L'Italo-Americano

L'Italo-Americano THURSDAY, MAY 2, 2019 www.italoamericano.org 6 NEWS & FEATURES TOP STORIES PEOPLE EVENTS Continued from page 4 finally succeeded. It's incredible. An enormous effort. I can say that the image of the black hole at the center of the M87 Galaxy is, simultane- ously, a great success of scien- tific research and an exciting representation of something we could only imagine until now. The success of research lies in a new proof of Einstein's Theory of Relativity, but above all it is a f u r t h e r c o n f i r m a t i o n o f t h e impact international collabora- tion and large infrastructures can have on the future of human knowledge. What was the role of Italian scientists in this project? Luciano Rezzolla (University of Frankfurt), one of the 3 PIs of BHC, and I, have been involved since 2014. Another researcher, Mariafelicia de Laurentis, full professor at the University of Naples and affiliated with Infn, joined the Frankfurt group as an expert on gravitation theories in 2016. In 2018, we introduced to BlackHoleCam two researchers from the Italian ALMA Region- al Center node (INAF - IRA in Bologna), Elisabetta Liuzzo and Kazi Rygl, who became mem- bers of the EHT Consortium through their affiliation with BHC. Then we should also include V i o l e t t e I m p e l l i z z e r i , w h o w o r k s i n C h i l e f o r A t a c a m a L a r g e M i l l i m e t e r A r r a y (ALMA), the largest terrestrial radio telescope, who contributed decisively to the collection of d a t a n e c e s s a r y t o o b t a i n t h e image of the supermassive black hole at the center of M87. As an astronomer and as responsible for the calibration of ALMA as a VLBI station, I carried out all the observing campaigns in the Atacama desert in Chile. With Violette, we spent many nights w a t c h i n g M 8 7 w i t h A L M A . Although not a full member, Violette is a co-signer of the article published in the Astro- physical Journal, which reported the image. From now on we can talk about a new era of research. What does this exactly mean? The certainty of being part of an epochal change, a passage between "before" and "after" is extremely exciting. We can real- ly say that, from today, physics are no longer the same. What u n t i l y e s t e r d a y w a s o n l y a n immaterial mathematical con- cept, a mathematical solution to a t h e o r y , h a s n o w b e c o m e a physical object, observable and m e a s u r a b l e b y s c i e n t i f i c method. A sort of laboratory where we can carry out experi- ments about gravity, to which we didn't have access before. This is what black holes are now. Our hope was, if we had ever succeeded in creating the first image of a black hole, that this photo could end up in textbooks. I hope this will really happen. History books will be divided between the times before and after this image was taken. The photo proved human theories — human imagina- tion — right… This experiment —its result — could be the beginning of a new era. For the first time we see the event horizon and we can study general relativity on a scale and regime unimaginable before. And the most surprising aspect is that everything we see is perfectly in agreement with the prediction provided by the Theory of Relativity. Einstein a l s o p a s s e d t h i s t e s t w i t h tremendous success! Incredible and excellent, Einstein, who ini- tially did not believe in the con- cept of black holes and had to struggle a bit with the idea of the event horizon. Today, after a hundred years, we showed it is a reality of the universe. This w o u l d h a v e b e e n a b s o l u t e l y incredible to him. Another great scholar of black holes, Stephen Hawking, died too early to see this result, but he would have had the same emotional reaction we had in finally seeing the ulti- mate limit of space and time. This is really the golden decade to study black holes. What's inside a black hole? W e d o n ' t k n o w , s i n c e w e can't access it. Perhaps there is matter that cannot be compacted, or perhaps matter has already been entirely concentrated into one sole enti- ty, just as it happened for the Big Bang (exciting no?),and has been "converted" into a curva- t u r e o f s p a c e - t i m e . . . w h o knows! S p e c u l a t i n g i s f r e e , s i n c e nobody can come back and tell us what's in it ! What about Einstein: was his theory correct or did your observations brought some corrections to it? The short answer is: yes, Ein- stein was right, at least for now. Overall, the observed image is consistent with the expecta- tions for the shadow of a rotat- ing black hole with a spin differ- ent from zero —also known as Kerr black hole — as foreseen by the Theory of Relativity. H o w e v e r , I c a n s a y t h a t t h e observations made are not con- sistent with many of the alterna- tives to Kerr black holes pro- posed by previous models. I t ' s s t i l l s c i e n c e f i c t i o n today, but could it be possible to open, sooner or later, a door in time? And is the fantasy-sci- e n t i f i c i d e a o f u s i n g b l a c k holes as "hyperspace slings" in any way theoretically possi- ble? For the moment, space travel is only possible within the Solar System. But it is also true that some mathematical solutions to E i n s t e i n ' s e q u a t i o n s ( a n d t o other theories of gravity) seem to suggest the possibility of trav- eling between any two points in space and time. This is a direct consequence of the space-time curve around an intense gravita- tional field, as predicted by Ein- stein's relativity. The most representative case is that of the so-called Worm- hole, which could be described a s a t u n n e l , a " s h o r t c u t " i n space-time. In addition to the three spatial dimensions, Ein- stein's equations include time as the fourth dimension: it follows that the presence of a black hole a l s o c u r v e s t i m e , a n d t h u s allows time travel. These, how- ever, are hypothetical considera- tions. I mean, here we go into s c i e n c e f i c t i o n . I n f a c t , t h e Wormhole is the preferred way for a writer or a science fiction director to explain space travel. Think of the 2014 Hollywood movie Interstellar, with Matthew McConaughey playing a NASA astronaut who has the task of exploring 3 planets in another galaxy with the hope that one can host humanity. And how does it get there? Through a Wormhole that allows you to cut through the 26.000 years you'd need to get there ... in short, McConaughey would have died a long time before arriving! What is your next research project? I will certainly continue to work on this project: we are only at the beginning. We have yet to fully study another black hole, the one at the center of the Milky Way, Sagittarius A*; the magnetic fields originated by polarized light from M87 and Sgr A *; to compare images from different eras. One of the next steps of the EHT project will be to move from a static image to a movie. S t a r t i n g f r o m 2 0 2 0 , w e w o u l d l i k e t o a d d n e w t e l e - scopes to the network, particu- l a r l y i n A r i z o n a , F r a n c e , Argentina and maybe Africa. Since the Earth has already been u s ed to its f u ll cap acity , w e would like to go into space and use the VLBI technique with satellites, which would allow us to go beyond the earth's dimen- sions as the diameter of our vir- tual telescope. Going into space would allow to observe shorter wavelengths or longer frequen- cies and have even higher reso- lutions. In short, in the next decade we will still be very busy with BlackHoleCam, with the aim of improving our measurements and testing even more precisely the general theory of Einstein's relativity. Ciriaco Goddi in his office © Ciriaco Goddi

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