Reading Comprehension

PT121 · S2 · P3 · Q18 Neutrinos

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According to the theory of gravitation, every particle of matter in the universe attracts every other particle with a force that increases as either the mass of the particles increases, or their proximity to one another increases, or both.

(Written summary below video)

Topic

Neutrinos and the Dark Matter mystery

Frameworks

Problem / Solution Answer a Question

Main Point

Question / Problem The observable matter in the universe only adds up to about 10% of the mass that would be needed for gravity to account for the observable structures in the universe. So given that we believe in gravity, and we believe we're correctly observing structures, where is the other 90% of the universe's mass?

Answer / Solution Neutrinos seem to account for about 20% of it, but more broadly the discovery that a tiny particle's crazy small mass might still add up to something significant (because of how numerous that type of particle is) is making scientists think that maybe the tiny masses of elementary particles is a big part of the missing mass.

Summary

P1 - Background on gravity, introduction to Curious Problem

After briefly summarizing what gravity means, this paragraph establishes the 90% missing matter conundrum, and says that cosmologists have postulated something called 'dark matter', which seems to just be a placeholder name.

P2 - A potential Solution that seemed non-viable

This paragraph introduces neutrinos as one possible answer/solution that cosmologists had considered, but ultimately rejected since they assumed that neutrinos had no mass.

P3 - New research brings back hope to possible Solution

This paragraph presents new research that suggests that neutrinos do have mass, so they're back as a contender for this dark matter problem we're trying to solve.

P5 - Implications of New research

The author's take on where we're at usually comes in the final paragraph of Science passages. Here, it sounds like neutrinos are promising as a Partial Solution, and they're also opening up new lines of inquiry that are potentially an encouraging step forward in the process of trying to find the Whole Solution.

Topic

The search for "dark matter" and the possible role of neutrinos in accounting for missing mass in the universe.

18.

Which one of the following phrases could replace the word "cohere" at the end of the second paragraph without substantively altering the author's meaning?

  1. exert gravitational force

    Bad Match

    Exerting gravitational force is what causes something to cohere. The cause and the effect can't be the same thing. Substituting it would make the sentence say force induces matter to exert force.

    16% picked this

  2. Correct

    form galactic structures

    Why this is right

    This doesn't seem super appealing at first because of its specificity about galactic structures. But forming galactic structures is an example of matter clumping together with other matter to form something bigger. Ultimately, this relies heavily on the context of how "cohere" was used at the end of P1, which was specifically talking about how much mass would be needed so that gravitational attraction could form huge structures like galaxies and galaxy clusters. Even though the force of gravity would cause smaller things (like stars) to also 'cohere', when it comes to the puzzle of the passage, it seems to be primarily based on figuring out the missing mass that it would take to explain why the universe is organized in the shape of galaxies and galactic clusters.

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

    64% picked this

  3. oscillate into another type of

    Out of Support Window

    Oscillation is the third paragraph's topic: neutrinos changing type as they travel. It has nothing to do with what gravity does to matter at the end of the second paragraph.

    3% picked this

  4. become significantly more massive

    Bad Match

    Gravity gathers matter; it does not increase the mass of individual matter. The sentence is about what gravitational force induces other matter to do. It's true that once different parts of matter clump together (i.e. cohere), the collective mass of that clump will be more than that of either of the parts separately, but it will equal the sum of the parts. Gravity is not making the matter itself more massive.

    4% picked this

  5. fuse to produce new particles

    Dictionary Bait

    Fusing is a literal kind of sticking together, but in the passage fusion is a nuclear process that creates neutrinos, not what gravity does to matter on the scale of galaxies. We want something that means "joining different clumps of matter together", not producing new particles.

    13% picked this

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