Posts Tagged ‘Carl Sagan’

Found on the Watson Critical Thinking Blog is this awesome graphic, featuring some of the best thinkers, doers, and inventors over the centuries. A good insight from this list: it is not confined to scientists, showing that critical thinking is applicable to many disciplines, interests, and occupations. On our part we’ve featured critical thinkers from various fields, and in the future we will definitely highlight the names included on this graphic as well.

Good stuff.

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Hypatia was a 4th-century Greek scientist, philosopher, and astronomer. A noted scholar from the great library of Alexandria, she was murdered on 415 AD by a Christian mob. Her death coincided with the beginning of the Dark Ages.

Her thoughts on:


All formal dogmatic religions are fallacious and must never be accepted by self-respecting persons as final.

Free Thought

Reserve your right to think, for even to think wrongly is better than not to think at all.


Life is an unfoldment, and the further we travel the more truth we can comprehend. To understand the things that are at our door is the best preparation for understanding those that lie beyond.


Fables should be taught as fables, myths as myths, and miracles as poetic fancies. To teach superstitions as truths is a most terrible thing. The child mind accepts and believes them, and only through great pain and perhaps tragedy can he be in after years relieved of them.

Superstition vs. Truth

In fact, men will fight for a superstition quite as quickly as for a living truth — often more so, since a superstition is so intangible you cannot get at it to refute it, but truth is a point of view, and so is changeable.

We previously featured the story of Hypatia on Carl sagan’s account of the last days of Alexandria–and the loss of all the classical knowledge of that time.

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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.

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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): (more…)

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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.


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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.


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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.

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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.

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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.

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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.

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