Lecture 25: Life in the Universe- LGM's and BEM's?

"It's Life, but not as we know it."

Spock, Star Trek

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    • Date: May 4, 1995
    Reading Assignment: pp. 636-658

    Description : the search for extraterrestrial life

    Objectives

  • be able to define cosmic evolution, in terms of galactic, stellar, and planetary evolution
  • be able to define chemical evolution and the evidence that complex organic molecules form in nature
  • be able to describe the basic steps in biological and cultural evolution
  • be able to describe the types of factors which determine the number of civilizations inside our galaxy
  • be able to describe the search for extraterrestrial life

    • Lecture Outline

    Slide # 1: Life in the Universe

  • BEM and LGM?
    • Slide # 2: It's Alive!
  • The "normal" server is working again.
    • Slide # 3: Today's Lecture
  • Why search for it?
  • Cosmological Evolution
  • What are the chances of finding it?
  • The Drake Equation
  • How do we communicate?
  • attempts to find life
    • Slide # 4: Why search for extraterrestrial life?
  • it might exist
  • finding it would be extremely important
    • Slide # 5: Life on Earth
  • the conditions on Earth are not typical compared to most of the universe
  • warm, but not hot
  • medium density
  • lots of complex elements
  • it is likely this type of place is not unique
  • we see other planets in our own solar system which are similar
    • Slide # 6: Evolution
  • we have talked about cosmological evolution already
  • hadronic and leptonic epochs
  • nuclear epoch
  • atomic epoch
  • galactic epoch
  • stellar epoch
    • Slide # 7: The Story so Far (GRAPHICS)
  • hydrogen and helium form in the big bang
  • heavier elements form in the cores of stars
  • complex chemicals form from these elements
    • Slide # 8: Chemical Evolution
  • organic molecules seen in
  • molecular clouds
  • atmospheres of planets
  • meteors
  • natural development of complex chemistry
    • Slide # 9: What is life?
  • self-replicating molecules that eat (?)
    • Slide # 10: Beginnings of Life
  • life on Earth is about 3.5 billion years old
  • first fossilized life
  • life arose nearly as soon as it was possible for it to exist
  • surface conditions were too hostile before this point
  • early life was very simple
  • single cell algae
    • Slide # 11: Evolution of Life
  • multicelled life arrived about 1 billion years ago
  • simple sponges
  • complexity of life increases
  • more advanced forms seem to survive more easily
    • Slide # 12: Evolution as an Experiment (GRAPHICS)
  • mutations occur randomly in cells
  • radiation and chemical damage alter DNA
  • most mutations are useless or worse
  • very rarely, some mutations might enhance survival
    • Slide # 13: Evolution as an Experiment
  • useful mutations survive
  • useless mutations die
    • Slide # 14: Misconceptions about Evolution
  • the fossil record is extremely incomplete
  • the probablity of life evolving is very low
  • the Universe is too young for life to evolve
  • evolution violates thermodynamics
    • Slide # 15: The Fossil Record
  • excellent evidence for evolution
  • DNA sequencing shows the types of changes
  • fossil evidence now is DNA evidence
    • Slide # 16: Chances of Life Evolving
  • evolution is seen in species today
  • very slow process, but it occurs
  • given sufficient time, life forms change
  • bacteria and virius change rapidly
  • early stages of formation seem to follow from chemical evolution
    • Slide # 17: Not Enough Time To Form Life
  • the Earth and universe are almost certainly not "young"
  • Hubble's law
  • age of globular clusters
  • radioactive dating
  • stellar evolution
  • pulsar spin rates
    • Slide # 18: 2nd Law of Thermodynamics
  • the level of Entropy increases in a closed system
  • Entropy is a measure of "disorder"
  • randomness increases over time
    • Slide # 19: 2nd Law of Thermodynamics
  • the Earth is NOT a closed system
  • energy input from the Sun
  • the total entropy of the Solar system increases, Earth does not
  • many every day examples of entropy decreasing if you add energy
    • Slide # 20: Development of Intelligence
  • intelligence seems to be fairly rare
  • only a few examples on Earth
  • intelligence developed in the last 100 million years
  • rather dim animals and plants seem to be the rule
  • we are somewhat unusual
    • Slide # 21: Development of Civilization
  • development of communications seems to be essential here
  • technology is not a natural consequence of intelligence
    • Slide # 22: Life Elsewhere
  • the same processes apply elsewhere
  • you need :
  • a good star
  • a nice planet
  • formation of single cells
  • multicellular organisms
  • intelligence
  • civilization and technology
    • Slide # 23: Constellation Corner (GRAPHICS)
  • Constellation De Jour
    • Slide # 24: Constellations on the Final
  • Lyra, Vega
  • Cygnus, Deneb
  • Aquila, Altair
  • Hercules
  • Sagittarius
  • Scorpius, Antaries
  • Ursa Major
  • Ursa Minor, Polaris
    • Slide # 25: Summer Sky (GRAPHICS)
  • Jun 15 - midnight - all sky
    • Slide # 26: Prospects of Intelligent Life
  • the Green Bank or Drake Equation
  • estimates the number of civilization in our Galaxy
    • Slide # 27: Star Formation Rate
  • number of stars formed per year averaged of Galaxy's lifetime
  • number of places to put planets
    • Slide # 28: Fraction having Planets
  • fraction of stars having a planetary system
  • planets seem to be common around stars
    • Slide # 29: Fraction of Planets Suitable for Life
  • not too hot and not too cold
  • nice atmosphere, good neighborhood
  • a few in our solar system seem ok for life
  • Mars?
  • atmosphere of Venus?
  • atmosphere of Jupiter?
  • Europa?
    • Slide # 30: Fraction which Life Arises
  • if conditions are ok, is life expected?
  • probably it is not VERY uncommon
  • seemed to occur early on Earth
    • Slide # 31: Intelligence
  • intelligence may not evolve easily
  • few examples on Earth
  • Dolphins
  • Whales
  • perhaps Humans
    • Slide # 32: Civilization
  • technology seems to be a new invention
  • only humans have developed it
  • really nice evolutionary advantage, but seems to be rare
    • Slide # 33: Lifetime of Civilizations
  • how long until we are destroyed?
  • easy to be both hopeful and hopeless about our future
    • Slide # 34: The Result
  • the number seems to strongly depend on the lifetime of a typical civilization
  • probably ten to a million civilizations in our Galaxy!
    • Slide # 35: Communication
  • how do we find and talk to them?
    • Slide # 36: Communications
  • message in a bottle
  • phone home- send a message
  • listen for signals
    • Slide # 37: Message in a Bottle
  • 4 messages have been attached to spacecraft which have left the Solar System
  • Voyager Records
  • Pioneer Plaques
  • Really low chance of them being found
    • Slide # 38: Sending a Message
  • a few messages have been sent out from Earth
  • lots of unintentional messages have also been sent
  • TV, radio
  • Radar
    • Slide # 39: Receiving a Message
  • SETI
  • search for ExtraTerrestrial Intelligence
  • now Project Phoenix
  • privately funded SETI search
    • Slide # 40: What about interstellar travel?
  • really really tough
  • invasion and abductions seem really unlikely
    • Slide # 41: Why Bother? (GRAPHICS)
  • sociological consequences of ETI would be profound
  • the search is cheap
    • Slide # 42: Final Comments
  • the Joy of Astronomy 106
    • Slide # 43: The Test
  • A >= 40
  • B >= 33
  • C >= 29
  • D >= 23
    • Slide # 44: Final Exam
  • March 16 at 1:30 pm
  • comprehensive
  • about 50% of the questions will be from the previous tests