Geo1 Hw
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School
University of California, Merced *
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Course
001
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
4
Uploaded by ProfAardvark3790
Module 1: Geosphere
Lab 1: An Introduction to Earth System Science, Online learning, and Hubble's Law
Learning Outcomes:
•
Be able to give a definition of "Earth Systems Science"
•
Become familiar with Canvas and the online site for this course
•
Practice graphing data and fitting the equation of a line to derive the Hubble constant
•
Note: All work should be typed and uploaded onto the class website under this week's
assignment by the deadline. Everything that you turn in from this point on must be answered in
complete sentences and be put into your own words.
Part I. What is Earth Systems Science?
So you've enrolled in this course, but do you know what you are going to study? Many people
don't have a clear idea of what "Earth Systems" means, and what exactly it encompasses – isn't
it just environmental science?Think for a few minutes on your own, and then write down a
one-sentence definition of "Earth Systems".
Now think about what the most important problems or questions related to Earth Systems. What
do you think is the most important Earth Systems problem? Write it down one sentence.
Turn In:
Definition (1 point) and most important Earth System problem (1 point).
Earth systems is the understanding of the geology, chemistry, (Astro)physics, biology, and
human interactions that determine the past and present states of the earth. I think the most
important earth system problem is the atmosphere because of how tainted and toxic it has
become.
Part II. How am I supposed to learn it online?
On your laptop, log in Catcourses. You should see ESS 1 under Courses. If you have not done
so already, go to the "Course Essentials" page and read through the information.
Become familiar with where to find course material, assignments, quizzes, and grades, and how
to send messages.
III.
Working with data: Hubble's Law
Background
Scientific understanding is built on observations and information – often generalized as "data".
Data comes in many different forms, and making graphs is a powerful and essential way to
understand and interpret data. There are a number of ways to graph data, and an important skill
to learn in this course is how to make and interpret different kinds of graphs. In this short
exercise, you will make a simple x-y plot, examine the relationship between the variables, and fit
a line to the data. You will then interpret your graph in terms of what is now known as Hubble's
Law, and discuss how it relates to the Big Bang theory for the origin of the Universe. This topic
is the first lesson in the online course materials.
In the 1920's, astronomer Edwin P. Hubble measured the velocities of galaxies (i.e., how fast
they are moving) and the distance to the galaxy from Earth using telescope images. When he
made a graph of his data, he noticed that there was a linear trend associated with these two
measurements.
A.
Using Excel, make an x-y graph of the data below with x = Distance and y = Velocity.
(Your instructor will show you if you don't know how to do this.)
Distance is given in megaparsecs (mpc):
1 megaparsec = 3.26 million light years (3.26 x106 light years) Velocity is given in kilometers per
second (km/s)
Speed of light = 300,000 km/s
Galaxy Distance (mph)
Velocity (km/s)
NGC-5357
0.45
200
NGC-3627
0.9
650
NGC-5236
0.9
500
NGC-4151
1.7
960
NGC-4472
2.0
850
NGC-4486
2.0
800
NGC-4649
2.0
1090
B.
In Excel, use the "trendline" function to fit a straight line through the data, and determine
the slope and y-intercept of the line. Plot the line and the equation on your graph.
How is the slope defined in the equation of a straight line? What is the value of the slope
from your graph? What are the units of the slope from the graph?
The Slope = 412.09
km(mph)/s which means that it would be distance^2/time
How is the intercept defined in the equation of a straight line? What is the value of the
intercept from your graph? What are the units of the intercept value from the graph?
The value of the intercept from the graph is 135.67. The units of the intercept value from
the graph are kilometers per second.
What does "R2" mean in the fit?
The R2 is the correlation between x and y, it is a strong correlation since it is close to one.
Turn in:
The answers to the previous questions (3.5 points) along with your plot with labeled axes, line of
best-fit, equation, and R2 value displayed on it (2.5 points).
C.
What is the range of distances in your graph from Earth to the galaxies you plotted?
Convert this range from megaparsecs (mph) to light years.
Turn in:
The range of distances in both megaparsecs and light years (2 points).
The range of distances is 2 - 0.45 = 1.55.
1.55 mpc is equal to 5055424 lightyears
D.
When Hubble made this type of a graph, he realized that the linear relationship between
the y and x variables was very profound:
Velocity (v) = slope (m) * Distance (d)
The equation above is now known as Hubble's Law, and the value of the slope (m) is named
after Hubble – the Hubble constant. If the slope of the line is always constant (i.e. linear), think
about what this equation means.
Turn in:
Write three to four sentences interpreting Hubble's Law – the constant relationship between a
galaxy's increasing velocity and its distance from the Earth (5 points). Summarize in your own
words what this equation means, and how Hubble's law supports the Big Bang theory (5 points).
See the online material in Lesson 1 and read links for more information.
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Hubble's Law is used to represent the relationship between velocities of distant galaxies and
their distance from Earth. This law takes the form of an equation, v=Ho x d, where v is the
velocity of the galaxy in question, Ho represents Hubble's constant, and d represents the
galaxy's distance from Earth. Even though Hubble's constant is still being researched, this law
can be applied like we did in this lab. Hubble's law helped measure and evaluate the distance
among galaxies and provide an estimate of when the Big Band occurred.