This work has been written in consequence of the great interest excited by my article, under the same title, which appeared simultaneously in The Fortnightly Review and the New York Independent. Two friends who read the manuscript were of opinion that a volume, in which the evidence could be given much more fully, would be desirable, and the result of the publication of the article confirmed their view. I was led to a study of the subject when writing four new chapters on Astronomy for a new edition of The Wonderful Century. I then found that almost all writers on general astronomy, from Sir John Herschel to Professor Simon Newcomb and Sir Norman Lockyer, stated, as an indisputable fact, that our sun is situated in the plane of the great ring of the Milky Way, and also very nearly in the centre of that ring. The most recent researches also showed that there was little or no proof of there being any stars or nebulæ very far beyond the Milky Way, which thus seemed to be the limit, in that direction, of the stellar universe. Turning to the earth and the other planets of the Solar System, I found that the most recent researches led to the conclusion that no other planet was likely to be the seat of organic life, unless perhaps of a very low type. For many years I had paid special attention to the problem of the measurement of geological time, and also that of the mild climates and generally uniform conditions that had prevailed throughout all geological epochs; and on considering the number of concurrent causes and the delicate balance of conditions required to maintain such uniformity, I became still more convinced that the evidence was exceedingly strong against the probability or possibility of any other planet being inhabited.
About the Author: Alfred Russel Wallace OM FRS (8 January 1823 - 7 November 1913) was a British naturalist, explorer, geographer, anthropologist, and biologist. He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858.[2] This prompted Darwin to publish his own ideas in On the Origin of Species. Wallace did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the faunal divide now termed the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion in which the animals are largely of Asian origin, and an eastern portion where the fauna reflect Australasia.