Tonight Show: SETI and Star Wars

Summary

The conversation centers on a wide-ranging discussion with Carl Sagan, introduced as a professor of astronomy and space sciences at Cornell and director of the Laboratory for Planetary Studies. The exchange begins with light banter about his book, The Dragons of Eden, and quickly moves into a critique of popular science fiction films, especially Star Wars and Close Encounters. Sagan explains that while he enjoyed these films as entertainment, he believed they often ignored basic scientific realities. He argues that human beings are the product of a highly specific evolutionary history on Earth, making it extremely unlikely that another planet would produce beings so similar to humans, especially as dominant rulers of a galaxy. He also points out the lack of diversity in the depiction of humans in Star Wars and jokes about the “anti-Wookiee discrimination” of the film’s ending. A major theme is the importance of scientific accuracy in science fiction. Sagan notes that even small errors, such as confusing distance with speed or using parsecs incorrectly, can undermine the credibility of a story. He suggests that filmmakers could easily improve accuracy by consulting knowledgeable experts, even joking that one “impoverished graduate student” could help get the facts right. He then turns to the physics of faster-than-light travel, emphasizing that according to Einstein’s relativity, nothing material can travel at or beyond the speed of light. He explains that if faster-than-light travel were possible, the orderly, quantitative understanding of the universe would break down, potentially allowing effects to precede causes. He illustrates this with a humorous poem about a woman traveling “in a relative way” and returning the preceding night. The discussion then shifts to extraterrestrial intelligence and the Search for Extraterrestrial Intelligence (SETI). Sagan describes how scientists are now, for the first time, technologically capable of searching for signals from other civilizations. He explains that the effort is based on radio astronomy and the use of large radio telescopes to scan the sky for patterns that would indicate intelligence. He outlines the logic of recognizing a signal: a sequence such as prime numbers would be highly unlikely to arise naturally and would suggest an intelligent source. He stresses that such a signal would likely be mathematical and regular, serving first as a beacon to attract attention before any more detailed communication could be decoded. Sagan also discusses humanity’s own transmissions into space. He notes that while radio astronomers generally listen rather than broadcast, Earth has already sent out signals unintentionally through television and radio. These broadcasts continue traveling outward at the speed of light, forming expanding spherical wavefronts that could, in principle, be detected by another civilization. He mentions the 1974 Arecibo demonstration signal sent by Frank Drake and explains that although it was largely symbolic, it showed that interstellar communication is possible. He also references the Pioneer plaques and Voyager record as examples of deliberate attempts to represent humanity to the cosmos. The conversation explores why such a search matters even if responses would take decades or centuries. Sagan argues that knowledge from another civilization could be profoundly valuable, much like books allow the dead to speak to the living. He suggests that another society might offer insight into art, music, science, politics, technology, or even solutions to problems humanity is still struggling with, such as war, medical challenges, environmental damage, and survival during what he calls technological adolescence. He also notes that a negative result would be meaningful, because it would imply that intelligent life may be rare and therefore especially precious on Earth. The interview closes with a reflection on astronomical scale. Sagan reminds the audience that even 50 or 100 light years is a tiny distance in cosmic terms, while the nearest star is about four light years away, the center of the Milky Way is about 30,000 light years away, and the nearest galaxy is about two million light years away. The segment ends with praise for his books, including The Dragons of Eden and The Cosmic Connection, and a brief transition to the next guest.