Author: James Wray, Professor of Earth and Atmospheric Sciences, Georgia Institute of Technology

The human mind may find it difficult to conceptualize: a cosmic cloud so colossal it surrounds the Sun and eight planets as it extends trillions of miles into deep space. The spherical shell known as the Oort Cloud is, for all practical purposes, invisible. Its constituent particles are spread so thinly, and so far from the light of any star, including the Sun, that astronomers simply cannot see the cloud, even though it envelops us like a blanket. It is also theoretical. Astronomers infer the Oort Cloud is there because it’s the only logical explanation for the arrival of a…