Reading Comprehension

PT113 · S1 · P2 · Q13 Marie Curie

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Spurred by the discovery that a substance containing uranium emitted radiation, Marie Curie began studying radioactivity in 1897.

Topic

Marie Curie's early research on radioactivity and its historical context

Framework

Old / New

Main Point

Marie Curie made foundational discoveries in radioactivity based on the evidence and scientific understanding available to her at the time, and any modern criticisms for not reaching later conclusions are misplaced because her work paved the way for those later breakthroughs. (Most Valuable Sentence: — last paragraph)

P1: Curie’s Pioneering Experiments

Marie Curie started her work on radioactivity after discovering that uranium emitted radiation. She found pitchblende was even more radioactive than uranium and, hypothesizing that a new element was responsible, discovered polonium and radium. She also noted that the emission rate for a given element seemed constant and couldn’t explain the underlying mechanism for radiation.

P2: Modern Understanding and Limits of Curie’s Evidence

Today we know that radiation is due to the decay of isotopes and that emission rates slowly decrease over time. Some have criticized Curie for not reaching these modern conclusions, but given what was available to her scientifically (especially since most radioactive isotopes of lighter elements don’t exist naturally), such criticisms are unfair.

P3: Scientific Context of Curie’s Era

During Curie’s time, the structure and nature of atoms were still being debated: physicists saw matter as eventually being indivisible, while chemists conveniently used the concept of atoms without worrying about whether atoms truly existed.

13.

Which one of the following most accurately expresses the meaning of the word "mechanism" as used by the author in the last sentence of the first paragraph?

  1. Correct

    the physical process that underlies

    Why this is right

    We were looking for "the underlying property or catalyst that results in radiation". That seems to match pretty well with the physical process that underlies radiation. Scientists can explain the mechanism by which magnetism works, for example. They can point to the phenomenon of magnetism and then explain the mechanism by which to explain it, referencing the physical process of charged ions that underlies this phenomenon. But they're not sure why some elements are emitting radiation. They can point to it happening but they couldn't provide provide you with a physical explanation of how it occurs.

    Skill tested: Meaning in Context · how this choice captures the passage's function is the move to repeat next time.

    53% picked this

  2. the experimental apparatus in which

    Bad Match: experimental apparatus

    The usage of "mechanism" here is not referring to a machine or gadget, like a garlic press is a mechanism / apparatus that forces a clove of garlic through tiny holes to output minced garlic. And the usage isn't related to specific experiments or laboratories. This sentence is talking about radiation, as a naturally occurring phenomenon in the world, as a mysterious property that we have observed in some elements but have no causal story to explain.

    4% picked this

  3. the procedure scientists use to

    Bad Match: used by scientists

    This last sentence isn't talking about how scientists bring abou radiation. Radiation occurs with or without scientists noticing that it does. Uranium is emanating radiation, independent of human study. Why is it emanating radiation? We don't know. What sort of mechanism / thing triggers it to happen? This answer could be semi-fixed by saying the procedure this universe uses to bring about the occurrence of a phenomenon

    7% picked this

  4. the isotopes of an element

    Bad match: isotopes

    We were looking for "the underlying property or catalyst that results in radiation". I don't know where isotopes is coming from, but we weren't saying that Curie was "unable to postulate an isotope by which to explain radiation".

    3% picked this

  5. the scientific theory describing a

    Weird Match

    This is a confusing (and tempting) answer choice, because a scientific theory describing radiation would definitely postulate a mechanism by which to explain radiation.. Einstein's Theory of General Relativity is a scientific theory that describes the phenomenon of gravity, by postulating the mechanism by which it occurs (objects move throughout a curved dimension of spacetime that is warped by objects of great mass; gravity is a straight line path through warped spacetime). Mendel's theory of genetics described hereditary traits, by postulating the mechanism by which they occur (traits are encoded in genes within an individual's DNA / offspring gets half its DNA from each parent / different genes "win out" in terms of which ones get expressed or repressed). In other words, before Curie could devise any scientific theory describing radiation, she would first need to postulate a mechanism by which radiation occurs (i.e. she needs to be able to describe the physical process that underlies radiation). At this stage in the passage (and in Curie's career), she's not about to propose a scientific theory. She's just futzing around with radiation and seeing that it's happening but having no clue why / how it's happening. Postulating a mechanism by which to explain it, in this context, shouldn't sound like some grandiose scientific theory she couldn't complete. It needs to sound more casual, like "she couldn't even begin to tell you what radiation was or how it was working". (E) sort of encompasses (A), where (A) would be happening either way, but (E) doesn't necessarily need to be happening.

    34% picked this

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