A little over 2,200 years ago, the Roman navy attached 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 wetting 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.
According to the reading passage, some ancient historians believed that in a war between Roman and Greek over 2,200 years ago, the Greek have used an ingenious weapon called burning mirror, a polished copper curved to concentration the sun's beams onto Raman ships led to catch the fire. However, there have been some reasons the story of the burning mirror is just a myth and never have been built by the Greek. But the speaker finds all the ideas dubious and presents some ideas to refute them all.
First, the ancient Greek were not able to technologically build such an advanced burning mirror with a large sheet of copper together with a very precise parabolic curvature. Conversely, the speaker states that the Greek used a great many of small pieces of copper, which their mathematicians were able to calculate the exact parabolic curvature.
Second, to set the fire on Roman ships by the burning mirror, it has been proven that it would have taken more time about 30 minutes in an unmoving object. On the contrary, the Roman would have used not only the woods in their ships, but also another substance called pitch to fill the spaces between woods, which was more likely to burn quickly, and then spread the fire.
Finally, the ancient Greek had another effective weapon called flaming arrows, to set the fire on enemy's ships. It seems that the invention of such a burring mirror does not make sense. In contrast, the professor dismisses this issue due to the fact that the Roman soldiers were familiar to the flaming arrows and after shooting them by the Greek they could have expected the location of fire and put it out quickly. With flaming mirror, the location of fire was not detectable by Roman soldiers and suddenly the fire might be initiated in Roman ships by focusing the sun's rays in unexpected directions.
Grammar and spelling errors:
Line 1, column 377, Rule ID: ADVERB_WORD_ORDER[7]
Message: The adverb 'never' is usually put between 'have' and 'been'.
Suggestion: have never been
...f the burning mirror is just a myth and never have been built by the Greek. But the speaker fin...
^^^^^^^^^^^^^^^
Transition Words or Phrases used:
also, but, conversely, finally, first, however, second, so, then, as to, in contrast, on the contrary
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 10.0 10.4613686534 96% => OK
Auxiliary verbs: 4.0 5.04856512141 79% => OK
Conjunction : 9.0 7.30242825607 123% => OK
Relative clauses : 7.0 12.0772626932 58% => More relative clauses wanted.
Pronoun: 15.0 22.412803532 67% => OK
Preposition: 44.0 30.3222958057 145% => OK
Nominalization: 5.0 5.01324503311 100% => OK
Performance on vocabulary words:
No of characters: 1522.0 1373.03311258 111% => OK
No of words: 316.0 270.72406181 117% => OK
Chars per words: 4.8164556962 5.08290768461 95% => OK
Fourth root words length: 4.21620550194 4.04702891845 104% => OK
Word Length SD: 2.34897967124 2.5805825403 91% => OK
Unique words: 167.0 145.348785872 115% => OK
Unique words percentage: 0.528481012658 0.540411800872 98% => OK
syllable_count: 466.2 419.366225166 111% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 8.0 8.23620309051 97% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 3.0 1.51434878587 198% => OK
Preposition: 6.0 2.5761589404 233% => Less preposition wanted as sentence beginnings.
Performance on sentences:
How many sentences: 11.0 13.0662251656 84% => 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: 28.0 21.2450331126 132% => The Avg. Sentence Length is relatively long.
Sentence length SD: 61.2518173115 49.2860985944 124% => OK
Chars per sentence: 138.363636364 110.228320801 126% => OK
Words per sentence: 28.7272727273 21.698381199 132% => OK
Discourse Markers: 9.18181818182 7.06452816374 130% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => 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: 2.0 4.27373068433 47% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.336277136828 0.272083759551 124% => OK
Sentence topic coherence: 0.121662737494 0.0996497079465 122% => OK
Sentence topic coherence SD: 0.121149518317 0.0662205650399 183% => OK
Paragraph topic coherence: 0.193125275735 0.162205337803 119% => OK
Paragraph topic coherence SD: 0.106706799062 0.0443174109184 241% => More connections among paragraphs wanted.
Essay readability:
automated_readability_index: 15.6 13.3589403974 117% => OK
flesch_reading_ease: 51.52 53.8541721854 96% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 13.0 11.0289183223 118% => OK
coleman_liau_index: 11.27 12.2367328918 92% => OK
dale_chall_readability_score: 8.27 8.42419426049 98% => OK
difficult_words: 65.0 63.6247240618 102% => OK
linsear_write_formula: 13.0 10.7273730684 121% => OK
gunning_fog: 13.2 10.498013245 126% => OK
text_standard: 13.0 11.2008830022 116% => 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.