Touching The Limits Of Knowledge

Cosmology and our View of the World


“Are We Alone?” Lead: Davida Harris


Summary by Michael Dunn

Search for Extraterrestrial Life/Intelligence

Davida opened the presentation with a familiar picture of the earth from the Voyager spacecraft, followed by a portion of a Carl Sagan speech from 1996 entitled “Pale Blue Dot” which he characterized the earth as “a piece of dust suspended in a sunbeam”, just as it looks in the famous Voyager photograph. Next, we were shown a famous zoom-out sequence from the opening scene of the film “Contact”, where the camera moves away from earth at a rapid rate as radio signals are fading back in time, attempting to give us another perspective on the vastness of the universe, and our miniscule role in it.

Davida then hashed out what is meant by the term “we” in the title of the talk and whether it means humans, intelligent life or simply life in general. It was decided that for the purposes of the talk, by “we”, we were referring to intelligent life. Davida explained that there are two primary scientific approaches that are used by scientists in the search for intelligent life. The first, called the direct approach, involves organizations like SETI (Search for Extraterrestrial Intelligence) and NASA who are actively focusing their technologies on the physical detection of new planets and solar systems which may be habitable for life. The second, referred to as the indirect approach, is more introspective and involves active research into our own origins of intelligent life, and then applying this knowledge as a model to search for life outside our planet.

Delving further into the indirect approach, the arguments for life arising on accident on our planet were laid out, with naysayers arguing that the complexity of life on earth could statistically never occur by a series of random events. Supporters counter this argument by explaining that life naturally evolves if given the right conditions and a long enough time scale, pointing towards the gradual progressive steps of evolution as proof of this concept.

Dr. deVries raised the question of whether this argument was addressing the evolution of a form of life with our exact genome arising out of nothing, or the creation of intelligent life in any form. Dr. Davis offered an interesting response to this statement, by saying that evolution works by utilizing and manipulating environmental constraints, and that any form of life that evolves on another planet is going to evolve things like legs or wings which are the most efficient means of transportation feasible. Evolution decides whether these traits are beneficial or not to a species, and these traits become channeled by the environment.

In hopes of actually quantifying the number of intelligent civilizations in our solar system, Davida presented us with the Drake Equation, which attempts to calculate the number of intelligent, communicating planets in existence. Using seven variables, from the number of habitable planets per star, to the approximate lifetime of an intelligent civilization, an online version of the Drake equation from was tweaked and manipulated to show the wide range of possibilities. Following a question by Erica, Dr. Moebius made sure to clarify that the variable in the equation that concerns “communicating” civilizations implied that these civilizations were able to communicate with other planets, not simply that they had a functional language. The Drake equation and its variables are pictured below:

        N = R* • fp • ne • fl • fi • fc • L


N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.

R* =The rate of formation of stars suitable for the development of intelligent life.

fp = The fraction of those stars with planetary systems.

ne = The number of planets, per solar system, with an environment suitable for life.

fl = The fraction of suitable planets on which life actually appears.

fi = The fraction of life bearing planets on which intelligent life emerges.

fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.

L = The length of time such civilizations release detectable signals into space

The values used by Drake and his colleagues when he devised this equation in 1961 were:

R* = 10/year (10 stars formed per year)
fp = 0.5 (half of all stars formed will have planets)
ne = 2 (2 planets per star will be able to develop life)
fl = 1 (100% of the planets will develop life)
fi = 0.01 (1% of which will be intelligent life)
fc = 0.01 (1% of which will be able to communicate)
L = 10,000 years (which will last 10,000 years)

Drake's values give N = 10 * 0.5 * 2 * 1 * 0.01 * 0.01 * 10,000 = 10.
Note: In the version of the Drake equation that Davida presented to the class, the variables N* (number of stars in the Milky Way galaxy) and fL (fraction of the age of the galaxy that a civilization was surviving) were substituted for R* and L in the original equation.

Picking the brain of Dr. Moebius, the class went through each of the seven variables, to get a rough answer to the Drake Equation given our best estimates. The last few variables, involving estimates on the number of planets that will develop intelligent life provided that they can sustain life, and then the number of intelligent civilizations that would be able to communicate with other planets were particularly debatable, as we really have no basis as to actual probabilities of these events. The largest point of contention was estimating the life of an intelligent, communicating civilization as the possible answers for this variable had a wide range of values, varying in orders of magnitude from one another. As an optimist data point, Dr. Davis suggested a value of 5 million years as a reasonable span of time, while other members of the class believed that a value of 1,000 years was much more feasible. Because our own civilization has only had the technological means to communicate extraterrestrially for 50 years, and given the current trend of events on earth, even 1,000 years seems like a generous estimation. After thoroughly discussing each of the variables further, Dr. Davis suggested that we scrap the intelligent life variable, as it is redundant with the “able to communicate” variable as an intelligent society will inevitably develop the means to communicate is given enough time. Or at the very least merge them together. Our calculated answer to the Drake equation was approximately 14 intelligent, communicating civilizations within our galaxy, much in line with Drake’s initial estimate, although our values for each of the variables varied.

Phil raised the hypothesis that planets could have existed billions of years ago and sent signals but we didn’t have the technology to receive them when they reached us or they have yet to reach us as they are light years and light years away still. Dr. Moebius explained that planets that would have evolved at this time early in the origins of the universe would have been orbiting “Population 2” stars which are unable to support life as not enough heavy elements had been formed within the stars.

Getting into more direct methods, Davida went on to say that before this new millennium, no planets had been discovered outside of our solar system, but by the year 2005, over 150 had been discovered. Just last week, scientists found the first “earth-like” planet outside of our solar system that could feasibly support life via liquid water, approximately 20.5 light years away. Following a question, Dr. Moebius attempted to explain how scientists are able to determine the masses of planets, their distance from the sun, and their ambient temperatures simply by analyzing the wobble of their star. I then asked Dr. Moebius if scientists could tell from this wobble whether there were multiple planets orbiting the star. He replied that yes, they are able to deduce the number of stars within a reasonable limit, but when the number gets too high the equations begin break down. Chris Ives then asked whether scientists could detect whether a planet had an atmosphere using this wobble, as it is known that the atmosphere surrounding a plant has a huge effect on its temperature, to which Dr. Moebius mentioned some spectroscopic methods that are useful in detecting trace gases on the surfaces of planets from great distances.

Another interesting development Davida shared with us involves the development of a machine that will be sent to Mars to detect and extract DNA on its surface. This may be done using microbes, as they are known to be incredibly resilient and can live in any environment on earth, no matter how extreme. Davida went on to say that microbes have even survived on the surfaces on spacecraft when they come back from the moon. Dr. Moebius raised the interesting point that we may have contaminated the moon/Mars simply by visiting it and inadvertently depositing microbes or DNA of some sort.

The discussion of microbes and the interesting prospect of discovering DNA material on Mars led into a long discussion about genetics and its variability. Dr. Davis explained that although there are a strict set of codons in a genetic code, there are many variations that would still work and be feasible for life, but for some reason, this is not the case and the genetic code of every species are almost identical to one another. Using this argument, he believed that this type of coincidence lends credence to the Panspermia theory that life on this earth was delivered via an asteroid or other heavenly being that crashed into our planet. Dr. DeVries countered that the reason for this uniformity may stem from the physics and connection of theses codons, which only allow for certain chains of code to be produced. Dr. Davis did not believe that the physics of the connector molecules were constraining the genetic code.

Adam then asked why we didn’t have multiple codes, one in our first form of life and another existing parallel to this as the genetic code of the life from space. Dr. Davis explained that if the seed of a more advanced form of life hit the primordial soup of the earth, the soup and the extraterrestrial form of life would not develop independently. Rather, the life from the seed would consume and destroy the native primordial life and evolution would progress from there. Adam asked whether we would be able to encounter evidence of this primordial life that was destroyed after the seed, to which Dr. Davis replied that there could be some signs. Dr. Moebius went on to ask why this type of seed scenario couldn’t have happened between two forms of life on earth which had developed independently of one another, but at different rates. Dr. Davis felt that the first situation was a bit different as the seed civilization in his example was leaps and bounds ahead of the primordial one, rather than slightly more evolved as described by Dr. Moebius’ scenario.