth is not an exact sphere; the diameter going round the North and South Poles is slightly less than the diameter round the Equator.