Earth General Knowledge: Its a common perception that the earth began billions of years ago as a huge ball of swirling dust and gases. Lightning strikes about 6,000 times per minute on earth. and atleast 2000 Number of lightning strikes over the earth per second. A bolt of lightning is about 54,000°F (30,000°C) which is actually six times hotter than the surface of the sun. Russia, Canada, USA, China, Brazil are the five countries with the biggest area on Earth. The earth was formed about 4.5 billion years ago. As the sun warms the earth’s surface, the atmosphere warms too. Some parts of the earth receive direct rays from the sun all year and are always warm. Warm air, which weighs less than cool air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow. The average lightning bolt is about an inch wide and five miles long. The names of the continents all end with the same letter with which they start. Scientists believes the invertebrate life began on earth about 600 million years ago. Fish evolved about 300 million years ago on the earth. Humans began to use clothing about 70 million years ago. The first words were spoken by humans about 40 thousand years ago. Cave paintings have been identified from about 30 million years ago. pyramids were build about 4.5k years ago. the Roman empire lasted about 500 years ago, from 0 to 500 AD the Greek civilization lasted about 2k years, from about 4k years ago to 2k years ago Agricultural habits began about 11k years ago when most of the large animals had been killed. Tools began to be used about 180k years ago 100 years ago the first virus was found in both plants and animals. The oldest known fossil is of a single-celled organism, blue-green algae, found in 3.2 billion year-old stones in South Africa. Oxygen is the most abundant element in the Earth’s crust, waters, and atmosphere (about 49.5%)