Earth and moon impact theory

The document discusses several scientific theories that explain the origin of the solar system. It begins by describing the nebular hypothesis proposed by Kant and Laplace, which suggests that the solar system formed from a cloud of gas and dust that collapsed under gravity. It then discusses the planetesimal and tidal theories which built upon this idea to explain how smaller planetesimals formed and were ejected from the sun. The protoplanet theory modified this view to incorporate modern knowledge about independent formation of matter in protoplanets within the rotating nebula.

This document discusses different types of galaxies including elliptical galaxies, spiral galaxies, and irregular galaxies. It provides details on the Milky Way galaxy, describing it as a spiral galaxy located between type b and c, and notes that our solar system is located in the disk of the Milky Way galaxy, about 14 light years above the equatorial plane and 26,000-28,000 light years from the center. The document also discusses quasars and black holes, noting that quasars are very luminous and energetic distant galactic nuclei that get their energy from black holes.

The document discusses plate tectonics and describes how the Earth's lithosphere is broken into plates that move over time. It explains that plate tectonics built upon Alfred Wegener's theory of continental drift, which proposed that the continents were once joined together in a supercontinent called Pangaea. There are nine major tectonic plates and three types of plate boundaries - divergent boundaries which create mid-ocean ridges and rift valleys, convergent boundaries which cause subduction and mountain building, and transform boundaries where plates slide past each other like the San Andreas Fault. Convection currents in the Earth's mantle provide the driving force for plate movements.

Earth's outer shell is divided into tectonic plates that slowly move over the mantle below. Plates interact at boundaries where they either converge and collide, causing volcanoes and earthquakes, diverge and form rift valleys and ocean ridges, or slide past each other along transform boundaries, also producing earthquakes. The movement of these plates over geological time scales shapes the earth's surface features and geography.

1. The formation and evolution of the Solar System began about 4.57 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center to form the Sun, while the rest flattened into a protoplanetary disk from which the planets, moons, asteroids and other small bodies formed. 2. According to the nebular hypothesis, Earth formed about 4.54 billion years ago from accretion of planetary material in the solar nebula. Within the first 100-200 million years, early Earth had formed extensive oceans and seas. 3. Key events in the development of early Earth included the formation of its layered internal structure through the sinking of

The document describes different types of stars: 1) Red giants are very large, cool stars that all main sequence stars evolve into. Nuclear fusion occurs in red giants, fusing helium into heavier elements. 2) White dwarfs are very small and dense remnants of red giants. They have high temperatures but low luminosities due to their small size. 3) Neutron stars form from massive stars and are very hot and dense, composed mostly of neutrons. Pulsars are rotating, magnetized neutron stars that emit beams of electromagnetic radiation.