Scientific Method & Astronomy PDF

Science is both a process and a body of knowledge\ When using the scientific method:\ First, we observe nature\ Create a hypothesis\ Use it to make a prediction\ Finally, test your prediction\ Based on the results one might reject your hypothesis or continue to refine it.\ Using the scientific metho...

Science is both a process and a body of knowledge\ When using the scientific method:\ First, we observe nature\ Create a hypothesis\ Use it to make a prediction\ Finally, test your prediction\ Based on the results one might reject your hypothesis or continue to refine it.\ Using the scientific method you may prove that your wrong\ Occam\'s razor says simpler theory is better\ The Night Sky\ A group of stars forming a pattern is called an asterism\ A pattern of stars and the surrounding area in the sky is a constellation\ From the Earth, the moon appears to be ½ a degree across.\ During the course of the night stars appear to move in circular arcs\ around the north star\ The sun appears to move slowly relative to the fixed stars.\ The path the sun travels through the stars once every year is called the ecliptic\ We need leap years because a year is not a whole number of days Today, the calendar we use is the Gregorian calender\ Our only natural satellite is the Moon\ Every month we see a cycle of phases\ We see phases of the Moon because because its half lit up and we're seeing diff sides\ sidereal means \"with respect to the fixed stars\".\ sydonic means \"between alignments of the Sun, Earth, and a third object\". History of Astronomy\ Ancient Greeks did not do what we would call science because they philosophically didn't believe in observation or experiments\ People started with a geocentric cosmology and thought everything moved in circles\ because they seemed most perfect and nice.\ The main problem was retrograde motion of planets\ Ptolemy fixed this with epicycles\ Centuries later it was advances in technology that made the theory less workable.\ Copernicus revives the idea of a heliocentric cosmology and does some math.\ He finds the orbital distance of the inferior planets using their \'maximum elongation\', which\ is \_largest angle between the sun and a planet\ Using the observable synodic period, he calculates their sidereal period\ Copernicus was not immediately believed partly because his predictions were not better\ because he has assumed circles\ Tycho Brahe had good data, a gold (really bronze) nose, and could tell that a supernova was\ far away using parallax\ Brahe made the best observations in the pre telescope era\ Kepler used Brahe\'s data to formulate Kepler\'s laws:\ 1.orbits are ellipses and sun is at one focus\ 2.planets sweep out equal area in equal time\ 3.a\^3=p\^2\ Galileo Galilei was one of the first people to point a telescope at the sky.\ He was able to observe moons of jupiter and phases of venus\ both of which support the heliocentric model\ Isaac Newton changes what we now call physics. After him a theory has to be mathematical\ and make predictions to not seem silly.\ He describes the force of gravity that has the form: F=Gm1m2/r2\ Foucault\'s pendulum is direct evidence that earth's rotating The plane of the Earth\'s orbit around the sun is also called the ecliptic\ We have seasons because earths axis is tilted It is warm in the summer because our hemisphere is tilted toward the sun\ A solar day is 24 hours, a sidereal day is 23 hours 56 minutes.\ We always see the same side of the moon because it is tidally locked\ which means its rotation period and orbital period are the same\ During a solar eclipse the moon blocks the sun.\ During a lunar the moon is in the shadow of the Earth.\ We don\'t have eclipses every month because plane of\ the moons orbit is not the ecliptic\ The altitude-azimuth (alt-az) coordinate system is local and fixed to a position on earth\ altitude is angle up from horizon\ azimuth is how far you rotate to the right of North\ The alt-az coordinates of a star depend on location and change over-time\ Right ascension and declination coordinates (R.A. and Dec.) are fixed to the stars\ with the earth spinning in the center.\ The R.A. and Dec. coordinates of a star stay the same\ R.A. is the angle to the left\ and is measured in hours and minutes\ Dec. is the angle up from the equator Newton uses a prism to show that white light is all colors put together\ Ole Rømer timed the eclipses of the moons of Jupiter and measured the speed of light\ Thomas Young shows that light is a wave with his double slit experiment\ James Clerk Maxwell shows that light is a wave of electric and magnetic fields\ Visible light is a small part of the electromagnetic spectrum\ Kirchhoff found that heated elements had unique emission spectrum\ and light passing through a gas showed unique absorption spectrum\ which were at the same wavelength.\ In fact, every element has its own unique spectral lines\ This is the beginning of spectroscopy which tells us lots things such as, there is iron\ in the sun\ A blackbody spectrum is emitted by matter based on temperature\ It allows us to measure temperature from far away.\ Thinking about the blackbody spectrum led Max Planck to guess that energy came in discrete chunks\ Einstein used this idea to say that light is made of photons\ Now we see that spectral lines of an element come from electrons jumping between orbitals\ When an electron goes from a high energy orbital to a low energy orbital it emits a photon\ When an electron goes from a low energy orbital to a high energy orbital it absorbs a photon\ Using spectral lines we can look at other galaxies and measure the radial velocity\ Telescopes\ A refracting telescope has two lenses and its total length is the sum of the focul lenths\ Newton built the first reflecting telescope, which has a mirror and a lens.\ Telescopes do three things: brighten, resolve (increase resolution), magnify\ Today images are captured on a CCD= charge coupled device\ As well as visible light, telescopes use the entire electromagnetic spectrum