It was written in 1907 when Wallace was living in Broadstone, Dorset (where I went to school).Indeed. In the introduction to the 1907 edition, the whole of which is scanned online, editor Charles H. Smith notes,
Wallace takes on Percival Lowell, a supreme icon of American astronomy. Lowell thought there were Martians and they used canals etc. Wallace blows up this theory, ending the book with the statement:
"Mars, therefore, is not only uninhabited by intelligent beings such as Mr. Lowell postulates, but is absolutely UNINHABITABLE."
Remember that Wallace has been derided for his beliefs in ID and spiritualism. Yet he was obviously not afraid to go against the scientific speculative spirit of the age.
For many years one of Wallace's least remembered books, Is Mars Habitable? is increasingly being recognized as one of the first examples of the proper application of the scientific method to the study of extraterrestrial atmospheres and geography-that is, as one of the pioneer works in the field of exobiology.Here is Wallace's conclusion:
To put the whole case in the fewest possible words:What made Wallace so unpopular compared to Darwin is that he insisted that in science, evidence matters. Carl Sagan-style proclamations like "They're out there! How could we be so arrogant as to think we are all alone!" do not become science just because they are proclaimed by scientists.
(1) All physicists are agreed that, owing to the distance of Mars from the sun, it would have a mean temperature of about -35̊ F. (= 456̊ F. abs.) even if it had an atmosphere as dense as ours.
(2) But the very low temperatures on the earth under the equator, at a height where the barometer stands at about three times as high as on Mars, proves, that from scantiness of atmosphere alone Mars cannot possibly have a temperature as high [[p. 110]] as the freezing point of water; and this proof is supported by Langley's determination of the low maximum temperature of the full moon.
The combination of these two results must bring down the temperature of Mars to a degree wholly incompatible with the existence of animal life.
(3) The quite independent proof that water-vapour cannot exist on Mars, and that therefore, the first essential of organic life--water--is non-existent.
The conclusion from these three independent proofs, which enforce each other in the multiple ratio of their respective weights, is therefore irresistible--that animal life, especially in its higher forms, cannot exist on the planet.
Mars, therefore, is not only uninhabited by intelligent beings such as Mr. Lowell postulates, but is absolutely UNINHABITABLE.
Boldly go, but why, exactly?
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