Are You at Rest?

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Are You at Rest?

Text of Are You at Rest?

  • 1. Are You at Rest?JackDempsey

2. Our Solar System Our Solar System orbits our Galaxy, the Milky Way Our Galaxy is part of the Local Group of Galaxies Galaxies exist throughout the Universe. 3. Our Knowledge of the Solar Systemand the Universe Aristotle in 340BC wrote book On the Heavens.Postulates Earth is a sphere not a flat disk. If flatshouldnt see sails of ships first on horizon. He could see five lights moving across sky at nightand called them planets - Greek name for wanderer. Aristotle claimed Sun and five planets move around astationary Earth; Mercury, Venus, Mars, Jupiter,Saturn. 4. Our Knowledge of the Solar System Eratosthenes, Chief Librarian, Great Library ofAlexandria in 200BC calculates the diameter of theEarth Ptolemy in 200AD created a model of the heavenlybodies that was reasonably correct Copernicus in 1514AD, claims Sun at centre of Solarsystem and planets move in a circular orbit. Galileo in 1600s, uses telescope to chart the skies Kepler, in 1600s claims planets move in ellipses. 5. Our Knowledge of the Solar System Roemer in 1676AD is first to calculate speed of lightusing Jupiters moons Newton in 1687AD publishes PrincipiaMathematica Einstein in 1915 published his General Theory ofRelativity Hubble in 1929 was first to detect other Galaxies. 6. Are You at Rest? The Earths circumference is 40,075 km A person on the Equator is travelling at 1,700 km/hr A person in Kirkcaldy, Latitude 57 degrees North istravelling at 900 km/hr The earth circles the Sun at 107,000 km/hr 7. Are You at Rest? The orbital speed of the Solar System is 792,000km/hr To complete one orbit around the Galaxy takes ourSolar System about 225250 million years The Sun is thought to have completed 20 orbitsduring its lifetime It has completed 1/1250 of a revolution since theorigin of humans 8. The Universe The human eye can observe about 5,000 stars This is about 0.0001% of all stars in Milky Way There are about 100 billion galaxies in the Universe Each Galaxy has about 100 billion stars 9. A Galactic Collision The Milky Way and Andromeda are separated by 2.5million light years The two galaxies are slowly moving towards eachother at 120 km/s They will collide in approximately 4 billion years 10. The Universe? In the 1920s astronomer Edwin Hubble discoveredthat galaxies are all moving away from us at a rateproportional to their distance This relationship is called the Hubble constant It establishes an expansion rate that is critical forestimating the age and size of the universe, so far itis estimated to be 14 billion light years 11. Any Questions? 12. Absorption lines in theoptical spectrum of asupercluster of distantgalaxies (right), ascompared to absorptionlines in the optical spectrumof the Sun (left). Arrowsindicate redshift.Wavelength increases uptowards the red and beyond(frequency decreases). 13. Hubble was first to detect other Galaxies A theory is a good theory if it satisfies tworequirements; It must accurately describe a large class ofobservations It can be used to predict future observations 14. Are You Resting? The Orbital speed of our Solar System around thegalactic nucleus is 217 km/s It takes 226 million years to complete one lap