Use the Sun scale apparatus constructed in this activity, to gain a better understanding of the diameter of the Sun and the distance from the Earth to the Sun.
- Diameter of the Sun
- Distance between the Sun and Earth
Card supports, 2*
Sun Scale Measurement Cards, 2*
*Materials included in kit.
Never look directly at the Sun. Follow all other laboratory safety guidelines.
- Obtain the half-meter track, two card supports, and two Sun Scale Measurement Cards.
- Punch a small hole in the center of each Sun Scale Measurement Card using the push pin.
- Place a Sun Scale Measurement Card into one of the card supports (see Figure 1).
- Repeat step 3 for the other Sun Scale Measurement Card and card support.
- Position the assembled Sun Scale Measurement Cards and supports on the half-meter track as shown in Figure 2. The first card should be placed at the 50 mm (5 cm) mark on the half-meter track. The printed sides of the Sun Scale Measurement Cards should face each other.
- While outdoors or near a window receiving a lot of sunlight, point one end of the half-meter track towards the Sun. Do not look directly at the Sun. Move the half-meter track until the Sun’s rays travels directly through the hole in the first Sun Scale Measurement Card (located at the 5-cm mark) and an image of the Sun is projected on the second Sun Scale Measurement Card (see Figure 3).
- Move the second card support and attached Sun Scale Measurement Card until the projected image of the Sun on the card is clearly focused and is about 2 mm in diameter.
- Measure and record the distance between the two support tips in millimeters on the Sun Scale Worksheet.
- Repeat steps 7 and 8 for a 3-mm diameter image and a 4-mm image. For each image, record the distances between the two card supports on the Sun Scale Worksheet.
- Complete the Sun Scale Worksheet to calculate the diameter of the Sun and answer the Post-Lab Questions.
- Enough materials are provided in this kit for one demonstration/student activity. The assembled apparatus may be reused indefinitely. This laboratory activity can reasonably be completed in one 50-minute class period.
- It is best to perform this activity outside or near a window receiving plenty of sunshine on a sunny day.
- Stress to students that they should not look directly at the Sun at any point during this activity.
- The tips of the card supports may be pinched if the supports do not fit on the half-meter track snugly.
- The calculated diameter of the Sun and distance to the Sun from the Earth values should be rounded off to four non-zero digits.
- The Sun scale track may be used to estimate the diameter of the Moon or the distance between the Earth and the Moon. The average distance from the Earth to the Moon is 384,203 km and the accepted diameter of the moon is 3474 km. As an interesting side note, tidal effects result in an increase in the distance between the Earth and the Moon of approximately 3.8 cm per year.
- The Sun scale track may also be used to indirectly view solar eclipses. Once again, be sure that students do not directly view the sun or solar eclipses.
- You may wish to have students set up distance and or diameter ratios between the Sun, Earth and Moon. The accepted diameter of the Earth at the equator is 12,756 km and at the poles is 12,714 km.
- Have students perform further research to determine the times of the year the minimum and maximum distance between the Sun and the Earth are reached. This may lead into an interesting discussion of the Earth’s seasons. In the northern hemisphere, the Earth is actually further away from the Sun during the summer than it is in the winter. This reinforces the fact that it is not the distance from the Sun that determines the seasons on Earth, but the Earth’s tilt (23.5°) and the angle at which the Sun’s rays hit the surface of the Earth.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Asking questions and defining problems
Developing and using models
Using mathematics and computational thinking
Disciplinary Core Ideas
MS-ESS1.B: Earth and the Solar System
HS-ESS1.B: Earth and the Solar System
Scale, proportion, and quantity
Systems and system models
MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures.
MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
MS-PS1-5: Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.
*Round off to four non-zero digits.
Answers to Questions
- Use Equation 1 to calculate the diameter of the Sun (given that Earth is approximately 150,000,000 km from the Sun.
- Calculate the average diameter of the Sun using the three calculated diameter values above ___1,373,000___ km
- Calculate the percent difference between your averaged measurement of the Sun’s diameter and the actual accepted diameter of the Sun (1,391,000 km).
- What factors could account for the difference between your calculated diameter of the Sun and the actual diameter of the Sun?
The calculated and actual Sun’s diameter values may be off due to measurement errors of the Sun’s image diameter and the tips of the card supports, etc.
- The actual distance between the Sun and the Earth varies from 147,097,000 km to 152,086,000 km due to Earth’s elliptical orbit around the Sun. For each Sun image diameter, recalculate the diameter of the Sun using Equation 1 and the minimum and maximum distances between the Earth and the Sun. Record the minimum and maximum calculated diameters of the Sun below.
- Calculate the average minimum Sun diameter in Question 5. Average the maximum values as well. Does the actual accepted diameter of the Sun value fall within these calculated averages?
Average diameter of the Sun using minimum Sun/Earth distance ___1,346,000___ km
Average diameter of the Sun using maximum Sun/Earth distance ___1,391,000___ km
Yes, the accepted Sun diameter falls within the minimum and maximum calculated ranges.
- Rearrange Equation 1 to solve for the distance (in km) between the Sun and the Earth using the 3-mm Sun image assuming the diameter of the Sun is known. Use the accepted diameter of the Sun to calculate the distance of the Sun from Earth. Does the value fall within the actual minimum and maximum distances between the Sun and the Earth?
Calculated Distance to the Sun from Earth = ___150,692,000___ km
This value falls within the accepted minimum and maximum range.