Article I, Section 8, of the Constitution, which enumerates the powers of Congress and provides Congress with the authority to make all laws necessary and proper to carry them out; also referred to as the elastic clause.
There is an exact numerical answer to this question. By definition, 1 light year is exactly 9,460,730,472,580,800 meters. By definition, 1 mile is exactly 1,609.344 meters. So, 1 light year is exactly 5,878,625,373,183 and 849/1397 miles, by definition.
A light-year is a unit of distance that is defined as the distance that light travels in one year. One light-year is approximately equal to 9,500,000,000,000 (9.5 trillion) kilometers, or 5,900,000,000,000 (5.9 trillion) miles.