The Surface of Last Screaming
"Consider an infinite field full of people screaming. The circles are their heads. You are screaming too. (Your head is the black dot.) Now suppose everyone stops screaming at the same time. What will you hear? Sound travels at 330 m/s. One second after everyone stops screaming you will be able to hear the screams from a `surface of last screaming' 330 meters away from you in all directions. After 3 seconds the faint screaming will be coming from 1 km away...etc. No matter how long you wait, faint screaming will always be coming from the surface of last screaming - a surface that is receding from you at the speed of sound (`vsound'). The same can be said of any observer - each is the center of a surface of last screaming. In particular, observers on your surface of last screaming are currently hearing you scream since you are on their surface of last screaming. The screams from the people closer to you than the surface of last screaming have passed you by - you hear nothing from them (gray heads). When we observe the CMB [Cosmic Microwave Background] in every direction we are seeing photons from the surface of last scattering. We are seeing back to a time soon after the big bang when the entire universe was opaque (screaming)."
Dying Star Screams As It Falls Into Black Hole
"As a doomed star spirals closer and closer to a black hole that's about to gobble it up, it lets out periodic bursts of light that scientists liken to dying screams, scientists say.
The star is falling into a gigantic black hole in the center of a distant galaxy that lies 3.9 billion light-years away in the direction of the constellation Draco. As the remains of the star get pulled in, it releases blips of light about every 200 seconds, with occasional lags.
"You can think of it as hearing the star scream as it gets devoured, if you like," Jon Miller, a University of Michigan astronomer, said in a statement. Miller was part of a team that detected the light blips using two orbiting X-ray telescopes: NASA and Japan's Suzaku, and Europe's XMM-Newton..... "In order for the black hole to feed from a star that its gravity has broken apart, the remains of the star must form an accretion disk surrounding the black hole," said the study's leader, University of Michigan astronomer Rubens Reis. "The disk gets heated up and we can see emissions from the disk very close to the black hole in X-rays. As this matter is falling in, it gives a quasiperiodic wobble and that's the signal we detected.
Though the dying star's signal comes to us in the form of light, the researchers liken it to sound because it comes at a characteristic frequency that, if converted to sound, would make an ultra-low D-sharp.
Never before have such screams been heard from a star falling prey to a black hole so distant, or one that had been thought to be dormant, like this one."
