Search for Extraterrestrial Life PHY 100

How life emerged on earth  Amino acids, “building blocks of life” form via chemical reactions  With help of nucleic acids, they combine to form proteins in living things  Sequence of chemical events that leads to creation of nucleic acids is unknown but two notable theories have emerged from research: Iron-Sulfur World Theory and RNA World Theory

Theories of Early Life  Iron-Sulfur World Theory  Early life may have formed on the surface of iron sulfide minerals in volcanic hydrothermal flow at high pressure and high temperature  Developed by retrodiction from extant biochemistry combined with various chemical experiments  RNA World Hypothesis  Theory that proposed that a world filled with life based on ribonucleic acid predates the current world we live in based on deoxyribonucleic acid (DNA) and protein.  The RNA world is proposed to have evolved into the DNA and protein world of today.

Miller Urey Experiment Amino acids can form via natural chemical reactions

Alternative Biochemistries For Extraterrestrial Life  Perhaps we are Carbon Chauvinists  Nitrogen and Phosphorous Make stable covalent bonds and could be a basis for biochemistry. Has a strong argument, however, is not plausible.  Silicon Based Organisms Has very similar chemical properties to Carbon but has a lot of drawbacks. Silicon is far more abundant than Carbon (925:1). May be plausible in different temperatures and pressures than earth.

SETI  Search for Extra-Terrestrial Intelligence (SETI) is the collective name for a number of activities involving the search for extra terrestrial life  Projects use various methods to search for electromagnetic transmissions from civilizations on distant planets  Formerly funded by U.S. Government, mostly privately funded currently

Radio Experiments  Since radio frequencies are able to penetrate our atmosphere, radio telescopes are often used to investigate the cosmos.  Earth emits considerable radio radiation as a result of TV and radio. These radiations are easy to recognize due to their short wavelengths and repetitive nature.  Therefore, one way of discovering extraterrestrial civilizations is to detect non-natural radio emissions from outside our solar system

SETI Radio Experiments  1960 Frank Drake performs first modern SETI experiment, Project Ozma  Ohio State University SETI Program and the Wow! Signal  SERENDIP and SERENDIP II at U.C. Berkeley

Further SETI Projects  Suitcase SETI and Sentinel  Project META (Megachannel Extra- terrestrial Assay)  Project BETA  Project Phoenix  Allen Telescope Array (ATA)

The 21 cm Line  The 21 cm Hydrogen line is considered a favorable frequency to search for signals from another civilization, as part of the SETI program.  Pyotr Makovetsky proposed to use for SETI a frequency which is equal to pi times MHz.  Since pi is a Transcendental number, such frequency couldn't possibly be produced in a natural way as a harmonic, and would clearly signify its artificial origin. Such signal would not be jammed by HI line itself, or any of its harmonics.

 Volunteer distributed computing project launched by U.C. Berkeley in 1999  Allows any individual to become involved in SETI research  Has over 180,000 active participants which gives this program a computational power greater than that of the fifth most powerful computer in the world

Criticism of SETI  The search for extra terrestrial intelligence is not an assertion that extra terrestrial intelligence exists in the first place  Other objections to SETI’s projects include questioning the amount of energy necessary to execute the projects and why advanced civilizations would use radio in the first place  Regardless of criticism, SETI does collect useful scientific information

The Drake Equation  An equation used to guess the potential number of extraterrestrial civilizations in our galaxy

Fermi Paradox  Contradiction between the high probability that extraterrestrial civilizations exist and the lack of contact with these civilizations  Extraterrestrial civilizations’ reasons for spreading beyond planet of origin  Exploration  Colonization  Survival

Solutions to Fermi’s Paradox  It is difficult for life to start and evolve to a point that is intellectually and technologically advanced and we are the only one in the galaxy  Advanced civilizations destroy themselves on short timescales so they may not have had time to reach us

Conclusion  Research on the existence of extraterrestrial life still remains inconclusive  SETI efforts continue to search spectrum for signals from outside sources but the increasing belief is that civilizations, if they did exist, did not have enough time to reach us

For your entertainment…  hU hU