EarthA Unique Planet Fifth largest plant of solar

Earth-A Unique Planet Fifth largest plant of solar system Third in position from the sun 4. 6 billion years old Only planet that supports life � Optimum distance from the sun � Ideal temperature conditions � Moderate atmosphere � Axial tilt

Earth-A Unique Planet One rotation- 23 hrs, 56 mins, 4 sec One revolution- 365 days, 5 hrs 45 min, 45. 1 sec 40, 000 km circumference 12, 756 km diameter across the equator 12, 714 km diameter between two poles

Realms of the Earth Lithosphere- land surface and ocean floor Hydrosphere- Oceans, seas, rivers, lakes Atmosphere- Blanket of air surrounding Earth Biosphere- existence of life at interfaces of three realms- few km above and few km below Earth’s surface

Shape of the Earth Spherical � Like an ‘orange’ Oblate Spheroid � Bulge at the equator � Flattened at poles Geoid- ‘earth shaped’

Evidences for spherical shape of the Earth Circumnavigation- Ferdinand Magellan Spherical celestial bodies- sun, other planets Increase in line of visibility with increased height Sunrise and sunset Circular Horizon Earth’s shadow on the moon during lunar eclipse Aerial photographs from satellites

Factors promoting life on Earth Distribution of Land Water Atmosphere � Nitrogen � Oxygen � Ozone Water Cycle Biosphere