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.
There is a heated discussion on the reality of the burning mirror during Roman times. The author in the reading passage explores three assumptions which deny the burning mirror's existence, while the professor, in the lecture, contradicts all these reasons respectively by using three specific points as supports.
First, the author asserts that building a huge copper burning mirror with a very precise parabolic curvature is technologically impractical, while the professor argues that Greeks could utilize a series of small mirrors instead, which would do the same job as a single huge mirror by experiment. What's more, Greeks mathematicians were excellent enough to arrange small mirrors into a parabolic shape.
Second, despite the statement in the reading passage stresses burning mirrors' ineffectiveness, however, the professor contends that wood is not the only material for a ship, and there are some materials that are easily burnt, such as pitch that used for waterproof. These materials could be burnt in seconds and the fire would spread to the wood quickly then.
Third, even though the reading passage presents flaming arrows could be more effective than the burning mirror, which Greeks already had, the professor opposes this claim by point out an invisible advantage of burning mirrors. Enemies could see flaming arrows and prepare the necessary defense, but they can not see burning rays from a mirror. Thus, the burning mirror could set a fire magically and suddenly at an unobserved place, resulting in a more effective attack than flaming arrows.
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Grammar and spelling errors:
Line 1, column 171, Rule ID: POSSESIVE_APOSTROPHE[2]
Message: Possible typo: apostrophe is missing. Did you mean 'mirrors'' or 'mirror's'?
Suggestion: mirrors'; mirror's
...hree assumptions which deny the burning mirrors existence, while the professor, in the ...
^^^^^^^
Line 5, column 297, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: What's
... as a single huge mirror by experiment. Whats more, Greeks mathematicians were excell...
^^^^^
Transition Words or Phrases used:
but, first, however, if, second, so, then, third, thus, while, such as
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 8.0 10.4613686534 76% => OK
Auxiliary verbs: 8.0 5.04856512141 158% => OK
Conjunction : 5.0 7.30242825607 68% => OK
Relative clauses : 8.0 12.0772626932 66% => More relative clauses wanted.
Pronoun: 9.0 22.412803532 40% => OK
Preposition: 21.0 30.3222958057 69% => OK
Nominalization: 3.0 5.01324503311 60% => More nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1335.0 1373.03311258 97% => OK
No of words: 248.0 270.72406181 92% => More content wanted.
Chars per words: 5.38306451613 5.08290768461 106% => OK
Fourth root words length: 3.96837696647 4.04702891845 98% => OK
Word Length SD: 2.68440293561 2.5805825403 104% => OK
Unique words: 148.0 145.348785872 102% => OK
Unique words percentage: 0.596774193548 0.540411800872 110% => OK
syllable_count: 405.0 419.366225166 97% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 1.0 3.25607064018 31% => OK
Article: 5.0 8.23620309051 61% => OK
Subordination: 3.0 1.25165562914 240% => Less adverbial clause wanted.
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 9.0 13.0662251656 69% => Need more sentences. Double check the format of sentences, make sure there is a space between two sentences, or have enough periods. And also check the lengths of sentences, maybe they are too long.
Sentence length: 27.0 21.2450331126 127% => The Avg. Sentence Length is relatively long.
Sentence length SD: 75.9011703093 49.2860985944 154% => OK
Chars per sentence: 148.333333333 110.228320801 135% => OK
Words per sentence: 27.5555555556 21.698381199 127% => OK
Discourse Markers: 7.77777777778 7.06452816374 110% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 2.0 4.19205298013 48% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 4.0 4.45695364238 90% => OK
Sentences with neutral sentiment: 1.0 4.27373068433 23% => More facts, knowledge or examples wanted.
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.152281805518 0.272083759551 56% => OK
Sentence topic coherence: 0.0673357949464 0.0996497079465 68% => OK
Sentence topic coherence SD: 0.0363715278636 0.0662205650399 55% => OK
Paragraph topic coherence: 0.0888213328053 0.162205337803 55% => OK
Paragraph topic coherence SD: 0.0366809684437 0.0443174109184 83% => OK
Essay readability:
automated_readability_index: 17.7 13.3589403974 132% => OK
flesch_reading_ease: 44.07 53.8541721854 82% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 13.8 11.0289183223 125% => OK
coleman_liau_index: 14.22 12.2367328918 116% => OK
dale_chall_readability_score: 9.05 8.42419426049 107% => OK
difficult_words: 64.0 63.6247240618 101% => OK
linsear_write_formula: 14.0 10.7273730684 131% => OK
gunning_fog: 12.8 10.498013245 122% => OK
text_standard: 14.0 11.2008830022 125% => OK
What are above readability scores?
---------------------
Rates: 85.0 out of 100
Scores by essay e-grader: 25.5 Out of 30
---------------------
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.