Search for Extraterrestrial Intelligence SETI Lecture 17 Post Midterm No copyright infringement is intended by the creation or use of these notes The Drake Equation o Astronomer Frank Drake s attempt to quantitatively estimate SETI s potential success o Estimate not truly scientific derivation o Conclusion The number of civilizations in the galaxy capable of communicating with us N is to the lifetime of intelligent and technological civilization Essentially N L is based on how optimistic you are on lifetime of intelligent and technological civilization For us L 100 years Fermi Paradox we are our s o If other civilizations are present they are most likely more advanced than o It is highly implausible that a civilization spawned in the same time as o Advanced civilization should be able to colonize the galaxy now o Solutions to Fermi Paradox We are alone Civilizations are common but colonization is not Technological problems self destruction They do not want to be discovered Prospects of SETI if self destruction is common o Even if they are self destructive we should see some and be able to communicate with them Distance between civilizations is d V N 1 3 Civilizations located in the disk of galaxy o V nR 2 T Volume of disk surface area of circle mutip by thickness of the disk If N is number of civilizations then V N is volume per civilization If d 3 is the volume of the cube then distance between cubes is d So d V N 1 3 Communication and What Where to Look o We look at the hydrogen line 21cm in the spectrum b c hydrogen is the most abundant element in the universe o Looking for irregular signals different from natural phenomena such as signals characterized by irrational numbers or primes o Arecibo Telescope Largest and most sensitive telescope for SETI search Sent out first message with it symbolic SETI is privately funded There is post detection protocol if we detect signal plausibility verification inform observers discovered make announcement confirmed data posted evidence should be available protect spectrum found no response until allowed Some messages already sent Voyage Pioneer Uranium decay