Accretion - When gravity causes matter to come together and form larger bodies, Accretion disk - A rotating disk of matter surrounding a large object in space, caused by the pull of gravity, Asteroid - a solid, irregularly shaped rock mass that is smaller than a planet and orbits the Sun, Heavy bombardment - A period of increased impact from meteorites, Lunar rocks - Rocks from the Moon, Planetary accretion - The accumulation of particles into a massive object by gravitationally attracting more matter, Planetesimal - A small body of accreted gas and dust thought to have orbited the Sun during the formation of the planets, Protoplanet - A large body of matter in orbit around the Sun or a star and thought to be developing a planet, Protostar - A contracting mass of gas that represents any early stage of the formation of a star, Radiometric dating - A technique used to date material such as rocks and carbon, Rock record - The rock that currently exists that geologists use to understand Earth's history, Earth’s early history begins with a cloud of dust and gas called a ________. - Nebula, Solar system - Our planet was formed during the formation of the ____________, the system that holds not only Earth but also the other planets that formed along with it.,

Earth's Early History

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