spiral galaxies similar to the milky way
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Spiral Galaxies Similar to the Milky Way. Edge view. View from above. 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. - PowerPoint PPT PresentationTRANSCRIPT
NATS 1311 - From the Cosmos to Earth
Spiral Galaxies Similar to the Milky Way
View from above
Edge view
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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
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Other Galaxies in Our Local Group
The Andromeda Galaxy 2.3 million LY away
A Ring Galaxy
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Deep field view - about 10 billion LY away
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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
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If the Universe was one year old (instead of 15 billion years)
The Cosmic Calendar (Carl Sagan)
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1027 meters = 1000 yottameters100 Billion Light Years
This image represents the size of the known universe -- a sphere with a radius of 13.7 billion light years.
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1026 meters = 100 yottametersTen 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.
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1025 meters = 10 yottametersOne 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.
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1024 meters = 1 yottameter100 Million Light Years
Clusters of Galaxies
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1023 meters = 100 zettameters10 Million Light Years
Within the Virgo Cluster
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1022 meters = 10 zettameters1 Million Light Years
The Local Group - Our galaxy with the Magellanic Clouds - two companion galaxies on the right.
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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.
1021 meters = 1 zettameter100,000 Light Years
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1020 meters = 100 exameters10,000 Light Years
Our Spiral Arm
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1019 meters = 10 exameters1,000 Light Years
The Stars of the Orion Arm
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1018 meters = 1 exameter100 Light Years
Stars within 50 Light Years
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1017 meters = 100 petameters10 Light Years
The Nearest Stars
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1016 meters = 10 petameters1 Light Year
The Oort Cloud
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1015 meters = 1 petameter0.1 Light Year
Sol - our Sun
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1014 meters = 100 terameters
Our Sun and a few rocks
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The solar system. Only the orbit of Pluto, the furthest planet from the Sun, is off the picture.
1013 meters = 10 terameters
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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.
1012 meters = 1 terameter
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Six weeks of the Earth's orbit. The orbits of Venus and Mars are just visible on either side.
1011 meters = 100 gigameters
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Four days of the Earth's orbit.
1010 meters = 10 gigameters
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The moon's orbit around the Earth, the furthest humans have ever traveled.
109 meters = 1 gigameter
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108 meters = 100 megameters
Earth
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North and Central America
107 meters = 10 megameters
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106 meters = 1 megameter
California
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105 meters = 100 kilometer
The San Francisco Bay Area
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104 meters = 10 kilometers
San Francisco
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103 meters = 1 kilometer
Golden Gate Park
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Japanese Tea Garden - one hectare (10,000 m2)
102 meters = 100 meters
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A pond with lily pads
101 meters = 10 meters
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A one-meter square
100 meters = 1 meter
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10-1 meters = 10 centimeters
A bee on a lily pad flower
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A bee's head
10-2 meters = 1 centimeter
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A bee's eye
10-3 meters = 1 millimeter
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Pollen
10-4 meters = 100 micrometers
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Bacteria
10-5 meters = 10 micrometers
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Virus on a bacterium
10-6 meters = 1 micrometer
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A virus
10-7 meters = 100 nanometers
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The structure of DNA
10-8 meters = 10 nanometers
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The molecules of DNA
10-9 meters = 1 nanometer
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Carbon's outer electron shell
10-10 meters = 100 picometers
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The inner electron cloud
10-11 meters = 10 picometers
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Within the electron cloud
10-12 meters = 1 picometer
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The nucleus
10-13 meters = 100 femtometers
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The nucleus of carbon
10-14 meters = 10 femtometers
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A proton
10-15 meters = 1 femtometer
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Within the proton
10-16 meters = 100 attometers
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Quarks and gluons
10-17 meters = 10 attometers
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We are “Star Stuff”
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The Orion Nebula
Located in the sword of the constellation Orion.
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The Orion Nebula
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The Orion Nebula
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Proplyds or Proto Solar Systems in the Orion Nebula
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Gaseous Pillars - Stellar Nursery
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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.
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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.
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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.
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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.
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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. . .
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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
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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.
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The Scientific Method
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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.
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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.
Occam’s Razor
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The most exciting words in science arenot “Eureka (I found it)” but “Now that’sfunny”.
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MOTIONS OF EARTH
1. ROTATION ON ITS AXIS - Day
2. REVOLUTION ABOUT SUN - Year
3. PRECESSION - Wobble of spin axis
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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
Motions of Earth
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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
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The Rotation of the Earth From Space
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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.
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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.
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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.
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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
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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.
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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.
ConstellationsWestern 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)