The radius of the universe is about 46 billion light years. Let's go to the largest size there is: the visible universe.Another way to view this is that your error by not using more digits of pi would be 10,000 times thinner than a hair! There are many different kinds of molecules, of course, so they span a wide range of sizes, but I hope this gives you an idea. How far off would your odometer be if you used the limited version of pi above? It would be off by the size of a molecule. That's how far you would travel if you circumnavigated the globe (and didn't worry about hills, valleys, obstacles like buildings, rest stops, waves on the ocean, etc.). It is 7,926 miles in diameter at the equator. We can bring this down to home with our planet Earth.We have a circle more than 78 billion miles around, and our calculation of that distance would be off by perhaps less than the length of your little finger. It turns out that our calculated circumference of the 25 billion mile diameter circle would be wrong by 1.5 inches. In other words, by cutting pi off at the 15th decimal point, we would calculate a circumference for that circle that is very slightly off. We don't need to be concerned here with exactly what the value is (you can multiply it out if you like) but rather what the error in the value is by not using more digits of pi. Using pi rounded to the 15th decimal, as I gave above, that comes out to a little more than 78 billion miles. Let's say we have a circle with a radius of exactly that size (or 25 billion miles in diameter) and we want to calculate the circumference, which is pi times the radius times 2. The most distant spacecraft from Earth is Voyager 1.I think we can even see that there are no physically realistic calculations scientists ever perform for which it is necessary to include nearly as many decimal points as you present. Let's look at this a little more closely to understand why we don't use more decimal places. For JPL's highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793. To start, let me answer your question directly. In fact, it was posed many years ago by a sixth-grade science and space enthusiast who was later fortunate enough to earn a doctorate in physics and become involved in space exploration. Thank you for your question! This isn't the first time I've heard a question like this. We posed this question to the director and chief engineer for NASA's Dawn mission, Marc Rayman.