Which of the following best paraphrases the Fermi paradox?
In 1950, a group of physicists met to discuss recent newspaper reports on sightings of UFO's (Unidentified Flying Objects). During this lunchtime conversation, Enrico Fermi, a Nobel Prize winner in physics, asked the question, "So, where are they?" -- by which he meant, "where are the aliens." His point was that, with so many stars in the Milky Way, it should be expected that the conditions for life would exist in many places in our galaxy -- not just on the Earth. If life exists, then evolution would be expected to lead to intelligent species and eventually technological civilizations. Yet science has so far found no trace of alien civilizations, despite the considerable effort devoted to projects such as SETI (Search for Extraterrestrial Intelligence).
While alien civilizations are typically the prerogative of science fiction, there is nevertheless a serious scientific purpose to the search of evidence of other civilizations. If humanity is indeed as singular case, there must be an explanation as to why our star (the sun), our solar system and our planet are unique. Many theories have been proposed to explain the apparent lack of other life forms. Life, and especially intelligent life, may in fact be exceedingly rare, or such life exists and we have neither found it, been able to contact it, or we simply have not noticed it. Each of these points of view has many different theories associated with it, making the "Fermi paradox" an active area of research and scientific thought, especially in the emerging field of astrobiology.
What is the purpose of the highlighted phrase?
In the Ptolemaic cosmology the earth is regarded as an fixed point with the other planets revolving around it.One reason for supposing that the earth is not moving is that if you drop an object it falls straight to the ground; if the earth was moving, Ptolemy reasoned that it would fall in a different place because the earth would move in between when you released the object and when it hit the ground. In fact, this is incorrect as can be demonstrated by dropping an object (keys for example) while walking. The keys do not fall to the ground at the place you stood when you release them but at the place you are, roughly speaking, when the keys hit the ground. In other words the keys move with you after you let them go, as long as you keep going with the same speed. This was first explained by Galileo in his famous work "Dialogue concerning the Two Chief World Systems," When the keys are released they have same forward velocity with respect to the earth as you, the walker, do. In addition they experience a gravitational force pulling them down. So they drop to the ground while maintaining the same forward velocity, assuming we can neglect the drag of air, and arrive at the same place as your feet. In a similar manner Galileo argue that you would you would not be able to tell if the earth is moving or not by experiments down on earth, thereby removing an important obstacle to the heliocentric (sun centered) cosmology of Copernicus. Today the principle that the laws of mechanics are the same in any fame moving with a constant velocity is called "Valilean Invariance, " and would play a crucial role in Einstein's development of special relativity.
In the information provided, the two portions in boldface play which of the following roles?
Sunscreen works through a combination of organic and inorganic chemicals that help block or absorb UV-B rays. UV-B rays cause sunburn and other sun-related skin damage. SPF, or Sun Protected Factor, is the gauge of how well sunsecreen will protect the skin from UV-B rays. Thus, those who use sunscreen with a higher SPF will suffer fewer sunburns and sun-related skin issues. It is important to use a sunscreen with a high SPF because, over time, sun damage can cause significant problems for the skin.
According to the passage, which of the following is probably NOT true of the surface of lo?
The four galilean stellites of Jupiter probably experienced early early, intense bombardment. Thus the very ancient surface of Callisto remains scarred by impact craters. The younger, more varied surface of Ganymede reveals distinct light and dark areas, the light areas featuring networks of intersection grooves and ridges, probably resulting from later ice flows. The impact sites of Europa have been almost completely erased, apparently by water outflowing from the interior and instantly forming vast, low, frozen seas. Satellite photographs of lo, the closest of the four to Jupiter, were revelatory. They showed a landscape dominated by volcanoes, many erupting, making lo the most tectonically active object in the solar system, since a body as small as to cannot supply the energy for such activity, the accepted explanation has been that, forced into a highly eccentric orbit, lo is engulfed by tides stemming from a titanic contest between the other three Galilean moons and Jupiter.
In the argument given, the two portions in boldface play which of the following roles?
The gaelic revival movement of late 19th and early 20th century Ireland attracted some of the leading social intellectual, and political figures of the time to the study of Gaelic. Primarily nationalistic in purpose, and located within the context of the Irish struggle for independence, the revival advocated the use of the traditional Irish language, Gaelic, in lieu of English. It was felt that a more robust use of a national language was necessary to crystalize ireland's' factious sense of national identity. The idea was not without parallel; modern Israel rescued its traditional language, Hebrew, from what was exclusively academic and liturgical use and reintroduced it into an active, living vernacular in the newly independent state of Israel. Prior to this unqualified success, however, was Ireland's attempted linguistic revival, which met with more debatable results. While many writers did incorporate Gaelic, and sometimes even write itn it, English is still far more prevalent, except in isolated, rural areas on the western coast, and did not become the primary native language of subsequent generations. This arrestingly similar set of historical and cultural circumstances, coupled with different results, subverts the notion that language and cultural identity are inseparable. The writers and intellectuals that did study Gaelic did so primarily because it provided a romanticized connection to their heritage, not because they wished to integrate it into the fabric of their daily lives.
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