Solar neutrinos
- Round
- Theory
- Points
- 10
- Level
- Bronze
- Taught in
- Section S2
Adapted from IOAA 2011 (Katowice), theory problem 14. We have restated it in our own words and kept the original data, adding the solar constant from the IOAA 2025 data sheet. The solution was last checked on 16 October 2026.
Estimate the number of solar neutrinos that pass every second through an area of 1 m² of Earth's surface, held perpendicular to the Sun's rays. Each fusion reaction in the Sun releases 26.8 MeV of energy and two neutrinos. Take the solar constant, the power of sunlight on 1 m² at Earth's distance, as 1361 W m⁻², and 1 eV as
- Each reaction releases
- Each second the sunlight crossing 1 m² carries the energy of
- Each reaction sends out two neutrinos, which pass almost unhindered through the Sun and through Earth, so
AnswerAbout
This problem also appears among the olympiad problems of Section S2, Exam technique and the problem-solving method, which teaches the ideas it uses. Equation and figure numbers refer to the course.