The first three strong radio sources, discovered by Reber in the 1930s and 1940s, included all of these EXCEPT Group of answer choices supernova remnant. distant galaxy. globular cluster. galactic nucleus

What would the difference of spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 cm on earth, be observed at 21.1 centimeters?

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

The diagram shows a series of volcanic island and a hot spot determine the direction of movement of the tectonic plate that for the island