Tomas Andrade at the Astronomical Society of Terrassa: «El sueño va sobre el tiempo: Agujeros negros y ondas gravitacionales»

ICCUB’s researcher Tomas Andrade delivered a talk named «El sueño va sobre el tiempo: Agujeros negros y ondas gravitacionales» to the Astronomical Society of Terrassa last Saturday, June 5. The conference was set in the context of the XIV Relativity Days of Terrassa 2021 and it also counted with the participation of other speakers such as Andreu Font Ribera (IFAE) and Pilar Gil Pons (UPC). In the presentation, Andrade initially discussed  black hole collisions and the gravitation waves resulting from them and then invited the audience to imagine what it would be like to have such a collision in a 6-dimensional universe and the differences we would observe with respect to what we detect in our 3+1 dimensional universe. 

In recent years, we were able to detect gravitational waves generated in black hole collisions thanks to the LIGO/VIRGO experiments. As the researcher explains, these are extremely energetic events (they emit 50 times more energy than that electromagnetically radiated by the entire known Universe) although if we could see it with our own eyes it would be completely dark, since all this energy is emitted as gravitational waves. The collision itself lasts less than a second and the amplitudes of the emitted waves are of the order of magnitude of  m. To wrap our heads around how little that is, imagine the nearest star to the sun, Proxima Centauri, moving away a distance equivalent to a single hair! These are very particular waves since the thing they vibrate is the fabric of spacetime itself as if it were the surface of a percussion instrument. In an analogy of sound waves, you could get an idea of the sound emitted by the collision in the following clip:

As Andrade tells us, this corresponds to a merger in our 4 dimensional universe (with 3 spatial dimensional and a temporal one). In recent years many theories have arisen with the goal of unifying quantum mechanics (the physics of small things) and General Relativity (the physics of large scale structure). Among these theories, the most popular one is String Theory. This theory could explain a lot of the phenomenology that the current paradigm cannot account for but it contains a small caveat: it assumes the existence of extra dimensions that we do not observe in the universe. This has partly motivated a new line of research to describe gravitational waves in more than 4 dimensions and led Dr. Andrade to pose the question of how a black-hole collision would look in 6 or 7 dimensions. To seek an answer, he ran a simulation at the Marenostrum supercomputer in Barcelona. The result of endless computing hours is depicted in the following simulation:

In this clip, we can notice that the system stretches out into a thinning thread that eventually breaks into back droplets, instead of relaxing into a single merged black hole as happens in the event detected by LIGO. 

As you can see in the talk, Andrade offers us a lot of fascinating insights on gravity that left the audience in awe. If your curiosity was also piqued, you can visualize the whole conference in this link.