CAT 2021 Slot 3 Question 14

Instructions

The passage below is accompanied by a set of questions. Choose the best answer to each question.

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 14

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

Solution

There is an evident confusion between Option B and Option C; however, the official answer key marked Option B as the correct choice. Let us try to rationalise this decision. Options A and D can be understood from the passage:

Option A follows from {...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...}

Option D follows from {...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...}

Option C: Pay heed to the following excerpt from the passage - {...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...}

A simple correlation is being highlighted: higher accuracy means higher entropy; however, this does not necessarily imply that higher entropy translates to higher accuracy. The example of a grandfather clock is highlighted to emphasise this point: we will come across higher entropy in this case, but it does not mean that the grandfather clock is any more accurate than an atomic clock. In a way, the author tries to point out that the accuracy could very well be similar. This accuracy is not in absolute terms but in the way accuracy is defined by the author earlier in the passage. Thus, in a way, Option C matches the idea conveyed by the author

Option B: Pay heed to the following excerpt from the passage - {...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 discussion about the price paid appears to be distinct from the earlier segment wherein the author states that when we push for higher accuracy, we will come across more heat. While talking about the cost at which higher accuracy is achieved, the author states that we "pour in" more 'ordered energy' and this subsequently leads to higher entropy. Hence, the focus seems to be on the connection between accuracy and entropy than between heat and its role in creating higher accuracy. We cannot conclusively infer that the "ordered energy" stated in the latter half refers to the "heat" mentioned earlier on. Thus, claiming that heat is the price we pay for generating higher accuracy might be difficult to substantiate. Hence, Option B is distorted. 


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