Where is the best Christmas getaway for sunbathing in the USA? Florida or Alaska?
This project demonstrates how to make a Sun & Earth rotation model and use light detection devices to explore the daylight difference in different locations at the same time over a year, and then analyze the length of day and night and light intensity based on the detected data graph.
Earth is a planet in our solar system. It orbits the Sun once every 365.25 days. Meanwhile, the Earth rotates on its axis, which causes day and night. Half of the earth faces the sun and experiences daytime and the other half faces away from the sun and experiences nighttime.
Due to the tilt of the Earth’s axis, the sun's rays are directly overhead along the Tropic of Capricorn in December(as shown in the figure below), and the bright side of the northern hemisphere is smaller than the dark side. Therefore, the days in the northern hemisphere are shorter and the nights are longer. At the same time, the further away from the subsolar point, the less direct the sunlight, and the less intense heat from the sun.
This sun & earth model simulates the position of the sun and earth on 22nd December. A flashlight will be used to represent the sun for emitting light. There is a light sensor on the“Earth”to collect light intensity. The micro:bit inside the ball will transmit the obtained light values via radio function to another micro:bit for data displaying, and then the data will be turned into a visual data graph in Mind+.
Bill of Material:
Mainboard 1IO x1
Self-locking Switch x1
Boson Expansion Board x1
Light Sensor x1
Motor Control Module x1
Motor Extension Shaft x2
Boson Battery Holder x1
micro USB Cable x2
AAA Battery x3
Foam Hollow Half Ball R=20cm x2
Carton Box x1
Flocking Light Absorbing Cloth x1
Worm Speed Reducer x1 Long Shaft x2
Hot melt glue, scissors, protractor, pencil/oil pen, utility knife, stapler, transparent tape, straw
1. Remake the carton box
2. Earth model & light detection
Download the sample program for the data collection, open it in Mind+, and upload to micro:bit.
Note: Upload the codes for data collection onto the micro:bit board before putting it inside the ball.
3. Rotation Control
4. Tilt Angle
5. Lighting and testing
Note: please watch the video for more details.
Activity: Location vs Light Intensity
When the position of the sun(flashlight) is fixed, the visual light data graph in Mind+ changes with the rotation of the earth. Switch the position of the light sensor to generate a new visual data graph, and analyze the length of the day and night and light intensity in this place.
Download the sample program for data displaying, switch Mind+ to offline mode, and then transfer the program into the micro:bit of data displaying end.
Switch Mind+ to online mode to view the real-time data in the stage.
1. Connect device and get ready to upload data.
2. Click the green flag, and input the number of columns(20) of the table in the pop-up box on the stage.
3. Tab the space key on the keyboard to generate a data table.
4. Click the red button on the stage to start plotting data. One turn of the ball represents a day. The black line in the graph is for night, red line for day. A continuous section of red and black lines is a whole day.
The program sets the threshold of light value to 10. If the light intensity is larger than or equal to10, it is in the daytime, otherwise, it’s in the nighttime. Or use the ambient light measured after turning off the lights in the room as the critical value for day and night. Besides, turn off the ambient lights, switch on the flashlight, put the light sensor to the solar terminator, and the light intensity measured at this time can also be used as a critical value.
By comparing the light data graph of Florida and Alaska, it is evident that the light intensity of Florida is higher than that of Alaska in December. So Florida is the best choice for a sunny Christmas holiday. The graph also shows that the nighttime in Alaska is much longer than its daytime, and there is only a small difference between the duration of the day and night in Florida, which means adequate daylight for enjoyable sunbathing can be easily available in Florida.