In this video adapted from NOVA scienceNOW, investigate the hypothetical scenario of a person falling into a hole through the center of Earth. Astrophysicist Neil deGrasse Tyson illustrates the thought experiment; first he defines the conditions—ignore the effects of air resistance, temperature, and Earth's rotation—and then he travels through the hole. A timer and speedometer show how his speed changes as he falls toward the center of Earth, passes the center, and slows to a stop at the opposite end of the hole.
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