Reading Comprehension

PT128 · S4 · P3 · Q18 Cecilia Payne

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In the early 1900s, most astronomers mistakenly believed that 66 percent of the sun's substance was iron.

Topic

How Cecilia Payne discovered the sun is mostly hydrogen and helium — and why her contemporaries resisted her finding.

Framework

Highlight Noteworthy. The author tells the story of Payne's pioneering discovery and the resistance it faced.

Main Point

Cecilia Payne pioneeringly argued the sun is mostly hydrogen and helium (not iron). Her finding was substantiated but resisted because contemporaries had no accepted explanation for how hydrogen and helium could produce the sun's energy. Once nuclear fusion was understood, her result was confirmed.

P1: Payne's claim

Most early-1900s astronomers thought the sun was 66% iron. As a graduate student in the 1920s, Payne argued the sun is mostly hydrogen and helium. Her claim, ultimately accepted, met strong resistance.

P2: Why the iron view held

Earth and asteroids contain iron; spectroscopy seemed to support iron in the sun. But how could iron produce the sun's energy? Lord Kelvin's contraction hypothesis required the sun to be only ~20 million years old — but fossil records suggested billions of years. For Payne, this meant the iron hypothesis (and the spectroscopic evidence behind it) had to be reexamined.

P3: Payne's reanalysis

Payne suspected preconceptions had skewed how the spectroscopic data were read. Analyzed without preconceptions, the data showed 90% hydrogen, most of the rest helium, and some iron and other elements. Most astronomers dismissed her interpretation; some explained it away by claiming she had only examined data about the sun's outer surface, not its interior.

18.

Which one of the following statements about spectroscopy is most strongly supported by information in the passage?

Its use during the 1920s
Too Strong: confined to
We don't have any support for the extreme claim that for the most part only astronomy used spectroscopy.
3% picked this
It yielded data about the
Out of Scope: doubted data
From the 2nd paragraph, we know that the spectroscopy yielded data that some people looked at and said, "Hey, the sun is mainly iron!" Payne doubted that inference and never accepted that inference. She never doubted the data itself; in fact she uses that same data to come to the conclusion that the sun is 90% hydrogen and helium.
10% picked this
It played a crucial, though
Unsupported Relationship
Nothing in our two available sentences suggests that spectroscopic data played a crucial and often overlooked role when it comes to nuclear fusion. We don't know if it played any role when it comes to nuclear fusion. it's only discussed in the passage as assisting our understanding of the chemical composition of the sun.
10% picked this
It was regarded by certain
Out of Scope: certain scientists
Our two little support blurbs say nothing about certain famous scientists calling out spectroscopy as a shady tool that has dubious reliability.
5% picked this
Correct
It was a technique advanced
Why this is right
Yowsa, this is tough. Certainly not something any of us could have predicted. But it is derivable from the available text in the 3rd paragraph. She found the (spectroscopic) data could be consistently read as indicating that, while the sun does indeed contain iron and other Earth elements, 90% of the sun is hydrogen and most of the remainder is helium. Let's break that down: 90% - hydrogen 10% - remaining most of that remaining 10% is helium, so it has to be more than 5%. Let's just say 6% to keep the numbers clean. 90% - hydrogen 6% - helium 4% - iron and other Earth elements This answer is testing those last two line items. If Payne could look at the spectroscopic data and figure out that there was helium (which was less than 10% of the sun's mass) and that there was iron (which was less than 10% of the sun's mass), then apparently spectroscopy could detect the presence in the sun of elements that constituted less than 10% of the sun's mass.
Skill tested: Locate Detail · how this choice captures the passage's function is the move to repeat next time.
72% picked this

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