In passage B's description of the developments leading to the rejection of Newton's theory of gravity, which one of t...

shunhe on August 12, 2020

Hi @fable,

Thanks for the question! Let me try to explain why Mercury is the correct answer, and not Neptune. So we’re asked here for an astronomical body in passage B that plays a role like the black swan in passage A. OK, well what does the black swan do in passage A? We should go to it and figure out, and we see that the black swan is brought up in line 5. We can’t prove that all swans are white no matter how many white swans we look at, but we can disprove it with one single black swan. So we’re looking for some observation, a single “black swan” piece of evidence, that would’ve rejected Newton’s theory of gravity.

Now we go to passage B to see what this is. Well, take a look at the last paragraph, starting at line 52. We’re told that astronomers used Newton’s laws to predict the orbit of Mercury, but the predictions were wrong! So they thought another planet existed. But there wasn’t another planet this time. And that disproved Newton’s theory of gravity. So it was Mercury that ended up disproving the theory, making (A) the correct answer here.

As for Neptune, where is that mentioned, and what does it do? Well, it’s mentioned in line 49. And it actually helps support Newton’s theory, since its existence helps show why Uranus had a funky orbit. So that means that it helped patch up a possible hole in Newton’s theory with Uranus, and so it’s definitely not the black swan we’re looking for.

Hope this helps! Feel free to ask any other questions that you might have.