PHYS2010

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PHYS2010 Life in The Cosmos S.E.T.I. (and
revisiting the Fermi Paradox)
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Overview

• History of SETI
• Drake Equation re-visited
• The Water hole
• Pioneer 10
• Terrestrial transmissions
• Messages sent and received

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Frank Drake astronomer and
SETI pioneer
In 1960 he carried out the first SETI
observations and in 1961 he first proposed his
now famous equation.
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History of SETI

• Project Ozma started in April 1960.
• Ozma mythical land of the Princess of Oz
• Led by Frank Drake, they observed 2 sun-like
  stars Tau Ceti Episilon Eridani.
• Observed at 21cm for 4 months

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Used the 85 foot radio telescope in Green Bank,
West Virginia, USA.
Searched for any regular patterns, or series of
prime numbers from the two stars but to no avail.
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1960s-1970s

• Many uncoordinated surveys carried out through
  various NASA-funded projects.
• BUT . in 1978 a US Senator awarded SETI his
  Golden Fleece award as the project that was
  most wasting government money.
• So all observations ceased till 1984.

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SETI Institute

• In 1984, thanks to the vigorous
  efforts of Carl Sagan, the SETI institute was
  established with government money.
• It undertook a 10 year sophisticated programme of
  carefully targeted stars.
• However, in 1993, once more, the US government
  cancelled all funding.

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But still it survives The SETI institute
(www.seti.org)
The mission of the SETI Institute is to
explore, understand and explain the origin,
nature and prevalence of life in the
universe. The SETI Institute is a private,
nonprofit organization dedicated to scientific
research, education and public outreach.
interestingly, although some (most?) would
consider SETI as being one of the most important
scientific questions of all, SETI is regarded
almost as fringe science by many
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• In 1995, thanks to private funding, SETI came
  back to life and began Project Phoenix.
• It buys time on Arecibo (the biggest radio
  telescope in the world) and Parkes in Australia,
  and is currently studying 1000 stars within 200
  lightyears at 2000 million frequencies.

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Parkes telescopes, Australia
Arecibo, Puerto Rico
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Allen Array

• In 2000 it was announced that Microsoft
  co-founder, Paul Allen, would donate 10m to
  build a huge array for SETI.

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• A few early dishes are being tested, and the
  whole array is supposed to be operational this
  year.

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SETI is a key goal for the Square Kilometer Array
To be constructed in Western Australia or South
Africa between 2015-2025 The largest
international collaboration in radio astronomy
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Radio searches The Water Hole

• If we want to listen for other civilisations we
  need to choose the quietest part of the
  electromagnetic spectrum.
• This turns out to be in the range
• 30cm gt ? gt 3cm
• This also conveniently contains the 21cm radio
  band which is considered by many to be the most
  universal / likely wavelength for communication
  between different civilisations

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• This gap is called the Water Hole because of
  emission from various water-related molecules.
• In addition, the famous ?21cm emission from
  neutral hydrogen sits in this band.

• Since H is the most common element, maybe ET
  will choose this wavelength?

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• Sending things in the other direction
• Human artefacts sent into space
• Radio / TV tranmissions
• Directed radio messages

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Messages sent

• In 1974 Arecibo was used to send out a deliberate
  message to stars in the globular cluster M13
• M13 is 21,000 ly away and contains 300,000
  stars.
• So we might get a reply in 43974 AD

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Messages received?

• On 15 August 1977 the most famous received
  message arrived on the 21 cm band.
• The Ohio State University Radio Observatory was
  scanning the Sagittarius region when they
  detected a large radio flare.

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SETI needs YOU SETI_at_home is a screen saver
program which will download a small packet of
radio data (currently from Arecibo) from the SETI
institute and use your computer to search through
it for ET-like signals 155 possible hits
have been followed up already Download
SETI_at_home from www.setiathome.berkeley.edu
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SETI Conclusions

• So far the SETI programme has no definite
  detections
• It will have a major upgrade with the Allen Array
  in the next few years, and is a key science goal
  for the Square Kilometre Array
• BUT is SETI a waste of time and money like the
  US Senator said back in 1978? Can we afford not
  to listen?

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End of course questionnaire (please hand in
before you go) Next Fermi Paradox
discussion Tomorrow final test
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The Fermi Paradox
Age of galaxy 14,000 M yr Time to colonize
galaxy, moving at attainable speeds 10 M yr
So there has been enough time for the galaxy to
be colonised 1400 times probably more like few
100 Plus the oldest civilisations should be at
least 5,000 M yr ahead of us !
(i.e. Our galaxy is much older than it is big)
So where is everybody ? ? ? (does this mean we
are alone ?)
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Where are they ? The Fermi paradox
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They are signalling but were missing it
They are here and/or we are a Zoo
They have no desire to communicate
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The transition to intelligence is rare (Rare
Earth)
The transition to life is simply too rare
Catastrophes always wipe out civilisations