PT140 · S2 · Q25 At one time, many astronomers

These astronomers were assuming that the stars revolve, and their whole argument is predicated on that idea. So they weren't assuming anything about a hypothetical world in which stars don't revolve around the Earth. This answer choice is doing some sort of Fake Opposite ju-jitsu. Since we spoke about a world in which stars do revolve around Earth and it was not possible for the stars to be more than a few million miles away, they're just writing an answer choice that flips those ideas.

On Necessary Assumption, we're extra-wary of extreme language, and it doesn't get much more extreme than this. The astronomers' argument and worldview wouldn't be undermined if some stars move at different speeds than others.

This is the opposite of what the astronomers believe. They are assuming that the Earth is motionless while the stars revolve around it.

This definitely feels like an idea we can infer. It's so weakly worded. The astronomers think it's unfeasible for stars to be 3+ million miles away because they'd have to go unrealistically quickly to make it back to roughly the same spot in the sky the next night. And the astronomers conclude that the stars are not more than a few million miles from Earth. So presumably they think within that range, it's feasible for a star to circle around back to roughly the same position. If we negate this, it'll say: if a star is more than a million miles away, a star could not reappear in the same spot Doesn't that jack up the astronomers' story? No, because the conclusion is "not more than a few million". If this negation is telling us "even at 1.1 million miles, you're already too far out to be able to feasibly zip around the Earth and arrive in the same spot, then the implication of that is that these stars must be even closer than 1 million miles! The thing is, that doesn't disagree with the author's conclusion. If we say, "I bet you Joey show up here with no more than twenty bucks", and then Joey shows up with $4, was I right or wrong? I was right. Anything $20 or less and I am right. It has to be more than $20 for me to be wrong. Similarly, concluding that the stars are "no more than a few million miles from Earth", means that you're right if stars are between 0 and 3,000,000 miles from Earth. You're only wrong if there are stars farther than 3,000,000 miles from Earth. Negating this answer isn't allowing us to argue that this author is wrong. It makes her conclusion actually seem truer than ever, since the stars seem closer than ever.