- Students will have an appreciation of the relative and actual size of the Sun.
- Students will have an appreciation of how fast the Sun moves across the sky.
In this activity, you have been measuring how long it takes the Sun to move a distance equal to its own diameter across the sky. The Sun will take 24 hours to travel 360 degrees all the way around the sky and return to the same position it was in on the previous day. The speed it travels at is:
= 360 deg/(24x60) minutes
= 0.25 deg per minute
= 0.00416 degrees per second or 1/240 degs per second
Calculate the size of the Sun as an angle:
Average duration (in seconds) × 1/240 (degrees per second) = ___ degrees
Congratulations! You have calculated the angular size of the Sun.
You can use your value for the angular size of the Sun to calculate the physical size of the Sun.
Your number for angular size converted into radians × distance from Earth to the Sun = size of the Sun
Angular size × (pi/180) × 92 955 887.6 miles = ___ miles OR
Angular size × (pi/180) × 149 598 000 km = _______km
Congratulations! You have measured and calculated the diameter of the Sun in miles/kilometers!
Country | Level | Subject | Exam Board | Section
— | — | — | —
UK | GCSE | Physics | AQA Science A | Not in current curriculum
UK | GCSE | Physics | Edexcel | P1.3.4
UK | GCSE | Physics | OCR A | P7.1: 1-4
UK | GCSE | Physics | OCR B | Not in current curriculum
UK | GCSE | Physics | WJEC | Not in current curriculum
UK | GCSE | Astrophysics | Edexcel | Unit 1.1.3: a, b
UK | KS3 | Physics | - | Space Physics: Our Sun as a Star
The activity concludes when all the steps have been completed and a size for the Sun has been calculated (and compared with a value listed in a text book). If there are multiple groups doing this activity, collect all the answers and see how much variation there is.
This activity can be used to start a discussion about many other astronomical concepts, such as size scales in the Solar System or unit conversions.