The inverse square law is a mathematical rule that describes the relationship between an object's distance from another object and the intensity of light it receives. The law states that if you double your distance from a source of light, you will receive only one-fourth as much illumination.
If you triple your distance, then only one-ninth as much illumination reaches you; quadruple it and just 1/16th reaches; etc. The inverse square law applies to all forms of radiation -- not just visible light but also radio waves, microwaves and X rays (and even sound).
It also applies to gravitational force: If two objects are twice as far apart they feel each other with half the strength (or vice versa). This means that if we want to know how strong gravity is at any point in space or on Earth's surface we can simply measure its effect on some known quantity such as mass or energy density -- which tells us how many particles there are per unit volume -- at different distances away from this point.
This simple formula has been used for centuries by astronomers who have observed celestial bodies like stars through telescopes. They've found out what happens when they move their instruments farther away from these sources so they can see them more clearly without being blinded by glare off their surfaces.
And physicists have used this same principle in order to determine what happens when electrons orbit around atomic nuclei because electrons emit electromagnetic radiation while orbiting around nuclei.
In addition, scientists use this rule every day in physics experiments involving lasers because laser beams travel along straight lines unless something interferes with them during transmission through air or water vapor molecules near Earth's surface where most experiments take place.
In fact, NASA uses an instrument called LIDAR (Light Detection And Ranging) aboard satellites orbiting our planet 24 hours a day measuring atmospheric conditions using laser pulses sent down toward Earth’s surface where scientists analyze data collected about wind speed patterns over oceans based upon measurements taken via satellite altimetry systems designed specifically for oceanographic research purposes.