Black holes are the jealous secrets of the universe. We all want to know what's going on in such exclusive space clubs, but the best we can do is stand outside and hear the beat.
Scientists organize their own parties. Sure, that's not as fun as twisted space time pits, but they're as close as if we were getting a VIP treatment on the dance floor of a black hole. UK does not contain real black holes. What It Has is a rippling water tank colored with green dye and a hole to send it down.
Physicists from the laboratory and the Universidade Federal do ABC in Brazil recently used this arrangement to identify the wave pattern in the water orbiting a drain that could help us understand the dulcet tones of a screaming newborn hole.
When black holes are put together to form larger black holes, the entire universe hears it: Space buzzes with a tone called a quasi-normal mode, indicating some of the characteristics of the new black hole, such as mass and angular momentum.
These modes have become ubiquitous in physics, with continued advances in gravitational wave astronomy, and physicists want to pick out as much detail as possible of the way space is shaking after these cosmic crashes.
To extract information from a quasi-normal mode, you need to know a few things about how the energy in a field dissolves and how certain features in the wave patterns change or persist over time.
One property that may affect the properties of a wave is vorticity ̵
In most simple models that describe the vibrations of a black hole, it is assumed that the space is little more than a calm background, due to the waves waves, which means that the vorticity is not considered normal.
This can not make much of a difference. Or it could be significant. It's not that we can take a closer look at these space-time swirls.
However, we can examine quasi-normal modes in other media and look for signs of interference.
Water is not necessarily the perfect metaphor for spacetime Safe, but the fundamentals work well. The analogy is even based on the theoretical work of the Canadian physicist William "Bill" Unruh almost 40 years ago, who have proven that the hydrodynamic equations accurately describe gravity by sufficiently large masses.
Downstream, waves on a surface tend to move faster than the current, allowing them to curl in almost any direction. However, when water flows in the direction of a black hole, it picks up speed and takes its wave pattern with it.
"The liquid velocity is much higher than the wave velocity, so the waves are pulled down by the water flow itself as they spread in the opposite direction," said physicist Maurício Richartz to José Tadeu Arantes of Agência FAPESP.
When measuring the oscillations, patterns appeared that stuck to the edge of the vortex for a long time B. its size and angle.
"Our main finding was that some oscillations faded away very slowly, or in other words were long active and spatially near the drain," Richartz told Agência FAPESP
"These vibrations were no longer quasi-normal modes, but rather another pattern called quasi-bound states. "
The researchers hope to purposely generate more of this long-lived "quasi-bound" energy status. It has been more than a century since Einstein's field equations have led to strange objects called singularities: strange distortions of space from which the monsters are born Gravity we call black holes.
Despite decades of research, we are not much closer to understanding the physics of black holes.
Luckily, black holes are not as quiet as they are dark. We just have to learn how to play their music.
This research was published in Physical Review Letters .