# Newtonian gravity in small objects and Cavendish Experiment

Going through the internet I've found claims (like the ones found on this MinutePhysics video) that Newton's law of gravitation could not be applied to small, everyday objects. However, after reading about the Cavendish Experiment for calculating the gravitational constant, how could these claims be considered true if at Cavendish's time the understanding of gravity was based solely on Newtonian Gravity?

P.s: If possible please mention scientific sources.

• Perhaps not everything on the internet is true? That seems to be the simplest explanation. Jan 23, 2020 at 20:47
• Not everything on the Tinkerwebs is true? Dang!
– Gert
Jan 23, 2020 at 20:51
• At what time mark in the video is the statement which you are querying? Please be more specific. Statements need to be read in context. Jan 23, 2020 at 23:08
• It for sure can be applied. But the effect will be negligible. That might often be what is meant by "can't" on most sites. But if you set up a precise experiment in a controlled environment - which Cavendish did - it might not be negligible anymore. Jan 24, 2020 at 0:01
• Cavendish's experiment didn't use "everyday objects" Jan 24, 2020 at 0:01

The video you link is making the point that we cannot measure the gravitational force if the masses are too small. Cavendish used two lead spheres weighing $$158$$kg as his large masses, and even though gravity is a weak force this mass is large enough to produce a detectable force. But suppose the masses were $$158$$g, $$158$$mg or $$158\mu$$g. At some point the gravitational force is going to get too small to be measured, and if we cannot measure the force we cannot know for certain that it obeys Newton's equation.