Astronomers watched in real time as the supermassive black hole at the center of a galaxy went from dim and quiet to bright and actively feeding on material, Adam Mann reported in “For the first time, scientists witness a black hole turning on” (SN: 7/13/24 & 7/27/24, p. 7).
“The seeming paradox arises because of the extreme time dilation near the event horizon,” says theoretical physicist Eduardo Martín-Martínez of the University of Waterloo in Canada. From the perspective of a distant observer, time seems to progress more slowly near the black hole’s edge. So infalling matter appears frozen in time, never crossing the event horizon, Martín-Martínez says. Light emitted by that matter becomes increasingly stretched to longer wavelengths, or redshifted, and eventually becomes invisible.
“However, from the point of view of the infalling material itself, time is experienced normally,” Martín-Martínez says. The matter crosses the event horizon after a finite amount of time and moves toward the black hole’s center, called the singularity. “If the distant observer were to approach the horizon themselves, once they are close enough, they would see matter cross the horizon at a finite time, and they themselves would cross the horizon at a finite proper time,” Martín-Martínez says.
If elite athletes are to ever reach humans’ projected maximum speed in running or swimming, they will need perfect technique, Erin Garcia de Jesús reported in “What’s the human speed limit?” (SN: 7/13/24 & 7/27/24, p. 36).
2024-09-07 06:00:00
Source from www.sciencenews.org
