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ÀÛ¼ºÀÏ : 17-02-28 11:02
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A little over 2,200 years ago, the Roman navy attacked the Greek port city of Syracuse. According to some ancient historians, the Greeks defended themselves with an ingenious weapon called a "burning mirror": a polished copper surface curved to focus the Sun's rays onto Roman ships, causing them to catch fire. However, we have several reasons to suspect that the story of the burning mirror is just a myth and the Greeks of Syracuse never rally built such a device.

First, the ancient Greeks were not technologically advanced enough to make such a device. A mirror that would focus sunlight with sufficient intensity to set ships on fire would have to be several meters wide. Moreover, the mirror would have to have a very precise parabolic curvature(a curvature derived from a geometric shape known as the parabola). The technology for manufacturing a large sheet of copper with such specifications did not exist in the ancient world.

Second, the burning mirror would have taken a long time to set the ships on fire. In an experiment conducted to determine whether a burning mirror was feasible, a device concentrating the Sun's rays on a wooden object 30 meters away took ten minutes to set the object on fire: and during that time, the object had to be unmoving. It is unlikely that Roman ships stayed perfectly still for that much time, Such a weapon would therefore have been very impractical and ineffective.

Third, a burning mirror does not seem like an improvement on a weapon that the Greeks already had: flaming arrows. Shooting at an enemy's ships with flaming arrows was a common way of setting the ships on fire. The burning mirror and flaming arrows would have been effective at about the same distance. So the Greeks had no reason to build a weapon like a burning mirror.


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Á¤ÅÂ±Ô 17-02-28 11:13
 183.¢½.53.158  
The lecture points out that their technology, at that time, in making parabolic mirror was available. Dozens of polished copper can be manufactured and can film a large width of the mirror. Professor, therefore, clarifies that the technician at that time can directly assemble mirror in parabolic shape. This contradicts the reading passage in that technology was not as advanced to make parabolic shape of burning mirror.
     
Á¤ÅÂ±Ô 17-02-28 11:44
 183.¢½.53.158  
The lecturer claims that there is other element that makes the ship on fire faster. Lecturer agrees with the example shown on the reading passage that woods will be set on fire in 10 minutes. However, there are other material known as pitch, which is used to seal the space between the wood and make it water proof, is easily set on fire. Within a second, this pitch can be burn and the fire can be spread out to nearby woods. This can even burn the wood when the ship is moving. This contradicts the reading passage in that ship has to stand-still for 10 minutes and it is impractical and inefficient.
¾çÀ¯¿µ 17-02-28 11:14
 183.¢½.53.158  
The reading passage asserts the idea that the ancient Greeks were not technologically advanced enough to make such a device. A mirror would have to be several meters wide and have a very precise parabolic curvature. The technology for manufacturing a large sheet of copper with such specifications did not exist in the ancient world. The professor casts doubt because the experiment shows that there are enough coppers to make large mirror. Ancient Greek could directly reassemble them.
     
¾çÀ¯¿µ 17-02-28 11:37
 183.¢½.53.158  
The reading claims that the burning mirror would have taken a long time to set the ships on fire. During that time, the object had to be unmoving. It is unlikely that Roman ships stayed perfectly still for that much time, such a weapon would therefore have been very impractical and ineffective. The professor refutes the idea because there are lots of things. Certain certain sticky substance can set on fire as well.
¼ÛÇÏ´Ã 17-02-28 11:14
 183.¢½.53.158  
First, the professor in the lecture points out that several meter wide mirror could be made through the sum of single individual mirrors. Even if ancient Greeks did not have the technology for making a large sheet of copper as a mirror, they could form a large mirror through the lots of single small mirrors. It challenges the point made in reading that the ancient Greeks did not have the technology for making large mirror.
     
¼ÛÇÏ´Ã 17-02-28 11:37
 183.¢½.53.158  
Next, the lecturer also states that burning mirror was effective weapon. Although wood was burned in 10 minutes, the sticky substance which was used in boat for water proof could be set on the fire in second. Even if ship was moving, mirror could effectively set the fire on the ship. Thus the mirror could be the practical weapon for ancient Greeks. This opposes the reading passage that burning mirror as a weapon was impractical and ineffective because it took a long time for burning the opponents.
±èÁö¿¬ 17-02-28 11:14
 183.¢½.53.158  
First, the lecture points out that a single sheet of cooper was not needed to make a burning mirror. Small pieces of polished cooper could form a mirror to be used as a weapon. The reading passage challenges the point made in the lecture that there was not enough technology to make a large sheet of cooper and the mirror.
     
±èÁö¿¬ 17-02-28 11:39
 183.¢½.53.158  
Second, the lecturer asserts that Roman ship was made not only of wood but also other materials such as p.. that catches fire quickly. When the p.. caught the fire, the fire would have been spread to wood in a second, eventually burning the entire ship. This contradicts the reading passage in that the mirror was an ineffective weapon because it took a long time to set the fire on Roman ship.
¹Ú¹ÎÁÖ 17-02-28 11:14
 183.¢½.53.158  
First of all, the reading argues that there were not technologically advance in the ancient Greeks to make such a weapon. They could not make such specification with a large amount of copper. Lecturer supports this idea that to manufacture large burning mirror, there were many small mirror pieces needed.
     
¹Ú¹ÎÁÖ 17-02-28 11:37
 183.¢½.53.158  
Secondly, the lecturer points out that the burning mirror was not just made by wood which takes time about 10 minutes to burn. There were other material, pitch. This material set the ship on fire in seconds and it was quick enough even the ship was moving. Thus, it challenges the argument in the reading passage that the weapon was impractical and time-consuming.
½ÅÀ¯ºó 17-02-28 11:14
 183.¢½.53.158  
The professor in the lecture argues that burning mirror consisted of not single mirror but several pieces of mirror. So ancient Greek would have arranged small pieces to make precise parabolic shape easily. This refutes the point made by reading passage that there were not technology enough to make such a device at that time.
     
½ÅÀ¯ºó 17-02-28 11:37
 183.¢½.53.158  
The lecturer states that the mirror was not used to set wood on fire. It takes ten minutes to set wood on fire, but there were other substances such as pitch which was a sealed material. It could be set on fire in a second. So the fire could spread wood even when ship was moving. This argument challenges the claim in the reading passage that the burning mirror is not feasible because it takes too long time to set objects on fire.
¹Ú»õ·Á 17-02-28 11:14
 183.¢½.53.158  
The lecturer argues that the burning mirror could have been an assembly of thin copper layers. A single sheet of copper packed into dozen layers could be arranged into a certain shape. Thus, it could be made into the precise parabolic curvature needed for the burning mirror. This goes against the reading's claim that the Greeks were not technologically developed enough to mold the copper into the mirror.
     
¹Ú»õ·Á 17-02-28 11:37
 183.¢½.53.158  
The lecturer points out that burning mirror was in fact, an effective weapon to set fire on the ships. The Roman ships were made of not only wood but also a material called pitch, which was used to make the ships water proof. While it takes a mirror about 10 minutes to set fire on wood, it takes merely seconds to lit up pitch. The initiated fire from the pitch would then spread to the wood, regardless of the ship's moving speed. This opposes the argument in the reading passage that burning mirror would have been ineffective: it took too long to catch a fire and the aim would be unstable because of the movement of ships.
ÀåÁö¼º 17-02-28 11:14
 183.¢½.53.158  
First, the professor in the lecture points out that ancient Greeks could use the large buring mirror with polish cooper. Moreover, they had so many small mirrors in that time. This is in opposition to reading that acient Greek did not have any kind of such advanced technology.
     
ÀåÁö¼º 17-02-28 11:37
 183.¢½.53.158  
Second, the lecturer states that the experiment with wooden boat that burned within 10minuites cannot be assumed that the Roman ship which made by only same material. In that time, people used to use pitch which can make the ship to waterproof. However, the pitch can be ignited the fire quickly on the ship. This challenges the point made in the reading that burning the ship would be take a long time.
¼Û¼ö¿¬ 17-02-28 11:30
 183.¢½.53.158  
First, the professor points out that there were large number of individual cooper experts. They was able to manufacture parabolic shape as well. New concept This reading passage provides the ancient Greek were not technologically advanced enough to make such a device.
     
¼Û¼ö¿¬ 17-02-28 11:37
 183.¢½.53.158  
Next, the lecturer states that with other materials, the mirror will be more effective compared to the reading passage's wooden object. With secret water proof materials and certain sticky substances, the mirror can set the object the fire just in second. Also, once setting the fire, the fire easily can stretch and move ships quickly. This is in opposition to the reading passage's claim that the mirror with wood was not impractical and inefficient.
³ªÀ±¼± 17-02-28 11:37
 183.¢½.53.158  
The lecturer argues that the burning mirror concentrate to set the object on fire such as patchy. Patchy is sticky substance that could be fired in a second by burning mirror, even if the ship is moving. This refutes the point made by reading passage that the burning mirror would have taken a long time to set the ships on fire.
±èÇýÁø 17-02-28 11:37
 183.¢½.53.158  
The lecturer argues that according the experiment, the boat made by not just wood could be fired since they used the water-proof pitch. The water-proof pitch could set on fire in a second even though they was moving. This challenges the point made in the reading passage that the object should not move when it was pointed to fire which took ten minutes.
·ùÇüÁø 17-02-28 11:59
 1.¢½.255.35  
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