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York University
Natural Science
NATS 1880
Paul Delaney

Chapter 1 - macroscopic (multicellular) life does not exist anywhere else in the solar system, although our search for microbial life continues - scientific method: observe, hypothesize, predict & devise an experiment, test and publish results, reiterate (2 to 4) - the scientific method is unprejudiced, independent of observer, repeatable, unbiased and falsifiable - observations : 1) hypothesis = limited validity 2) model = hypotheses verified in limited circumstances 3) theory or law = hypotheses confirmed by multiple experiments - 3 sciences, astronomy, biology and planetary science - First exoplanet was found in 1995 - Habitable planets = planets that have the right conditions for life, does not necessarily mean they have life - Laws of physics are universal throughout the universe - Building blocks of life (organic molecules) have been found elsewhere in the universe - Extremophiles = life that can withstand a variety of extreme conditions (frigid temperatures, etc) - What is needed for life? Liquid (water?) seems essential, a source of heat or energy, enough time to develop long chain complex organic molecules, protection from radiation - Mars, and the moons of Jupiter (europa) and Saturn are likely candidates where life may be found - Our galaxy contains approximately ~200 billion stars and is 100000 light years across - Light year = distance light travels in 1 year - Seti = search for extraterrestrial life - Seti uses radio telescope searches to look for signs of intelligent life, and has been ongoing since 1959 - astrobiology is sometimes referred to as exobiology and bio-astronomy - Studies the conditions conducive to the origins and ongoing existence of life - Looks for suitable conditions for life on other planets Chapter 2 Models of the solar system - Geocentric model of the solar system = the plants and sun revolved around the earth - Heliocentric model = the earth and the other 7 planets revolve around the sun - Ancient people all over the world observed with great accuracy the motion of the sun, moon and planets - Ancient Greeks believed the earth was a perfect sphere - Animaxander – celestial sphere - Our days of the week come from the 5 known planets at the time + the sun and moon - Retrograde motion – planets normally move eastwards but sometimes move westwards, this was explained when Ptolemy refined the geocentric model and said that planets move in “perfect circles” while also orbiting the earth in a larger circle - Earth was believed to be special so the heliocentric model was rejected - Heliocentric model explained retrograde motion by explaining that planets look like they are moving the opposite direction once we pass them in orbit, in a sort of catch up way - Major contradiction to this point was the fact that retrograde motion did not apply to stars and that stellar parallax was not observed, this was explained because the stars are very far away Early ideas of life beyond earth - 2 major schools of thought concerning extraterrestrial life emerged 1)atomists led by Democritus believed that earth air fire and water, the four fundamental elements, made up the unverse 2)Aristotelians led by Aristotle believed that the 4 elements resided on earth alone and th the 5 element made up the heavens (aether) - Civilizations in the middle east were the first to advance the fields of science and math - Muslims preserved and enhanced knowledge they received from the Greeks while Europe was in its dark ages Key scientists - Copernicus reproposed the sun-centered model (1543) and used this model to determine the layout of the solar system but his model was still inaccurate because it still used perfect circles for the orbits of planets - Brahe compiled the most accurate measurements (1 arminute) using his naked eye ever made of planetary positions - Could not detect stellar parallax so believed that the universe must still be geocentric (but he recognized that the planets still orbit the sun) - Tycho hired kepler - Kepler discovered that orbits were not perfect circles, but ellipses - Read kepler’s 3 laws st - Galileo 1 law: an object in motion will stay in motion unless a force acts to slow it down - Galileo (along with kepler and tycho who observed supernovas) discovered that the universe was not perfect as he viewed imperfections on the moon and sun using his telescope - Galileo also used his telescope to prove the stars were too far away to exhibit any parallax - Movement of venus along with galileo’s observations proved that the universe was heliocentric\ - Galileo was forced to recant his theories by the catholic church - Newton discovered that the laws of physics were universal – they were the same throughout the universe - He discovered the laws of gravity and motion - Read newtons 3 laws - Universal law of gravity: every mass attracts other mass, attraction is directly proportional to the product of their masses and attraction is inversely proportional to the square of the distances between the centers Chapter 3 Size & scale
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