SAT Subject Physics Practice Question 152: Answer and Explanation

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Question: 152

15. Redshift of distant galaxies is evidence for which of the following?

A. Expansion of the universe
B. The Uncertainty Principle
C. Black holes
D. Dark matter
E. Superconductivity

Correct Answer: A


Redshift occurs when light sources move away from the observer. If all the galaxies in the universe are moving away from us, that’s evidence that the universe is expanding. The Uncertainty Principle is a quantum mechanical phenomenon having to do with subatomic particles, not galaxies. The evidence that black holes exist is their gravitational effects on visible objects near them, not redshift. Dark matter has to do with anomalous rotation curves in galaxies, not redshift (though redshift—specifically, increasing redshift—is evidence for dark energy). Superconductivity has to do with conducting electricity, not galaxies.

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