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 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 the 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.
Both the passage and the lecture discuss whether the ancient Greeks defended themselves with a weapon called burning mirror. The passage lists three reasons to support its argument that the burning mirror was just a myth. However, the lecture casts doubt on the reasons proposed by the passage.
First of all, the passage states that the ancient Greeks were not technologically advanced enough to create a mirror that was several meters wide. Notwithstanding, the lecture refutes the passage by mentioning that an experiment has shown that dozens of small polished coppers could be arranged to form a large mirror. Thus, it is likely that the ancient Greeks was able to make the burning mirror.
Secondly, the passage cites an experiment that indicates the burning mirror took ten minutes to set a wooden object on fire, so a burning mirror was too weak to set ships on fire. Nevertheless, the lecture counters the passage by pointing out that ancient Romans' ships were not built only by wood. Instead, they also used a material called pitch to build ships, which is a material that can catch fire in seconds. Therefore, it is possible that the burning mirror was a weapon to set ships on fire.
Finally, the passage argues that the Greeks already had flaming arrows, which are more effective way than the burning mirror to set the ships on fire. Yet the lecture disagrees with the passage by arguing that the Romans were familiar with flaming arrows, so they would put more attention on incoming flaming arrows. In contrast, they probably did not hear of the burning mirror, hence, they would not be aware of it.
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Transition Words or Phrases used:
also, finally, first, hence, however, nevertheless, second, secondly, so, therefore, thus, as to, in contrast, first of all
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 14.0 10.4613686534 134% => OK
Auxiliary verbs: 4.0 5.04856512141 79% => OK
Conjunction : 2.0 7.30242825607 27% => More conjunction wanted.
Relative clauses : 14.0 12.0772626932 116% => OK
Pronoun: 21.0 22.412803532 94% => OK
Preposition: 30.0 30.3222958057 99% => OK
Nominalization: 4.0 5.01324503311 80% => OK
Performance on vocabulary words:
No of characters: 1350.0 1373.03311258 98% => OK
No of words: 275.0 270.72406181 102% => OK
Chars per words: 4.90909090909 5.08290768461 97% => OK
Fourth root words length: 4.07223819929 4.04702891845 101% => OK
Word Length SD: 2.42222218852 2.5805825403 94% => OK
Unique words: 138.0 145.348785872 95% => More unique words wanted.
Unique words percentage: 0.501818181818 0.540411800872 93% => More unique words wanted or less content wanted.
syllable_count: 407.7 419.366225166 97% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 5.0 3.25607064018 154% => OK
Article: 7.0 8.23620309051 85% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 1.0 2.5761589404 39% => More preposition wanted as sentence beginning.
Performance on sentences:
How many sentences: 13.0 13.0662251656 99% => OK
Sentence length: 21.0 21.2450331126 99% => OK
Sentence length SD: 34.9493293398 49.2860985944 71% => OK
Chars per sentence: 103.846153846 110.228320801 94% => OK
Words per sentence: 21.1538461538 21.698381199 97% => OK
Discourse Markers: 9.46153846154 7.06452816374 134% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 0.0 4.19205298013 0% => OK
Sentences with positive sentiment : 2.0 4.33554083885 46% => More positive sentences wanted.
Sentences with negative sentiment : 7.0 4.45695364238 157% => OK
Sentences with neutral sentiment: 4.0 4.27373068433 94% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.209763250454 0.272083759551 77% => OK
Sentence topic coherence: 0.0895140606754 0.0996497079465 90% => OK
Sentence topic coherence SD: 0.0753570748135 0.0662205650399 114% => OK
Paragraph topic coherence: 0.142716396903 0.162205337803 88% => OK
Paragraph topic coherence SD: 0.0431811211231 0.0443174109184 97% => OK
Essay readability:
automated_readability_index: 12.3 13.3589403974 92% => Automated_readability_index is low.
flesch_reading_ease: 58.62 53.8541721854 109% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 10.3 11.0289183223 93% => OK
coleman_liau_index: 11.2 12.2367328918 92% => OK
dale_chall_readability_score: 7.84 8.42419426049 93% => OK
difficult_words: 55.0 63.6247240618 86% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 10.4 10.498013245 99% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
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Rates: 66.6666666667 out of 100
Scores by essay e-grader: 20.0 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.