Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
Cosmos is Carl Sagan's personal guided tour of the Universe as he envisions it.
"The Cosmos is all that ever is, was or will be." Cosmos hashardly begun before Sagan reveals some of his personality. What does this statement mean?If "the cosmos" includes every imaginable entity, for example, God, then thestatement is trivially true. That is, it's true, but so what? We don't learn anything wedidn't already know. The statement is a tautology: "everything there is is everythingthere is." Sagan probably means "the material universe is all that ever was, is,or will be", a statement that many people, of course, reject.
Sagan personally was a thoroughgoing materialist, but in his writings he displayed adeeper respect for religion than most people give him credit for. He was especiallysympathetic toward the numinous aspect of religions: awe at the power and scope ofthe Universe.
The other aspect of Sagan that comes across clearly is that he was not afraid to stepon toes, an attribute that often earned him the label "arrogant."
"Stars of diamond - atoms as massive as stars." An allusion to some ofthe exotic forms of matter found in stars. Some dwarf stars have cores of carbon which,according to theoretical calculations, would have a regular arrangement of atoms: acrystalline structure. Neutron stars are essentially gigantic atomic nuclei.
"To find the truth we need both imagination and skepticism. We will be careful todistinguish fact from speculation"
"We are made of star stuff". For the most part, atoms heavier thanhydrogen were created in the interiors of stars and then expelled into space to beincorporated into later stars. The Sun is probably a third generation star.
Cosmos got high marks for its use of music. The main theme was written byVangelis, best known as composer of the score for Chariots of Fire. Also prominentin this program are Beethoven's 7th Symphony (during the montage of human images) andRimsky Korsakov's Russian Easter Overture (during the re-enactment of 17th-centuryHolland. Unfortunately, in the VHS videos, some of the best music was replaced withmediocre "elevator music."
The "ship of the imagination" is a visual convention used throughout theseries to move across space and time.
We emerge in a distant cluster of galaxies and head to Earth, on the way getting a feelfor the scale of the universe and some basic facts about galaxies.
"The patterns of nature and the laws of nature are the same everywhere."This strikes many people as an outrageously arrogant remark, but in fact there are manyobservational tests we can make to verify this idea. There have been many theories inphysics and astronomy that have postulated changes in the laws of nature over time, butnowhere in the Universe do we see any phenomena that have required physical laws differentfrom those we observe on Earth. Many people have looked for evidence that the laws ofphysics change in space in time; so far, all such tests have failed. Either the laws ofnature vary in such a way that everything just happens to look like things we know fromEarth, or the laws of nature really are the same everywhere
Throughout Cosmos, there is extensive use of artists' conceptions. Inparticular, galaxies are not as bright as pictured in the video. After all, we are just assurrounded by galaxies as any other part of the Universe. If we don't see our night skysplattered with galaxies, intergalactic voyagers wouldn't, either.
Once within the Milky Way Galaxy, Sagan describes the structure of the Galaxy and theconcept of star formation.
"Rare forms of matter" Most of the matter in the Universe is eithervery hot or very cold gas. Solid matter larger than dust grains is relatively rare,liquids rarer still because they can only exist in narrow ranges of temperature. Life, asfar as we now know, is still unique to Earth.
Sagan uses the ancient Library of Alexandria as a recurring theme in the series. Hesees it as the birthplace of Western science and as a cautionary symbol of the victory ofirrationalism over reason. The library was destroyed and its contents mostly lost. (Theactual history is a lot more complex than Sagan implies: the library was repeatedlyplundered by Roman emperors to start libraries elsewhere, heavily damaged by Christianmobs and apparently finished off by the Moslems about 650 A.D.)
Eratosthenes was the first person to correctly deduce the size of the Earth, by notingthat the elevation of the Sun differed from one place to another. The key observation wasthat on June 21, the Sun was directly overhead at Syene in southern Egypt, but not inAlexandria. By knowing the difference in elevation angle, and the distance from Alexandriato Syene, he was able to calculate the circumference of the Earth.
Two important morals of Eratosthenes' discovery
Sagan and many other modern writers give Eratosthenes credit for being within a few percent of the right answer. Older astronomy books once made the error a good deal larger. Tomake such an assertion, we would have to know:
The plain fact is we simply do not know any of these facts well enough to say he waswithin only a few per cent, and it's doubtful that Eratosthenes knew any of the firstthree to be that close. He was in the ballpark, a remarkable enough accomplishment.
The Cosmic Calendar compresses the history of the Universe into a year. On this scale:
On this scale, the Universe forms on January 1, but the Solar System does not formuntil September. Life appears on Earth not long after, but complex life does not appearuntil December. The dinosaurs appear the day after Christmas. Humans appear at 11 P.M. onDecember 31, and all recorded history occupies the last ten seconds of the year.
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Created 13 January 1998, Last Update 15 January 2020