Logical Reasoning

PT117 · S3 · Q24 Science journalist: Brown dwarfs are

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Science journalist: Brown dwarfs are celestial objects with more mass than planets but less mass than stars.

Facts

causality (identified by, because, and so)

Mass + >> indicates whether Brown Dwarf Atmos Lith

incomplete mixing stars as big as Sun of elements in >> still have lithium nuclear furnace

complete mixing stars smaller than Sun of elements in >> have no lithium nuclear furnace

BD lacks fully funct >> BD still has lithium nuclear furnace in its atmosphere

comparison MASS planets < BD's < stars

Evaluate

Well what should we do with this hot mess of celestial facts? There are bunch of causal ideas, but they don't seem to form any causal chain because they're about three different categories of things (stars as big as the Sun, stars smaller than the Sun, and brown dwarfs).

The overlapping concepts are things like whether or not your nuclear furnace is fully mixed, how massive you are, and whether or not you still have lithium.

If we think about the 2nd sentence, saying that we use how massive you are and whether or not you have lithium to figure out whether something is a brown dwarf, we could now spell out what that means, based on the last three facts:

To be a brown dwarf, we'd expect you to still have lithium in you, but be smaller than a star, and bigger than a planet.

Goal

As always on Most Supported, we just want the most provable/derivable answer. It's hard to guess where this one is headed.

24.

Which one of the following is most strongly supported by the science journalist's statements?

  1. Any celestial object without lithium

    Reversal / Negation

    We heard about three categories of things: 1. stars as massive as the Sun (have lithium) 2. stars less massive than Sun (no lithium) 3. brown dwarfs less massive than stars (have lithium) We can say, "if you're a stay with less mass than the Sun, then you are a celestial object without lithium in the atmosphere". But this answer is the reversal of that. We don't know if smaller-stars are THE ONLY celestial objects that have no lithium in their atmosphere. Maybe planets, moons, comets, or asteroids are also celestial objects without lithium in their atmosphere.

    6% picked this

  2. Any celestial object with lithium

    Reversal / Negation

    We heard about three categories of things: 1. stars as massive as the Sun (have lithium) 2. stars less massive than Sun (no lithium) 3. brown dwarfs less massive than stars (have lithium) It is true that the two things from this list (1 and 3) that have lithium in their atmosphere also have incomplete furnace mixing. But we don't know if big-stars and brown dwarfs are THE ONLY celestial objects that have lithium in their atmosphere. Maybe planets, moons, comets, or asteroids are also celestial objects with lithium in their atmosphere. They don't even have nuclear furnaces!

    12% picked this

  3. Correct

    No celestial object that has

    Why this is right

    The double negative is tough, so consider a couple moves: 1. rewrite one of the negatives so that it doesn't sound like a second negative. e.g. let's rewrite "has no lithium in its atmosphere" as "Lithium-Free". No celestial object that's Lithium-Free is a brown dwarf. That's easier to translate. "If it's Lithium-Free, then it's not a brown dwarf" 2. The other move is to turn into a logic robot and cite your translation rule for "No A's are B". Robot knows that looks like "If A, then ~B". We knew that to be a brown dwarf you had to have lithium and be in between the mass of planets and stars. So it's true to say, "If something is Lithium-Free, then it's not a brown dwarf". This answer is really just derived from the final sentence.

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

    63% picked this

  4. No celestial object with lithium

    Contradicted

    We heard about three categories of things: 1. stars as massive as the Sun (have lithium) 2. stars less massive than Sun (no lithium) 3. brown dwarfs less massive than stars (have lithium) #3 contradicts this answer. Brown dwarfs are celestial objects with lithium in their atmosphere, and they do have less mass than the Sun.

    12% picked this

  5. No celestial object less massive

    Too Strong (nothing smaller)

    We heard about three categories of things: 1. stars as massive as the Sun (have lithium) 2. stars less massive than Sun (no lithium) 3. brown dwarfs less massive than stars (have lithium) We can't assume that 1 and 3 are the only things in the universe with lithium in their atmosphere, just because they're the only things mentioned in the paragraph. Maybe planets, moons, comets, or asteroids have lithium in their atmosphere (they're all celestial objects less massive than a brown dwarf).

    7% picked this

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