One of the classic speculations of astronomy and biology is the uniqueness or likelihood of intelligent life in the universe. Dr. Frank Drake who is now Professor of Astronomy and Astrophysics at University of California proposed, in 1960, a mathematical framework to estimate the number of extraterrestrial civilizations in our galaxy. The equation, now known as the Drake Equation.

What’s fascinating about the equation are the kinds of variables Drake chose as contributors to the existence of a civilization. In this video, astronomer Carl Sagan describes the equation’s components and its implications to the existence of intelligent life in the galaxy:

Come up with your own estimate of life using the Drake Equation using this interactive version from Nova.

How accurate is the Drake Equation? That’s the problem. No one can really say at this point–although it does provide a plausible framework. Most of the variables are just simply guesses. Criticisms of the Drake Equation in wikipedia:

Criticism of the Drake equation follows mostly from the observation that several terms in the equation are largely or entirely based on conjecture. Thus the equation cannot be used to draw firm conclusions of any kind. As T.J. Watson states:

The Drake equation consists of a large number of probabilities multiplied together. Since each factor is guaranteed to be somewhere between 0 and 1, the result is also guaranteed to be a reasonable-looking number between 0 and 1. Unfortunately, all the probabilities are completely unknown, making the result worse than useless.

Likewise, in a 2003 lecture at Caltech, Michael Crichton, a science fiction author, stated:

The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. [...] As a result, the Drake equation can have any value from “billions and billions” to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless…

One reply to such criticism is that experiments by SETI scientists do not attempt to address the Drake equation for the existence of extraterrestrial civilizations anywhere in the universe, but are focused on specific, testable hypotheses (i.e., “do extraterrestrial civilizations communicating in the radio spectrum exist near sun-like stars within 50 light years of the Earth?”).

Another reply to such criticism is that even though the Drake equation currently involves speculation about unmeasured parameters, it stimulates dialog on these topics. Then the focus becomes how to proceed experimentally.

The Drake Equation is simply another one of those questions that have to wait for more advanced instruments, theories, and discoveries in order to shed more insight. Meanwhile we can only guess.

In 1990, the Voyager 1 spacecraft completed its primary mission, having completed its Saturn fly-by. One of the last instructions sent to the spacecraft by NASA was for it to take photographs of all the planets in the Solar System from its present position.

One photo–that of the Earth from approximately 4 billion miles away, has become one of the most popular photographs in our times. On the grainy image, the Earth barely appears as an insigificant blue dot–a indicator of our place in the vast universe and the fragility of the totality of human experience.

Many videos have since been published to honor the photograph. I’ve selected the two videos below to give a better appreciation of the photo. The first is a finalist at the Portobello Film festival in London, and the Concorto Film festival in Italy 2007. It ends with a quote from Sagan about the importance of maintaining a skeptical mindset, which is very appropriate for this blog. The second video below features an actual speech from Carl Sagan on his thoughts about the Pale Blue Dot.

A transcript of Sagan’s speech from wikipedia: (read in the second video above):

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.

In an earlier interview on Charlie Rose, Carl Sagan explains the context and issues related to manned and unmanned space exploration and poses critical questions to justify it.

Sagan also describes humanity’s current context in the environment and universe and the challenges ahead of us as an intelligent species.

In 1996, Carl Sagan was interviewed on the Charlie Rose Show where he warned about the dangers of being ignorant of science in an age when society is practically based on science and technology. When the general public is ignorant of science, who makes the decisions on science and technology?

Sagan also describes the proliferation of psuedo-science (e.g. UFOs), superstition, and literal interpretations under religion as problematic to society. He encourages skepticism as a way forward both to accumulate knowledge, and as a way to keep society from self-destructing.

Sagan’s opening line captures the flavor of this wonderful episode very succinctly:

There are two ways to view the stars: as they really are, and as we might wish them to be.

In this 3rd instalment of Carl Sagan’s popular series, he probes into beliefs about stars and the science of astronomy that developed after. He also looks at prevailing scientific models about the earth and the solar system (e.g. earth-centric) and how this had changed going into modern times.

The second episode in Cosmos: A Personal Voyage, by Carl Sagan which covered a wide range of scientific subjects including the origin of life and a perspective of our place in the universe.

This is the first episode of the popular PBS series: Cosmos: A Personal Voyage, hosted by Carl Sagan which covered a wide range of scientific subjects delving into the origin of life and the universe.

British journalist Magnus Magnusson brings together an interesting panel: theoretical physicist Stephen Hawking, astronomer Carl Sagan and science author Arthur C. Clarke. The panel tackles big questions about the origin of our universe and life and the existence of creation myths that religions pose to explain the origin of the universe. A rare talk with the great thinkers of our time.

Carl Sagan explains the common roots of the science of Astronomy and the art of Astrology–and why astrology remains within the realm of pseudo-science and superstition.

In an excerpt from the popular PBS series: Cosmos, Carl Sagan recounts the story of the great library of Alexandria, the fate of Hypatia, the last scientist to teach there, and the stagnationa and destruction of the library under the hands of Christian fanatics.

Most of Alexandria’s great works are lost in time for ever, and is a cautionary tale of how ignorance and supersitious fanaticism threatens the progress and development of science, and holds humanity back from its true potential.