Astronomy clicker question: entering the event horizon

Get into vortex you say, by ?rico Lopez
icanhascheezburger.com
January 3, 2008

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q10.1

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

[0.3 points.] Why is entering the event horizon (the "Schwarzchild radius") surrounding a black hole considered a "point of no return?"
(A) All matter is crushed into nothingness.
(B) All matter is instantly converted into energy.
(C) The escape velocity is faster than the speed of light.
(D) Time runs backwards.

Correct answer: (C)

If students ask about what's inside the event horizon of a black hole, point out that they could certainly try to enter it and find out for themselves. However, in the very unlikely event that would be able to survive the journey, they would not be able to tell anyone in the outside universe about their discoveries, as nothing, not even light would be able to escape from within the event horizon. So they should bring a friend to share in the experience. Otherwise, it'd be lonely in there...

And yes, the expression on the middle kitten is priceless.

Student responses
Section 4160
(A) : 9 students
(B) : 4 students
(C) : 17 students
(D) : 0 students

Section 5166
(A) : 7 students
(B) : 7 students
(C) : 23 students
(D) : 0 students