[image: Deucalion-and-Pyrrha.jpg] *Deucalion and Pyrrha:* Stone Throwers Zeus was known to have looked askance at mortals from time to time. In his uncharitable estimation, the Earthbound peons were exasperatingly frivolous little things. They fought incessantly over trifles; quarreled with their relations; and lusted madly after those who were best left alone. Moreover, they were quick to anger, relished acts of revenge and were by nature incorrigibly wicked. In summary, mortals were appallingly god-like except they didn't live forever. One day, Zeus felt in a particularly sour mood toward humans and decided to descend onto Earth in the guise of a pheasant. He wanted to observe mortal behavior more closely and he knew full well that if he manifested himself in his usual divine form complete with luxuriant beard, rocky pectorals and resplendent regalia, people wouldn't behave naturally around him. While in pheasant form, Zeus happened upon a gathering of Pelasgians, the forerunners to the Hellenes, known more popularly as "Greeks." Being in their company didn't improve his mood very much. He soon found himself in the home of Lycaon, an Arcadian king who sired three daughters and fifty sons on his wife Cyllene, a naiad nymph. During the afternoon of Zeus' visit, forty-nine of the sons and their wives had congregated outside the king's palace and were exhibiting the most licentious behavior Zeus ever beheld (outside of Olympus, of course.) The disgust that this wantonness engendered was nothing compared to his reaction when Lycaon approached him and offered him pieces of the son who wasn't in attendance. It is thought that Lycaon somehow realized the pheasant was a disguised god and tried to feed him pieces of his son to test his omniscience. In another version, he had no idea what to feed lost pheasants and opted to present it with human flesh. Whatever his reasoning, Lycaon's decision to kill and dismember his son was costly. Zeus transformed him into a wolf (hence, lycanthropy) and resurrected the unfortunate young man. This resurrection was a rather strange -and some would insist pointless- act because at that moment Zeus had resolved to destroy all the mortals. He summoned his brother Poseidon and persuaded him to cast a nine-day rain onto the world while drawing all the rivers and seas together into one large confluence. "Wash the mortals from Earth entirely!" Zeus thundered. "Let no trace of their filth stain its face!" Soon after the torrential rain started, Deucalion, a son of Prometheus, the Titan who delivered fire to mortals, realized that the unusual rains were a sign of divine disfavor. (He inherited his father's wisdom.) He and his wife Pyrrha rapidly built a large chest which they then hastily stocked with provisions. As soon as their home was submerged by the flood waters, they locked themselves in the chest and were swept out by the high crests and deep troughs of the turbulent waters. After many days the chest came upon the only spot of land that remained above flood: the summit of Mount Parnassus. Zeus watched them as they stepped out of their chest and stood uneasily on the mountain top. Their survival did not infuriate Zeus. In fact, he was pleased that these two devout Zeus-worshippers had proven to be so resourceful. Zeus allowed the flood waters to recede enough to uncover the mountain and the region around its base. Deucalion and Pyrrha saw a world devoid of mortals, except for themselves. The homes had been reduced to rubble and the temples, though more durable, were slime-coated and abandoned. They visited a nearby temple and devoted themselves to cleaning it thoroughly and then sanctifying it with a series of rituals. They then prayed to the gods to help them repopulate the world. They then heard a loud voice in the temple which told them to "cover your heads and toss the bones of your mother over your shoulder." This pronouncement shocked Deucalion for he initially believed he was required to kill his mother Hesione, an oceanid who most assuredly had survived the flood and was lurking somewhere within the receding sea. Pyrrha then realized that the "mother" referred to their mother Earth. The bones, she knew, were the stones jutting out of the soil. Although it required all their remaining strength, Deucalion and Pyrrha promptly grabbed stones and threw them over their shoulders. They tossed as many as they could find and were certain to not look at them after they landed. The stones that Deucalion tossed were transformed into men as soon as they touched the ground. Pyrrha's stones changed into women. This next generation of mortals were often called the "iron race," in reference to both their toughness and the rigidity of the moral code by which they all had unfailingly abided. Zeus was pleased with that race and allowed it to persist even though he suspected that the rigid moral code that so distinguished the new race would likely become more lax with subsequent generations. Heavens, was he ever wrong! THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet <http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A> 70 Falmouth Street Portland, Maine 04103 43.6667° N 70.2667° W Altitude: 10 feet below sea level Founded January 1970 Julian Date: 2459052.16 2019-2020: CLXXXI THE DAILY ASTRONOMER Tuesday, July 21, 2020 Remote Planetarium 68: Exo-Planets IV - Finding Aliens As recently as thirty years ago, the existence of planets outside our solar system still remained hypothetical. The issue neatly divided the astronomical community into the optimists who subscribed to Giordano Bruno's then heretical remark that an "infinite number of worlds"populate the Universe and the pessimists who suspected that planets were quite rare. According to the latter group, planetary formation resulted from infrequent close passages of stars. The mutual tidal forces drew out their gases which then coalesced to form planets. The former group believed that planet formation was a natural consequence of star formation. Planets arose from the residual gases, dust and other debris that enveloped around them. Now, in 2020, we can safely assume that the optimists were correct. Astronomers have discovered more than 4000 planets -4295 as of this date since the early 1990s. Based on these detections, astronomers estimate that the galaxy might contain more than one trillion planets, forty billion of which are potentially habitable. By "potentially habitable," they mean that the planets are "Earth-like" worlds within their parent stars' habitable zones. We should mention that the term "Earth-like" can be misleading. According to this definition, an Earth-like planet is small, rocky and dense. Each of our solar system's four inner planets -Mercury, Venus, Earth and Mars- could all be described as "Earth-like." Three of these planets -Venus, Earth and Mars- are located within the Sun's habitable zone. A 'habitable zone' is one in which conditions could allow water to remain a liquid on the planet's surface. This definition presupposes that water is as essential to other beings as it is to us humans. This assumption is one that we believe to be safe...until we find out it isn't. The determination that planets abound in the galaxy and that many of them are potentially habitable bodes well for those Earthlings who hope the Milky Way teems with life. Again, however, we find yet another divide separating the optimists and pessimists. The optimists assert that the Universe is so prodigiously creative that life must proliferate through the cosmos wherever conditions are conducive to its development. The pessimists argue that perils to life are as abundant as planets. After all, examine our own neighborhood: asteroids have pummelled our planet through the aeons; harsh cosmic radiation constantly washes over Earth; and the geological record contains numerous instances of mass extinctions. Life might begin in many places, but the probability of life progressing through the evolutionary process to an advanced state is highly improbable. "We've been lucky," the pessimist would insist. Well, as was true with the planet issue, the matter of other life won't be resolved until we detect evidence of life. We should point out that we will NEVER be able to prove that alien life doesn't exist. Even if thousands of years pass without a single detection, alien races could still exist and in abundance. They just might be undetectable or too far away for us to ever find them. (How could we possibly find a fern covered planet populated by spores and lemurs tucked away in the Andromeda Galaxy?) How can astronomers try to detect life on other planets since even the closest exo-planet, Proxima Centauri b, is 4.2 light years away? We know technological limitations currently preclude interstellar travel. Our most distant robotic probe, Voyager 1, is only 20.6 light hours from the Sun and it was launched 43 years ago! The farthest any human has ever gone from Earth is 248,655 miles, or 1.33 light seconds.* Our race hasn't exactly reached the Star Trek phase of our technological development yet. For this reason astronomers must do what astronomers have always done: make their discoveries through the analysis of radiation. *RADIO SIGNALS?* [image: _110916333_81a4f6cc-0918-4c77-80d9-9a118cbd4fab.jpg] Searching for radio signals has been the aim of the SETI (Search for Extra Terrestrial Intelligence) since its founding in 1984. The theory is that an alien race could, like humans, have developed radio communication technology. Many of our radio signals propagate through outer space at light speed and so could be detectable by beings on worlds within the signals "sphere of propagation." For instance, radio waves from a 1970 broadcast are still moving away from Earth along a sphere extending fifty light years from Earth. One hundred and thirty-three stars exist within this fifty-light year radius. It is conceivable that extraterrestrial astronomers might be able to detect these waves. Due to the high attenuation, they couldn't actually listen to the program. Instead, they could discern "strange" waves exhibiting signs of manipulation, unless the indistinct radio energy that pervades the cosmos. SETI's aim is to detect such radio signals from other parts of the galaxy, evidence of the existence of an alien race. The limitation of this method is that it requires those races to have advanced sufficiently so as to have been able to develop radio technology. Life first appeared on Earth about 3.7 billion years ago. Different forms of radio technology first developed in the late 19th century. The span of time between life's inception and the period when we were first able to "announce" ourselves to the Universe well exceeds three and a half billion years! If aliens were trying to detect signals from our solar system a couple of thousand years ago when Rome was at its apex, they wouldn't have found anything at all. *CHEMICAL TRACES?* [image: new_calibration.jpg] Another possible method of extraterrestrial life detection involves detecting chemical "life signatures" from the atmospheres of Earth-like planets within their parent stars' habitable zones. Star light emitted by the parent star passes through the exo-planet atmosphere. The gases within the atmosphere absorb some of that light before it continues through outer space. Gases absorb light at various frequencies. Each type of molecule absorbs light at a specific number of wavelengths. By analyzing the spectrum of this light, astronomers can identify the chemicals present within the atmosphere. [image: Simulated-spectra-of-small-exoplanet-atmospheres-Reflected-light-spectra-are-presented.png] The graphic above shows simulated chemical signatures of various types of exo-planets. [Note: Archean Earth refers to Earth during the "Archean Eon" between 2.5 - 4 billion years ago.] Astronomers seeking evidence of life on other worlds are looking for certain chemicals that might be indicative of metabolic activity on the planet's surface. These include: - water vapor - methane - carbon dioxide - molecular oxygen We know that such gases are necessary for life to persist on Earth. We assume -perhaps incorrectly- that life on other worlds would leave such traces within the atmospheres of their home planets. The search for extraterrestrial life continues. That astronomers haven't found anything yet shouldn't concern alien lovers. The number of star systems to be searched is vast. However, by knowing which star systems harbor Earth-like worlds within the habitable zones at least narrows the search slightly. We do know that the age-old question "Are we alone?" could one day be answered in the negative. By the nature of science, it will never be answered in the positive. * Jim Lovell, Fred Haise and John Swigert attained this distance when their ill-fated Apollo 13 mission brought them all to the far side of the moon. _________________________________________ *SKYWATCHING TIP FOR THE DAY:* Don't forget to look for Saturn! Saturn reached opposition yesterday. Tonight, Saturn rises at 8:07 p.m. and will remain visible for the rest of the night. Find it in the eastern evening and western morning sky. At magnitude 0.1, Saturn is slightly brighter than Vega. Unfortunately, its magnificent ring system is not resolvable with the unaided eye. All the same, Saturn is well worth a look this week! ____________________________________________ To subscribe or unsubscribe from the Daily Astronomer: https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A= <https://lists.maine.edu/cgi-bin/wa?SUBED1=DAILY-ASTRONOMER&A=1>