Since the sun is one giant ball of gas, what force holds its consistent shape and size? Why doesn't it expand and burn up quickly?
Asked by: J.J. True
The Sun maintains its size and shape against the outward pressure of fusion energy by the force of gravity. In other words, its own weight keeps the Sun from growing larger.
It is the stable balance of outward gas pressure vs. the inward pull of gravity that determines the size of any star.
The predominantly spherical shape of all but the smallest astronomical bodies (asteroids, for example) is due to the radially symmetric nature of the gravitational force.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '