User:Serendipodous/indigo/page 3

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 * SETI operates on the assumption that their species is typical:
 * Aliens would contact us via a message folded into a carrier wave and transmitted at a fixed frequency from an antanna at a volume above the natural radio noise
 * Aliens would be interested in attracting our attention and would make their message as easily recievable as possible
 * Aliens would customise their signals to Earth-like atmospheres by focusing on a signal that passes through them
 * Aliens would anticipate the problem of the myriad of frequencies by choosing the wavelength of hydrogen, which would be known to all sentient life
 * Modern seti searchers scan billions of radio channels between 1 and 10 hertz
 * Even if aliens chose radio to communicate for our benefit, the technological changes between the 1950s and the 1980s would be negligible if they had been around for millions of years
 * Optical seti searches for laser communication
 * durign the cold war, seti speculated that advanced races had finite lifespans
 * guessing the political priorities of an alien civilization is futule; they may have priorities we couldn't even understand
 * HG Wells's martians employed 19th century economics- empire, land, machinery
 * today our economy rests on information
 * again, their ecoomy may be based on somethign we have yet to grasp
 * the fundamental problem with SETI is that no one knows the probability of an alien civilization forming
 * Fred hoyle: It is easier to believe a tornado spontaneously created a 747 in a junkyard than a microorganism appeared only by chance
 * There is nothing in chemistry that suggests that life is inevitable. Life's ingredients may be everywhere, but life may not necessarily be.
 * Could Darwinian evolution have started at the pre-cellular level? Could autonomous chemical replicators have been shaped by evolution into complex cells.
 * if life were found to have begun independently on Earth, then it seems likely that the universe is teeming with it.
 * alternate life might be found in hostile condotitions, such as temoperatures in excess of 170 C
 * teh scientific method, though approached many times, emerged just once, in Europe durig the Renaissance, under the joint influence of Greek philosophy and monothesitic religion
 * Is high technology possible without the scientific method? (yes, to our level in our time)
 * radio signals are fading as we shift to buried fiber optics.
 * Aliens 1000 light years away would see not our civilization, but the world as it was in 1015. tehy would wait util they knew.
 * We may get a message itended for someone else, or a galactic world service but these are ulikely- one is random, one is too costly
 * We might detect low-frequecy leakage from a planet, ala television, but Seti does not search in that range. New telescopes such as lofar, a telescope array located in several countries, has the range, but not the strength
 * different trasmisstion techniques- eutrinos?
 * Wow signal, lormer's pulse
 * technology is indistinguishable from magic
 * tech not made of matter, no fixed size or shape, no well defined boundaries or topology, dynamical on all spacetime scales, does not do anything that we can discern, a system or organizatiion of things, rather than a discrete object

First cotact Bova Preiss

Seti's "year one" is 1959, year of Project Ozma and of the Cornell paper

200 thousand search hours by 1990, 90 percent in the hydrogen line

Seti searches for radio signlas sent to us by aliens

"magic frequeciea" the spectral lines of common atoms

dedicated searches: The Ohio SETI program- Wow! Signal

SETI signals will be narrow band to save power

Paul Harowitz Harvard META

electromagnetic radiation is the best choice miimal interferece, absorbtion and relative efficiency

microwave is the best wavelength- radio and you risk interference by the galaxy's radio sources, too shrot and you run into shot noise

the sender would make it easy for us to receive their signal

Pure carrier or a regular train of pulses

2841 Mherz, the second neutral hydrogen band

Ohio state survey: Project Cyclops

strong anrrow band matched atena patter (lunar distnace at least- 21 centimrre line

cicconi morrison suggested hydrogen line

Contact with alien civilizatios

1977 Morrison report coined SETI

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Saturn's rings
letter to the grand duke of tuscany 30 july 1610

"So! We have foudn the court of Juopiter, and two servants for this old man, who help him walk and never leave his side."

to Giuliano de Medici

"What is to be said concerning so strange a metamorphosis? Are the two lesser stars consumed after the manner of the solar spots? Have they vanished or sudenly fled? Has Saturn, perhaps, devoured his own children? Or were the appearances indeed illusion or fraud, with which the glasses have so long deceived me, as well as many others to whom I have shown them? ... I do not know what to say in a case so surprising, so unlooked for, and so novel. The shortness of the time, the unexpected nature of the event, and the weakness of my understanding and the fear of being mistaken have greatly confounded me"

1612 letter

Galileo nonetheless predicted that the attendants would reappear.

Saturn's slow orbit meant that studies of the rings proceeded over decades, and even then came to hasty conclusions. Some, including Galileo, suggested that Saturn was an oval with two "handles" attached to it like the handles of a vase. Others suggested that it might be some kind of emanation from Saturn's surface.

In 1655, after discovering Saturn's moon Titan, Huygens turned to the problem of the ansae or "handles", believing that Titan had opened the way to solving them.

To support his thesis, Huygens made the prediction that the handles would reappear in April 1656- he was wrong, though they did reappear in October.

July, 1659: Systema Saturnum

"it is surrounded by a thin flat ring, nowhere touching, and inclined to the ecliptic"

Initial reaction to Huygens's idea was largely negative; his friends and colleagues were largely sceptical, and Leopoldo de medici, to whom the book was dedicated, failed to respond.

Those who had proposed alternate explanations for the phenomena around Saturn attacked Huygens with polemical pamphlets, accusing him of lying and fraud. Leopold, conversely, congratulated the (anonymous) author of the pamphlet, saying he would suspend judgement until evidence for the alternate hypotheses could be found. "That," Huygens opined, "might take a long time."

By 1661, even Huygens's most ardent critics began to grudgingly accept the reality of his ring.

1675: Cassini division

In 1714, Jacques Maraldi noticed that the rings appeared to be of varying thickness, as one side appeared larger than the other. More than that, he noted that the larger end reappeared on the other side of Saturn, showing that the rings orbited the planet. He therefore concluded that the rings had to be solid. However, Cassini, and his son Jacques, who succeeded him at the Observatory, both concluded that this was impossible, since the inner part of the ring orbited more quickly than the outer part, indicating it had to be made of independently orbiting particles. Still William Herschel also assumed the ring to be solid.

Hwerschel concluded by comparing the thickness of the rings to the thickness of the satellites, that they could not be thicker than 300 miles, a prediction that, uniquely for him, was too conservative.

Throughought the early to mid 19th century, saturn's ring was assumed to be solid.

no evidence could be found of anything between the ring and the planet

Astronoemrs in the 1830s had noticed subdivisions in the rings of Saturn but their difficulty in discerning them led them to believe they were not permanent.

In the mid 1840s, many of the same crew that would squabble over Neptune were insturmental in determining the first observerd permanent subdivision in the ring since Cassini. 1837, Encke saw the A ring divided by a thin black line

William lassell (brewer), james challis

1850: Two astronomers named Bond, one in England, one in America, identify the C[repe] ring,

Lassel: (amateur astronomer) "It appeared as if something like a crepe veil covered part of the sky within the inner ring

Otto Struve named the A B and C rings (Grandfather was the Otto Struve who inspired Frank Drake)

In 1853, Saturn's sphere was seen behind the C ring

Lassel also noticed a similar transparency in the cassini division

Edouard Roche ran mathematical models that suggested that the rings had formed when a fluid satellite with the density of Saturn was disrupted by passing too close to the planet

1857: James Clerk Maxwell- a fluid ring would not have demonstrated the observed subdivisions, and that competing gravitational attractions would have led to waves, which would have broken the rings into tiny fluid satellites.

"The only system of rings which can exist is one composed of an indefinite number of unconnected particles, revolving around the planet with different velocities accordign to thei respective distances"

1867: Kirkwood gaps in saturns' rings thanks to resonances with the inner satellites (mimas, enceladus, tethys and dione)

1895: Keeler determined with spectrograph and the doppler effect that the rings were not only rotating around Saturn, but that the outer edge was rotating more slowly than the inner edge, confirming once and for all Maxwell's model.

"an infinite number of unconnected particles" maxwell

Peter goldeirch, scott tremaine :Standing waves, 1979

D ring, tenuous, dark, below the C ring. Foudn by voyager 1

E ring, a thin thread outside the main system. Found by the voyagers

F ring, inclined and braided, found by Pioneer 11

G ring, narrow and tenuous found by voyager 1

VOyager found that the particles in the rings range from the size of grains of sand to the size of houses

Kinks spokes