PHASES OF THE MOON
PHASES OF THE MOON
The astronomy labs may take several days of observation, especially if the sky gets cloudy. Start these labs soon after you start this course. A. OBJECTIVES This lab is presented to show what can be observed of the moon’s motions and how they are manifested in its illuminated shape. B. BACKGROUND Most of the movement we detect in the sky is due to the earth spinning under the sky. The sun, moon, and stars appear to rise each day or night in the east and set in the west, but this is merely apparent motion caused by the earth’s rotation. We must find other more subtle indications of actual movement in celestial objects. The Moon: We can observe the phases of the moon in order to detect the moon’s movement as it orbits the earth. When it is between the earth and the sun, it is not visible and is called the NEW MOON. On the other extreme, 2 weeks later, it is on the opposite side of the earth from the sun. This is the FULL MOON phase, and the entire face of the moon that we can see is illuminated. Halfway between new and full phase, the moon is in its first quarter or third quarter phase, and we then see only half of the circle that faces us. Less than a quarter moon is a “crescent,” and more than a quarter is a “gibbous” moon. The different phases of the moon actually tell us that the moon has changed its location and we are seeing it in a different perspective. They tell us that the moon is moving. C. EQUIPMENT A compass will be very helpful, but if you know your directions in relationship to city streets, you can estimate directions. Most calendars will inform you of the dates for major moon phases. D. PROCEDURES Check the calendar to see when the next NEW MOON is scheduled. 1. Observe the western sky at sunset, and verify that the moon is not visible. Take a compass reading of the sun just as it hits the horizon. Is it due west? You can use this information for the laboratory about the sun.
Observe the sky at sunset every subsequent night (the moon may still be invisible the next night, but don’t give up). Notice that the moon has different stars around it each time you observe. This also shows that the moon is moving in a separate manner from the sky. Record the shape of the moon and its position. Estimate both the compass direction of the moon at sunset as well as the approximate elevation of the moon in the sky (vertical is 90o and halfway up is 45o, or just say low, moderate, or high). By the time the moon reaches first quarter phase, you should be able to see the moon throughout the afternoon. It will be in the southeast sky as it is rising to its high point close to sunset.
Continue your observations until the moon is not yet up at sunset. What phase of the moon is it now? How long did it take to go from new moon to this point?
RESULTS AND CONCLUSIONS Make a chart of your observations, and answer the following questions. How long does it take the moon to go through all its phases? If you consider that the moon travels 360° in its orbit, how many degrees does it travel in one day (360 divided by number of days for a complete orbit)? This is the amount of change in the compass direction you should have observed from one day to the next, if you observed at the same time each night. Depending on the time of year, there may be a very bright object in the western sky at sunset. This is the planet Venus. It is a striking object and emphasizes the change in position of the moon from night to night. If you are an early riser, you can continue your moon observations in the morning before dawn. The third quarter moon dominates the very early morning hours and continues to be visible during morning daylight. Try to see when the 3/4 moon sets. Summarize your observations.
APPLICATIONS 1. Make a drawing showing the earth, sun, and moon. Show where the moon would be positioned at the new, first-quarter, full, and third-quarter phases. The Islamic calendar uses 12 lunar months of 30 days each. If the month of Ramadan begins this year on October 15th (western calendar), on what day will it begin next year?
laboratory report should contain the following sections: (1) Hypothesis, (2) Procedures,
(3) Observations and Results, and (4) Conclusions. Make certain you include all four headings with at least a short paragraph for each. In addition, tables, graphs, and answers to questions may be necessary in the latter two sections.
Scientific research should contain a preliminary statement of the expected outcome of the experiment. This can include predictions of the specific experiment or the general anticipated result. If you are merely doing an observation and have no idea of the outcome, you cannot make an actual hypothesis. Instead, make a short statement of the purpose of the observation. However, if you have preconceived ideas of the outcome, include them in this section, and then see how they compare to the results.
Even though you are told what to do, write a paragraph of the specific steps you actually took in doing the experiment or observation. Because you are coming up with your own equipment, your procedures will be of particular interest.
OBSERVATIONS AND RESULTS
This is where you should make a detailed statement of the outcome of your experiment. Record all your pertinent observations in a clear, readable form. Arrange your data in tables (such as measurements and calculations you make). Answer any questions asked in this Study Guide, marking these clearly so that they can be easily found.
Your conclusions should include a comparison between the outcome of the experiment and your initial predictions made in the hypothesis. In cases where you are attempting to recreate a physical constant, compare your number to the accepted value, using the formula for experimental error:
Experimental Error Equation
If you find a large difference in your results from the expected value or if your anticipated observations are not the same as your actual observations, try to identify possible sources of error or reasons for the difference in the hypothesis and results