Astronomy Exam #1 – Flashcards
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What is a star?
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A star is a large luminous ball of gas that generates heat and light through nuclear fusion.
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What is a planet?
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A planet is a moderately large object that orbits a star. It shines by reflected light. Planets may be icy or rocky
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What is a moon?
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A moon (or satellite) is an object that orbits the planet.
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What is an asteroid?
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An asteroid is a small and ROCKY object that orbits a star.
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What is a comet?
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A comet is small and ICY object that orbits a star.
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What is the SOLAR SYSTEM?
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The solar system is a star and all of the material that orbits it; including it planets, moons and asteroids. Our Solar System is the Sun, Earth, Mars...
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What is a nebula?
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A nebula is an in stellar cloud of gas and or dust and it is indicative of star birth or star death.
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What is a galaxy?
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A galaxy is a great is a great island of stars in space, all held together by gravity orbiting the common center. An example: The Milky Way
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What is a Local Supercluster?
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A local supercluster is groups of galaxies that are typically clustered
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What is the definition of a Universe?
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The universe is the sum total of all matter and energy that is everything within and between all galaxies.
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What are the two elements that everything comes from since the Big Bang?
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The two elements are Hydrogen and Helium. H + He
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How big is a Light Year?
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a light year is 300 thousand kilometers per second or 300 million minutes per second. 3x10⁸ m/s About 10 trillion kilometers
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What is the equation for one light year and what does a light year measure?
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A light year equals the speed of light times one year. A light year measures distance.
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Powers of 10
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10⁶ = 1,000,000 10⁰ = 1 10⁻¹ = 0.1
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Powers of 10: Rule of Multiplication
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10^A x 10^B = 10^(A+B)
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Powers of 10: Rule of Division
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10^A / 10^B = 10^(A-B)
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The LARGE Scale Nomenclature
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Kilo = 1,000 = 10³ Mega = 1,000,000 =10⁶ Giga = 1,000,000,000 = 10⁹ Tera = 1,000,000,000,000 = 10¹²
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The SMALL Scale Nomenclature
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Milli = 0.001 = 10⁻³ Micro = 0.000001 = 10⁻⁶ Nano = 0.000000001 = 10⁻⁹ Pano = 0.000000000001 = 10⁻¹²
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How Big Is The Universe?
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The universe is about 400 billion stars in the Milky Way. The Milky Way is one of about 100 billion galaxies There are as many stars as the amount of grains of sand. 10¹¹ stars times 10¹¹ galaxies equals about 10²² stars in the universe.
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What is the Cosmic Calendar?
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The cosmic calendar is a scale on which we compress the history of the universe into 1 year. For example: In a cosmic year, human existence in about a second.
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In what ways do humans employ scientific thinking?
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Scientific thinking is based on everyday ideas of observation and trial-and-error experiments.
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What are the dangers of common sense?
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Common sense often works well for humans and typically breaks down at the frontiers of science. For example, by saying the earth is not flat being compared to earth orbits the sun needs science to prove it.
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What are facts?
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Facts are sometimes referred to as empirical evidence and derived from experiments and they must be repeatable.
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What is a hypothesis?
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A hypothesis is an untested idea that can explain a phenomenon.
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What is a theory?
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A theory is a hypothesis which test have failed to disprove. It is not an undisputed facts. It's predictions must be correct. It can be disproved.
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What is Physical Law?
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Physical Law are theories that have become very well tested and are of fundamental importance.
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What is the Cosmological Principle?
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The Cosmological Principle: "There is nothing special about our place in the universe."
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More of The Cosmological Principle
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Our view from Earth isn't special or unique. On a large scale, the universe is the same everywhere. Matter and energy obey the same physical laws everywhere. We can learn about distant objects by studying nearby ones. All scientific knowledge is provisional. Scientific Theories must be able to be falsifies and rejected. This is how science progresses. Science's vulnerability is its great strength. Existing accepted ideas are subject to change from the scientific method; even idea accepted as the truth.
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What is Scienta?
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The word Scienta comes from the Latin word meaning knowledge.
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The Hallmarks of Science #1
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Modern science seeks explanations for observed phenomenons that rely solely on natural causes.
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The Hallmarks of Science #2
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Science progresses through the creation and testing of models of nature that explain the observation as simply as possible. For example: Occam's Razor = Simplicity
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Does Astrology have any scientific validity?
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Scientists tests have shown that serological prediction are no more accurate than we should expect from pure chance. For example: Horoscopes
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Motions in the sky: A day
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It is the rotation of the earth about its axis.
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The moon, our constant companion: a month
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The moon orbits around the earth.
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The reason for seasons: a year
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The earth orbits around the sun.
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Precision of the earth's axis: millennia
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a wobbling of the earths axis.
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What is the celestial equator?
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It is the extension of the earth equator onto the celestial sphere.
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The Milky Way
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If you see the the band of light across the sky. Our galaxy is shaped like a disk and our solar system is in that disk.
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Daily Motion: As the earth rotates
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The sky appears to us to rotate in the opposite direction.
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Daily Motion: The sky appears to rotate around the
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North or South celestial poles.
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Daily Motion: If you are standing at the poles
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nothing rises or sets (on a single night)
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Daily Motion: The altitude of the celestial pole
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Is your latitude.
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Daily Motion: Stars at an angle less than your latitude away from:
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your celestial pole never sets (circumpolar). the other celestial pole are never seen by you.
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Annual Motion: As the earth orbits the sun
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the sun appears to move eastward with the respect to the stars.
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Annual Motion: What is the Ecliptic Path?
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It is the sun appearing to circle the celestial sphere once every year.
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Annual Motion: The earths axis is tilted
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23.5 degrees from being perpendicular to the plane. Therefore the celestial equator is tilted 23.5 degrees to the ecliptic.
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Annual Motion: How many months does the Earth spend in the north and in the south?
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6 months in the North and 6 months in the South.
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Annual Motion: What are the seasons caused by?
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The earths axis' tilt, NOT from the earth to the sun.
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Why did ancient societies keep track of time and seasons?
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For practical purposes including agriculture, religious and ceremonial purposes.
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Why did ancient societies use astronomical observations as an aid to navigation?
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The elevation of the North Star gives you your latitude.
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The days of the week are named after
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The sun, moon and visible planets
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What did ancient civilizations achieve in astronomy?
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Daily Time Keeping Tracking the seasons and calendar (agriculture) Monitoring lunar cycles (planet wide clock) Monitoring planets and cycles (navigation) Predicting eclipses (magic?)
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The Stonehedge England 1550 BC
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The stones that could tell time and the seasons based on their placement in the circle. The sun would line up with the stones.
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Earliest known supernova explosions (1400 BC) China
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Bone or tortoise shell inscrip.on from the 14th century BC. "On the Jisi day, the 7th day of the month, a big new star appeared in the company of the Ho star." "On the Xinwei day the new star dwindled."
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Who was Aristarchus? (310-230BC)
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Astronomer who championed the heliocentric theory of the universe , correctly believed that the earth and other planets moved around the sun. His heliocentric model was incorrect but most correct to use about the movements in space.
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What was Eratosthenes?
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Was the first to have calculated the Earth's circumference of 24,860 mi.
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What is the actual circumference of earth?
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24,901 miles
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Why were the findings in astronomy unspoken of for so long?
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the dark ages happened The findings were preserved or lost in libraries In the 12th century many scientists were suppressed or executed
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The Geocentric Universe > Then Retrograde Motion
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Was believed by most and best described by Ptolemy. Then the Retrograde motion took over the geocentric model
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What were Epicycles?
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After geocentric model we came up with epicycles. HELP
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Who was Copernicus?
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He Proposed Sun centered model (published 1543) and used model to determine layout of solar system Created planetary distances measured in Astronomical Units "AU" - the distance between the Earth and the Sun) BUT ... Model was no more accurate than Ptolemy's Earth Centered model in predicting planetary positions, because it still used perfect circles.
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How do we measure the distance between Earth in the Sun?
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In Astronomical Units: "AU" 1 AU is the distance from the earth to the sun.
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Who was Tycho Brahe?
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Compiled the most accurate one 1 to the 60th of a degree naked eye measurements ever made of planetary positions at the observatory he built. Hired Kepler, who used Tycho's observations to discover the truth about planetary motion.
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Who was Johannes Kepler (1571-1630)?
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He first tried to match Tycho's observations with circular orbits but an 8-arcminute discrepancy led him eventually to make a model of planet orbits using ellipses... "If I had believed that we could ignore these eight minutes [of arc], I would have patched up my hypothesis accordingly. But, since it was not permissible to ignore, those eight minutes pointed the road to a complete reformaDon in astronomy."
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What is an ellipse?
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An ellipse looks like an elongated circle
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What were Kepler's 3 Laws of Planetary Motion?
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First Law: The orbit of each planet around the sun is an ellipse with the sun at one focus. Second Law: As a planet moves around its orbit, it sweeps out equal areas in equal times. It is faster near the sun and slower further from the sun. Third Law: More distant planets orbit the Sun at slower average speeds, obeying the relationship p²=a³
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p²=a³
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p = orbital period in years a = average distance from Sun in AU means that planets closer to the sun travel faster than planets further from the sun. Mercury is faster than Neptune.
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Who was Galileo Galilei?
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His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism. Galileo has been called the "father of modern observational astronomy", the "father of modern physics", the "father of science", and "the Father of Modern Science".
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What did Galileo do?
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He significantly developed the telescope for astronomy He discovered of the four largest satellites of Jupiter (named the Galilean Moons). He did the observation and analysis of sunspots. Galileo also worked in applied science and technology, inventing an improved. Created confirmation of the phases of Venus. He proponent of the Heliocentric model
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Because of Galileo's discoveries...
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The Catholic Church ordered Galileo to recant his claim that Earth orbits the Sun in 1633 He was held under house arrest for the remainder of his life His book on the subject was removed from the Church's index of banned books in 1824 Galileo was formally vindicated by the Church in 1992
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3 Key Objections: Galileo overcoming Copernican view
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Galileo overcame major objections to Copernican view. Three key objections rooted in Aristotelian view were: 1. Earth could not be moving because objects in air would be lep behind. 2. Non-circular orbits are not "perfect" as heavens should be. 3. If Earth were really orbiting Sun, we'd detect stellar parallax, our view of nearby stars would change as we move around.
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Overcoming the first objection (nature of motion) Galileo
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Galileo's experiments showed that objects in air would stay with a moving Earth. Aristotle thought that all objects naturally come to rest. Galileo showed that objects will stay in motion unless a force acts to slow them down (foreshadowing Newton's first law of motion).
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Overcoming the second objection (heavenly perfection) Galileo
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Tycho's observations of comet and supernova already challenged this idea. Using his telescope, Galileo saw: Sunspots on Sun ("imperfections") and Mountains and valleys on the Moon (proving it is not a perfect sphere)
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Overcoming the third objection (parallax): Galileo
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Tycho thought he had measured stellar distances, so lack of parallax seemed to rule out an orbiting Earth. Galileo showed stars must be much farther than Tycho thought — in part by using his telescope to see the Milky Way is countless individual stars. If stars were much farther away, then lack of detectable parallax was no longer so troubling.
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How did Galileo solidify the Copernican revolution?
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Galileo also saw four moons orbitng Jupiter, proving that not all objects orbit the Earth
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What is precision?
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It is the speed (or rate) at which the object moves. speed = distance ÷ time (in units of meters per second)
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What is velocity?
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It is the speed and the direction, example 10 meters per second due east.
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What is acceleration?
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It is any change in velocity. units of speed ÷time (meters per second ²)
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The acceleration due to gravity
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All falling objects accelerate at the same rate (not counting friction of air resistance) On earth g≈10m/s² Speed increases 10 m/s with each second of falling.
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Without air resistance
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Everything falls at the same rate. The Moon
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Momentum and Force
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momentum = mass × velocity
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Net Force
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changes momentum, which generally means acceleration (change in velocity)
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Angular Momentum
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Rotational momentum of a spinning or orbiting object
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Mass
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the amount of matter in an object. it stays the same (bits of matter)
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Weight
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The force that acts upon an object. can change with gravity.
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On the Moon
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My weight is less, my mass it the same.
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Does gravity exist in space?
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Yes!
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Why are astronauts weightless in space?
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There is gravity in space. You still have the same mass as you do on earth. Weightless is due to the constant state of free fall.
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Weightlessness in space.
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Astronauts and other objects inside a spacecraft don't fall to the floor of the spacecraft. The astronauts are accelerating towards Earth, but they are not accelerating towards the floor of the spacecraft.
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In order to move in space
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You must have an opposing force! (Movie Wall E example)
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How did Isaac Newton change our view of the universe?
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He realized the same physical laws that operate on earth also operate in the heavens - one universe. He discovered the laws of motion and gravity. Used experiments with light, first reflecting telescope and calculus.
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What is Newtons first Law of motion?
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An object moves at constant velocity unless a net force acts to change its speed or direction.
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What is Newtons second law of motion?
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Force = mass × acceleration
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What is Newton's third law of motion?
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For every force, there is always an equal and opposite reation force.
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Is the force the Earth exerts on you larger, smaller, or the same as the force you exert on it?
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Earth and I exert equal and opposite forces on each other.
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Conservation of Momentum
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The total momentum (mass × velocity) of interacting objects cannot change unless an external force is acting on them. Interacting objects exchange momentum through equal and opposite forces.
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Conservation of Angular Momentum
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The angular momentum of an object cannot change unless an external twisting force (torque) is acting on it. angular momentum = mass × velocity × radius
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Angular momentum conservation explains why:
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objects rotate faster as they shrink in radius. Example: spinning ice skater.
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What are the 3 basic types of energy?
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Kinetic Energy (motion) Radiative Energy (Light) Stored or potential energy Energy can change type but cannot be destroyed.
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What is thermal energy?
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the total kinetic energy of many particles (for example, in a rock, in air, in water) • Thermal energy is related to temperature but it is NOT the same. Temperature is the average kinetic energy of the many particles in a substance.
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What is temperature?
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it is the average kinetic energy of the many particles in a substance. (Kelvin, Celsius, Fahrenheit)
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Gravitational Potential Energy The earth depends on:
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1. Object's mass (m) 2. Strength of gravity (g) 3. Distance object could potentially fall
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Gravitational Potential Energy Objects of gas clouds:
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In space, an objecst or gas clouds have more gravitational energy when it is spread out than when it contracts. A contracting cloud converts gravitational potential energy to thermal energy.
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Mass and Energy
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Mass itself is a form of potential energy E = mc² A small amount of mass can release a great deal of energy Concentrated energy can spontaneously turn into particles (for example, in particle accelerators)
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The Conservation of Energy
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Energy can be neither created nor destroyed. It can change form or be exchanged between objects. The total energy content of the Universe was determined in the Big Bang and remains the same today.
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The Universal Law of Gravitation
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Every mass attracts every other mass. Attraction is directly proportional to the product of their masses. Attraction is inversely proportional to the square of the distance between their centers. Fg = G ( M₁M₂ ÷ d² )
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How does gravity cause tides?
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Moon's gravity pulls harder on near side of Earth than on far side. Difference in Moon's gravitational pull stretches Earth.
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How does Newtons laws of gravity extend Keplers laws?
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Total orbital energy (gravitational + kinetic) stays constant if there is no external force • Orbits cannot change spontaneously. • More gravitational energy; • Less kinetic energy • Less gravitational energy; More kinetic energy • Total orbital energy stays constant
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What can make an object gain or lose orbital energy?
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Friction or atmospheric drag. A gravitational encounter.
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Escaping Velocity
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If an object gains enough orbital energy, it may escape (change from a bound to unbound orbit) Escape velocity from Earth ≈ 11 km/s from sea level (about 40,000 km/hr)
