Relative gravimeters are instruments used to measure small variations in gravitational acceleration at different locations. They work by comparing the gravitational pull at a specific site to a reference point, allowing scientists to detect changes in the Earth's density, which can indicate geological features like caves, mineral deposits, or fault lines. These devices are essential in fields such as geophysics and geodesy, where understanding the Earth's gravitational field helps in resource exploration and environmental studies. By providing precise measurements, relative gravimeters contribute to our knowledge of the Earth's structure and dynamics.