1. The Search for Extraterrestrial Intelligence

2. What is SETI searching for?
Intelligent life elsewhere
Evidence that points to intelligent life elsewhere
Messages from other civilizations

3. Can the search be successful?
How many civilizations are out there?
How do we define and measure intelligence?

4. The Drake Equation
A simple equation for determining the number of civilizations out there.
It cannot give a definitive result!
Number of civilizations = NHP x flife x fciv x fnow
NHP = number of habitable planets in the galaxy
flife = the fraction of habitable planets that actually have life.
fciv = the fractions of life-bearing planets upon which a civilization capable of interstellar communication has at some time arisen.
fnow = the fraction of civilization-bearing planets that happen to have a civilization now!
A big drawback to the equation…. WE DON’T KNOW THE VALUE OF ANY OF IT’S TERMS!

5. Numbers in the Drake Equation
We can make an educated guess on the number of planets out there.
We don’t know if they are habitable.
We have no way to guess the fraction of habitable planets that life arose on.
We have no idea how many life-bearing planets lead to civilizations.
We don’t know how many civilizations are surviving now. (We don’t know of any at present… Fermi Paradox!)

6. Intelligence
What is the probability that life will give rise to intelligence?
SETI is likely only to be successful if intelligent civilizations are widespread. Are they??
2 classes of thoughts:
Life is common but intelligence isn’t (we have lots of life, but only humans made it to intelligence)
Intelligence is common (if we hadn’t managed it, another species would have) (convergent evolution)

7. Convergent Evolution
Even if two lifeforms start at different points, they converge (evolve) to the same point through natural selection.
If an adaptation is necessary for survival, many species may evolve toward that adaptation.
Is intelligence such an adaptation?
(we’re trying to figure that out)
Dolphins and Sharks (mammal and fish) evolved to the optimal streamlined swimming shape
Eyes have evolved at least 8 different times (from at least 2 different types of cells)

8. Measuring Intelligence
How do you measure the intelligence of an animal that can’t take an IQ test?
Look for a higher ratio of brain to body mass. (decent approximation for complex behavior)
Encephalization Quotient (EQ) (EQ>1 for higher ratios)
Measuring fossil cranial cavities leads us to the EQs for extinct species. Dolphins and primates seem to be evolving to higher EQs.

9. Pre-Adaptations
You need a good metabolism to work the bigger brain. (Better metabolisms in warm-blooded creatures)
Larger body to house the larger brain. (maybe. Contested.)
Extended parenting (for teaching the brain)

10. So, which creatures get the intelligence?
Possible selection criteria:
Interaction among individuals (understanding social positions and getting better mates)
Competition (if you must compete for food, mates, etc., you are forced to think more to be successful)
If all pre-quals are met, which creatures are selected for higher intelligence?

11. Communication through Space
Even if you do get an “intelligent” civilization, will it be one that can (or will) communicate through space?
No matter how smart they are, body design may make a difference in their communication and in their studies. (If they can’t detect light, would they ever use it for communication?)

12. Before SETI Began Early 1900s
A couple of unconfirmed alien radio broadcasts.
A search for alien radio broadcasts.
A search for Martian radio broadcast.
NO LUCK.

13. SETI: The Early Years
Cocconi and Morrison and Frank Drake propose to search the radio sky at 1420 Mhz.
Drake searched to star systems for 2 weeks at this frequency without luck. (Project Ozma)

14. Broadcasting We’ve done very little.
The most powerful was the 1974 Arecibo message.
Should we broadcast?

15. The Arecibo Message
The message sent in 1974 from the Arecibo radio telescope toward the globular cluster M13 consisted of 1679 “bits” of information. A “0” is represented by an “off” radio pulse,while a “1” is represented by an “on” radio pulse.
Note: M13 is about 21,000 light years from us!

16. The Arecibo Message

17. The Arecibo Message
This picture was generated by arranging the 1679 bits above into 23 columns of 73 rows, 23 and 73 being the two prime numbers, which when multiplied together equal 1679.

18.  Numbers 1-10
Atomic numbers for H, C, N, O, P
 Formulas for sugars, bases and phosphate in DNA nucleotides
Double helix structure of DNA surrounding binary number that represents the number of nucleotides in the human genome.
 Height of human being marked on the left and human population marked on right
Schematic of solar system (human stands on 3rd planet)
Arecibo transmitting telescope
Diameter of telescope

19. Arecibo Message Explained

20. Signals Signal beacon! Intentional and what we hope to find.
Local communication signals.
Longer distance communication signals (to a colony, spacecraft, etc.)
Local communication – not broadly or powerfully sent, may not be picked up far away.
Longer distance has the same problem, but might be a bit easier.
Our best bet is the beacon. As they are deliberate, you would expect them to be powerful. You would also hope they were made to be decoded.
Of course, the beacon only happens if a society decides they WANT to broadcast themselves.
We’ve done it. In 1974 for three minutes the Arecibo telescope sent the pictorial message above to M13 (globular cluster) light years from Earth.
Should we do it again? Would need a long term broadcast commitment to try to be successful. Lots of $$.
DO YOU THINK IT IS SAFE FOR US TO BROADCAST TO THE STARS?

21. Other ways of searching?
Have aliens been here and left things behind? Where to look?
Try the Lagrange points! (Where gravity can cancel in such a way that objects stay there.)
A survey of the Lagrangian points has NOT yielded anything yet.

22. Other ways of searching? (2)
Look for an astroengineer! Civilizations that use the resources of their star and surrounding area.
Could they make a Dyson sphere? Would be detect it if they had?

23. SETI Now Radio searches Optical searches
Limited by telescope time and terrestrial interference
Optical searches
Shorter range (dust), costs more, good for focused communications (morse code?)
X-ray? UV? (more energy/money)
Exotic stuff- neutrinos, gravity waves (harder, more expensive, benefits??)
Optical – shorter range due to dust, costs more (more energy used), good for focused communications (use a lens). Could use it like Morse code
Could use other forms of light, but require more energy (and $)

24. How do we measure a SETI success?
Narrow band signals
Short bursts of light pulses
A message (content)

25. What if we got a signal?
Would need verification by several observatories.
Analysis to show it isn’t a natural phenomenon or a man-made signal.
Notification of governments and the world population.
We learn from it! (Maybe language or beliefs, art or body structure, possibly an encyclopedia of knowledge. Maybe just that we aren’t alone.)