According to the shell theorem the gravitational force on a test mass inside a hollow sphere is every where zero. This paper argues that this situation is not equivalent from the standpoint of General Relativity to the situation where gravity falls to zero far outside the sphere. They conclude that General Relativity predicts that a clock located inside a hollow sphere should run slower than a clock located outside the hollow sphere. (By contrast most people are familiar with the fact that General relativity predicts a clock should run faster as the force of gravity approaches zero far from a gravitational body) This could provide a laboratory test of Newtonian gravity which predicts that both clocks should run at the same rate.
https://arxiv.org/pdf/1203.4428.pdf Harry
