by Carl Sagan
Robert's Supertruth Book List of the BIG Picture
“ In our tenure on this planet, we've accumulated dangerous evolutionary baggage: propensities for aggression and ritual, submission to leaders, hostility to outsiders. All of which puts our survival in some doubt. … But up there in the cosmos, an inescapable perspective awaits. National boundaries are not evident when we view the Earth from space. Fanatic ethnic or religious or national identifications are a little difficult to support when we see our planet as a fragile blue crescent, fading to become an inconspicuous point of light, against the bastion and citadel of the stars.”– Carl Sagan, “Cosmos”, Episode 13: “Who Speaks for Earth?”
This is a great book, beautifully written, that consistently manages to express itself concisely and yet eloquently. Praised and emulated by writers as the epitome of science writing. A joy to read.
Available in Hardcover, Trade Paperback, Small Paperback, and as the Television Series on 7 DVDs
The Cosmic Perspective – What Is It?
In “Cosmos”, what does Carl Sagan mean by “the Cosmic Perspective?” He doesn't give us a precise definition that I know of, but I think to some extent it means trying to perceive, to understand, and to be conscious of what we would call “the big picture” or “the grand scheme of things.” This is not an easy task, and to maximize our chances for progress, we need to approach the problem in a spirit of both lively curiosity and healthy skepticism. Most recently, astrophysicist Neil deGrasse Tyson has been talking about “the Cosmic Perspective” again, and I think it is wonderful that he is challenging new generations of science enthusiasts to see things in new ways. (See link at end of this section.)
While “the Cosmic Perspective” may not have a universally recognized, official list of concepts associated with it, there are certainly two important concepts on the list that I can illustrate with the help of the Milky Way galaxy photo shown here.
Concept 1: Stars are numerous. The Milky Way galaxy is a huge, rotating disk of stars of which our star (the Sun) as well as the Earth, the planets, and ourselves are also a part. In the photo, we are seeing our galaxy edge-on looking toward its center. Stars in the foreground are relatively large, individual white dots. At greater distances, the stars’ dots become smaller and greater in number until they become so numerous that they seem to merge together. The dark areas running diagonally across the photo are clouds of dust that obscure still more stars behind them and the galactic center. The Milky Way is just one of countless galaxies in the universe. Thus, stars are so numerous as to be almost literally infinite in number. As numerous as all the grains of sand on all the beaches of the world.
Concept 2: Space is vast. To give you an idea of some of the distances involved, consider this: light travels at a speed of 186,000 miles per second. At that speed, it takes 1.3 seconds for light to travel the quarter million miles or so from the Earth to the Moon. The nearest stars are 4.4 years away at this speed, and it would take 30,000 years to reach the center of our galaxy. The next nearest large galaxy in our part of the universe, Andromeda, also known as M31, would take 2½ million years to reach at light speed and, on the scale of the universe as a whole, we haven't even left our immediate neighborhood. There are almost countless other galaxies at much greater distances.
Well, if you have been interested enough to read down this far, you're probably asking, “Robert, how do I get more of this Cosmic Perspective for myself?” Answer: “Dude, go to the library and check out “Cosmos” or go online or to the store and buy it!”
And while you're waiting for “Cosmos” to arrive, check out Neil deGrasse Tyson's “Cosmic Perspective” at NOVAscienceNOW.
“Cosmos,” The Search for Extra-Terrestrial Life, and NASA's Kepler Mission
As recently as the 1970s, if you had polled people about the possibility of life on other planets or elsewhere in the universe, most would have been very skeptical. Today, the opposite is true, and I think “Cosmos” has been one of the major factors accounting for the change. For that reason, it is easy to have the impression that “Cosmos” deals almost exclusively with the search for extra-terrestrial life, but that would not be true. It is also very much about us—the story of how we got here and where we are. Also where we might be going (1) if we’re thoughtful and (2) if we’re not. Nonetheless, “Cosmos” is an excellent guide to understanding the issues involved in the search; the Drake equation; the habitable zones of solar systems; the composition of the primordial soup; the emergence of self-replicating molecules on our planet and their development into life as we know it today, etc.
NASA's Kepler Mission
This is probably a good place to mention the search for extra-terrestrial life in connection with NASA's Kepler Mission. I didn't find out about Kepler until second-quarter 2009, which probably indicates that news coverage of science topics still tends to be neglected. This tendency was one of Carl Sagan's primary motivations for writing “Cosmos,” in fact. Some news people claim that the public isn’t interested in science. I suspect that millions of people are interested, but that not many news people can be counted among them.
In any case, Kepler, a specialized space telescope for detecting planets around other stars, was launched into an Earth-following orbit in March 2009. From its vantage point in space, over its 3-year mission, Kepler is designed to stare, with very few interruptions, at a field of over 145,000 stars along the Milky Way galaxy’s Orion spiral arm, of which we are also thought to be a part. The patch of sky under observation has about the same area as your hand held in front of your face at arm’s length. If, during this time of nearly unblinking surveillance, an extrasolar planet should transit ( pass in front of ) its sun along Kepler’s line of sight, Kepler’s sensitive photometers will register the drop in light level, even if it is only a decrease of 20 parts per million—two-thousandths (0.002) percent.
NASA expects to find anywhere from 50 to hundreds of habitable earth-size planets this way, an astonishing number considering that we now know of none. A “habitable” planet is at a distance from its sun where some liquid water can be expected on its surface—that is, a planet between the extremes of being far away from its sun and completely frozen or near its sun with its water completely vaporized. This is the so-called “Goldilocks zone.” Liquid water is a requirement for life as we know it. It may not be a requirement for all possible forms of life, but it is a good starting point for a first search. Of course, the possibility of liquid water on a planet does not guarantee that life will exist there. But plans are on the drawing boards for powerful telescopes capable of making that determination.
How Kepler Finds Planets
The photo at right shows the planet Venus (small dot) viewed from the Earth in 2004 as it transits (passes in front of) our Sun—an event lasting several hours. If the orbit of a planet beyond our solar system happens to be tilted favorably, the planet will, from Kepler's point of view, regularly transit its sun. But it would be too far away and our telescopes too weak to give us a photo similar to the one shown here. However, in the event of a transit, the amount of light reaching Kepler is reduced by a very small amount, quite possibly enough to be detected by its very sensitive instruments. In this way, Kepler uses the “transit method” to detect planets.
( Caution: Never look at the sun directly, or through binoculars or a telescope. A projection method is easy to implement and much safer. )
So, is anything (or anyone) out there? Our ancestors have wondered about it for many thousands of years, and we're only a few years away from getting a good, preliminary answer. A very exciting prospect.