Why can centrifuges separate both heavier and lighter isotopes?

Centrifuges are capable of separating both heavier and lighter isotopes because the process relies on the relative differences in mass between the isotopes rather than their absolute mass values.1

When a mixture of gaseous molecules is subjected to a high-speed centrifugal field, a radial pressure gradient is established. Because of this force, the heavier species tend to concentrate near the outer walls of the spinning rotor, while the lighter species are concentrated toward the axis.12

The effectiveness of this separation is governed by the centrifugal force, which is directly proportional to the mass of the object. By spinning the mixture at high speeds, the centrifuge creates a field that acts upon these mass differences, allowing for the isolation of specific isotopes. This method is highly effective for various elements, including the enrichment of uranium-235 for nuclear power applications.321