1992 Study Puts Sun’s Photon-Diffusion Time at 170,000 Years, Not 500,000
Updated
Updated · Earth.com · Aug 21
1992 Study Puts Sun’s Photon-Diffusion Time at 170,000 Years, Not 500,000
2 articles · Updated · Earth.com · Aug 21
Summary
Mitalas and Sills’ 1992 Astrophysical Journal paper estimated radiation takes about 170,000 years to diffuse from the Sun’s core to its surface in the present Sun.
That figure comes from a random-walk, model-based calculation using solar-model step lengths averaging 0.035 inches, not from a direct measurement or a recent high-end simulation.
The report says earlier simplified estimates used longer 0.2- to 0.4-inch step lengths and that no peer-reviewed source was found to support a commonly repeated 500,000-year value.
It also stresses the timescale tracks statistical energy transport through dense solar plasma: photons are repeatedly absorbed, re-emitted and scattered, so the visible photon reaching Earth is not the same one born in the core.
Once light escapes the photosphere, the contrast is stark—crossing roughly 93 million miles to Earth takes only about 8 minutes.