Review Tests Nats 1525 PDF - Plurality of Worlds, Geocentric Universe

Review tests Nats 1525 Important Principles ​ Murphy’s law which states that if anything can go wrong it will go wrong (based on principle of plentitude) ​ Occam’s razor which states that when two competing theories make exactly the same prediction, the simpler one is better....

Review tests Nats 1525 Important Principles ​ Murphy’s law which states that if anything can go wrong it will go wrong (based on principle of plentitude) ​ Occam’s razor which states that when two competing theories make exactly the same prediction, the simpler one is better. ​ Copernican Principle which states that the universe appears the same from every point and in every direction. ​ Principle of relativity which states that the laws of physics are the same everywhere in the universe. No genuine potentiality of being can remain unfullled and the extent and abundance of creation is as vast as the possibilities of existence and commensurate with the productive capacity of a perfect and inexhaustible source (atoms or God) Ancient Greeks ​ Atomists argued in favour of many inhabited worlds: ​ Matter is made of indivisible units called atoms ​ Innite number of atoms ​ Random Motion of atoms ​ Innite number of universes Argument Relies on Principle of Plentitude Plurality of the Worlds in Ancient Greece ​ Two main schools of thought existed in Ancient Greece : ○​ Aristotle rejected ET life ○​ Atomists believed in ET life ​ The Atomist school was founded and supported by figures such as Leucippus, Democritus, Epicurus, and Lucretius….. ​ Main arguments: ○​ All that exists is made of atoms (indivisible and imperishable chunks of matter that form the building blocks of everything). ○​ The present state of nature is the result of a long evolutionary process. ○​ Atoms are infinite in number and Atoms are in random motion. ○​ There is nothing special about Earth. ​ Note: how the views of Ancient Atomists are remarkably close to our modern beliefs in science ○​ The infinite number of atoms and their random motion implies infinite universes. ​ One of the most prominent figures of the school of atomism was Epicurus. ​ Belief in ET life is quite conspicuous in Epicurus's writings: ○​ “There are infinite worlds both like and unlike this world of ours. For atoms being infinite in number…are borne far out into space. For those atoms…have not been used up either on one world or on a limited number of worlds, or on all the worlds which are alike, or on those which are different from these. So that nowhere exists an obstacle to the infinite number of worlds…… we must  believe that in all worlds there are living creatures and plants and other things we see in this world.” ​ Atomists did not believe in god ○​ Some of these stars have planets orbiting them, and a few of these planets might be at just the right distance to support liquid water—and potentially life. ​ In ancient cosmological models, such as the geocentric model proposed by thinkers like Epicurus and later refined by others, the universe was thought to be much smaller and Earth-entered. ○​ This model placed Earth at the centre, surrounded by the Moon, the Sun, and five known planets (Mercury, Venus, Mars, Jupiter, and Saturn). ○​ Beyond these, a sphere of fixed stars enclosed the entire universe. This was considered a self-contained unit, with each "universe" being independent of others. ​ The geocentric (earth) model (from the Greek “geo,” meaning Earth) dominated scientific thought for over 2,000 years before being replaced by the heliocentric model (which places the Sun at the centre of the solar system). ○​ In the geocentric view, the Moon, and Sun were also considered planets, as they appeared to move around Earth. ​ The idea of multiple, independent “universes” or self-contained cosmic bubbles has evolved into modern theories like the multiverse, where each universe operates under its own physical laws. ​ Before 300 bc, the moon and sun were considered plants ​ Principle of platitude is very important, memorize for exam ○​ Quantum mechanics and parallel universes rely on the principle of platitude ​ Occam Razor: when there are two competing theories that explain the same thing, the simpler explanation should be chosen ​ Ancient Understanding of Celestial Bodies ○​ Before 300 BC, the Moon, and Sun were considered planets because they appeared to move around Earth in the geocentric model. ​ This model placed Earth at the centre of the universe, with the Moon, Sun, and five known planets (Mercury, Venus, Mars, Jupiter, and Saturn) orbiting around it. Beyond these lay the sphere of fixed stars, which enclosed the entire universe. ​ Other views: (1) Universe has evolved to its current state. (2) There is no God Aristotelian Universe ​ Plato and his student Aristotle argued against plurality of the worlds. ​ Plato’s arguments were primarily philosophical. ○​ Uniqueness of creator implies uniqueness of creation. ○​ If the universe were composite, it would be subject to decay and decomposition ​ Aristotle’s argument however was primarily based on his physics.  ​ Aristotle’s universe was a geocentric, finite universe that was governed by the doctrine of natural places. ○​ Aristotle’s universe was made of concentric crystalline spheres to which celestial bodies were attached. ○​ While change and corruption belonged to the “sublunary” sphere, the heavens were perfect and unchanging. ​ Aristotle argued against the existence of other worlds: ​ Earth’s centre coincides with the centre of the universe, towards which everything fell. ​ There can be no two centres….. Aristotle & Other Earths ​ A piece of Earthly substance can be raised by a forced or violent motion, but this is against the natural tendency of the element. ​ Suppose now that we had two Earths: ○​ A piece of Earthly substance is falling towards the centre of Earth number 1, seeking its natural place. ○​ With respect to Earth number 2, this piece of earthly substance might be moving upward, which is a violent motion. ​ This is a contradiction, since this earthly substance can only be moving either in a violent motion or seeking its natural place. ​ The Universe cannot have two centres, so there is only one Earth. Important Points of A True Story ​ Considered by many to be the first work of science fiction ​ The protagonists gets caught in a whirlwind and end up on the Moon, only to find that the King of Lunarians is an Earthling who was abducted in his sleep and brought to the Moon. ​ Lucian of Samosata populates the Moon, Sun and many other stars and planets. ​ The book discusses the potential plans for colonization of planet Venus. ​ The Colony was to be made of the poorest people of the kingdom of the moon who were going to start a new life on planet Venus which was empty and uninhabited. Early Christians ​ Early Christian Scholars rejected the idea of plurality of the worlds based on the teachings of Aristotle. ​ This however begged an answer to the following question: ​ Is the rejection of the plurality of the worlds in contradiction with Omnipotence of God? —-> Condemnations of 1277  ​ The idea of plurality of the worlds was rejected by most of the early Christian scholars ○​ The most important figure among these was Augustine of Hippo, who attacked the idea of plurality of the worlds in his book City of God. ○​ Gradually, however, as Christian scholars gained access to the writings of antiquity during the 13th century, they started discussing the possibility of plurality of the worlds. ○​ Albertus Magnus wrote: ​ “Since one of the wondrous and noble questions in Nature is whether there is one world or many,…. it seems desirable for us to inquire about it” After the 1277 Condemnations ​ So God could have made many worlds. But what about the doctrine of atonement? ○​ Question: Do extraterrestrials live in Sin? ​ Can Christ by dying on Earth redeem the inhabitants of another world or does he travel from one world to another and die to redeem the inhabitants? ○​ Doctrine of atonement: Forgiving of the original sin through the death and resurrection of Jesus Christ. ​ Possible Answer: Maybe extraterrestrials have never committed the original sin so are not in need of redemption. ​ After 1277, a re-examination of Aristotle’s anti-pluralist views started, with many arguing that God could have created many worlds but did not do so. ○​ Some scholars however stood out with some fascinating proposals to defend plurality of the worlds. ​ Jean Buridan hypothesized that God could create worlds composed of other elements, having their own natural places. ​ William of Ockham hypothesized that in different locales the same elements would have correspondingly different natural places ​ Based on the writings of St. Augustine who believed that God could have created a perfect man, William of Ockham further hypothesized that God could create a better world than ours. ​ The question as to why most of these Christian scholars accepted the possibility that God could create many worlds but denied that God has actually done so is an interesting one. ​ Possible Explanation: ○​ Doctrine of atonement: Forgiving of the original sin through the death and resurrection of Jesus Christ ○​ William Vorilong (1390-1463) was a French theologian who considered whether extraterrestrials lived in sin or not.  ​ “As to the question whether Christ by dying on this Earth could redeem the inhabitants of another world, I answer that he was able to do this even if the worlds were infinite, but it would not be fitting for Him to go unto another world that he must die again.” ​ Nicolas of Cusa was amongst the very first to attribute life to the Moon and the Sun but the nature of his extraterrestrials is different from humankind. ○​ “Life as it exists on Earth in the form of men, animals and plants, is to be found, let us suppose, in higher form in the solar and stellar regions. Rather than think that so many stars and parts of the heavens are uninhabited and that this earth of ours alone is peopled …., we will suppose that in every region there are inhabitants, differing in nature by rank and all owing their origin to God…..It may be conjectured that in the area of the sun, there exists solar beings, bright and enlighten denizens, and by nature more spiritual than such as may inhabit the moon - who are possibly lunatics.” ​ Some however vehemently rejected the possibility of plurality of the worlds on the basis of Doctrine of Atonement. Philip Melanchthon, one of the prominent figures of Protestantism wrote: ○​ “The Son of God is One; our master Jesus Christ was born, died, and resurrected in this world. Nor does he manifest Himself elsewhere, nor elsewhere has he died or resurrected. Therefore it must not be imagined that Christ died and was resurrected more often, nor must it be thought that in any other world without the knowledge of the Son of God, that men would be restored to eternal life.” The Great Chain of Beings ​ But how did the pioneers of extraterrestrial life compare potential extraterrestrials to humankind? ​ Chain of Beings: Every existing thing in the universe has its place in a divinely planned universal hierarchy that stretches from God to inanimate matter. ○​ The placement depends on the relative proportion of spirit and matter that existed in the being. i.​ God ii.​ Angels iii.​ Extraterrestrials iv.​ Humans v.​ Animals vi.​ Plants vii.​ Matter The Great Chain of Beings ​ Chain of Beings: Every existing thing in the universe has its place in a divinely planned hierarchical order.  ​ The placement depends on the relative proportion of spirit and matter that existed in the being. ​ No matter how small a being, there is a place for everyone. ​ ET was usually placed between Humans and Angels. ​ But how did the pioneers of extraterrestrial life compare potential extraterrestrials to humankind? ​ Chain of Beings: Every existing thing in the universe has its place in a divinely planned universal hierarchy that stretches from God to inanimate matter. ○​ The placement depends on the relative proportion of spirit and matter that existed in the being. ​ God ​ Angels ​ Extraterrestrials ​ Humans ​ Animals ​ Plants ​ Matter Geocentric Universe ​ Earth at the centre; all celestial bodies in orbit around Earth. ○​ Retrograde motion of the planets: planets generally move from west to East every night with respect to the background stars BUT sometimes they stop and moved westward. This is called the Retrograde Motion. ○​ Ptolemaic model (or Aristotelian Model) was unable to produce accurate enough predictions for the position of planets. ○​ The heliocentric model was proposed as an alternative model to simplify the complicated mathematics of the geocentric universe. ○​ As put forward by Copernicus, the planets in the heliocentric model had circular orbits. ​ ​ The ideas of Aristotle about the structure of the universe were put into a rigorous mathematical framework by Claudius Ptolemy. ​ The geocentric universe as defined by Ptolemy remained a powerful description of how the heavens go for many centuries but it suffered from some shortcomings. ​ The Geocentric Model (also called Aristotelian or Ptolemaic Model) provided a reasonably good description of the universe. ​ Geocentric Universe Main Characteristics: ○​ Earth is at the centre. ○​ Sun, Moon and other planets orbit the Earth in circular orbits. ​ The geocentric universe was mathematically very complex ​ Some believe that upon hearing about the extremely complicated mathematics of the geocentric universe, Alfonso X said: “If the Lord Almighty had consulted me before embarking on creation thus, I should have recommended something simpler.” Heliocentrism ​ Despite a very mathematically complicated model, Ptolemy’s Geocentric model was unable to predict the position of planets with good enough accuracy. ​ In 1543, a book entitled De revolutionibus orbium coelestium (on the revolution of celestial spheres) appeared. ​ This was a highly mathematical book that proposed a model of the universe with the Sun at the Centre in an attempt to simplify the mathematics. ​ Main characteristics of Copernican model: ○​ The Sun is at the centre of the Universe. ○​ Planets orbit the Sun in circular orbits ​ Earth is not immobile and is no longer at the centre. ​ Earth orbits the Sun just like any other planet. In other words, Earth is a planet. ​ Parallax: apparent motion of nearby stars with respect to far away stars due to the change of position of Earth in its orbit. ​ Lack of Observation of Parallax led many to reject heliocentrism Heliocentrism Implies Plurality of The Worlds? ​ By introducing a heliocentric universe Copernicus promoted Earth to the rank of a planet. ​ This immediately can be followed by another question: “If the Earth is a planet and it is inhabited, could other planets in the solar system also be inhabited? ​ Another consequence of the Heliocentric model of the universe was that it meant stars were located much farther compared to a geocentric universe. This meant a waste of space unless stars were suns serving other Earths (plurality of the worlds). ​ The heliocentric model however was met with a lot of resistance! ​ Heliocentrism made the case for plurality of the worlds stronger: ○​ (1) If the Earth is a planet (orbiting the Sun) and it is inhabited, could other planets in the solar system also be inhabited? ○​ (2) Another consequence of the Heliocentric model of the universe was that it meant stars were located much farther than what they thought. This meant a wastage of space unless stars were suns serving other Earths (plurality of the worlds). ​ (1)Distance between stars is measured in light years. 1 light year is the distance that is traveled by light in 1 year. ​ (2)Example: Polaris is at 434 light years: it takes light to travel the distance between Earth and this star 434 years. (3)We see polaris as it was 434 years ago! Tycho Brahe ​ A new system of Universe called Geocentric-Heliocentric. ○​ Provided the best observational data for the orbit of Mars. ○​ Despite all his efforts Tycho failed to observe parallax and thus rejected the heliocentric view ​ The greatest of all observational data before the invention of the telescope was acquired by a Danish nobleman named Tycho Brahe. ​ Despite his greatest efforts, Brahe never managed to observe parallax of stars, thus he never accepted the heliocentric model. ​ Tycho Brahe devised a different system of universe with Earth at the centre where other planets orbit the Sun but the whole system of Sun and planets orbits the Earth. This system was called geo-heliocentric. ​ Brahe also did not believe in pluralism since he rejected Copernicanism. ​ Brahe argued that if the Copernican system is correct, then stars are at immense distances which in turn translates into a wastage of space unless there were stellar inhabitants. This argument he found to be absurd and thus he rejected the plurality of the worlds. Galileo Galilee ​ Believed in a Copernican System Discovered the four largest moons of Jupiter, that the milky way resolves into many stars, that the moon looks terraneous rather than perfect. Provided ample evidence against an Aristotelian Universe. Argued against life on the moon. Was aware of the fact that moon did not have an atmosphere. Knew that lack of atmosphere and long days and nights on the moon results in huge temperature variations which is not friendly to life forms as we know them. ​ In 1610, Galileo Galilee became the first person to look at the skies using his telescope ​ Galileo’s observations provided a number of powerful pieces of evidence against the geocentric model of the universe. ​ Even though the Aristotelian Universe continued to be dominant for some time after Galileo, his observations brought some strong pieces of evidence against the veracity of the Aristotelian Universe. ​ Galileo published his observations in a book entitled Sidereus Nuncius (1610) or the Starry Messenger. ​ A number of Galileo’s discoveries did not agree with an Aristotelian world view. ​ In his telescope, the moon appeared terraneous. ​ Using his telescope, Galileo discovered 4 moons of Jupiter, known as the Galilean moons. ​ In Galileo’s writings one comes across six passages where extraterrestrial life is mentioned.  ○​ His comments “range from rejection to cautious reserve concerning it” ​ “I… [regard] as false and damnable the view of those who put inhabitants on Jupiter, Venus, Saturn, and the moon, meaning by “inhabitants” animals like ours, and men in particular. Moreover, I think I can prove this. If we could believe in any probability that there were living beings and vegetable on the moon or on any planet, different not only from the terrestrial ones but remote from our wildest imaginings, I should for my part neither affirm nor deny it, but should leave the decision to wiser men than I. (Letters on Sunspots 1613). ” ​ Here is Galileo’s argument against the existence of life on the moon in his own words: ○​ “[O]n Earth, the sun in every 24 hours illuminates all parts of its surface, each half of the moon is alternately in sunshine and darkness for 15 continuous days of 24 hours. Now if our plants and animals were exposed to ardent sunshine every month for 360 consecutive hours, and then for a similar time were plunged in cold and darkness, they could not possibly preserve themselves, much less produce and multiply.” Galileo and Life on the Moon ​ Galileo never espoused the idea of existence of life on the Moon. ​ He was aware of the huge temperature variations that the moon went through. ​ Today we know: ○​ Day time temperature on Moon: 117 C ○​ Night time temperature on Moon: -173 C ​ Today, we know that like our own Moon, none of the four Galilean moons possess a significant atmosphere. ○​ Discoveries over the past few decades have shown that the Galilean moons however are not dead worlds but are very active and might possibly host life! Johannes Kepler ​ Galileo’s German contemporary, Johannes Kepler was hired by Tycho Brahe as a human computer to analyze Tycho’s data. ​ He was to end the closest match for the orbit of Mars using Tycho’s state-of-art data. ​ After years of painstaking work, Kepler did not acquire the desired outcome. ​ In a bold move, he abandoned the circular orbits (dictated by Aristotelian Universe) and tried an ellipse instead. ​ His breakthrough resulted in three laws which we call Kepler’s laws of planetary motion. ​ Kepler’s laws are still in use today and they work for every planetary system. ​ Kepler was not opposed to life elsewhere in the solar system though he rejected the idea of planets revolving around other stars. After receiving a letter from Galileo regarding his discovery of the moons of Jupiter, Kepler writes:  ○​ “Those four little moons exist for Jupiter, not for us. Each planet in turn, together with its occupants, is served by its own satellites. From this line of reasoning we deduce with the highest degree of probability that Jupiter is inhabited. (Kepler’s Conversations, p.42)”. ​ Kepler also speculates about Venus and Mars having moons, as well as life existing on Saturn. Finally, he speculates on space travel: ○​ “But as soon as somebody demonstrates the art of ying, settlers from our species of man will not be lacking….Given ships or sails adapted to the breezes of heaven, there will be those who will not shrink from even that vast expanse” (Kepler’s Conversations, p.39) ​ Teleology: is the attempt to describe the existence of something by seeing it serve a purpose. Kepler’s Somnium ​ Finally came up with the correct model of the solar system by replacing perfect circles with eclipses contrary to Aristotelian belief. Kepler used the most accurate data of Tycho to t a curve to the orbit of Mars. Kepler was also an early believer in the Copernican System of the universe. ○​ Kepler believe that Life existed on other planets in the solar system He used teleology to argue life exists on Jupiter Wrote a book called Somnium Talks about existence of life on the moon His main purpose was to show: (1) Earth is in motion but we do not feel it (2) The universe appears the same everywhere (Copernican Principle) ○​ Teleology is the attempt to describe the existence of something by seeing it serve a purpose. ​ Some of the most fascinating views of Kepler on extraterrestrial life can be seen in his book Somnium (The Dream). ​ Kepler’s Primary objective in writing the Somnium was to develop an argument for the motion of the Earth and to oppose any of the arguments expounded in favour of a geocentric universe. ​ Somnium, is the adventure of a young boy from islandia, Duracotus, who is sold by his mother to the captain of a ship heading for Norway. On their way, they stop in Denmark to deliver a letter to Tyco Brahe from a Bishop in Iceland. Since Duracotus is seasick, the captain leaves him there with Tycho who takes upon himself to educate the boy in Astronomy. After 5 years, Duracotus sails back home and finds out his mother is not dead. She reveals to him that she is also familiar with the science of astronomy and her teacher is the Daemon of Lavinia, the spirit of the moon. Duracotus and his mother go on a journey to the moon with the assistance of the daemon of Lavania. This journey takes 4 hours and they have to take precautions to keep safe in the extreme cold and lack of moisture……. ​ Amazingly enough, Kepler was aware of the protective action of the atmosphere and states that the lunar voyage happened during a lunar eclipse so the travellers were protected against the scorching sun rays by passing through a tunnel.  ○​ During a Lunar Eclipse, the Earth blocks the sun by casting a shadow on the moon. ​ One significance of this story is that Kepler argues that the universe looks the same as seen from the moon. ○​ In this story, moon is divided into two hemispheres: Subvolva and Privolva ○​ The residents of the subvolva have their own moon called volva (this is the Earth). The residents of the privolva never see the volva (Can you guess why?). ○​ A day and night together lasts one month on Lavinia, with two weeks of scorching heat followed by two weeks of extreme cold. ​ Despite this, Kepler believed in anthropocentrism: the idea that man is the predominant creature and that “there is no globe nobler or more suitable for man than Earth”. Synchronous Rotation ​ Period of rotation of a moon around its own axis is equal to period of revolution around the parent planet. The moon is in synchronous rotation around the Earth ​ The Galilean moons, as well as moons of Saturn such as Titan and Enceladus are also in synchronous rotation. ​ Interestingly enough, in Cosmotheoros, Huygens speculates about different types of waters on other planets. It is an amazing coincidence that he also discovered another body in the solar system that might in fact possess a different type of “water” on its surface ​ Huygens discovered Titan, the huge moon of the Saturn, and the second largest moon in the solar system, after Ganymede. ​ Titan is larger than our Moon and even planet Mercury. ○​ Titan is the only moon with a significant atmosphere in the solar system. It is in synchronous rotation around Saturn (15 days and 22 hours). ​ The atmosphere is primarily made of N2, nitrogen, along with other hydrocarbons such as Ethane (C2H6) and Methane (CH4) and some CO2. ​ Its surface is covered with lakes filled with liquid hydrocarbon including Methane and Ethane. ​ Can Life exist on Titan? ○​ The question is whether liquid methane or ethane can replace water in chemical reactions of life. ​ In July 2017, it was announced that a molecule (vinyl cyanide) that could possibly be used to form cell membranes in the Hydrocarbon environment of Titan was discovered. ​ As you might have heard, we always see one side of the moon. This moon’s rotational period is equal to its orbital period. This is called a synchronous rotation. On average, how long is the length of daylight in a lunar day-night  cycle, if the moon orbits the Earth in the course of one month (orbital period = 1 month)? ○​ (a) 24 hours ○​ (b) 15 days ○​ (c) 1 week ○​ (d) 12 hours ​ (d) There was no use for Jupiter to have moons. 1.​ Which one of the following moons are in synchronous rotation around their parent planet? ​ (a) The Moon ​ (b) Europa ​ (c) Ganymede ​ (d) Io ​ (e) All of the above 1.​ As you might have heard, we always see one side of the moon. This moon’s rotational period is equal to its orbital period. This is called a synchronous rotation. On average, how long is the length of daylight in a lunar day-night cycle, if the moon orbits the Earth in the course of one month (orbital period = 1 month)? ○​ (a) 24 hours ○​ (b) 15 days ○​ (c) 1 week ○​ (d) 12 hours