Extra-terrestrial Civilizations

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Extra-terrestrial Civilizations
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Are we alone? Contact

• Direct contact through traveling to the stars and
  their planets
• Will be a challenge because of the vast distances
  involved and the (slow) speeds we can travel

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Are we alone? Contact

• Radio communication more likely possibility for
  contact
• Electromagnetic radiation travels at the speed of
  light.

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Civilizations

• Will life always develop technology? Some
  societies on Earth have not developed the means
  to communicate with ETs.
• Will a society want to communicate? A society
  may develop the means to search for ET but elect
  not to attempt to reach out.

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Consider ...

• How many intelligent civilizations exist?
• How long on average do they last?
• How does communication proceed?

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Drake Equation

• One possible way to estimate the number, N, of
  civilizations.
• N
• Ns x fs x ps x ls x lc x L

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Stars in the Galaxy, Ns

• The number of stars in the Milky Way galaxy
  about 300 billion.

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Suitable stars (fraction), fs

• Star must be old enough to allow life to develop
  spectral types F, G, K
• Star must have enough heavy elements to form
  planets 0.005

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Suitable planets in a Solar System, ps

• To date, extra-solar planets have been hot
  Jupiters
• Planets to sustain life need to be in the
  habitable zone around a star 1.0

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Fraction of planets suitable for life, ls

• Very speculative sample of 1 only to date
  (Earth)
• If a planet is suitable for life, good reason to
  think life will develop
• Conservative approach suggest Earth and Mars
  could produce life 0.5

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Life develops a civilization, lc

• Again, very speculative.
• Simple life started on Earth nearly 3.5 billion
  years ago.
• Extinction level events common for example 250
  and 65 million years ago.

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Life develops a civilization, lc

• As long as some form of life exists after an
  extinction event occurs, natural selection should
  continue and life redevelops.
• Assuming life develops then a case can be made
  that a form of civilization is inevitable 0.33

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Lifetime of a civilization, L

• Firstly, the age of our Milky Way galaxy is 10
  billion years.
• How long have we had the ability to communicate
  with ET about 50 years.
• How many times have we sent a communication not
  many!
• Radio telescope, Pioneer and Voyager

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Drake Equation Result

• Substituting into
• N Ns x fs x ps x ls x lc x L
• N 300x109x0.005x1x0.5x0.33xL/10x109
• L/40
• Large numbers top and bottom tend to cancel out.

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Range of answers

• Depending upon your optimism or pessimism, N can
  vary significantly
• From 10L (Carl Sagan,1978) to a very optimistic
  120L to a pessimistic L/10 billion
• If civilization survives for 100s or 1,000s of
  years then N could be very large indeed.

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Survival lifetimes

• Dinosaurs lived for 150 million years can we
  survive for longer thus increasing L
  substantially?
• Some species of life have lived for over 200
  million years on Earth.
• Humans are living outside the laws of Natural
  Selection may well reduce L.
• Upper limit based upon life of a star 10
  billion years.

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More than the Milky Way

• Ours is not the only galaxy in the universe

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Why communicate at all?

• Curiosity
• The urge to talk and listen!
• The hope to learn/gain knowledge
• The need for resources and/or living space
• Because we can!

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Why not?

• Fear (enslavement, destruction, etc)
• Inertia happy as we are
• Economics expensive to try and need to deploy
  resources appropriately.
• Of course, contact may happen by accident
  leakage of radio and TV signals.

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How far away is a civilization?

• Even assuming optimistic values for the Drake
  Equation, the closest civilization maybe 100s of
  light years away!
• Average stellar separation in the outskirts of a
  galaxy 5 to 10 light years.
• Two way communication then becomes a problem.

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People or Photons?

• People have mass and that requires enormous
  amounts of energy to accelerate.
• People have needs (food, water, air, etc) which
  means more mass to transport! How much mass per
  person to take?
• Space ships travel very slowly
• Photons are mass-less and travel at the speed of
  light!

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Current spaceship technology

• Spacecraft travel at speeds much less than
  100,000 km per hour
• At this speed, travel to the nearest star would
  take 46,500 years!

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Photons

• Sending a signal has its own energy challenges
• Signal strength drops off as the square of
  distance.

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Photons

• Thus for any given signal strength, sending it
  say one million times further requires (one
  million)2 times as much energy that is, one
  trillion.
• This is technically possible (bigger
  transmitters, shorter messages, etc) but is not
  cheap. It is cheaper than sending people in
  spacecraft though.

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Space Travel

• (12) Humans have gone to the Moon
• Machines have traveled in our Solar System out to
  Neptune and en route as we speak to Pluto
• As a species we have the urge to explore and
  colonize.

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Challenges to travel to the stars

• Distances involved are enormous and will take us
  time to traverse
• The energy requirements are equally immense and
  very difficult to satisfy (even if we are willing
  to pay the price).

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Power for the trip

• Chemical combustion is our current form of energy
  in rockets very inefficient.
• Solar power works well near stars but is also
  inefficient
• Nuclear power for both on-board power (to live,
  etc) as well as thrust is possible with our
  technology.
• Matter and anti-matter more efficient certainly
  but also beyond our means at present.

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Exotic power

• Interstellar Ramjets
• Ion propulsion prototypes already tested.
• Warp drive dilithiunm crystals anyone?

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Time Dilation

• As you travel faster, your own clock (in your
  frame of reference) slows down from an outside
  perspective.

• Traveling at a significant fraction of the speed
  of light means you experience a smaller passage
  of time compared to an Earth based observer

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Relativity

• T T0 / Sqrt (1 v2/c2)
• where T0 is the time elapsed in the moving frame
  of reference
• where T is the time elapsed in the stationary
  frame of reference
• where v is the speed you are moving relative to
  the stationary observer.

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A solution? Perhaps traveling at high speed will
allow people to survive interstellar treks.
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Time dilation example

• You and your friend synchronize your watches.
• You remain on Earth and your friend flies off
  at 99 the speed of light.
• Your friend returns when 1 hour of time has
  elapsed according to their watch.
• You have waited approximately 7 hours for your
  friend to have returned!

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One more danger ..

• At higher speeds for our spacecraft, the
  particles in the ISM are now moving at enormous
  velocities relative to you.
• If your spaceship is moving at 99 the speed of
  light, the kinetic energy of a particle in the
  ISM will seem like a very energetic bullet and
  could do serious damage to the spacecraft
  shields anyone?!

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Automated Messengers

• Instead of people in spaceships, send automated
  messengers.
• Pioneer and Voyager spacecraft already carry
  messages from Humanity

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Von Neuman machines

• Build an automated robotic spacecraft and send it
  to a distant star/planet.
• When there, let it mine resources and replicate
  itself, sending copies of itself to other
  stars/planets.
• In short order, such robots could be everywhere!
• So where are they? the Fermi Paradox (later)

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Radio contact A test?

• If civilizations are common, then why have we not
  yet heard them?
• To find the signals from ET may involve solving
  technology not yet known to us.
• Is the search for contact a test in itself are
  we worth talking to?

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Consider

• You can see a cell phone but cannot hear what
  it hears.
• Electromagnetic signals pass through your body
  all the time and you cannot detect them.
• Thus the human body is limited to what
  information it can process as is the cell phone.

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Direct or Accidental signals

• Realizing that signals from ET may well be very
  weak, where should we look? what frequency?
• We may be lucky and detect signals not beamed at
  us eavesdrop on Star Trek, Friends ,etc.
• What type of signal should we look for?
• What direction/star (planet) should we listen to?

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Where to look

• Closer civilizations if they are sending signals
  will presumably have the strongest signals and be
  easier to detect.
• Signal strength drops off as the square of
  distance.

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Type of Stars

• As discussed, stars like our Sun first targets.
• In the Milky Way galaxy, stars with similar
  spectral types (F, G, K) constitutes 10 or more
  of all stars (30 billion or more).
• Double, multiple, very luminous (and thus short
  lived) stars not suitable targets.
• Specialization regarding how many planets contain
  technologically advanced civilizations.

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What frequency to choose?

• Recall our discussion about electromagnetic
  radiation and the multitude of frequencies
  associated with it.

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Wavelength and Frequency
43

• Because of its electric and magnetic properties,
  light is also called electromagnetic radiation
• Visible light falls in the 400 to 700 nm range
• Stars, galaxies and other objects emit light in
  all wavelengths

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Familiar Frequencies

• AM dial radio stations tuned in with
  frequencies 500 1500 KHz
• FM dial radio stations tuned in with
  frequencies 88 110 MHZ
• TV channels with frequencies 70 1,000 MHZ

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(No Transcript)
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ET listens to CBC?

• How to decide what frequency ET will listen to?
• Is there a galactic, common hailing frequency?
• We assume that a civilization technologically
  advanced enough to send/receive radio signals
  will know the language of science.

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Considerations

• Economical to send a radio photon than say, a
  (visible) light photon. If we are sending to
  many stars, cost needs to be controlled (low).
• The selected frequency must be able to traverse
  significant distances without interference or
  loss.

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Arecebo Observatory
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Problems during transmission

• Photons of energy at the wrong frequency will be
  absorbed you cannot see through a brick wall
  but your phone can pick up a signal through the
  same wall.
• Long wavelength radiation can travel further with
  less absorption best for sending/receiving
  signals

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Natural background

• The galaxy is quote noisy stars would wash out
  a visible light signal (even if it could travel a
  long way through the dust).
• The cosmic background radiation is an echo/hiss
  left over from the Big Bang (high frequency
  cutoff).
• Charged particles (mostly electrons) spiral
  around the magnetic field lines producing
  synchrotron radiation (low frequency cutoff).

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The water hole

• In between the upper and lower cut-offs in
  frequency is a relatively radio quiet area near
  where the hydrogen atom flips giving a unique
  signal at 1420 MHZ or 21.1 cm (wavelength).

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The spin-flip transition in hydrogen emits 21-cm
radio waves
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The water hole continued

• Near by is a similar transmission from the OH
  radical(1612, 1665, 1667, 1720 MHz).
• Thus the Water Hole is a likely spot to search
  for a signal from ET.

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Doppler Effect the wavelength is affected by
therelative motion between the source and the
observer
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The question of Bandwidth

• The spread of frequencies examined during a
  search for ET.
• A broad bandwidth (like for TV) has coned the
  term channel.
• A bandwidth of as small as 1 Hz increases the
  chances of detecting an artificial signal.
• A 1 Hz bandwidth requires LOTS of searching in a
  given frequency range.

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Signal characteristics

• Narrow band can have more power
• Narrow can be dispersed by the Interstellar
  Medium (ISM).
• Broad band carries more information.
• AM bandwidth 10KHz
• FM Bandwidth 200 KHz
• TV bandwidth 6 MHz
• For all, half the power of signal confined to 1
  Hz!

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Common Transmissions from Earth
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Can we conclude ET from these signals?

• TV signals may well vary their frequencies
  periodically as a result of Earths rotation (on
  its axis) and revolution (around the Sun)
  Doppler shifts.

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The First Search Project Ozma

• Frank Drake mounted the first SETI search
• July 1960, 85 foot radio telescope at Green Bank
  in West Virginia
• Searched at a wavelength of 21 cm.
• Tau Ceti and Epsilon Eridani were targets

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Brief History

• Philip Morrison and Guiseppe Coconni published
  Searching for Interstellar Communication
• 1960 Project Ozma (Frank Drake)
• 1961, first SETI Conference, Order of the Dolphin
  and the unveiling of the Drake Equation.
• 1972-1973 Pioneer Probe Plaques.

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History continued

• 1973 Ohio State University begins a major SETI
  project at its Big Ear Observatory in Delaware
• 1974 Drake transmission to M13
• 1977 WOW signal
• 1977 Voyager probe disks
• 1979 Planetary Society founded (Carl Sagan et al)
• 1984 The SETI Institute is founded

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1974 Message to M13

• 20 trillion watt transmission, lasting about 3
  minutes
• Message 1679 bits, arranged 73 lines x 23
  characters (prime numbers!)
• DNA, a human being, the Solar System, etc.

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SETI Searches to-date
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The Wow! Signal

• August 15 1977
• Ohio State University Radio Observatory (Big Ear)
• 72 seconds in length and VERY strong

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Current major SETI efforts

• Project Phoenix uses many radio telescopes from
  around the world in targeted searches (SETI
  Institute www.seti.org).
• The Allen Telescope Array of up to 500 radio
  telescopes in a linked array.
• Project SEREBDIP uses radio telescopes piggy
  back to listen in to 1420 MHz. (University of
  California at Berkley)

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Data, data everywhere

• SERENDIP generates vast quantities of data that
  need to be searched for a signal (from ET).
• SETI_at_home links idle computers (like yours) from
  around the world to analyze data
  (setiathome.berkeley.edu

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Other search techniques

• Optical SETI assumes the use of lasers in a
  pulsed manner to signal existence.
• Masers are microwave equivalents to lasers and
  are being investigated as a possible signaling
  medium.

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The Flag of Earth
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The Fermi Paradox

• So where is everyone?

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Enrico Fermi1901-1954
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The Fermi Paradox

• The belief that the universe contains many
  technologically advanced civilizations, combined
  with our lack of observational evidence to
  support that view, is inconsistent. Either this
  assumption is incorrect (and technologically
  advanced intelligent life is much rarer than we
  believe), our current observations are incomplete
  (and we simply have not detected them yet), or
  our search methodologies are flawed (we are not
  searching for the correct indicators).

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Logic

• We are not special in our development (life on
  Earth)
• Thus via the Drake Equation, life should be
  relatively common in the Milky Way.
• Even traveling at slow speeds, colonization
  should have lead to outposts everywhere by now.
  (Milky Way is 10 billion years old.)

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Even worse Von Neuman machines

• Build self replicating machines and let them
  explore the galaxy.
• In this way, while colonization is not performed,
  the presence of civilizations would be felt
  everywhere in the galaxy.
• Probes are not encumbered by the physical
  limitations of life (air, water, aging etc.).
  Relatively easy to produce.

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An aside

• Von Neuman machines might consume all the
  resources in a galaxy! (They could develop
  exponentially.)
• If so, any civilization capable of producing
  these machines would not!

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The contradiction

• Colonization should have occurred
• No evidence of such rampant colonization

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Solution 1

• We are the first technologically advanced
  civilization capable of interstellar travel and
  communication.
• If so, SETI is a waste of time no one out there
  to talk to.
• This solution sounds much like the Geocentric
  Model of the Solar System Earth special
  (unique, rare) and does not seem likely. Nothing
  in astronomy or biology suggests we are special.

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Cosmic Calendar(inspired by Carl Sagan)

• Imagine the age of the universe (and thus life on
  Earth) compressed to 1 calendar year.
• January to November inclusive. Each month is 1
  billion years, each second is 390 years.

August
March
November
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The power of the media

• This type of reporting stems from alack of
  understanding and a lack of research into the
  facts.
• Sound familiar remember to not necessarily take
  information at face value. A report in any media
  is not always accurate be skeptical!

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December .
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To note

• The dinosaurs existed from December 25 through
  30!
• The entire human history is less than 30 seconds
  long (10,000 years)!
• Planets capable of harboring life in our galaxy
  could have formed in July!
• Almost any assumptions you make result in a
  conclusion that civilizations have had ample time
  to form and develop and colonize

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Comparable age and development?

• Perhaps a more useful question to ask is Are
  other civilizations technologically comparable to
  us?
• We have had space travel and interstellar
  communication capability a short time. How long
  will we keep it?
• More likely other civilizations very advanced or
  very inferior technologically speaking.

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Colonization

• Like the Von Neuman machines, interstellar
  colonization would result in the relatively rapid
  spread of settlements throughout the Milky Way
  galaxy. The coral model.
• Note that colonization does not represent a
  solution to the population explosion on a planet
  (like Earth).

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Human Population

• Humanity is experiencing an exponentially growing
  population which is, arguably, unsustainable.
• Approximately 100 million people born annually.

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Why colonize?

• Assuming the attitudes associated with life on
  Earth are not unique, then our history is
  resplendent in voyagers of exploration and
  colonization
• Other civilizations may colonize to avoid their
  culture becoming extinct (existing on more than
  one planet).
• Perhaps colonization is spurred on by the need to
  flee persecution, etc.

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Other solutions to the Fermi Paradox Solution 2

• Civilizations common but have not colonized the
  galaxy.
• TECHNICALLY TOO DIFICULT (OR TOO EXPENSIVE IN
  TIME AND ENERGY)
• THE DESIRE TO COLONIZE IS NOT COMMON (WE ARE
  ATYPICAL)
• DESTRUCTION OF THE CIVILIZATION OCCURS BY
  THEMSELVES OR THROUGH NATURAL CAUSES (ASTEROIDS,
  ETC.)

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Other solutions to the Fermi Paradox Solution 3

• There is a galactic civilization out there and
  they have chosen to keep us isolated (Star Treks
  Prime Directive). Thus there is no paradox!
• Sometimes called the Zoo hypothesis but we may
  still yet detect their signals even if they
  choose not to communicate with us.
• Time likely needed for SETI to succeed.

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Other solutions to the Fermi Paradox Solution 3
cont.

• The Sentinel hypothesis suggests that galactic
  civilizations are indeed monitoring us, waiting
  for us to reach the right level of technology
  allowing us to join the Galactic Club.

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Too expensive?

• It often comes down to money
• It is fine to argue about the number of
  civilizations that may exist. After the
  argument, there is no easy substitute for a real
  search out there we owe the issue more than
  mere theorizing. Philip Morrison
• Answering the Fermi Paradox will arguable be a
  turning point in our history.