A Meteorite That Recently Fell to Earth Was Found to Contain

question 108

Multiple Choice

A meteorite that recently fell to Earth was found to contain evidence of the existence earlier in its history of a short-lived radioactive isotope of aluminum, ²⁶Al, which can be produced only under extremely energetic conditions and in nuclear reactions. What conclusion can be drawn from this observation?

• A) An energetic nuclear event, a supernova, occurred near the formation site of the Sun, and it produced the ²⁶Al at about the time the meteorite was formed.
• B) The meteorite became so hot on its descent through Earth's atmosphere that it became radioactive, and the ²⁶Al was formed at that time.
• C) The meteorite had probably passed through radioactive clouds in space and collected the ²⁶Al before hitting Earth.
• D) Radioactivity occurs spontaneously in normal matter, so this finding is not surprising.

---

Definitions:

Escape Responding

A behavior modification strategy where the subject learns to avoid or escape an unpleasant stimulus.

Classical Conditioning

A process whereby education happens through the pairing of a naturally occurring stimulus with one that is environmental.

Positive Reinforcement

A process in behavior analysis in which a desirable stimulus is presented after a behavior, increasing the likelihood of the behavior being repeated.

Fixed-Interval

A type of reinforcement schedule in operant conditioning where the first response is rewarded only after a specified amount of time has elapsed.