A nanometer (nm) is a unit of length equal to one billionth of a meter. It's used for very small measurements, like atoms and molecules.

A light-year is the distance that light travels in a vacuum in one Julian year. It's a unit of astronomical distance.

This conversion is rarely used in practical science. It's primarily for illustrating the immense difference in scale between the microscopic and the cosmic.

There are an enormous number of nanometers in a light-year, approximately 1 x 10^23 nanometers. 50,000,000 nanometers is a minuscule fraction of a light-year.