Which of the following describes our current solar system model? planets revolve around a star, and moons revolve around planets. planets and moons all revolve directly around a star. planets, stars, and moons wander aimlessly in the universe. planets revolve around a star and moons wander throughout the solar system.

What was dr. willem johan kolff’s first step in using the scientific process to invent the hemodialysis machine? he built the machine and tried it with various patients, collecting data about its effectiveness. when a patient’s kidneys failed, he wondered if it would be possible to perform kidney functions with an external machine. he researched and collected data about numerous patients who exhibited symptoms of kidney failure. he drew conclusions from studies of various symptoms of kidney failure, and drew a design for the ideal external blood-processing machine.