PHY 1060 Study Guide - Spring 2018, Comprehensive Midterm Notes - Planet, Solar System, Gravity

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12 Oct 2018
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PHY 1060
MIDTERM EXAM
STUDY GUIDE
Fall 2018
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Astronomy PHY 1060
Chapter 1: Why Learn Astronomy?
Modern astronomy is more than cataloging objects
It also covers:
o How do stars (matter and energy) work?
o What is the universe?
Our place in the universe
Earth is a small planet, orbiting a medium sized star, in a galaxy of 100 billion stars,
which is just one of billions of galaxies in a universe that is 13.7 billion years old
The universe is vast
Billions of galaxies are separated by thousands of trillions of miles.
Astronomers need to be able to talk about great distances
o Use the travel time of light to measure distances.
o We often use times to denote distances
o Compare distances by the amount of time it takes to travel them
Speed of light
o Light travels 300,000 km ever second
186,000 mph
o Universe’s greatest speed
o Light-year: distance light travels in one year
o Light could travel around Earth in 1/7 second.
o Light takes:
1.25 seconds to arrive from the moon
8.3 minutes to arrive from the sun
5.5 hours to get to Pluto from the sun
4.2 years to arrive from the nearest star
100,000 years to cross the galaxy
2.5 million years to get to the nearest big galaxy
10 billion years to come from distant galaxies
Studying the universe can reveal many things
o For example, all the atoms in our body were made in stars (except for the
hydrogen in water)
o Stars generate energy by making heavier elements out of light ones
Seen through the spectrum of light
Dying stars eject these elements into space in massive explosions
(stardust)
Can be collected by other things
All material on earth and anywhere is from other stars that have
died and ejected that material out into space
Astronomy uses measurements to…
o Test scientific ideas by observation
o Space exploration has expanded our view of planets and the Solar System
o Telescopes, satellites, etc. extend our view
Science involves the use of theories, hypotheses, and principles
o A scientific hypothesis is an idea that leads to testable or falsifiable predictions
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o The cosmological principle is a very important underlying assumption
“There is nothing special about one singular place in the universe”
Anything we calculate or measure should be able to be used
elsewhere
o This is how we can come up with testable predictions
The cosmological principle:
o On one level:
Our view from the earth is not special or unique
Distant objects should behave like nearby ones, which we can study in
greater detail
o On another level:
Matter and energy obey the same physical laws everywhere
By doing calculations based on things here, we can study distant objects
o Essentially: the same rules work everywhere in the universe
The scientific method
o Begins with an idea, forms a hypothesis, and tests it
o The test will support or invalidate the hypothesis
o The scientific method broken down:
Start with an observation
Suggest a hypothesis
Make a prediction
Perform an experiment or additional observation
If false, we have to revise our hypothesis
If true, we make more predictions and run more tests
o Concept quiz:
What is a scientific way of viewing nature?
Nature informs us about the usefulness of our ideas
Mathematics works when used to describe nature and its patterns
o Basic tools:
Scientific notation: handling large or small numbers based on powers of
10
Ratios: comparison of measurements
Geometry: shape and orientation
Algebra: representation
Proportionality: understanding the relationships between quantities
o Graphs are used to represent relationships between quantities
Can be linear or nonlinear
For linear, the slope is the change of the vertical axis divided by the
change of the horizontal axis
Can you draw a straight line through all the points?
o ^ this is a way to tell if it is linear
Chapter 6: The Tools of the Astronomer
The oldest and most important tool is the telescope
o To gather light of all kinds
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