[OU.03] A star is moving away from Earth. An astronomer plans to measure the distance of the star from Earth by observing the blue shift in its spectrum. Which of these statements best explains why the astronomer's method of measuring the star distance is inappropriate? The spectral shift of moving stars cannot be observed. Common instruments cannot measure the blue shift accurately. A blue shift can be observed when the star moves towards Earth. Rate of motion of stars cannot be matched with the rate of measuring distances.

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Ronald wants to see if a new shower cleaner works better in removing soap than his old cleaner. he uses the new cleaner on one half of the shower tiles and his old cleaner on the other half. identify the independent and dependent variables in this experiment. enter your answer in the space provided.

Which statements best describe the differences or similarities between a comparative investigation and an experimental investigation? check all that apply. experimental investigations are best for showing cause-and-effect relationships, while comparative investigations do not necessarily show this type of relationship. comparative investigations are often impractical and unrealistic, while experimental investigations are the most practical and realistic kinds of investigations. comparative investigations allow for the use of a wide range of variables but do not have a control group, while experimental investigations involve variables that can be controlled. both experimental investigations and comparative investigations are designed to answer scientific questions. both experimental investigations and comparative investigations focus on making observations rather than collecting new data.