John of Worcester, an English monk, recorded the sighting, on December 8, 1128, of two unusually large sunspots. Five...

Saira on October 17, 2014

???

Was confident about this one but was completely off!

2 Replies

Melody on October 24, 2014

So we are told that John of Worcester recorded seeing sunspots on December 8, 1128. Five days after this, a brilliant aurora borealis was observed in southern Korea. We are told that sunspot activity is typically followed by the appearance of aurora borealis after a span of five days. The argument then concludes that the Korean sighting of aurora borealis helps confirm John of Worcester's sighting.

What should immediately pop out at you is that we are told that when sunspots are sighted, aurora borealis is usually sighted about five days later. But we do not know that this is the only time aurora borealis occurs.

Aurora borealis could be sighted when many different things happen, not just sunspot sighting. Thus, we want to find an answer choice that helps strengthen the idea that the aurora borealis sighting in Korea helped prove the sunspot sighting made by John of Worcester.

Answer choice (C) states: "Only heavy sunspot activity could have resulted in an aurora borealis viewable at a latitude as low as that of Korea."

So we can rewrite this: "If aurora borealis occurs in a low latitude such as Korea, then heavy sunspot activity had resulted."

(C): ABK ==> SPS
not SPS ==> not ABK

P: ABK

C: SPS

Since the stimulus tells us that five days after John of Worcester sighted the sunspots, aurora borealias was, in fact, sighted in Korea, then if we take answer choice (C) to be true, this information helps confirm the John of Worcester sighting.

Hope that clears things up! Please let us know if you have any other questions.

Samuel on October 26, 2018

Why not E? The drawing would support the conclusion. I can see why C is "more right" but I couldn't eliminate E