Much of the mass in galaxies and clusters of galaxies is dark matter. Which of these techniques is NOT useful for detecting evidence of this dark matter?
A) measuring the speed of stars in their orbits around a galactic center
B) gravitational lensing of very distant galaxies by a nearby galaxy (or cluster) and its accompanying dark matter
C) observing the aftermath of a collision such as that in galaxy cluster 1E0657-56
D) gravitational waves

Question

Quizplus · Accepted Answer

Gravitational waves are ripples in spacetime caused by some of the most violent and energetic processes in the universe, such as colliding black holes. They are not directly used to detect dark matter. The other options (A, B, C) involve observing the effects of gravity and are methods used to infer the presence of dark matter by its gravitational influence on visible matter or light.

Much of the Mass in Galaxies and Clusters of Galaxies