Context-based study

Passage 1:

Originally named after the Roman goddess of love, the planet Venus also used to be known as the morning star and the evening star because it shines so brightly that it is visible on Earth even when the Sun is only partially visible in the morning and the evening.

Why does Venus shine so brightly? One reason is certainly because Venus is so close to Earth; it is, in fact, the closest planet to Earth. However, its proximity to Earth is not the only reason that Venus appears to shine so brightly. Another reason that Venus shines so brightly is that it is covered in thick white clouds that reflect sunlight off of them.

For quite some time, all that we have been able to see of Venus is the thick clouds that surround it, and little else was known of the planet itself. Dozens of space probes were sent to Venus in the last part of the twentieth century, and most of them were destroyed before they were able to send back information about Venus’s surface. One probe, however, did manage to transmit some messages before it, too, failed.

From this one partially successful probe, numerous amazing facts about Venus have been learned. The thick clouds that cover Venus, for example, are made of sulfuric acid rather than oxygen, and these thick clouds never part to let any sunshine in at all. Most amazingly, the temperature on Venus is extremely hot, somewhere around 900 degrees Fahrenheit.

Passage 2:

It was really surprising to scientists when they found out that Venus was so hot because the clouds around Venus reflect almost all the light from the Sun back into space. The small amount of sunlight that’s able to filter through the clouds doesn’t seem like anywhere near enough light to make the temperature on Venus so high. Instead, because it’s always so cloudy on the surface of Venus, the temperature should be rather cool.

You might think that the temperature on Venus is so hot because Venus is so close to the Sun, but this isn’t really a good explanation for the heat on Venus. The temperature on Venus is even hotter than the temperature on Mercury, which is closer than Venus to the Sun, so the proximity of Venus to the Sun doesn’t explain the high temperature on Venus

Scientists are still not certain why the temperature on Venus is so high, but one possible explanation is Venus’s carbon dioxide atmosphere. The very dense atmosphere on Venus is almost entirely carbon dioxide. This carbon dioxide may create a barrier that traps any heat that gets through beneath it and doesn’t let it escape.

Passage 3:

The library at Alexandria was said to have been a marvel, the greatest collection of scholarship in the ancient world. It was founded by Ptolemy I, the general that Alexander the Great installed as ruler of the city named after himself. It was Ptolemy’s son, Ptolemy II Philadelphus, who had the vision of expanding the library to make it the largest collection imaginable.

Under Ptolemy II and those who followed, the library was expanded tremendously. Ptolemy II’s vision was to create a library with every Greek work ever written as well as with as many works from other parts of the Western world as could be gathered together. The number of volumen, or scrolls, in the library has been estimated at anywhere between 3000,000 and 700,000.

A huge number of people’s were employed in preparing scrolls for the library, inasmuch as each scroll to enter the library had to be copied by hand. Manuscripts were bought or borrowed or taken from all over the Western world to be copied and placed in the library (although it was rather common to copy an original manuscript and then return the copy to the owner and keep the original for the library). Ptolemy II often asked for manuscripts from foreign powers in return for traded goods, and manuscripts were often demanded from citizens to pay debts to the government. In addition, any time that manuscripts were found on trading ships in the port at Alexandria, the manuscripts were taken and copied and added to the library. It was in these ways that so many manuscripts were collected in the library at Alexandria.

Passage 4:

The great library of Alexandria no longer exists, but it’s not known for sure when the library was destroyed. There’s actually considerable debate among historians about who destroyed the library and when.

One culprit who has traditionally been accused of destroying the library at Alexandria is Julius Caesar. It’s true that Julius Caesar led an invasion of Alexandria in 48-47 B.C. and that, at that time, his forces set the fleet of ships sitting in the Alexandria harbor on fire. Some historians believe that this fire in the harbor that was set by Caesar’s forces, spread into the city of Alexandria and burned the library down, but this belief is no longer widely held today. The main reason that the theory that Julius Caesar destroyed the library at Alexandria isn’t widely believed is that there are numerous references to the library in works written long after Caesar’s death.

The conclusion that seems to be most accepted today is that the library at Alexandria existed, at least in part, until the late fourth century, centuries after the death of Julius Caesar, so it could not have been completely destroyed by Caesar. At that time, at the end of the fourth century, there was a large movement to destroy pagan temples and libraries. It seems likely that whatever remained of the library of Alexandria was destroyed at this time.