What evidence do we have that Earth's magnetic field reverses its polarity every 250,000 years?
A. Earth's magnetic field strength and direction change constantly.
B. The direction of the magnetic field is "frozen" into new crust as it cools.
C. historical documents from ancient Egypt and other civilizations
D. Core samples from Antarctica show a regular change in polarity.
E. All of these choices are correct.
Answer: B
You might also like to view...
Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?
A) The 10-pound weight will hit the ground before the 5-pound weight. B) Both will hit the ground at the same time. C) Both weights will float freely, since everything is weightless on the Moon.
Instructions: On occasion, the notation 
will be a shorthand notation for 
.
Given that 
and 
, what is 
?
A.
B.
C.
D.
E.
A 30-year-old woman takes a trip on a rocket, leaving her 20-year-old brother behind. She travels at a speed of 0.8 c, and is gone 20 years, according to the younger brother. When she returns, how many years older/younger is she than her brother?
a. 2 years younger b. 2 years older c. 3 years older d. 10 years older e. 8 years older
Weight and g: An object weighs 432 N on the surface of the earth. The earth has radius R. If the object is raised to a height of 3R above the earth's surface, what is its weight?
A. 108 N B. 48.0 N C. 27.0 N D. 305 N E. 144 N