"Let me give you a handle on that. Say the distance between the Earth and the sun is, oh, one centimeter. Mercury orbits the sun at a range of a toasty two millimeters. Jupiter is six centimeters out; the span of your outstretched arms, fingertip to fingertip, will just about encompass the orbit of Eris, which it’s taken me so many years to reach. Got that? Well, on this scale, Proxima Centauri, our nearest star, is two and a half kilometers down the road. And we’re going to Tau Ceti, three times as far away as that."