Supertechz

  UN IVERS E The universe is everything that exists , including all matter , energy , time and space . The universe is believed to have started with the Big Bang , a huge explosion that occurred about 13 billion years ago . G AL AX Y A galaxy is a collection of stars , dust and gas held together by gravity . There are billions of galaxies in the universe . The Milky Way is one of them . S OL AR SYSTEM The solar system consists of the sun and the planets orbiting around it . There are eight planets in the solar system : Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uran us and Neptune . PL AN ET A planet is a large , round object that orbits around a star . There are eight planets in the solar system : Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uran us and Neptune . STAR A star is a huge , bright object that is made of hot ...

  EAR TH The Earth is the third planet from the Sun and the only astronomical object known to harbor life . According to radi ometric dating and other sources of evidence , Earth formed over 4 . 5 billion years ago . Earth ’ s gravity interacts with other objects in space , especially the Sun and the Moon , Earth ’ s only natural satellite . Earth revolves around the Sun in 365 . 26 days , a period known as an Earth year . During this time , Earth rot ates about its axis about 366 . 26 times . EAR TH ’ S ATM OS PH ERE Earth ’ s atmosphere is the layer of gases , commonly known as air , that surrounds the planet Earth and is retained by Earth ’ s gravity . The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth ’ s surface , absorbing ultraviolet solar radiation , warming the surface through ...