Transcript NATS 1311-From the Cosmos to Earth

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
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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 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.
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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.
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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.
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1024 meters = 1 yottameter
100 Million Light Years
Clusters of Galaxies
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1023 meters = 100 zettameters
10 Million Light Years
Within the Virgo Cluster
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1022 meters = 10 zettameters
1 Million Light Years
The Local Group - Our galaxy with the Magellanic
Clouds - two companion galaxies on the right.
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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.
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1020 meters = 100 exameters
10,000 Light Years
Our Spiral Arm
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1019 meters = 10 exameters
1,000 Light Years
The Stars of the Orion Arm
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1018 meters = 1 exameter
100 Light Years
Stars within 50 Light Years
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1017 meters = 100 petameters
10 Light Years
The Nearest Stars
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1016 meters = 10 petameters
1 Light Year
The Oort Cloud
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1015 meters = 1 petameter
0.1 Light Year
Sol - our Sun
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1014 meters = 100 terameters
Our Sun and a few rocks
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1013 meters = 10 terameters
The solar system. Only the orbit of Pluto, the furthest
planet from the Sun, is off the picture.
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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.
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1011 meters = 100 gigameters
Six weeks of the Earth's orbit. The orbits of Venus
and Mars are just visible on either side.
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1010 meters = 10 gigameters
Four days of the Earth's orbit.
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109 meters = 1 gigameter
The moon's orbit around the Earth, the
furthest humans have ever traveled.
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108 meters = 100 megameters
Earth
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107 meters = 10 megameters
North and Central America
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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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102 meters = 100 meters
Japanese Tea Garden - one hectare (10,000 m2)
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101 meters = 10 meters
A pond with lily pads
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100 meters = 1 meter
A one-meter square
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10-1 meters = 10 centimeters
A bee on a lily pad flower
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10-2 meters = 1 centimeter
A bee's head
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10-3 meters = 1 millimeter
A bee's eye
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10-4 meters = 100 micrometers
Pollen
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10-5 meters = 10 micrometers
Bacteria
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10-6 meters = 1 micrometer
Virus on a bacterium
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10-7 meters = 100 nanometers
A virus
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10-8 meters = 10 nanometers
The structure of DNA
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10-9 meters = 1 nanometer
The molecules of DNA
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10-10 meters = 100 picometers
Carbon's outer electron shell
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10-11 meters = 10 picometers
The inner electron cloud
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10-12 meters = 1 picometer
Within the electron cloud
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10-13 meters = 100 femtometers
The nucleus
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10-14 meters = 10 femtometers
The nucleus of carbon
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10-15 meters = 1 femtometer
A proton
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10-16 meters = 100 attometers
Within the proton
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10-17 meters = 10 attometers
Quarks and gluons
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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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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.
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The most exciting words in science are
not “Eureka (I found it)” but “Now that’s
funny”.
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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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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
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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.
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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.
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.
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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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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.