Lab 7 - Coordinates & Seasons - Worksheet
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Name: Basic Coordinates & Seasons – Student Guide
There are three main sections to this module: terrestrial coordinates, celestial equatorial
coordinates, and understanding how the ecliptic is related to seasons on the Earth. Each
of these sections has its own simulator(s). The background material necessary to utilize
these tools is contained in each section. Terrestrial Coordinates
Work through the explanatory material on units of longitude and latitude
, finding
longitude and latitude
, and a bit of history
(optional).
Open the flat map explorer
.
Familiarize yourself with the cursor and how it prints out the longitude and
latitude of the active map location.
Note that you can vary the central meridian of the map (i.e. change its longitude).
Use the “shift map” arrows at the top of the simulator to affect large rapid
changes. Use the shift-click feature of the cursor for finer control.
Note what information is accessible through the show cities
and show map
features
check boxes.
Center the cursor on your present location. Click the open Google Maps button to
launch the Google Map tool focused on this location. Experiment until you get a
good feeling for the Google Map’s capabilities and then close this window. (Note
that you must be connected to the Internet to make use of this feature.)
Question 1: Use the flat map explorer to complete the following table. You are
encouraged to try and predict the answers and then use the map’s cursor and other
features to check the accuracy of your estimates. Location
Longitude
Latitude
The center of the island of
Madagascar.
46.5º E
18.2º S
Hawaiian Islands, United States
157.5º W
21.2º N
Esneye, England
Prime Meridian
51.8º N
Havana, Cuba
82.1º W
Tropic of Cancer
Sao Paulo, Brazil
46.3º W
Tropic of Capricorn
Diomede, Alaska, United States
International Date Line
Arctic Circle
New Orleans, Luisiana, United States
90º W Meridian
30º N Parallel
NAAP – Basic Coordinates & Motions 1/8
Latitude- 38º 53’ N Longitude- 77º 2’ W
Question 2: Determine which of the 50 states defines the farthest extent of the United
States in each of the 4 map directions.
Direction
State
North
Alaska
South
Texas
East (there are two ways
of thinking about this) Maine
West
Hawaii
Question 3: The exact coordinates of the white house in Washington D.C., are 77.0365º
W and 38.897º N. What are these exact coordinates in sexagesimal notation? Show your
calculation in the box below. (You can use the Google Map tool to check your answer.)
Open the globe explorer. You are encouraged to use the Terrestrial Coordinate
Explorers link which opens both simulators at the same time for the following two
questions. Familiarize yourself with the features noting that they are very similar
to those in the flat map explorer. Question 4: A) Where is the north pole on the flat map explorer
? What is its shape? 90º N, 0º E. North pole is by the black and white bar on the explorer It doesn’t
look like anything B) Where is the north pole on the globe explorer
? What is its shape? 90º N, 0º E. the north pole is at the top with ocean all around it looks like a
period
NAAP – Basic Coordinates & Motions 2/8
C) Your answers to parts A and B should be different. Explain why. There
is
nothing there but a flat map. When you look at online maps it looks like thefre is but
nothing is actually there.
Question 5: Compare the relative sizes of Greenland and Australia in the two maps? The
true values of the surface areas for these countries are Greenland (2.2 million km
2
) and
Australia (7.7 million km
2
). Does each map demonstrate these true values? Greenland looks small and Australia looks larger on the globe
map
No one seems off
Celestial Equatorial Coordinates
Work through the introductory material on the page entitled Celestial Equator,
Declination, Right Ascension
.
Open either the Flat Sky Map Explorer
or the Sky Map Explorer
.
Familiarize yourself with the same set of features (cursor movement, shifting the
map, decimal/sexagesimal) that were available on the previous maps.
Make sure that you understand what each check box does. Where is the star Polaris located on this map? What are its coordinates? Dec: 89.2º, RA 1.4h. North celestial pole on sky map
Question 6: Find the constellation of Orion shown in the box below and measure the
right ascension and declination of its brightest stars Betelgeuse and Rigel. Note that
Orion is located on the celestial equator. NAAP – Basic Coordinates & Motions 3/8
RA
5.9 h
DEC
7.7
º
RA
5.2h
DEC
-8.1
º
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Question 7: Which direction is east on the flat sky map? Relate this to a coordinate of the
celestial equatorial system. To the right. DEC: 0.0 º, RA 18h Question 8: Complete the following table of positions on the ecliptic. Ecliptic Location
Approximate Date
Right Ascension
Declination
Vernal Equinox
March 21
0.0h
0.0 º
Summer Solstice
June 21
6.0h
23.7 º
Autumnal Equinox
September 22
12.0h
0.5 º
December 21
18.0h
-23.7 º
Question 9: Write out a description of the ecliptic on the flat sky map. What does the
shape look like? Describe the ecliptic in terms of its average and range of declination
values. A line that is turned up and down like the mountains highest point is
DEC: 23.7 º and RA: 5.9h. and lowest is DEC: -23.7 º and RA: 18.0h Seasons and the Ecliptic
Work through the introductory material on the page entitled Orbits and Light
.
Open the
Seasons and Ecliptic Simulator
.
Note that there are three main panels (left, upper right, and lower right) each of
which have two different views. Controls run along the bottom of the simulation
that affect more than one panel. Click animate and then move through the six
views to get an overview this simulator’s capabilities. We will address each of
these six views separately.
Experiment with the various methods to advance time in the simulator. You may
click the start animate/stop animation button, drag the yearly time slider, or drag
either the sun or the earth in the left panel to advance time.
Note that this animation does not illustrate the rotation of the earth. Because the
timescales of rotation and revolution are so different, it isn’t possible to
effectively show both simultaneously. NAAP – Basic Coordinates & Motions 4/8
Tip:
Once the stick figure
is selected you can gain
greater precision over its
motion by
moving the
mouse a distance away
from the figure.
Left Panel – Orbit View
Practice clicking and dragging in this panel to change the
perspective. Change the perspective so that you are
looking directly down onto the plane of the Earth’s orbit
Click labels. Note that you can see how the direct rays of
the sun hit at different latitudes throughout the year.
Experiment with this view until you can quickly create the two views shown
below. Note that these images explain the shape of the elliptic on the celestial
sphere. In the image on the left (summer solstice) an observer on the Earth sees
the sun above the celestial equator. In the image on the right (winter solstice) an
observer on the Earth sees the sun below the celestial equator. Left Panel – Celestial Sphere
This view shows the earth at the center of the celestial sphere.
The celestial equator and the ecliptic with the sun’s location
are shown. Note that you may click on the sun and drag it and
read out its coordinates.
Experiment with this view until you can quickly create the
image to the right – the direct rays of the sun hitting the earth
on the summer solstice. Upper Right Panel – View from Sun
This view shows the earth as seen from the sun. It gives the
best view of the subsolar point – the location on the earth
where the direct rays of the sun are hitting. The noon
observer’s location on the Earth is indicated by a red parallel
of latitude which can be dragged to new latitudes (this affects
the appearance of the lower right panel). It is possible for the
red parallel to be at an inaccessible location in this view.
Create the image shown to the right – an observer at latitude
80°N on the summer solstice.
Upper Right Panel – View from Side
NAAP – Basic Coordinates & Motions 5/8
Tip:
Note that if you
click and drag the
Earth,
you
will
change the date and
location rather than
the perspective.
This view shows the earth as seen from a location in the plane of the ecliptic
along a line tangent to the Earth’s orbit. It allows one to easily see the regions of
the Earth that are in daylight and those that are in shadow.
Dragging the stick figure allows one to very conveniently change latitude.
Dragging the stick figure on top of the subsolar point
effectively puts the observer at the latitude where the
direct rays of the sun are hitting.
Although rotation is suppressed in this simulation,
keep in mind that the stick figure is on a planet that is
rotating with a period of 24 hours about an axis
connecting the north and south poles. Thus, 12 hours
later it will be on the other side of the earth.
Set up the simulator for the image at right – the winter solstice for an observer at
80
N. Since this observer’s parallel of latitude is located entirely in the shaded
region, this observer will not see the sun on this day. Lower Right Panel – Sunbeam Spread
This view shows a “cylinder” of light coming from the sun. It is projected on a
grid to convey the area over which the light is spread. As this light is spread over
a larger area, its intensity decreases. Lower Right Panel – Sunlight
Angle
This view shows the angle
with which rays of sunlight
are striking the Earth. It lists
the noon sun’s angle with
respect to the horizon (its
altitude).
Verify that when the noon
observer is at the latitude
where the most direct rays of
the sun are hitting, the sun is
directly overhead making an
angle of 90
with the ground.
Verify that when the noon
observer is at the latitude where the least direct rays of the sun are hitting, the sun
is on the horizon.
NAAP – Basic Coordinates & Motions 6/8
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Question 10: The table below contains entries for the coordinates for the sun on the ecliptic as well as the latitude at which the most direct and least direct rays of the sun are hitting. Use the simulation to complete the table. Date
RA
DEC
Latitude of
Most Direct Latitude of Least
Direct Ray
February 5
21.3h
-15.8
16.5 ºS
90 º N
March 21
23.9H
0.0 º
0.0 º
90 ºS
May 5
2.9 h
+16.5°
16.5° N
73.5° S
June 21
6.1h
16.5 º
23.4ºN
90 ºS
August 5
9.2h
-0.6 º
16.5 ºN
90 ºN
September 21
12.1h
-0.6 º
0.0 º
90 ºN
November 5
14.9h
-16.6 º
16.5 º
90 ºN
December 21
18.1h
-23.4 º
23.4 º
90 ºN
Question 11: Using the data in the table above, formulate general rules relating the
declination of the sun to the latitude where the most direct and least direct rays of the sun
are hitting. Neg. sun is coming to southern hem. The positive is in the northern with
more sun
Question 12: The region between the Tropic of Cancer and the Tropic of Capricorn is
commonly known as the tropics. Using the sunlight data table from question 11, define
the significance of this region. Question 13: Using the sunlight data table from question 11, define the significance of
the region north of the Arctic Circle commonly referred to simply as the Arctic. Direct
sunlight a place where there is no sunlight at specific seasons
NAAP – Basic Coordinates & Motions 7/8
Question 14: Use the simulator to complete the table below. For each latitude write a
short paragraph which describes the variations in sunlight (seasons) that are experienced
at this latitude throughout the year. Latitude
Description of Yearly Pattern of Sunlight
0°
The noon sun’s angular height above the horizon ranges from 90° on the
vernal equinox, to 66.5° on the summer solstice, to 90° on the autumnal
equinox, and back to 66.5° on the winter solstice. Thus, the equator always
receives very direct intense sunlight throughout the year which accounts for
the very high temperatures. 23.5° N
sun at noon has an angular height of 66.5° on the vernal equinox, 90°
during the summer solstice, 66.5° during the autumnal equinox, and 43°
during the winter solstice. Direct sunlight hits the latitude for about 3 mnths
out of the year
41° N
sun at noon has an angular height of 49° on the vernal equinox, 71.9°
on the summer solstice, 49° on the autumnal equinox, and 25.5° on the
winter solstice. no direct sunlight on this latitude so cooler temps.
66.5° N
sun at noon’s angular height is 23.5° during the vernal equinox, 47.1°
during the summer solstice, 23.5° during the autumnal equinox, and 0°
during the winter solstice. 3mnths out of the year barely any sunlight
no more for the rest of the year and colder around here.
90° N
sun at noon has an angular height of 0° during the vernal equinox,
25.5° during the summer solstice, 0° during the autumnal equinox, and
-21.0° during the winter solstice. Half of the year there is little sunlight, and
not direct sunlight for the rest of it. Cold all the time only warmer when there is sun.
NAAP – Basic Coordinates & Motions 8/8