<span>noun1.an act or instance of nullifying.2.the state of being nullified.3.(often initial capital letter) the failure or refusal of a U.S. state to aid in enforcement of federal laws within its limits, especially on Constitutional grounds.</span>
Answer:Astronomers estimate the age of the universe in two ways: 1) by looking for the oldest stars; and 2) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang; just as crime detectives can trace the origin of a bullet from the holes in a wall.
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