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ET Life 25
Origin of Intelligence Drake Equa8on
Fermi Paradox
FINAL PAPERS!
• Papers are due Thursday @ 11:59 pm • 8 pages of text (including references) • Turni8n.com
– “Revised Paper”
• Remember to add a response to your reviewers.
"organizing our ignorance"
Values Drake used in 1961
R* = 10/year on average for the galaxy fp = 0.5 (stars with a planet) ne = 2 (2 planets per star capable of life) fl = 1 (50% of these develop life) fi = 0.01 (1% will be intelligent) fc = 0.01 (1% will be able to communicate) L= 10000 years (life8me of communica8ve civiliza8on)
N=10*0.5*2*1*0.01*0.01*10000=10 !!!!
Kepler's Goal
• To discover the frequency of Earth‐size planets on habitable orbits around Sun‐like stars (η⊕=fp*ne)
• Kepler should reach this goal by the end of its 7 year mission (2016)
Wild Extrapola8on Warning!
What has been observed
What is “predicted” if you draw a straight line on a log‐log plot
Other wild guess values…
N=R* *fp*ne*fl*fi*fc*L Drake: N=10*0.5*2*1*0.01*0.01*10000=10 !!!!
Just as plausible: N=7 × 1 × 0.2 × 0.13 × 1 × 1 × 10^9= 182 million
A zero ANYWHERE means N=0…..
The Rare Earth Thesis • Peter Ward and Don Brownlee at the
University of Washington, 2000 – microbial life should be widespread in the
universe – Complex life such as plants and animals
will be very rare • Earth is “lucky”
• Complex life on Earth is the result of extraordinary condi8ons and lots of random chance – Microbial life appeared quickly (ONLY
400‐800 Myr) – Complex life came very late ~2‐4 Gyr
• Earth is special – In the habitable zone – Life‐friendly atmosphere – Jupiter & the Moon protect us – Boring part of the Galaxy (boring = safe)
Intelligence? • We have never discussed the ideas behind fc.
– Life must become intelligent and develop technology to become communica8ve.
– We have only become communica8ve in the last 60 years….AFTER 4 billion years of evolu8on.
– The Cambrian explosion gave rise to different body plans – why? Chance?
– Or, there is always evolu8onary pressure for intelligence
Brain Size?
EQ
• Encephaliza8on Quo8ent (EQ) of 1 is right on that average line – Above means above average brain mass – Below…
• We weight in at EQ = 7 – Chimps~2.5, and dolphins ~4‐5. – Largest known value for anything known or ex8nct
• Mass isn’t everything (easy basic measure) – Brain folding.. Neural connec8ons….
Brain Size?
Dolphins
• Dolphins EQ increased drama8cally about 35 Myr (echoloca8on)
• Again about 15 Myr ago
• Intelligence has survival value…
Challenges any theory must address
There are some consequences to our intelligence, and the benefits must outweigh the consequences
– Large brain = more energy use (lots more >20% of our energy use…all that hot air) – Larger female pelvis (human babies have HUGE heads) – This also leads to much more dangerous pregnancies
– Longer infan8le stage (seriously, Bambi was walking at one day old, compara8vely we’re sixng ducks for our first year) – Longer juvenile stage (human children, in hunter‐gather socie8es, don’t support their own energy intake un8l they’re 18!)
Primate brains have been expanding exponen8ally for the last 4my…
• Posi8ve feedback? – ‘smarts’ selected for in mates – Ability to pass skills selected for as these tools provide a selec8ve advantage
– Social interac8ons (more individuals more mental powers) – Predator‐prey interac8ons…as they got more intense the ability to not ‘wait for evolu8on’ became a huge advantage
• Idea is that, once we passed a point where brain size did ma{er, it was aggressively selected for and intelligence increased exponen8ally
Intelligence ‐> technology….?
• Dolphins are nearly as smart (EQ) as humans – No hands… live in water
• Humans reached present form around 150,000 years ago – Had similar intelligence 20,000‐30,000 years ago – Our ability to communicate is directly linked to the development of
science in the last 2500 years.
• Can the events that transpired on our planet guarantee that intelligence will or will not emerge – Technology? – Science?
• fc will be very very hard to measure without a single data point!
How To Answer The Big Questions?
• Put this in the scien8fic context of hypothesis tes8ng.
• Study of early life on Earth • Explora8on of our solar system (Mars, Europa) • Search for terrestrial‐like extrasolar planets • Search for signatures of life on extrasolar planets • Search for ETL by SETI‐type searches
Distances between signaling socie8es
• Volume of the Galaxy is V= (pi*R^2 x T) , where T is disk thickness ~1000ly, and R is disk radius ~ 50000 ly
N is total number of civiliza8ons, V/N is then the volume per civiliza8on
Distance d between civiliza8ons is d^3=V/N d=(V/N)^(1/3)
• For N=10,000 civiliza8on, then d=900 ly
SETI
• Nikola Tesla postulated in 1896 that radio could be used to contact ET life. – Spent some 8me in Colorado Springs – Built world's first commercial‐grade
alterna8ng‐current power plant in Telluride CO.
• In 1899 Tesla observed repe88ve signals – very different than typical signals (from storms as such). – He thought this was Mars… rather it
was simply new equipment…
Scien8fic approach to SETI
• Morrison & Cocconi in 1959 – The galaxy is much older than the Solar System – So, some civiliza8ons could be much older than ours.
– Where to point? – at stars… • What channel to listen too?
– The larger the bandwidth the more spread out the signal gets
– Rather, just blast one channel with LOTS of power, so you get no8ced.
– They proposed 1420 Mhz. Neutral Hydrogen gas emits at, produced “inter‐stellar white noise”
• Also, any technological civiliza8on would know this and be capapble of listening at that frequency…
Project Ozma
Frank Drake in 1960 used a 26m radio telescope at Green Bank, West Virginia searched for ETI for 2 weeks.
Called it Project Ozma (L. Frank Baum’s Land of Oz ‐ “very far away,difficult to reach, and populated by strange and exotic beings”) ‐Looked at two solar‐like, solar‐aged stars. ‐Looked for repeated series of pa{erned pulses or a series of prime numbers. ‐False alarm caused by a secret military experiment. ‐Only found sta8c and meaningless wiggles on the paper recorder.
Showed systema8c searches are feasible
Types of signals?
1. Signals used for local communica8on
– TV or radio or radar
2. Inter‐planetary communica8on
– Us talking to a spacecra} or colony etc.
3. Inten8onal signal beacons
– Something like what Ozma was trying
Our own signals?
• We have been broadcas8ng TV for 60 years
• However, since it is not meant as a beacon, it is not directed and its power is directed widely
• With out technology we could only detect our OWN signal 1 ly away.
The “WOW” Signal
Received on August 15, 1977 Short dura8on very high energy pulse. “Wow” wri{en by a SETI volunteer indica8ng it was strange. High likelihood it had an ET source. But is it ETI?? Was only picked up by one of the telescopes at Ohio State University. The signal is not a message ‐ is an unmodulated signal.
Perhaps it switched on just briefly?
It has never been seen again even with more sensi8ve equipment.