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.
Because 6 trillion miles is such a huge number, we really need to break it down to understand just how far it is. So let's start by looking at a light second. Since light moves at 186,000 miles per second, a lightsecond is 186,000 miles. The moon is about 1.3 lightseconds away. Since the circumference of the earth is about 25,000 miles, light could travel all the way around the earth 7 and a half times in one second.