Passage 1 – Determining the Ages of the Planets and the Universe

1. According to paragraphs 1 and 2, what evidence leads astronomers to believe that all the planets formed at approximately the same time?

  • Samples of rocks from all the planets are the same age.`
  • All the planets orbit the Sun in the same direction and in about the same plane.
  • All planets have the same igneous and metamorphic processes.
  • The gravitational field of each planet is about the same strength.

2. The word ”inevitable” in the passage is closet in meaning to

  • continuous
  • obvious
  • certain
  • easy

3. Which of the following is NOT mentioned in paragraph 2 as a cause of constant change to Earth’s crust?

  • Water
  • Igneous processes
  • Metamorphic processes
  • Meteorites

Paragraph 1

The planets of our solar system all revolve around the Sun in the same direction and in orbits that lie in nearly the same plane. This is strong evidence that the planets formed simultaneously from a single disk of material that rotated in the same direction as the modern planets.

Paragraph 2

Precisely when the planets came into being has been a difficult issue to resolve. While Earth’s water is necessary for life, its abundance near the planet’s surface makes rapid erosion inevitable. Continuous alteration of the crust by erosion and also by igneous (volcanic) and metamorphic (pressure and heat within Earth) processes makes unlikely any discovery of rocks nearly as old as Earth. Thus geologists have had to look beyond this planet in their efforts to date Earth’s origin. Fortunately, we do have samples of rock that appear to represent the primitive material of the solar system. These samples are meteorites, which originate as extraterrestrial objects, called meteors, that have been captured in Earth’s gravitational field and have then crashed into our planet.


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