Moon Observation
Materials:
White ball
Compass
Ruler
1. Go outside and observe the moon. Record what it looks like, where it is in the sky, and the
angle between the sun and the moon (see instructions below).
2. Hold your ball at arm’s length so that it appears to be right next to the moon and compare its
appearance to the moon.
3. Hold the Styrofoam ball at arm’s length in other directions and observe what the lit part
looks like. Where do you have to hold it to make it look like a full moon?
Measuring the angle between the sun and the
moon
The angle between the top and bottom of your
fist, held at arm's length, is about 10 degrees.
Start with your fist right next to the moon, and
count "fistfuls" across the sky until you get to the
sun.
It isn't easy to do this accurately, especially when
the sun and moon are in very different directions.
Measuring the angle several times in a row will
give you a better value.
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Moon 1
4. The compass needle points north. Turn the compass so that the N on the case is next to the
needle. Then determine approximately where the sun and moon are in the sky (north, northwest, west, southwest, …).
5. Holding the plastic ruler at arm’s length, determine how many centimeters of it are needed
to just cover up the moon. Also measure the width of your fist, in centimeters. Use the
paper tape to measure how far it is from your eye to your fist, at arm’s length.
Sunplot
Where is the sun in the sky?
In the course of the semester we are going to observe where the sun is in the sky. To do this we
will use an apparatus that is on the porch on the Rose Street side of the Chemistry-Physics
Building. It consists of a round level platform with a small cone at the
center. We will call the cone “the gnomon” (pronounced “No-mon”),
which is Greek for “indicator.” The gnomon is a cone that is 4.1 cm tall.
When the sun is shining, it makes a shadow on the platform. We can
record where the end of the shadow is by marking on a piece of paper
taped to the platform. The completed sunplot is a set of dots on the paper,
representing where the end of the shadow was at every time someone
recorded it; connecting the dots gives a curved line across the paper.
Suppose this is the piece of paper.
The gnomon was at the center, where the small circle is.
Where will the end of the shadow be early in the morning?
Where will it be late in the afternoon? Where will it be
near noon? Draw these in on the diagram. (You probably
don’t know; you are making hypotheses to test. Thinking
about this is useful, because it makes you aware of how
this experiment is related to things that you already know).
We can reconstruct where the sun was at various times of
the day. The shadow is long in the morning and evening,
but becomes short in the middle of the day. As indicated in the diagram at right, we can
determine the angle between the sun and the vertical by making a drawing.
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Moon 2
Theories
1. UK always starts class on Wednesday, both fall and spring semester. Here is a list of the first
day of class of the fall semester for several recent years:
Year
2010
2011
2012
2013
2014
2015
2016
2017
First day of class, fall semester
August 25
August 24
August 22
August 28
August 27
August 26
August 24
2. Thanksgiving this year is November 26. Margie wonders, what was the date of Thanksgiving
in 2010? Looking at the table above, Louise says it must have been November 25. What
hypothesis did Louise use to decidc this?
Explain Louise’s hypothesis in terms of the calendar.
3. What will be the date of the first day of class in 2017? To answer this, you will have to
figure out the pattern. Explain the pattern for the table of first days of class.
4. Solving this puzzle involve making hypotheses and testing them against the data. What
hypotheses did you try – including the ones that didn’t work?
09/04/2015
Moon 3
Sometimes at the grocery store they make a triangular pyramid of oranges. How
many oranges does it take to make a pyramid 10 layers high?
5 As a first step, consider how many oranges there are in a triangle (one layer of
the pyramid) with a few oranges on a side, and then look for a pattern
A stack of 10 oranges
Number on side
1
2
3
4
5
6
Total number
1
3
6
What is the pattern that generates this table?
6. Now consider the pyramid. A pyramid is made of layers; to make a larger pyramid, we add
a layer. So we can construct the table for the pyramid by adding the numbers in the prevous
table.
Number on side
1
2
3
4
5
6
Total number
1
4
10
10
What is the pattern this time?
09/04/2015
Moon 4
Siphons
How siphons work.
Materials
For each group
Some containers with water
2 calibrated cups, for measuring volume
1 small tray
A length of tubing
timer
Definitions
A siphon is a way to move a fluid from one place to another, using a pipe or tube. The middle
of the tube can be higher than the ends, so that the fluid is (temporarily) flowing uphill.
One way to describe a flowing fluid is to determine the flow rate, which is the volume of liquid
that is transferred divided by the time it takes to deliver it.
Flow rate = volume produced / time to produce it
What to do
1. Make a working siphon. To do this, push most of a tube into the water, so that it fills up.
Then block the open end, and pull the tube up and over so that it is just above the container you
wish to put the water in. Then unblock the open end (and look for a towel, if you aren’t careful).
2. Design a method for measuring the flow rate of a drinking fountain. Briefly describe the
method.
3. Measure the flow rate of a drinking fountain out in the hall. Give your result. For
consistency, always use cubic centimeters (cc) or milliliters (ml) (they are the same thing) for
your volume measurements.
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Moon 5
4. What determines which way the water flows in the siphon tube?
Al says, "It flows from the container that has more water in it."
Becky says, "It depends on which end of the tubing is higher."
Carla says, "It depends on the water levels in the containers."
David says, "It depends on which container is taller."
Enid says, "You can make it go either way, depending on how you start it."
Investigate this system and determine who (if anyone) is right.
Give a rule that tells which way the water flows.
Use your rule to predict which way the water flows in each of the cases shown below (and check
your prediction if you are at all unsure).
Check #1: Discuss your rule (and other activity so far) with an instructor.
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Moon 6
5. While you were outside, you compared the size of the moon to the length of a ruler held at
arm’s length, and measured the width of your fist. Make a scale drawing of arm, fist, and eye
(representing 10 cm as 1 cm on the paper) and then measure
the angular size of your fist.
The angular size of the moon is smaller, in the same proportion as the measurements you made.
So what is the angular size of the moon?
2. In the diagram below the triangle represents the gnomon for the sunplot device.. Note that it
is 4.1 cm tall on the paper. The dark line represents the shadow at a particular time, which we
can measure on the sun plot. The sun is far away to the left (93 million miles, which will not fit
on the paper). What is the angle between the sun and the vertical for this diagram?
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Moon 7
Each group should hand in one copy of this page at the end of class
Group:
Names of group members present:
10. You would not want to go over Cumberland Falls in a canoe, and it would be dangerous to
try to swim in the pool below the falls. A few miles upstream or downstream you can barely tell
that the river is flowing. Yet the flow rate is the same! Explain this.
11. There are two ways to move water across a
valley: you could run a straight pipe across it, or
let the pipe follow the curve of the ground. The
Romans used the design on the left, because their
pipes were somewhat leaky. The design on the
right has the advantage that you don’t need to build the support structure.
Why is leakiness of the pipes relevant to the decision?
Jerry claims the design at right is better (if the pipes don’t leak) because the water will go faster.
Is this right? How is this related to an experiment you did?
You may leave when your group has turned in the yellow copy of this page.
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Moon 8
The sunplot hypothesis
We observed that the sun is to the south-east. It rose in the east (though perhaps not exactly due
east) and will set in the west (though perhaps not exactly due west); it should be highest in the
sky near noon (but perhaps not exactly at noon). The shadow points away from the sun as we
were observing – so we might expect the sunplot to look like this:
How a siphon works
A working siphon has the tube full (or almost full) of
water. When water moves in the tube, the flow rate is
the same all along it: the same amount of water has to
enter the tube as leaves it
The siphon seems paradoxical, because at some parts of
the tube the water is going uphill. But at other parts it is
going down, and the net effect of the siphon flow always
is to deliver water from the higher water level to the lower water level. The important
difference between the two cases shown in the diagram is that in the first case water can get
lower if the siphon flows to the right (and so it does), while in the second diagram the water will
go to the left.
To get the siphon started there has to be enough water in the tube in the right places. The water
will flow if the effect is that more water goes down than goes up. A few bubbles in the siphon
tube don’t matter, and they will probably get carried by the flow and leave the tube.
If a siphon could move water uphill, we could use it to fill a pond that would run a waterwheel,
giving us energy for free. No one has ever succeeded in making this work, and physics is based
on the assumption that it is impossible. Water always goes downhill, even in a siphon system.
09/04/2015
Moon 9
Science and the scientific method
People get the impression that science is a pile of facts, or a set of unbreakable laws that are known to
be true. However, scientists understand the situation rather differently. The starting point of science
is the assumption that the forces of nature are predictable and can be understood; science is a process
for learning about nature and how to control it.
Science is based on observation. It does start as a pile of facts. But a pile of facts is no more interesting
than a telephone book or a dictionary, and no one would be able to remember all the facts, just as no
one can memorize the telephone numbers of all the people in Lexington. So scientists look for patterns
that allow us to represent many observations with a simple statement.
One example is the constellations. The stars are scattered randomly across the sky, but observers
noted that they don’t move relative to each other, and gave names to clusters that are easy to recognize
(perhaps the stars look like a dipper or a man carrying a shield).
These patterns are useful for telling someone
where to look in the sky. But they have limited
use, because there isn’t really any connection
between the stars. Looking through a telescope
you will not see more detail to this pattern.
We observed the moon, and recorded what we saw. On other days and other times it will be elsewhere
in the sky, and will look different. When have many observations, we will begin to see a pattern. We
can use this pattern to fill in what the moon would have looked like on a day that we forgot to observe
it, or when the weather didn’t allow us to see it, and to anticipate what it will look like in the future.
Scientists call this kind of pattern a theory. The important point is that it includes most of the
observations already made, and predicts the results of observations that have not yet been made.
If we make careful measurements, we will discover that the pattern of the moon isn’t completely
regular, and will have to come up with a more complicated model that accounts for the irregularity. As
the theory improves, it gets harder and harder to think of an alternate explanation; the theory seems to
always apply.
Scientists always leave open the possibility that the theory is not quite right, and look for tiny
exceptions, because these can lead to completely new phenomena. One scientist noticed that the leg
of a thoroughly dead frog twitched when he touched it, and in this way discovered a way to create and
control electricity. Another scientist noticed that a compass needle wiggled when he turned on an
electrical circuit; up until then, scientists had thought that electricity and magnetism were unrelated,
and his discovery made possible electric generators and totally changed the way we live.
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Moon 10