Comprehension
Direction for Reading Comprehension: The passages given here are followed by some questions that have four answer choices; read the passage carefully and pick the option whose answer best aligns with the passage.
Keeping time accurately comes with a price. The maximum accuracy of a clock is directly related to how much disorder, or entropy, it creates every time it ticks. Natalia Ares at the University of Oxford and her colleagues made this discovery using a tiny clock with an accuracy that can be controlled. The clock consists of a 50-nanometre-thick membrane of silicon nitride, vibrated by an electric current. Each time the membrane moved up and down once and then returned to its original position, the researchers counted a tick, and the regularity of the spacing between the ticks represented the accuracy of the clock. The researchers found that as they increased the clock’s accuracy, the heat produced in the system grew, increasing the entropy of its surroundings by jostling nearby particles . . . “If a clock is more accurate, you are paying for it somehow,” says Ares. In this case, you pay for it by pouring more ordered energy into the clock, which is then converted into entropy. “By measuring time, we are increasing the entropy of the universe,” says Ares. The more entropy there is in the universe, the closer it may be to its eventual demise. “Maybe we should stop measuring time,” says Ares. The scale of the additional entropy is so small, though, that there is no need to worry about its effects, she says.
The increase in entropy in timekeeping may be related to the “arrow of time”, says Marcus Huber at the Austrian Academy of Sciences in Vienna, who was part of the research team. It has been suggested that the reason that time only flows forward, not in reverse, is that the total amount of entropy in the universe is constantly increasing, creating disorder that cannot be put in order again.
The relationship that the researchers found is a limit on the accuracy of a clock, so it doesn’t mean that a clock that creates the most possible entropy would be maximally accurate – hence a large, inefficient grandfather clock isn’t more precise than an atomic clock. “It’s a bit like fuel use in a car. Just because I’m using more fuel doesn’t mean that I’m going faster or further,” says Huber.
When the researchers compared their results with theoretical models developed for clocks that rely on quantum effects, they were surprised to find that the relationship between accuracy and entropy seemed to be the same for both. . . . We can’t be sure yet that these results are actually universal, though, because there are many types of clocks for which the relationship between accuracy and entropy haven’t been tested. “It’s still unclear how this principle plays out in real devices such as atomic clocks, which push the ultimate quantum limits of accuracy,” says Mark Mitchison at Trinity College Dublin in Ireland. Understanding this relationship could be helpful for designing clocks in the future, particularly those used in quantum computers and other devices where both accuracy and temperature are crucial, says Ares. This finding could also help us understand more generally how the quantum world and the classical world are similar and different in terms of thermodynamics and the passage of time.
Question: 1

Which one of the following sets of words and phrases serves best as keywords of the passage?

Updated On: Jul 22, 2025
  • Electric current; Heat; Quantum effects.
  • Silicon Nitride; Energy; Grandfather Clock.
  • Measuring Time; Accuracy; Entropy.
  • Membrane; Arrow of time; Entropy.
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The Correct Option is C

Solution and Explanation

The question asks for the best set of keywords from the passage provided. Analyzing the passage, we can identify the central themes as follows:
  • Measuring Time: The core of the discussion revolves around how time is measured accurately, involving clocks and the associated principles of accuracy and entropy.
  • Accuracy: The passage discusses how the accuracy of a clock is achieved and relates it to the amount of entropy produced.
  • Entropy: A significant portion of the text covers the concept of entropy, how it increases with accuracy, and its relation to the "arrow of time".
Given these key ideas, the set of words and phrases
Measuring Time; Accuracy; Entropy
best captures the essence of the passage, touching on its main points of discussion. Other options involve unrelated concepts such as "Quantum effects" and "Grandfather Clock" which do not encapsulate the full scope of the passage's themes.
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Question: 2

The author makes all of the following arguments in the passage, EXCEPT that:

Updated On: Jul 22, 2025
  • The relationship between accuracy and entropy may not apply to all clocks.
  • Researchers found that the heat produced in a system is the price paid for increased accuracy of measurement.
  • There is no difference in accuracy between an inefficient grandfather clock and an atomic clock.
  • In designing clocks for quantum computers, both precision and heat have to be taken into account.
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The Correct Option is B

Solution and Explanation

To address the question of identifying the statement that the author does not make in the passage, we start by analyzing the comprehension provided and match it against each of the options:
  • The relationship between accuracy and entropy may not apply to all clocks. This statement aligns with the passage, as it mentions uncertainty about the universality of the relationship across different clock types.
  • Researchers found that the heat produced in a system is the price paid for increased accuracy of measurement. This is an argument made by the author in the passage, which states that as accuracy increases, so does the heat and entropy produced.
  • There is no difference in accuracy between an inefficient grandfather clock and an atomic clock. The passage makes the point that a large, inefficient clock is not more accurate than an atomic clock, hence this argument is made in the passage.
  • In designing clocks for quantum computers, both precision and heat have to be taken into account. This is mentioned in the context of understanding the relationship between accuracy and entropy, which informs the design of quantum clocks.
The answer is thus the second statement since it does appear accurately in the passage. The task required us to find an argument not made, hence there was confusion in the provided prompt where the "correct" label was on an argument that was indeed in the passage. This aligns with the restated requirements that the question was to find an argument not found in the passage.
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Question: 3

“It’s a bit like fuel use in a car. Just because I’m using more fuel doesn’t mean that I’m going faster or further . . .” What is the purpose of this example?

Updated On: Jul 22, 2025
  • If you go faster in a car, you will tend to consume more fuel, but the converse is not necessarily true. In the same way, increased entropy does not necessarily mean greater accuracy of a clock.
  • The further you go in a car, the more fuel you use. In the same way, the faster you go in a car, the less time you use.
  • If you measure the speed of a car with a grandfather clock, the result will be different than if you measured it with an atomic clock.
  • The further and faster you go in a car, the greater the amount of fuel you will use, the greater the amount of heat produced and, hence, the greater the entropy.
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The Correct Option is A

Solution and Explanation

The purpose of the example, “It’s a bit like fuel use in a car. Just because I’m using more fuel doesn’t mean that I’m going faster or further,” is to illustrate the non-linear relationship between fuel consumption and speed/distance in a car and draw a parallel to the concept of entropy and clock accuracy discussed in the research.

The passage explains that while increasing the accuracy of a clock correlates with increased entropy, this does not mean that maximum entropy results in maximum accuracy, similar to how using more fuel doesn’t always mean a car is going faster or further.

The Correct Interpretation:

From the given options, the correct interpretation is:

“If you go faster in a car, you will tend to consume more fuel, but the converse is not necessarily true. In the same way, increased entropy does not necessarily mean greater accuracy of a clock.”

This interpretation aligns with the analogy described. It emphasizes that while there can be a correlation between inputs (fuel consumption/entropy) and outcomes (speed/accuracy), one does not unconditionally dictate the maximal or direct result in real-world scenarios.

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Question: 4

None of the following statements can be inferred from the passage EXCEPT that:

Updated On: Jul 22, 2025
  • the arrow of time has not yet been tested for atomic clocks.
  • quantum computers are likely to produce more heat and, hence, more entropy, because of the emphasis on their clocks' accuracy.
  • grandfather clocks are likely to produce less heat and, hence, less entropy, because they are not as accurate.
  • a clock with a 50-nanometre-thick membrane of silicon nitride has been made to vibrate, producing electric currents.
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The Correct Option is B

Solution and Explanation

The goal is to identify the statement that can be correctly inferred from the passage, meaning it aligns with the information presented. Evaluating the options against the passage content allows us to find the correct choice:
The passage discusses the relationship between the accuracy of clocks and entropy. Specifically, accurately measuring time increases a clock's entropy because it generates more heat. The following analysis evaluates each option's fit to the passage:
  • The option: "the arrow of time has not yet been tested for atomic clocks" - The passage states the principle is untested for atomic clocks but doesn't mention the arrow of time directly in this context.
  • The option: "quantum computers are likely to produce more heat and, hence, more entropy, because of the emphasis on their clocks' accuracy" - The passage asserts that increased accuracy in clocks correlates with increased entropy, supporting this statement.
  • The option: "grandfather clocks are likely to produce less heat and, hence, less entropy, because they are not as accurate" - The passage notes that grandfather clocks are less precise than atomic clocks but does not explicitly say they produce less heat or entropy.
  • The option: "a clock with a 50-nanometre-thick membrane of silicon nitride has been made to vibrate, producing electric currents" - While mentioned, this detail doesn't connect to inference but describes the clock's construction.
The statement that can be correctly inferred from the passage, based on the passage's information, is: "quantum computers are likely to produce more heat and, hence, more entropy, because of the emphasis on their clocks' accuracy."
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