Cosmic Connection Read Online Free PDF

extraterrestrial organism that may not have developed the sense of sight at visible wavelengths. The answer is derived simply from the laws of physics. Planetary atmospheres absorb light from the nearby sun or suns because of three molecular processes. The first is a change in the energy state of individual electrons attached to atoms. These transitions occur in the ultraviolet, X-ray, and gamma-ray parts of the spectrum and tend to make a planetary atmosphere opaque at these wavelengths. Second, there are vibrational transitions that occur when two atoms in a given molecule oscillate with respect to each other. Such transitions tend to make planetary atmospheres opaque in the near infrared part of the spectrum. Third, molecules undergo rotational transitions, due to the free rotation of the molecule. Such transitions tend to absorb in the far infrared. As a result, quite generally, the radiation from the nearby star, which penetrates through a planetary atmosphere, will be in the visible and in the radio parts of the spectrum–the parts that are not absorbed by the atmosphere.
    In fact, these are the principal “windows” that astronomers use for surveying the universe from the Earth’s surface. But radio wavelengths are so long that no organisms of reasonable size can develop pictures of their surroundings with radio wavelength “eyes.” Therefore, we expect optical frequency sensors to be developed quite widely among organisms on planets of stars throughout the Galaxy.
    However, even if we imagine organisms whose eyes work in the infrared region (or, for that matter, in the gamma-ray region) and who are able to intercept Pioneer 10 in interstellar space, it is probably not asking too much of them to have contrivances that scan the plaque at frequencies to which their eyes are insensitive. Because the engraved lines on the plaque are darker than the surrounding goldanodized aluminum, the message should be entirely visible even in the infrared.
    Gombritch also takes us to task for portraying an arrow as a sign of the spacecraft’s trajectory. He maintains that arrows would be understandable only to civilizations that have evolved, as ours has, from a hunting society. But here again it does not take a very intelligent extraterrestrial to understand the meaning of the arrow. There is a line that begins on the third planet of a solar system and ends, somewhere in interstellar space, at a schematic representation of the spacecraft–which the discoverers of the message have at “hand”: The plaque is attached to the spacecraft. From this I would hope they would be able to argue backward to our hunter-gatherer ancestors.
    In the same way, the relative distances of the planets from the Sun, shown by binary notation at the bottom of the plaque, indicate that we use base-10 arithmetic. From the fact that we have 10 fingers and 10 toes–drawn with some care on the plaque–I hope any extraterrestrial recipients will be able to deduce that we use base-10 arithmetic and that some of us count on our fingers. From the stumpiness of our toes they may even be able to deduce that we evolved from arboreal ancestors.
    There are other respects in which the message has proved to be a psychological projective test. One man writes of his concern that the message has doomed all of mankind. American movies of Second World War vintage, he argues, are very likely propagating via television transmission through interstellar space. From such programming, the extraterrestrials will easily be able to deduce (1) that the Nazis were very bad fellows, and (2) that they greeted each other with their right hand extended outward. From the fact that the man on the plaque is portrayed as making what our correspondent erroneously perceives as the same sort of greeting, he is concerned that the extraterrestrials will deduce that the wrong side won World War II and promptly mount a punitive expedition to Earth to set matters straight.
    Such a letter more