L3：
讲座
1. What is the lecture mainly about
The effect of Earth’s magnetic field on rock samples from the Moon
Evidence of how some rocks on the Moon became magnetized
Competing theories about the origin of the Moon
The differences between two recently analyzed Moon rocks
2. According to the dynamo theory, what two processes contribute to the creation of Earth’s magnetic field
An intense magnetic event at the time Earth formed
The impact of meteorites on Earth’s surface
Circulating molten iron in Earth’s core
The Earth’s rotation
3. Why does the professor mention the Moon’s size
To explain how scientists determined the composition of the Moon
To explain how scientists determined when the Moon was formed
To explain why scientists believed the Moon could never have had a molten core
To explain why scientists believed the Moon and Earth’s core were formed through similar processes
4. Why does the professor discuss meteorites and asteroids
To explain how some scientists thought lunar rocks became magnetized
To provide details of how the Moon was formed
To explain unusual geologic formations on some parts of the Moon
To explain how the Moon could have generated a dynamo
5. What did scientists learn about the trocto
It is the youngest Moon rock collected to date.
It had been in a magnetic environment for millions of years.
It was probably not formed through the solidification of molten iron.
It was most likely magnetized by an impact with a large object.
6. What is the professor’s opinion of the lunar dynamo theory
A. He believes it should be accepted by all scientists.
He is concerned that it does not explain irregularities in some Moon rocks.
He thinks it contradicts a widely accepted hypothesis regarding the Moon’s origin.
He believes there is enough evidence to justify further research.
