Vladimir had been prince of Novgorod when his father Sviatoslav I died in 972. He was forced to flee to Scandinavia in 976 after his half-brother Yaropolk had murdered his other brother Oleg and taken control of Rus. In Scandinavia, with the help of his relative Earl Håkon Sigurdsson, ruler of Norway, Vladimir assembled a Viking army and reconquered Novgorod and Kiev from Yaropolk. As Prince of Kiev, Vladimir's most notable achievement was the Christianization of Kievan Rus', a process that began in 988. The Primary Chronicle states that when Vladimir had decided to accept a new faith instead of the traditional idol-worship (paganism) of the Slavs, he sent out some of his most valued advisors and warriors as emissaries to different parts of Europe. They visited the Christians of the Latin Rite, the Jews, and the Muslims before finally arriving in Constantinople. They rejected Islam because, among other things, it prohibited the consumption of alcohol, and Judaism because the god of the Jews had permitted his chosen people to be deprived of their country. They found the ceremonies in the Roman church to be dull. But at Constantinople, they were so astounded by the beauty of the cathedral of Hagia Sophia and the liturgical service held there that they made up their minds there and then about the faith they would like to follow. Upon their arrival home, they convinced Vladimir that the faith of the Byzantine Rite was the best choice of all, upon which Vladimir made a journey to Constantinople and arranged to marry Princess Anna, the sister of Byzantine emperor Basil II.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): When did the Christianization of Kievan begin?
Ah, so.. 988

Han-era astronomers adopted a geocentric model of the universe, theorizing that it was shaped like a sphere surrounding the earth in the center. They assumed that the Sun, Moon, and planets were spherical and not disc-shaped. They also thought that the illumination of the Moon and planets was caused by sunlight, that lunar eclipses occurred when the Earth obstructed sunlight falling onto the Moon, and that a solar eclipse occurred when the Moon obstructed sunlight from reaching the Earth. Although others disagreed with his model, Wang Chong accurately described the water cycle of the evaporation of water into clouds.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What did astronomers believe the shape of the Sun to be during this era?
Ah, so.. spherical

Until recently, in the absence of prior agreement on a clear and precise definition, the concept was thought to mean (as a shorthand) 'a division of sovereignty between two levels of government'. New research, however, argues that this cannot be correct, as dividing sovereignty - when this concept is properly understood in its core meaning of the final and absolute source of political authority in a political community - is not possible. The descent of the United States into Civil War in the mid-nineteenth century, over disputes about unallocated competences concerning slavery and ultimately the right of secession, showed this. One or other level of government could be sovereign to decide such matters, but not both simultaneously. Therefore, it is now suggested that federalism is more appropriately conceived as 'a division of the powers flowing from sovereignty between two levels of government'. What differentiates the concept from other multi-level political forms is the characteristic of equality of standing between the two levels of government established. This clarified definition opens the way to identifying two distinct federal forms, where before only one was known, based upon whether sovereignty resides in the whole (in one people) or in the parts (in many peoples): the federal state (or federation) and the federal union of states (or federal union), respectively. Leading examples of the federal state include the United States, Germany, Canada, Switzerland, Australia and India. The leading example of the federal union of states is the European Union.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Before new research, what was the definition of federalism? 
Ah, so..
a division of sovereignty between two levels of government