A little over 2200 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 really 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 arrow. 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 Greek had no reason to build a weapon like a burning mirror
The lecturer challenges the topic proposed in the reading that several reasons can used to suspect that the story of the burning mirror is just a myth and the Greeks never rally built such a device. And she thinks that these reasons are all unconvincing.
First, the article suggests that the ancient Greeks were not technologically advanced enough to make such a device. However, the professor points out that experiments show that dozens of polish mirrors can be directly assembled to a large mirror which could be set on a ship. Thus, the large burning mirror could be manufactured easily.
Second, the essay supposes that the burning mirror would have taken a long time to set the ships on fire. But the lecturer supports that there are other materials on ships except woods. For example, there is a water-proof sticky material called pitch, which could be set on fire in seconds. Then the fire could spread to wood materials on ships. Therefore, the burning mirror is not impractical and ineffective.
Third, the passage indicates that a burning mirror does not seem like an improvement on flaming arrows. Nevertheless, the professor argues that romans are already familiar with the causes of flaming arrows. So by using the burning mirror, roman ships cannot figure out the reason of the fire, which is much more surprising and effective. Hence, the burning mirror is feasible.
Transition Words or Phrases used:
but, first, hence, however, nevertheless, second, so, then, therefore, third, thus, for example
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 13.0 10.4613686534 124% => OK
Auxiliary verbs: 8.0 5.04856512141 158% => OK
Conjunction : 5.0 7.30242825607 68% => OK
Relative clauses : 13.0 12.0772626932 108% => OK
Pronoun: 12.0 22.412803532 54% => OK
Preposition: 23.0 30.3222958057 76% => OK
Nominalization: 1.0 5.01324503311 20% => More nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1159.0 1373.03311258 84% => OK
No of words: 231.0 270.72406181 85% => More content wanted.
Chars per words: 5.01731601732 5.08290768461 99% => OK
Fourth root words length: 3.89854898053 4.04702891845 96% => OK
Word Length SD: 2.57265992935 2.5805825403 100% => OK
Unique words: 131.0 145.348785872 90% => More unique words wanted.
Unique words percentage: 0.5670995671 0.540411800872 105% => OK
syllable_count: 351.9 419.366225166 84% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 0.0 3.25607064018 0% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 0.0 2.5761589404 0% => More preposition wanted as sentence beginning.
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 16.0 21.2450331126 75% => The Avg. Sentence Length is relatively short.
Sentence length SD: 42.6256246588 49.2860985944 86% => OK
Chars per sentence: 82.7857142857 110.228320801 75% => OK
Words per sentence: 16.5 21.698381199 76% => OK
Discourse Markers: 6.78571428571 7.06452816374 96% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 0.0 4.19205298013 0% => OK
Sentences with positive sentiment : 5.0 4.33554083885 115% => OK
Sentences with negative sentiment : 6.0 4.45695364238 135% => OK
Sentences with neutral sentiment: 3.0 4.27373068433 70% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.142907462434 0.272083759551 53% => OK
Sentence topic coherence: 0.0520902124472 0.0996497079465 52% => OK
Sentence topic coherence SD: 0.0322071188527 0.0662205650399 49% => Sentences are similar to each other.
Paragraph topic coherence: 0.0859099688119 0.162205337803 53% => OK
Paragraph topic coherence SD: 0.0279164064038 0.0443174109184 63% => OK
Essay readability:
automated_readability_index: 10.5 13.3589403974 79% => Automated_readability_index is low.
flesch_reading_ease: 63.7 53.8541721854 118% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.4 11.0289183223 76% => OK
coleman_liau_index: 11.54 12.2367328918 94% => OK
dale_chall_readability_score: 8.05 8.42419426049 96% => OK
difficult_words: 53.0 63.6247240618 83% => More difficult words wanted.
linsear_write_formula: 11.0 10.7273730684 103% => OK
gunning_fog: 8.4 10.498013245 80% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
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Rates: 80.0 out of 100
Scores by essay e-grader: 24.0 Out of 30
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Note: the e-grader does NOT examine the meaning of words and ideas. VIP users will receive further evaluations by advanced module of e-grader and human graders.