Recently, photons and neutrinos emitted by a distant supernova, an explosion of a star, reached Earth at virtually th...

Angie on November 26, 2014

Can you please explain this answer?

Thank you in advance.

1 Reply

Melody on December 2, 2014

Alright, so what is our conclusion? Einstein's claim: gravity is a property of space itself because a body curves the space around it.

Why? We know that the finding that "photons and neutrinos emitted by a distant supernova, an explosion of a star, reached Earth at virtually the same time supports Einstein's claim."

Again, the last sentence tells us that the simultaneous arrival of the photons and neutrinos is evidence that the space through which they traveled was curved, i.e. their simultaneous arrival was evidence for our conclusion.

Answer choice (B) states: "If gravity is not a property of space itself, then photons and neutrinos emitted simultaneously by a distant event will reach Earth at different times."

So, essentially, we are saying: if the conclusion is not true, then photons and neutrinos did not arrive simultaneously.

(B) not C ==> not PNAS
PNAS ==> C

However, the argument tells us that the recent finding shows that photons and neutrinos reached Earth at virtually the same time. Thus, the contrapositive of (B) lets us properly infer that the conclusion must be true. So, answer choice (B) strengthens the argument.

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