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NATS 1311 - From the Cosmos to Earth Spiral Galaxies Similar to the Milky Way Edge view View from above NATS 1311 - From the Cosmos to Earth The Milky Way The Sun is located on the Orion spiral arm about 30,000 LY from the galactic center It takes about 230 million years for the sun to complete one orbit around the galactic center NATS 1311 - From the Cosmos to Earth Other Galaxies in Our Local Group A Ring Galaxy The Andromeda Galaxy 2.3 million LY away NATS 1311 - From the Cosmos to Earth Deep field view - about 10 billion LY away NATS 1311 - From the Cosmos to Earth In our galaxy there are about 200 billion stars In our universe there are over 100 billion galaxies There are more stars in the universe than there are grains of sand on the Earth NATS 1311 - From the Cosmos to Earth If the Universe was one year old (instead of 15 billion years) The Cosmic Calendar (Carl Sagan) NATS 1311 - From the Cosmos to Earth 1027 meters = 1000 yottameters 100 Billion Light Years This image represents the size of the known universe -- a sphere with a radius of 13.7 billion light years. NATS 1311 - From the Cosmos to Earth 1026 meters = 100 yottameters Ten Billion Light Years Light from galaxies on the edge would require 5 billion years to reach the center. Observers at the center are seeing light that was emitted by these galaxies before the solar system formed. The largest scale picture ever taken. Each of the 9325 points is a galaxy like ours. They clump together in 'superclusters' around great voids which can be 150 million light years across. NATS 1311 - From the Cosmos to Earth 1025 meters = 10 yottameters One Billion Light Years Astronomers have determined that the largest structures within the visible universe - superclusters, walls, and sheets - are about 200 million light years on a side. NATS 1311 - From the Cosmos to Earth 1024 meters = 1 yottameter 100 Million Light Years Clusters of Galaxies NATS 1311 - From the Cosmos to Earth 1023 meters = 100 zettameters 10 Million Light Years Within the Virgo Cluster NATS 1311 - From the Cosmos to Earth 1022 meters = 10 zettameters 1 Million Light Years The Local Group - Our galaxy with the Magellanic Clouds - two companion galaxies on the right. NATS 1311 - From the Cosmos to Earth 1021 meters = 1 zettameter 100,000 Light Years Our galaxy - the Milky Way - looks rather like a whirlpool. It has spiral arms curling outwards from the center and rotates at about 900 kilometres per hour. It contains about 200 billion stars. NATS 1311 - From the Cosmos to Earth 1020 meters = 100 exameters 10,000 Light Years Our Spiral Arm NATS 1311 - From the Cosmos to Earth 1019 meters = 10 exameters 1,000 Light Years The Stars of the Orion Arm NATS 1311 - From the Cosmos to Earth 1018 meters = 1 exameter 100 Light Years Stars within 50 Light Years NATS 1311 - From the Cosmos to Earth 1017 meters = 100 petameters 10 Light Years The Nearest Stars NATS 1311 - From the Cosmos to Earth 1016 meters = 10 petameters 1 Light Year The Oort Cloud NATS 1311 - From the Cosmos to Earth 1015 meters = 1 petameter 0.1 Light Year Sol - our Sun NATS 1311 - From the Cosmos to Earth 1014 meters = 100 terameters Our Sun and a few rocks NATS 1311 - From the Cosmos to Earth 1013 meters = 10 terameters The solar system. Only the orbit of Pluto, the furthest planet from the Sun, is off the picture. NATS 1311 - From the Cosmos to Earth 1012 meters = 1 terameter Within the orbit of Jupiter - the orbits of the inner four planets : Mercury, Venus, Earth and Mars. All four have rocky crusts and metallic cores. NATS 1311 - From the Cosmos to Earth 1011 meters = 100 gigameters Six weeks of the Earth's orbit. The orbits of Venus and Mars are just visible on either side. NATS 1311 - From the Cosmos to Earth 1010 meters = 10 gigameters Four days of the Earth's orbit. NATS 1311 - From the Cosmos to Earth 109 meters = 1 gigameter The moon's orbit around the Earth, the furthest humans have ever traveled. NATS 1311 - From the Cosmos to Earth 108 meters = 100 megameters Earth NATS 1311 - From the Cosmos to Earth 107 meters = 10 megameters North and Central America NATS 1311 - From the Cosmos to Earth 106 meters = 1 megameter California NATS 1311 - From the Cosmos to Earth 105 meters = 100 kilometer The San Francisco Bay Area NATS 1311 - From the Cosmos to Earth 104 meters = 10 kilometers San Francisco NATS 1311 - From the Cosmos to Earth 103 meters = 1 kilometer Golden Gate Park NATS 1311 - From the Cosmos to Earth 102 meters = 100 meters Japanese Tea Garden - one hectare (10,000 m2) NATS 1311 - From the Cosmos to Earth 101 meters = 10 meters A pond with lily pads NATS 1311 - From the Cosmos to Earth 100 meters = 1 meter A one-meter square NATS 1311 - From the Cosmos to Earth 10-1 meters = 10 centimeters A bee on a lily pad flower NATS 1311 - From the Cosmos to Earth 10-2 meters = 1 centimeter A bee's head NATS 1311 - From the Cosmos to Earth 10-3 meters = 1 millimeter A bee's eye NATS 1311 - From the Cosmos to Earth 10-4 meters = 100 micrometers Pollen NATS 1311 - From the Cosmos to Earth 10-5 meters = 10 micrometers Bacteria NATS 1311 - From the Cosmos to Earth 10-6 meters = 1 micrometer Virus on a bacterium NATS 1311 - From the Cosmos to Earth 10-7 meters = 100 nanometers A virus NATS 1311 - From the Cosmos to Earth 10-8 meters = 10 nanometers The structure of DNA NATS 1311 - From the Cosmos to Earth 10-9 meters = 1 nanometer The molecules of DNA NATS 1311 - From the Cosmos to Earth 10-10 meters = 100 picometers Carbon's outer electron shell NATS 1311 - From the Cosmos to Earth 10-11 meters = 10 picometers The inner electron cloud NATS 1311 - From the Cosmos to Earth 10-12 meters = 1 picometer Within the electron cloud NATS 1311 - From the Cosmos to Earth 10-13 meters = 100 femtometers The nucleus NATS 1311 - From the Cosmos to Earth 10-14 meters = 10 femtometers The nucleus of carbon NATS 1311 - From the Cosmos to Earth 10-15 meters = 1 femtometer A proton NATS 1311 - From the Cosmos to Earth 10-16 meters = 100 attometers Within the proton NATS 1311 - From the Cosmos to Earth 10-17 meters = 10 attometers Quarks and gluons NATS 1311 - From the Cosmos to Earth We are “Star Stuff” NATS 1311 - From the Cosmos to Earth The Orion Nebula Located in the sword of the constellation Orion. NATS 1311 - From the Cosmos to Earth The Orion Nebula NATS 1311 - From the Cosmos to Earth The Orion Nebula NATS 1311 - From the Cosmos to Earth Proplyds or Proto Solar Systems in the Orion Nebula NATS 1311 - From the Cosmos to Earth Gaseous Pillars - Stellar Nursery NATS 1311 - From the Cosmos to Earth Science What is Science? – Observation and experimentation directed toward understanding of the natural world. Why study science? – We live in a world surrounded by science and technology. – Our problems and their solutions are bound up with science. – We are called upon to make decisions, to vote, hopefully informed, on issues affecting our lives. – Many of these issues have a significant scientific component. NATS 1311 - From the Cosmos to Earth Why study science? (Continued) – For the convenience of the study of science, the subject is frequently divided into neat packages called biology, chemistry, geology, physics, astronomy --– Nature is not so divided - Each scientific discipline views nature from a different perspective, but all are studying the same world. – This course will focus on a fundamental or general look at nature. It will be based on physics, the study of the principles that govern the natural world. NATS 1311 - From the Cosmos to Earth Why are we able to study nature? • Fundamental assumptions about nature: – Order exists in nature – in the universe. – Order can be discovered by observation and experimentation. – Laws of nature are constant in time and place. Philosophical approach to the study of nature. • Aristotle, Plato – Senses cannot be relied on – Must use reason and insights of human mind. NATS 1311 - From the Cosmos to Earth Scientific approach to the study of nature • Copernicus and Galileo introduced observation and experimentation in the 16th century. • Science is not a set of facts. • It is a way of conducting a dialogue about our physical surroundings. • The scientific method consists of careful observation of nature and an open-minded creative search for general ideas that agree with and predict those observations. • To be scientific, a statement must be capable of being proven wrong. NATS 1311 - From the Cosmos to Earth Scientific approach to the study of nature. • Observation and experimentation set science apart from other ways of knowing - ways that are not less important - just different – Philosophy – Reason – Logic – Art – Appreciation of form – Beauty • Pseudoscience statements: – Hypothesis that cannot be tested with reproducible results; Cold fusion, ufo's, astrology. . . NATS 1311 - From the Cosmos to Earth Scientific approach to the study of nature. • Scientific Law: – Statement of observed regularity in nature - attempts to describe the observations – has a well documented history of successful replication and extension to new conditions • Scientific Theory: – Statement of observed regularity in nature - attempts to explain the observations – General principle offered to explain a set of phenomena or observed facts. – Not all scientific predictions can be tested directly • Core of earth • Sun—energy • Expansion of the universe • Require models—creative thought – No ultimate truths—all Provisional • Ok as long as they are not contradicted NATS 1311 - From the Cosmos to Earth Scientific approach to the study of nature. • Model: – Simplified version of reality used to describe aspects of nature. – Not synonymous with reality. – Based on assumptions that may simplify some aspects of nature, or may be incomplete statements about nature – Useful to make predictions that can be verified by experimentation or observation. NATS 1311 - From the Cosmos to Earth The Scientific Method NATS 1311 - From the Cosmos to Earth Hallmarks of Science • Modern science seeks explanations for observed phenomena that rely solely on natural causes. • Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. • A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations. NATS 1311 - From the Cosmos to Earth Occam’s Razor The idea that scientists should prefer the simpler of two models that agree equally well with observations - the second hallmark - after medieval scholar William of Occam (1285 - 1349). For instance, original model of Copernicus (Sun-centered) did not match the data noticeably better than Ptolemy's model (Earth-centered). Thus, a purely data-driven judgment based on the third hallmark might have led scientists to immediately reject the Sun-centered idea. Instead, many scientists found elements of the Copernican model appealing, such as the simplicity of its explanation for apparent retrograde motion. Was kept alive until Kepler found a way to make it work. NATS 1311 - From the Cosmos to Earth The most exciting words in science are not “Eureka (I found it)” but “Now that’s funny”. NATS 1311 - From the Cosmos to Earth MOTIONS OF EARTH 1. ROTATION ON ITS AXIS - Day 2. REVOLUTION ABOUT SUN - Year 3. PRECESSION - Wobble of spin axis NATS 1311 - From the Cosmos to Earth Motions of Earth Motion Typical Speed rotation 1,000 km/hr or more around axis, with one rotation taking 1 day orbit of Sun 100,000 km/hr around Sun, with one orbit taking 1 year motion within local solar neighborhood 70,000 km/hr relative to nearby stars rotation of the Milky Way Galaxy 800,000 km/hr around galactic center, with one galactic rotation taking about 230 million years motion within Local Group 300,000 km/hr toward Andromeda Galaxy universal expansion more distant galaxies moving away faster, with the most distant moving at speeds close to the speed of light NATS 1311 - From the Cosmos to Earth Rotation The Earth rotates about its axis axis once per day - one rotation equals one day. The axis goes through the north and south poles and through the center of the Earth. It rotates counterclockwise when looking down on the north pole which means that the sun rises in the east and sets in the west. NATS 1311 - From the Cosmos to Earth The Rotation of the Earth From Space QuickTime™ and a YUV420 codec decompressor are needed to see this picture. NATS 1311 - From the Cosmos to Earth Earth’s rotation causes the stars - the celestial sphere - to appear to rotate around the Earth. Viewed from outside, the stars (and the Sun, Moon, and planets) therefore appear to make simple daily circles around us. The red circles represent the apparent daily paths of a few selected stars. NATS 1311 - From the Cosmos to Earth The Celestial Sphere Envisioned by the ancients, the celestial sphere had Earth at the center with the stars emblazoned on the sphere. They thought the stars rose and set because the celestial sphere (the sky) rotated, carrying the stars from east to west. All stars appear to move around two points on the celestial sphere, the north and south celestial poles—projections of earth’s axis of rotation. Earth's equator projected on the celestial sphere becomes the celestial equator. NATS 1311 - From the Cosmos to Earth Our lack of depth perception when we look into space creates the illusion that the Earth is surrounded by a celestial sphere. Thus, stars that appear very close to one another in our sky may actually lie at very different distances from Earth. NATS 1311 - From the Cosmos to Earth Constellations Constellations - groupings of stars named after mythical heroes, gods, and mystical beasts - made up over at least the last 6000 years - maybe more - used to identify seasons: - farmers know that for most crops, you plant in the spring and harvest in the fall. - in some regions, not much differentiation between the seasons. - different constellations visible at different times of the year - can use them to tell what month it is. For example, Scorpius is only visible in the northern hemisphere's evening sky in the summer. - many of the myths associated with the constellations thought to have been invented to help the farmers remember them - made up stories about them NATS 1311 - From the Cosmos to Earth Picture at right shows a start chart of the region around the constellation Orion. Picture at the left is an ornate star chart printed in 1835 - shows the great hunter Orion. He is holding a lion's head instead of his traditional bow or shield. He is stalking Taurus, the Bull in the upper right hand corner. Behind him, his faithful dog, Canis Major, is chasing Lepus, the Hare. NATS 1311 - From the Cosmos to Earth Constellations Western culture constellations originated in Mesopotamia over 5000 years ago - added to by Babylonian, Egyptian, and Greek astronomers - current list based charts of Roman astronomer, Claudius Ptolemy (~140 AD) In modern world - constellations redefined so now every star in the sky is in exactly one constellation. In 1929, the International Astronomical Union (IAU) adopted official constellation boundaries that defined the 88 official constellations that exist today.