One of the properties of place on Earth is that we know its whereabouts. We can make very accurate measurements of distances and locations. Going on vacation? Have to drive or fly 700 miles? You know the distance and the approximate time of the journey. Not so with some of those sparkly things in the sky. Take UW Canis Majoris, a blue supergiant star that is 200,000 times brighter than our sun and that has a diameter 13 times bigger than Old Sol. UW Canis is monstrous. We seem to know a great deal about it, but not so much about its distance. Some measurements place UW Canis at about 3,000 light years, whereas others place it in widely ranging distances, from 2,000 to as much as 5,000 light years away. One to three thousand light years! That’s a big margin of error in the measurements, if one considers that each light year is about 5.8 trillion miles. Would you knowingly set out on a journey to some place of unknown distance, a place where the margin of error in distance is itself greater than your ability to cross?
How is it that we can know so much while at the same time knowing so little about something, especially, about its distance from us? It’s not as though that distant place is like someone from whom we’ve grown apart, someone about whom we know much except the measure of the intervening distance.
Maybe a journey across an unknown distance is worth the effort. We already know much about that place we intend to visit—or revisit. It would be interesting to see whether or not the place we think we know has undergone any significant changes and also whether or not we can learn something we did not know. Can't tell too much from a distance, especially an unknown distance.