Measurements of the motion of the

Answer choices

1. A

   Strengthens, if anything1% picked this

   Pluto was not discovered until

   The date of discovery doesn't change anything about this conversation. It's not providing an alternate explanation for what's tugging Uranus outward, and it isn't hurting the author's storyline that there's an undiscovered planet out there. If anything, the fact that we didn't even realize Pluto existed until this past century helps the plausibility of the author's notion that there might be yet another planet we still haven't discovered.

   1%
2. B

   Correct80% picked this

   There is a belt of comets beyond the orbit of Pluto with

   Why this is right

   This provides the Alternate Explanation we were looking for. We're trying to figure out what force is pulling Uranus away from the Sun. The author thinks it must be some undiscovered planet, but this answer raises the possibility that what's really providing the outward gravitational pull is the belt of comets beyond Pluto.

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

   80%
3. C

   No Impact: comparing mass3% picked this

   Neither Neptune nor Pluto is as massive

   This doesn't pose an alternate explanation for what is pulling Uranus away from the Sun, nor does it hurt the storyline that there's an undiscovered planet in the solar system. Thus, it does nothing for the conversation. We don't care which of these three planets is most or least massive. We actually don't care about Neptune and Pluto at all anymore, since we were told that they are not massive enough to be the mystery source of what's tugging Uranus away.

   3%
4. D

   No Impact14% picked this

   The force the Sun exerts on Uranus is weaker than the force it exerts on

   Those of us familiar with gravity will not be surprised to hear that the farther something is from the Sun, the less gravitational pull the Sun exerts. Since this is a common sense fact about the world, it could probably never be correct on Strengthen / Weaken / Paradox (where the correct answer should be a new thing we didn't already know). This doesn't pose an alternate explanation for the outward tug on Uranus, nor does it hurt the storyline that there's an undiscovered planet in our solar system.

   14%
5. E

   No Impact2% picked this

   Uranus’ orbit is closer to Neptune’s orbit than it is

   Those of us familiar with our Solar system will not be surprised to hear that Uranus is closer to Neptune than it is to Pluto, the outermost planet in the solar system (although it's not actually considered a planet any more). Since this is a common sense fact about the world, it could probably never be correct on Strengthen / Weaken / Paradox (where the correct answer should be a new thing we didn't already know). This doesn't pose an alternate explanation for the outward tug on Uranus, nor does it hurt the storyline that there's an undiscovered planet in our solar system. We already knew that Neptune and Pluto aren't the solution to the mystery of the outward tugging on Uranus, so there's no reason we'd be interested in hearing anything more about them.

   2%