This is one of those ideas that is so wrong that it is right:

> He reasoned that such particles, emerging from the surface of a star, would have their speed reduced by the star’s gravitational pull, just like projectiles fired upward from the Earth. By measuring the reduction in the speed of the light from a given star, he thought it might be possible to calculate the star’s mass.

>Michell asked himself how large this effect could be. He knew that any projectile must move faster than a certain critical speed to escape from a star’s gravitational embrace. This “escape velocity“ depends only on the size and mass of the star. What would happen if a star’s gravity were so strong that its escape velocity exceeded the speed of light? Michell realized that the light would have to fall back to the surface.