PLANETS STARS GALAXIES Midterm 2 Review General Knowledge COVER ALL THE TOPICS IN CHAP 1 9 Who were Aristotle Ptolemy Galileo Kepler and Newton and what were their main contributions to science 1 Aristotle Started the geo centric view of the universe He said that it was a celestial sphere rotating around the Earth 2 Ptolemy Theorized Retrograde Motion of the planets or that they move in a small epicycle circle while moving in a larger deferent circle around the Earth counterclockwise As the planets move closer to the Earth they would halt their eastward motion and begin to move westward for a few months 3 Galileo Studied the phases of Venus and understood that they always appear different sizes unlike the Moon which orbits the Earth heliocentric view and the telescope 4 Kepler Discovered that planets must orbit in an ellipse heliocentric view the telescope studied Venus 5 Newton Invented calculus formed laws of gravitation and motion Constellation the celestial equator the ecliptic the celestial poles right ascension and declination Constellation Formally used to describe an entire area of the celestial sphere Celestial Equator Projection of the Earth s equator on the celestial sphere Ecliptic The Sun s path on the celestial sphere Eclipses only occur when the moon crosses it Celestial Poles Points on the celestial sphere directly above either pole Right Ascension Analogous to the Earth s longitude running between the North and South poles Declination Runs parallel to the celestial equator The synchronous motion of the Moon the tides Moon Orbits from West to East with a 5 tilt relative to the ecliptic Has Lunar Phases which result from its changing position relative to the Sun in the order New Waxing Crescent First Quarter Waxing Gibbous Full Waning Gibbous Third Quarter Waning Crescent Sidereal Month is the time it takes the Moon to orbit Earth about 2 2 days shorter than the Lunar month which is 29 5 days long because as the Moon is orbiting the Earth the Earth is moving around the Sun Tides Caused by a gravitational attraction between the Sun the Earth and the Moon The gravitational forces of the Sun and the Moon distort the oceans from a spherical shape to that of an American football When the Sun Earth and the Moon are lined up they produce Spring tides where the ocean is most pronounced When they form a right angle with the Earth at the vertex the ocean is least pronounced and form a Neap tide The Earth actually moves through the friction of the tides This causes the slowing of the Earths orbit Kepler s three laws elliptical orbits law of equal areas 1 1st Law The orbit of each planet around the sun is an ellipse with the sun at one foci Ellipses have 2 extremes It is a circle when the foci merge orbital eccentricty of 0 and becomes nearly a straight line orbital eccentricity of 1 0 when they elongate 2 2nd Law aka Law of Equal Areas A line joining a planet and the Sun sweeps out equal areas in equal intervals of time 3 3rd Law The square of a planet s sidereal period around the Sun is directly proportional to the cuve of the length of it s semimajor axis in orbit P2 a3 where P Planet s sidereal period around the Sun in years and A Average distance from the Sun in AU 1 AU Distance from the Sun to Earth Newton s four laws Inertia Action and Reaction Motion and Gravity 1 Law of Inertia Inertia is the property of matter that keeps an object at rest or in motion in a straight line at a constant speed UNLESS acted on by a net external force or friction 2 Force Law The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass Force Mass x Acceleration 3 Law of Action and Reaction Whenever one object exerts a force on a 2nd the 2nd object exerts an equal and opposite force on the 1st 4 Law of Universal Gravitation Two objects attract eachother with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them FG Gm1m2 r2 r the distance between m1 and m2 Midterm II Ch 3 9 Basic properties of light speed frequency wavelength Gamma rays x rays ultraviolet rays light infrared radio Electromagnetic Radiation is all forms of light which are composed discrete packets of particles known as photons that have properties of waves however they do not have any electrical charge Although light may appear to be white it is not Instead it can be perceived as a spread out spectrum of colors when refracted or directed from one medium to another This spectrum includes red orange yellow green blue and violet and can not be split beyond these colors Wavelength is the distance between two successive crests Lights with shorter wavelengths can knock electrons off mediums From longest to shortest wavelengths Radio Waves Microwaves Infrared Radiation Visible Light Ultraviolet Radiation X Rays and Gamma Rays From shortest to longest wavelengths 400 700nm Visible Light is as follows Violet Blue Green Yellow Orange and Red Speed of light is usually designated by c and is equal to 3 0 x 105 km s or 1 86 x 105 mi s but will travel slower through any medium Frequency is the number of wave crests that pass a given point per second measured in Hertz One Hertz is one cycle per second Why is the setting sun red the sky blue When the Sun is setting in the atmosphere it is getting further away which means that more of the light is scattered and reflected As less light is reaching the Earth the Sun appears less bright appearing more and more red and more of the shorter wavelength blue and green lights are scattered creating the blue sky Black body radiation laws temperature vs radiation As an object gets hotter it gets brighter emitting more electromagnetic radiation at all wavelengths The brightest color or most intense wavelength of the emitted radiation changes with temperature Blackbody An object that absorbs all the radiation that hits it To stay in thermal equilibrium it must emit all the radiation that it absorbs Laws Wien s Law The peak wavelength of radiation emmited by a blackbody is inversely proportional to its temperature OR the hotter an object becomes the shorter its max wavelength becomes Stefan Boltzmann s Law An object emits energy per unit area at a rate proportional to its temperature in Kelvins OR the hotter an object becomes the more energy it emits Emission absorption spectra spectral lines Emission The spectrum created by a chemical when heated over a flame