ASTR 101 1st Edition Exam 1 Study Guide Lectures 1 17 Below I outline the key concepts of chapters 1 5 and 10 There are review questions here and also includes vocabulary words 1 1 Our modern view of the universe How big is the universe Over 100 billion stars in the Milky Way galaxy Our galaxy is one of more than 70 galaxies How old is the universe 7 billion years old 1 2 The History of the Universe What is our place in the universe We are in the Milky Way galaxy inside a local group of over 70 galaxies in a local supercluster in the universe How do our lifetimes compare to the age of the universe If the universe is 1 year old human civilization is a few seconds old 1 3 spaceship earth How is earth moving in our solar system it rotates on its axis once a day and orbits the Sun at a distance once a year How do galaxies move within the universe all galaxies move beyond the local group are moving away from us The more distant they are the farther they are away from us Hubble s law Are we ever sitting still NO 2 1 Patterns in the sky What does the universe look like from earth We re on a celestial sphere divided into constellations Why do stars rise and set This is due to the earth s rotation Circumpolar 2 2 Reasons for Seasons Why do the constellations we see depend on the latitude and time of year Our night sky points to different directions in space as the earth rotates which affects the constellations we see What causes the seasons Why do we have 4 seasons the tilt on earth s axis How does the orientation of Earth s axis change in time Precession changes the orientation but overall the tilt remains about 23 degrees 2 3 The moon Why do we see phases of the moon The phases depend on the moon s position relative to the Sun as it orbits the Earth What causes eclipses lunar is when the earth s shadow falls on the moon solar is when the Moon blocks our view of the sun Half of the moon is illuminated by the sun and half is dark We see a changing combination of the bright and dark faces as the moon orbits earth 2 4 Ancient mystery of planets Why was planetary motion so hard to explain Apparent retrograde motion Why did the ancient Greeks reject the explanation of planetary motion They couldn t detect stellar parallax 3 1 Ancient roots of Science In what ways do all humans use scientific thinking How is modern science rooted in ancient astronomy Ancient astronomers set the root for modern science 3 2 ancient Greek Science Modern science traces roots to the Greeks because they gave us models How did the Greeks explain planetary motion With the geocentric and Ptolemaic models 3 3 Copernican revolution How did Copernicus Tycho and Kepler challenge the earth centered model know these names What are Kepler s three laws of planetary motion How did Galileo solidify the Copernican revolution 3 4 The nature of science How can we distinguish science from nonscience There are three ways What is a scientific theory A simple but powerful model that explains observations and tests them 4 1 describing motion How do we describe motion Velocity acceleration momentum force How is mass different from weight Mass is always the same weight varies with strength of gravity Weightless free fall 4 2 Newton s Laws How did newton change our view of the universe What are Newton s three laws of motion 4 3 conservation laws What keeps a planet rotating and orbiting the Sun Conservation of angular momentum Where do objects get their energy Kinetic relative potential 4 4 force of gravity What determines the strength of gravity Universal law of gravitation How does newton s law of gravity extend Kepler s laws Bound orbits unbound How do gravity and energy together allow us to understand orbits Orbital energy escape velocity How does gravity cause tides Tidal force is proportional to the distance cubed If the distance of the moon is doubled than the tidal force will be weaker by 8 times 5 1 properties of light and matter What is light Electromagnetic wave photons radio waves microwaves infrared visible light ultraviolet X rays gamma rays What is matter Atoms protons neutrons electrons isotopes molecules How do light and matter interact 5 2 learning from light What are the 3 basic types of spectre Absorption emission and continuous Hoe does light tell us the temperatures of planets and stars The speed and distance of an object Thermal radiation Doppler Effect blue and redshifts 5 3 collecting light with telescopes How do telescopes help us learn about the universe Light collecting area angular resolution interferometry Why do we put telescopes in space Light pollution and adaptive optics 10 1 detecting planets How do we detect planets around other stars Astrometric method Doppler method 10 2 natures of planets around stars What properties of extrasolar planets can we measure How do extrasolar planets compare with planets in our solar system 10 3 formations of other planetary systems Do we need to modify our theory of solar system formation Somewhat yes we do Are planetary systems like ours common