[Ramius]

They seem to be assuming that it has a constant diameter. Isn’t it possible that the sun’s diameter changes from time to time? As a great big ball of burning gas and plasma it might swell up and contract back again, if only a little, every now and then.

And why exactly do we need to know this with such precision? Are we buying it a new pair of pants?

[U-238]

They seem to be assuming that it has a constant diameter. Isn’t it possible that the sun’s diameter changes from time to time?


The Sun expands and contracts because it made from gas. Gravity pulls the sun together and the heat and light of the fusion process expands it. So there is a balance between the forces and has a steady radius. Why scientists want to know?Maybe they want to know how far along the Main Sequence the Sun in evolving. See Hydrostatic equilibrium