sk05 wrote:
How is D the correct answer choice? It mentions that smaller planets relative to the size of the stars are difficult to detect. Th option is not talking about all the small planets. It is talking about the size of the planets relative to the size of the stars.
Here's the claim the support for which we have to weaken:
earthlike worlds form a very low percentage of the planets orbiting stars in the galaxy other than the sunHere's the support for that claim:
Of over two hundred planets that astronomers have detected around other stars, almost all are hundreds of times larger and heavier than the earth and orbit stars much smaller than the sun.Notice that the evidence is the characteristics of "planets that astronomers
have detected around other stars."
Those characteristics of planets that astronomers have detected are that "almost all are hundreds of times larger and heavier than the earth and orbit stars much smaller than the sun."
So, the reasoning of the argument is basically that, since most planets detected are larger and heavier than the Earth and orbit stars smaller than the Sun, Earthlike worlds form a very low percentage of the planets orbiting stars in the galaxy.
Now, let's consider choice (D).
D. The smaller a planet is relative to the star it orbits, the more difficult it is for astronomers to detect.At first this information may seem irrelevant to the argument, but if we consider it carefully, we can make the following connection.
Choice (D) says that planets that are small and orbit large stars are hard to detect. So, it may be that the reason most "planets that astronomers have detected" are large and orbit small stars is simply that astronomers have not succeeded in detecting planets like Earth, which are small relative to the stars they orbit.
Thus, (D) shows that the conclusion that "earthlike worlds form a very low percentage of the planets" doesn't necessarily follow from the evidence about "planets that astronomers have detected because the planets astronomers have detected may not be a representative sample of "the planets orbiting stars in the galaxy."
Quote:
Our argument says that the stars are smaller as compared to the sun. What if the size of the stars and the planets are almost the same? How is D making sense then?
A planet almost the same size as a star would be a very big planet because stars are generally much larger than planets. Also, notice that the argument doesn't say that the detected planets are similar in size to stars. Rather, it says that the planets are "hundreds of times larger and heavier than the earth," meaning that they are still much smaller than stars.
In any case, (D) still works even if some planets are close in size to the stars they orbit because it could still be the case that planets that are small relative to the stars they orbit, as Earth is to the sun, would not be detected.