Q10 - A ring of gas emitting

[ManhattanPrepLSAT1]

So I wouldn't use formal notation to map out the conditional relationships on this one because the the information can be picked up on without it. But there is conditional logic employed here.

What does the Question Stem tell us?
Inference (Most Strongly Support)

Break down the Stimulus:
1. There is a ring of gas around a black hole.
2. The gas ring could not be in an orbit so close, unless the black hole was spinning.

Any prephrase?
I guess the black hole is spinning.

Answer choice analysis:
A) is unsupported. We really don't know about those black holes with orbiting rings of gas more than 49 kilometers.

B) is unsupported. There could be other kinds of black holes that also emit x-rays.

C) Looks good.

D) goes way too far. Nothing about causation is implied.

E) is unsupported. There could be stationary black holes that orbited by rings of gas.

The correct answer is C.

Takeaway/Pattern: Inference questions are testing our ability to combine multiple facts together to derive some other true fact. They usually use Conditional, Causal, Comparative, or Quantitative language to combine ideas. This one used a Conditional statement and a fact that triggers the conditional statement.

#officialexplanation

[pinkdatura]

kinda bogged by scientific terms and details
radius 49-->450 times per s flickering rate explained
maintain an orbit so close=radius 49-->bh spinning

ring of gas : 450 times per s, stable orbit = radius 49

B bh: spinning

A ~ radius 49-->~spinning
E ~spinning-->~radius 49

Why E is not correct? Pls correct my diagram, thx

[cyruswhittaker]

This one was tricky for me diagram and I actually did it without diagramming.

But here's my thoughts on the diagram, if you were to try to express the passage with conditionals:

(black hole w/ rate of flicker 450/sec) --> (radius of 49 km)
(orbit so close: referring to 49 km) --> (black hole spinning)

Thus it looks to me like this relationship (w/o all the technical jargon):

A-->B
B-->C

Hence A-->C.

So we can deduce if the statements are true that the black hold is spinning.

Choice E is incorrect because it discusses black holes that are "stationary," we have no information about. Even if we negated the last part of the above conditional relationship, it still wouldn't allow us to infer E. Furthermore, there isn't an "exact" necessary/sufficient conditional flow in this passage, as scientists say that the flickering can "best be explained," so new information in a question choice should be closely evaluated.

[irenaj]

I am confused by E, so it says:

stationary--> more than 49
less than/ equals to 49--> not stationary

since the stimulus says the blackhole would be spinning if less than/ equals to 49, is it to the opposite of "stationary" and thus E is correct?

Or did I unwarrantly presume spinning as the opposite to stationary?

Could anyone please point out the error above?

Thanks a lot!

[americano1990]

Yea my best bet is that NOT spinning is not same as Stationary.

I mean...just bring up any relevant example from your life.
Lets say you are walking to class, and you are NOT spinning as you are doing so. Are you stationary? No...you are walking..remember?

Yea...LSAC often plays tricks on your like this, so that NOT good does not mean its BAD, or NOT hungry does not mean you are Full. Simple stuff, but when you are so used to Complete negation, things might not click so well in the actual testing condition. Oh well.

In another perspective, even if you somehow equate those two values, we can get: Stationary (Not spin)--> NOT orbited by ring of gas with orbit 49km or less. This does not mean in order for the hole to be Stationary there has to be an orbit LARGER than 49km. All we have to make sure is that the orbit is NOT smaller than 49km. Kind of an extension of the caution against Total negation concept that i talk about above...

Does this help?

[ManhattanPrepLSAT1]

Nice work americano1990! I agree that "being stationary" is not necessarily the same thing as "not spinning." But I do think the LSAT writer was expecting us to see "stationary" as "not spinning." Generally I try to give them more flexibility on language and only tighten up on the meaning of words if I end up with more than one answer choice.

Notice the relationship in the last sentence. If a gas ring is going to maintain an orbit so close around a black hole, then the black hole must be spinning. The correct contrapositive of this relationship is, "if a black hole is not spinning, then a gas ring could not maintain so close an orbit around the black hole." So the issue isn't whether the black hole requires an orbiting ring of gas, as answer choice (E) suggests, but rather that a gas ring requires an orbit of more than 49 kilometers in order to orbit a "stationary" black hole.

Hope that helps!

[ymcho2013]

Could someone please explain the function of the second sentence in this premise?

Also, is E wrong because the stimulus only states that stationary black holes (if you equate not spinning to stationary) must have gas rings that cannot maintain an orbit so close to the black hole? From this statement, you can't really say (like E is saying) that the ring of gas must have a specific radius (aka greater than 49km).

Any help would be appreciated!

[ying_yingjj]

I was not able to get why E is wrong bc it looked like a contrapositive to C.

But I re-read the stimulus several times and got what is wrong with E. As giving back to Manhattan LSAT geeks, sharing my thoughts.

The last sentence "But the gas ring could not maintain an orbit so close to a black hole unless the black hole was spinning."
To rephrase this last sentence generated from the whole stimulus:
the gas ring that flickers at 450 times/second in a stable orbit around the black hole and also emits X rays could not maintain an orbit so close as 49 km to a black hole unless the black hole was spinning.

Contrapositive:

If a black hole is not spinning (I think we can say it is stationary) -----> only if a ring orbit the black hole that flickers at 450 times/second in a stable orbit around the black hole and also emits X rays has to maintain an orbit not so close as 49 km to the black hole

E says: (E) A black hole is stationary only if it is orbited by a ring of gas with a radius of more than 49 kilometers.

You see the difference of the contrapositive and the choice E? Choice E's necessary condition missed "the gas ring that flickers at 450 times/second in a stable orbit around the black hole and also emits X rays ".

When E states "A ring of gas with a radius of more than 49km", it means " ANY ring of gas with a radius of more than 49km", it may be flickering at 450 times/second, it may not flickering at 450 times/second; this ring of gas may be emitting Y ray, not X ray. But the stimulus specifically refers to the gas ring that flickers 450 times per second, and emitting X ray, so E is not exactly the contrapositive of the last sentence of the stimulus.

Yet, C is much logically tighter than E, says "the ring of gas observed by the astronomers is spinning".

"the ring of gas observed by the astronomers " = the gas ring that flickers at 450 times/second in a stable orbit around the black hole and also emits X rays; not " ANY ring of gas with a radius of more than 49km".

It is difficult to catch when English is not our first language. But, hey so what? now you have learned! LSAT is beatable!

[IrisH894]

So I wouldn't use formal notation to map out the conditional relationships on this one because the the information can be picked up on without it. But there is conditional logic employed here.

What does the Question Stem tell us?
Inference (Most Strongly Support)

Break down the Stimulus:
1. There is a ring of gas around a black hole.
2. The gas ring could not be in an orbit so close, unless the black hole was spinning.

Any prephrase?
I guess the black hole is spinning.

Answer choice analysis:
A) is unsupported. We really don't know about those black holes with orbiting rings of gas more than 49 kilometers.

B) is unsupported. There could be other kinds of black holes that also emit x-rays.

C) Looks good.

D) goes way too far. Nothing about causation is implied.

E) is unsupported. There could be stationary black holes that orbited by rings of gas.

The correct answer is C.

Takeaway/Pattern: Inference questions are testing our ability to combine multiple facts together to derive some other true fact. They usually use Conditional, Causal, Comparative, or Quantitative language to combine ideas. This one used a Conditional statement and a fact that triggers the conditional statement.

#officialexplanation

I hate to say this but your initial explanation for E was not only confusing but also wrong.

E is wrong because it overlooks the possibility that black holes could exist without orbiting rings of gas. For example, there could be a stationary black hole in the middle of the universe, and there aren't any rings of gas around it, and that would be perfectly fine. No physics rules violated here.
In other words, E would be correct it said "A black hole orbited by a ring of gas could be stationary only if the radius of the ring of gas is more than 49 km."

E is "unsupported because there could be stationary black holes that orbited by rings of gas"? What the hell?