10 27 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.
10 26 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.
10 25 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.
10 24 meters = 1 yottameter 100 Million Light Years Clusters of Galaxies
10 23 meters = 100 zettameters 10 Million Light Years Within the Virgo Cluster
10 22 meters = 10 zettameters 1 Million Light Years The Local Group - Our galaxy with the Magellanic Clouds - two companion galaxies on the right.
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. 10 21 meters = 1 zettameter 100,000 Light Years
10 20 meters = 100 exameters 10,000 Light Years Our Spiral Arm
10 19 meters = 10 exameters 1,000 Light Years The Stars of the Orion Arm
10 18 meters = 1 exameter 100 Light Years Stars within 50 Light Years
10 17 meters = 100 petameters 10 Light Years The Nearest Stars
10 16 meters = 10 petameters 1 Light Year The Oort Cloud
10 15 meters = 1 petameter 0.1 Light Year Sol - our Sun
10 14 meters = 100 terameters Our Sun and a few rocks
The solar system. Only the orbit of Pluto, the furthest planet from the Sun, is off the picture. 10 13 meters = 10 terameters
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. 10 12 meters = 1 terameter
Six weeks of the Earth's orbit. The orbits of Venus and Mars are just visible on either side. 10 11 meters = 100 gigameters
Four days of the Earth's orbit. 10 10 meters = 10 gigameters
The moon's orbit around the Earth, the furthest humans have ever traveled. 10 9 meters = 1 gigameter
<ul><li>Science </li></ul><ul><li>What is Science? </li></ul><ul><ul><li>Observation and experimentation directed toward understanding of the natural world. </li></ul></ul><ul><li>Why study science? </li></ul><ul><ul><li>We live in a world surrounded by science and technology. </li></ul></ul><ul><ul><li>Our problems and their solutions are bound up with science. </li></ul></ul><ul><ul><li>We are called upon to make decisions, to vote, hopefully informed, on issues affecting our lives. </li></ul></ul><ul><ul><li>Many of these issues have a significant scientific component. </li></ul></ul>
<ul><ul><li>Why study science? (Continued) </li></ul></ul><ul><ul><li>For the convenience of the study of science, the subject is frequently divided into neat packages called biology, chemistry, geology, physics, astronomy --- </li></ul></ul><ul><ul><li>Nature is not so divided - Each scientific discipline views nature from a different perspective, but all are studying the same world. </li></ul></ul><ul><ul><li>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. </li></ul></ul>
<ul><li>Why are we able to study nature? </li></ul><ul><li>Fundamental assumptions about nature: </li></ul><ul><ul><li>Order exists in nature – in the universe. </li></ul></ul><ul><ul><li>Order can be discovered by observation and experimentation. </li></ul></ul><ul><ul><li>Laws of nature are constant in time and place. </li></ul></ul><ul><li>Philosophical approach to the study of nature. </li></ul><ul><li>Aristotle, Plato </li></ul><ul><ul><li>Senses cannot be relied on </li></ul></ul><ul><ul><li>Must use reason and insights of human mind. </li></ul></ul>
<ul><li>Scientific approach to the study of nature </li></ul><ul><li>Copernicus and Galileo introduced observation and experimentation in the 16 th century. </li></ul><ul><li>Science is not a set of facts. </li></ul><ul><li>It is a way of conducting a dialogue about our physical surroundings. </li></ul><ul><li>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. </li></ul><ul><li>To be scientific, a statement must be capable of being proven wrong. </li></ul>
<ul><li>Scientific approach to the study of nature. </li></ul><ul><li>Observation and experimentation set science apart from other ways of knowing - ways that are not less important - just different </li></ul><ul><ul><li>Philosophy – Reason – Logic </li></ul></ul><ul><ul><li>Art – Appreciation of form – Beauty </li></ul></ul><ul><li>Pseudoscience statements: </li></ul><ul><ul><li>– Hypothesis that cannot be tested with reproducible results; </li></ul></ul><ul><ul><li>Cold fusion, ufo's, astrology. . . </li></ul></ul>
<ul><li>Scientific approach to the study of nature. </li></ul><ul><li>Scientific Law: </li></ul><ul><ul><li>Statement of observed regularity in nature. </li></ul></ul><ul><li>Scientific Theory: </li></ul><ul><ul><li>Statement of observed regularity in nature. </li></ul></ul><ul><ul><li>General principle offered to explain a set of phenomena or observed facts. </li></ul></ul><ul><ul><li>Not all scientific predictions can be tested directly </li></ul></ul><ul><ul><ul><li>Core of earth </li></ul></ul></ul><ul><ul><ul><li>Sun—energy </li></ul></ul></ul><ul><ul><ul><li>Expansion of the universe </li></ul></ul></ul><ul><li>Require models —creative thought </li></ul><ul><ul><li>No ultimate truths—all Provisional </li></ul></ul><ul><ul><ul><li>Ok as long as they are not contradicted </li></ul></ul></ul>
<ul><li>Scientific approach to the study of nature. </li></ul><ul><li>Model: </li></ul><ul><ul><ul><ul><li>Simplified version of reality used to describe aspects of nature. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Not synonymous with reality. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Based on assumptions that may simplify some aspects of nature, or may be incomplete statements about nature </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Useful to make predictions that can be verified by experimentation or observation. </li></ul></ul></ul></ul>
Hallmarks of Science <ul><li>Modern science seeks explanations for observed phenomena that rely solely on natural causes. </li></ul><ul><li>Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. </li></ul><ul><li>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. </li></ul>
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 - 1 349). 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. Occam’s Razor
The most exciting words in science are not “Eureka (I found it)” but “Now that’s funny”.
MOTIONS OF EARTH <ul><ul><ul><li>1. ROTATION ON ITS AXIS - Day </li></ul></ul></ul><ul><ul><ul><li>2. REVOLUTION ABOUT SUN - Year </li></ul></ul></ul><ul><ul><ul><li>3. PRECESSION - Wobble of spin axis </li></ul></ul></ul>
Motions of Earth more distant galaxies moving away faster, with the most distant moving at speeds close to the speed of light universal expansion 300,000 km/hr toward Andromeda Galaxy motion within Local Group 800,000 km/hr around galactic center, with one galactic rotation taking about 230 million years rotation of the Milky Way Galaxy 70,000 km/hr relative to nearby stars motion within local solar neighborhood 100,000 km/hr around Sun, with one orbit taking 1 year orbit of Sun 1,000 km/hr or more around axis, with one rotation taking 1 day rotation Typical Speed Motion
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. Rotation
The Rotation of the Earth From Space Earth Rotation Movie
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.
The Celestial Sphere <ul><li>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. </li></ul>
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.
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
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.
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. 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)
Star Names Brightest stars named thousands of years ago - most come from ancient Arabic Astronomers now use Bayer designations for the brighter stars - introduced by Johann Bayer in his star atlas Uranometria in 1603 - consists of a Greek letter followed by the genitive (in Latin) of the name of the constellation in which the star lies: Aries -> Arietis; Taurus -> Tauri; Gemini -> Geminorum; Virgo -> Virginis; Libra -> Librae; Pisces -> Piscium; Lepus -> Leporis. <ul><li>brightest star of the constellation given the designation Alpha, the next brightest Beta, and so on. </li></ul><ul><li>Flamsteed designations (introduced by John Flamsteed in 1712) - used when no Bayer designation exists - use numbers instead of Greek letters. Numbers were originally assigned in order of increasing right ascension within each constellation - due to the effects of precession they are now slightly out of order in some places. </li></ul>
<ul><ul><li>A model of the celestial sphere shows the patterns of the stars, the borders of the 88 official constellations, the ecliptic, and the celestial equator and poles. </li></ul></ul>
Latitude and Longitude We can locate any place on the Earth's surface by its latitude and longitude. Latitude measures angular distance north or south of the equator. Longitude measures angular distance east or west of the prime meridian (which passes through Greenwich, England). Dallas: latitude = 32.78 º N longitude = 96.78º W
Zenith is the point directly overhead, nadir is the point directly underneath. The meridian is the line drawn from the horizon in the south through zenith to the horizon in the north.
<ul><li>A circumpolar constellation never rises or sets - they are always visible. </li></ul><ul><li>Your latitude determines the portion of the celestial sphere visible in your sky and what constellations/stars are circumpolar. </li></ul><ul><li>(a) A Northern Hemisphere sky. </li></ul><ul><li>(b) A Southern Hemisphere sky. </li></ul><ul><li>At what latitude would you see the entire sky? </li></ul>
The Earth's rotation causes stars to trace daily circles around the sky. The north celestial pole lies at the center of the circles. Over the course of a full day, circumpolar stars trace complete circles, and stars that rise in the east and set in the west trace partial circles. Here, the time exposure lasted about 6 hours - we see only about one-quarter of each portion of the full daily path. Star Trails The Northern Hemisphere The Southern Hemisphere
Finding the Celestial Poles You can always find north using the North Star. Polaris can be found using the big dipper. Draw a line through the two “pointer” stars at the end of the big dipper and follow it upwards from the dipper about four outstretched hand’s width. The big dipper is circumpolar in the US so is always above the horizon. The south celestial pole can be found using the Southern Cross. There is no “South Star”