Light from the Moon
Research the Moon for a month in the twinkling of an eye……………
Spot the difference between the two Moon-months? Can you explain why they are both correct even though they are different?
If you are stuck for an answer, go to: http://www.woodlands-junior.kent.sch.uk/time/moon/hemispheres.html.
(The children in this school explain the reason for the difference very well.)
There are lots of things to measure about light from the Moon but it is difficult to do for real because it takes a month of cloudless nights! So we use a model to help us research. The light probe measures the reflected light from the ball in the same way that astronomers measure the light from the Moon.
To understand more about the phases of the Moon, Todd Timberlake has created a super demonstration of the Moon going round the Earth showing how the moon is illuminated by the Sun.
The Phases of Moon model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Once downloaded, double clicking the ejs_MoonPhases.jar file will run the program if Java is installed.
The Amount of Light Reflected from a Model Moon
Set up a model of the Moon, Earth and Sun. Use it to measure the amount light which is reflected from the model Moon as it goes around the model Earth. Light from the torch acts as light from the Sun.
Click here if you need help setting up and using a model Moon.
Download and watch the Phases of Moon demonstration directly from the Physcis To Go website or by clicking here. Decide on about 8 model Moon positions to take readings. Use the light probe to measure the amount of reflected light from the model Moon. For each position, find out what the angle is between probe, Moon and Sun.
For each position you investigate you should:
|1||Find out the how many days it is after a New Moon.
|2||Click on the picture below showing the phases of the Moon over 28 nights.
|3||Use this collection of pictures of the Moon on the different days to estimate the fraction of the Moon that is lit up in your investigations. Print this page and write each fraction as a decimal in the chart on the appropriate days.
|4||Record your data in a table or spreadsheet on your handheld. Click here to see how you should create your datasheet.
Create a graph of your results.
|5||You could create a graph. Describe what the graph looks like.
More about the Moon
There is a lot more information about phases of the Moon in the TI-Nspire teacher resource.
To see more about the Moon, use the View in TI-Nspire link.
|1||The number of days it takes for the Moon to orbit the Earth is not 28 days exactly.
You can see a good explanation by clicking here.
Make a table of the number of days in between each Full Moon for this year and the year of your birth.
|2||Find out what a ‘Blue Moon’ month is and see if there is a Blue Moon in either of the years you have researched. If not, find when the last Blue Moon was.|
Explanation of the Moons orbit around the Earth
The Sidereal and Synodic Months
The sidereal month is the time the Moon takes to complete one full revolution around the Earth with respect to the background stars.
However, because the Earth is constantly moving along its orbit about the Sun, the Moon must travel slightly more than 360° to get from one new moon to the next. Thus, the synodic month, or lunar month, is longer than the sidereal month.
A sidereal month lasts 27.322 days, while a synodic month lasts 29.531 days.
The original website content can be found here.
What I have covered and achieved
Across Assessment Focuses and Levels
|AF1||L5||Use abstract ideas or models or more than one step when describing processes or phenomena
|AF1||L6||Describe some scientific evidence that supports or refutes particular ideas or arguments, including those in development
|AF2||L5||Link applications of science or technology to their underpinning scientific ideas
|AF3||L4||Select appropriate ways of presenting scientific data
|AF3||L5||Use appropriate scientific and mathematical conventions and terminology to communicate abstract ideas
|AF4||L5||Repeat sets of observations or measurements where appropriate, selecting suitable ranges and intervals
|AF4||L6||Collect data choosing appropriate ranges, numbers and values for measurements and observations
|AF5||L5||Draw valid conclusions that utilise more than one piece of supporting evidence, including numerical data and line graphs
|AF5||L6||Select and manipulate data and information and use them to contribute to conclusions|
Setting up and using a model Moon
A 5 cm diameter white, polystyrene ball makes a good model Moon but a table tennis ball will do. We used a boules ball. Tennis balls will do but are not very good as they do not have a smooth, reflective surface. Glue a piece of cotton thread to it. Hang the model Moon up.
Shine a narrow beam from a torch from about two metres away at the model Moon.
Make the rest of the room as dark as possible.
Use a light probe to measure the amount of reflected light from the model Moon. Put the probe in a toilet roll inner to cut down stray light and aim the probe at the model Moon.
Start with the light probe very near the Model Moon and move it away to get a sensible reading. You can also try moving the torch nearer and further away to see what effect this has. Once you are satisfied set the handheld to take in and store the individual readings.
You can now start investigating the different positions of the Moon going round the probe (the Earth).
At each position measure the angle of reflection at the model Moon between the narrow beam of light from the torch and the probe.
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