The synthesized beam is analogous to the point-spread function in a kind of these devices (-5[1])that measure visibility in u-v space, which is Fourier transformed to generate an image. Test masses suspended from four pendulums reduce seismic noise in one of these devices (10[1])consisting (10[1]-5[1])of two four kilometer-long (10[5]-5[2])étalons (10[20]-5[4])(“ay-tuh-LON”). Some (10[3]-5[1])of (10[2])these (10[1])devices (10[6])use (10[2])aperture synthesis (10[2]-5[1])to achieve a resolution (10[2]-5[1])on (-5[2])the order of wavelength (10[1]-5[1])divided (-5[1])by baseline, (10[1])which (-5[1])the EHT (-5[1])used (10[2]-5[2])to take the first image (-5[3])of (-5[1])a black (-5[1])hole. (10[3]-5[8])Two of these (-5[1])devices in Louisiana (10[1])and Washington (-5[2])detected (10[1])a (10[1])2017 (10[2]-5[2])neutron (-5[1])star (-5[1])merger, (10[2]-5[2])which (10[1]-5[1])was the first (10[1])gravitational wave signal. (10[1]-5[2])The LIGO (10[1]-5[1])observatory (10[2])uses (10[1])Michelson’s (10[1])design (10[1])for these (10[1])devices. (10[5]-5[1])For 10 points, what devices measure the phenomenon (-5[1])that occurs when two waves are (10[1])superimposed? (10[1]0[1])■END■ (10[20]0[21])