Excited atoms give back the very light they absorbed, yet dark absorption lines still survive. Why?

1. A cool gas in front of a hot source absorbs photons at its own wavelengths. 2. Those atoms do not hold the energy long, and re-emit it within a very short time. 3. But the re-emission goes out in every direction, not back along the original beam. 4. Only a small fraction of it heads toward the observer. 5. So the beam you receive is still missing most of that light, and the lines stay dark. 6. In a star, much of the re-emitted light heads back into the star and never reaches us. 7. The energy is not kept for good, and it is not turned into heat, so those two options fail on the physics. _Source: OpenStax Astronomy (CC BY 4.0), Ch 4 "Earth, Moon, and Sky" and Ch 5 "Radiation and Spectra", section 5.5 Formation of Spectral Lines_