Liberal Arts Blog — Space VI: Alien Life: Harlow Shapley , Enrico Fermi, Frank Drake
Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day
Today’s Topic — Space VI: Alien Life: Harlow Shapley (1885–1952), Enrico Fermi (1901–1954), Frank Drake (1930 — )
If there is alien life out there, what are the odds that it is DNA or RNA based? And what are the odds of alien life anyway? If scale and probability argue for the existence of extraterrestrial life, why is there no real evidence of it? What, if anything is wrong with the reasoning of Harold Shapley, Frank Drake, and Enrico Fermi? And what about God? Experts — please chime in. Correct, elaborate, elucidate.
HAROLD SHAPLEY — head of Harvard Observatory (1921–1952)
1. “The universe has 10 million, million, million suns (10 followed by 18 zeros) similar to our own.”
2. “One in a million has planets around it.”
3. “ Only one in a million million has the right combination of chemicals, temperature, water, days and nights to support planetary life as we know it.”
NB: “This calculation arrives at the estimated figure of 100 million worlds where life has been forged by evolution.”
THE DRAKE EQUATION: Seven Variables Drive the Probability of Extraterrestrial
Life in the Milky Way Galaxy — R x fp x ne x f1 x fi x fc x L
1. First Three Variables: rate of star formation in the galaxy (R), the fraction of those stars that have planets (fp), the average number of planets that can support life per star that has planets (ne).
2. The Second Three: fraction of planets that could support life that do (f1), the fraction of those that have intelligent life (fi), the fraction of those that develop civilizations that release detectable signals (fc).
3.The seventh variable: the length of time for which the civilizations release signals (L)
NB: The original meeting of Drake and colleagues concluded that there were probably between 1000 and 100,000,000 planets “with civilizations” in the Milky Way galaxy.
THE FERMI PARADOX — “Where is everybody?”
1. “Few intelligent civilizations ever arise. This is an argument that a least one of the first few terms (R, fp, ne, f1, or fi) has a low value. The most common suspect is f1, but explanations such as the rare earth hypothesis argue that ne is the small term.”
2. “Intelligent civilizations exist, but we see no evidence, meaning fc is small. Typical arguments include that civilizations are too far apart, it is too expensive to spread throughout the galaxy, civilizations broadcast signals only for a brief period fo time, communication, is dangerous, and many others.”
3. “The lifetime of intelligent, communicative civilizations is short, meaning the value of L is small. Drake suggested that a large number of extraterrestrial civilizations would form, and he further speculated that the lack of evidence of such civilizations may be because technological civilizations tend to disappear rather quickly. Typical explanations include: it is the nature of intelligent life to destroy itself, it is the nature of intelligent life to destroy others, they tend to be destroyed by natural events, and others.”
NB: Is looking for extraterrestrial life a really bad idea? Stephen Hawking for one has argued that human history argues that we “lay low.” Others disagree. Any strong opinions?
FINAL QUESTION — the God thing
How would the existence of God impact your calculation of the odds of alien life? Would the existence or non-existence of God make the odds of alien life higher or lower?
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