Earth science with all questions

1. we start with 400 atoms of uranium-238. how many remain after 4.5 billion years?
after 9 billion years
after 13.5 billion years

Aspectroscope breaks light up into its colors, allowing scientists to analyze light from the solar system and universe. by studying the spectral line patterns, widths, strengths and positions, scientists can determine the speed, position, and of celestial bodies. a) age b) origin c) rotation d) temperature