[ 11 ] Earth and Space Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • A ____________ is a system of stars, stellar dust, and dark matter bound together by gravity. The ____________ comprises the sun and all planets and other objects that orbit it (including Earth). Explain why the northern hemisphere experiences warming in the summer. Answer briefly. The length of an Earth day is determined by the time it takes for one A. Earth rotation. B. Earth revolution. C. sun rotation. D. sun revolution.