The understanding that mass attracts mass is not solely based on the Cavendish experiment, but rather on a combination of experimental observations and theoretical understanding.
Observations of planetary motion: The observation of the motion of celestial bodies, such as planets orbiting the Sun, provided significant evidence for the gravitational interaction between masses. The mathematical description of planetary motion developed by Isaac Newton in the 17th century, known as Newton's law of universal gravitation, successfully explained the observed motion of planets and other celestial objects.
Falling objects on Earth: Everyday observations of objects falling towards the Earth's surface also provide evidence for mass attracting mass. When you drop an object, it accelerates towards the Earth due to the gravitational force. The behavior of falling objects can be precisely described and predicted using the laws of motion and the law of universal gravitation.
Geodesy and satellite motion: Precise measurements of Earth's shape and the motion of artificial satellites around the Earth confirm the existence of a gravitational field. The orbital motion of satellites, including their precise paths and velocities, is consistent with the gravitational force exerted by Earth's mass.
Gravitational lensing: Gravitational lensing is a phenomenon where the path of light is bent by the gravitational field of massive objects. The observation of this effect provides indirect evidence for mass attracting mass. The bending of light around massive galaxies or clusters of galaxies can be observed and measured, confirming the gravitational influence of their mass.
General theory of relativity: Albert Einstein's general theory of relativity provides a deeper understanding of gravity as the curvature of spacetime caused by the presence of mass and energy. This theory has been extensively tested and confirmed through various experiments and observations, including the bending of starlight during a solar eclipse and the precise predictions of the motion of Mercury's orbit.
While the Cavendish experiment played a crucial role in the direct measurement of the gravitational constant, our understanding of mass attracting mass goes beyond this single experiment. The cumulative evidence from multiple experiments and observations supports the existence of gravitational forces between masses.