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Lecture 2- AST251 - Einstein’s law of gravity the mass of...

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Lecture 2: The Universe and Its Physics Copernicus: heliocentric system more logical to have Sun in the centre Kepler: found that heliocentric system works best with ellipses Keplers laws : Newton ’s law of gravity, universal law of gravitation , strength of the gravitational attraction b/w the 2 objects. F g = (GM 1 M 2 )/d 2 Based on Newton’s gravity law, Neptune was discovered, after it was predicted. Uranus was accidently discovered Newton’s law of gravity explains motion of ALL celestial bodies… small corrections may be needed…conceptual problem: works at a distance? Newton’s 3 laws of motion : 1. Object moves at constant velocity, unless a force acts upon it 2. F= ma 3. Forces appear in equal but opposites pairs of forces.
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Unformatted text preview: Einstein’s law of gravity: the mass of the Sun causes spacetime to curve, so freely moving objects (eg. planets) follow the straightest possible paths. Energy Kinetic E: motion of bodies Potential E: energy stored in a body and can be used Radiation: electromagnetic radiation (waves/photons) or subatomic particles Sun contains same elements as the elements on Earth (helium present in Sun) Other stars & galaxies also have same spectral lines. Conclusion: physics is same. Universe Look at slides Andromeda galaxy-like ours Three different types of galaxies: elliptical (no gas, not forming stars), spirals (a lot of gas, stars forming), irregulars(some gas, still forming stars). Lecture 3...
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