The vicinity of a black hole displays the splendor of the entire universe. Near the so-called “photon sphere”, light can be trapped by gravity on a circular orbit around the black hole, just as the Earth moves around the Sun. For the four-million solar mass black hole at the center of the Milky Way, Sagittarius A*, the radius of the photon sphere is ten times smaller than the Earth-Sun separation. Near the photon sphere, light rays from all directions are gravitationally curved, allowing a properly-positioned observer to look through a telescope in one direction and see the entire Universe.
In analogy, every person is a display of the entire world. The black hole metaphor gives a new meaning to the insight from the Mishnah: “Saving one person’s life is like saving an entire world.”
But the analogy continues further. In their youth, supermassive black holes are often enshrouded in an opaque cloud of dust that blocks external light from reaching them. As a result, the early display of light at their photon sphere has nothing to do with the Universe at large. It only reflects their immediate environment.
Similarly, early in our life we display the limited world of our immediate family and educators. As we grow up, we have the opportunity to clear up the fog, think independently and open our mind to all colors of the rainbow with fairness and balance. However, social media bubbles bring back the opaque clouds of prejudice and unsubstantiated belief to our sky and obscure the view of what we are missing. It is our personal responsibility to avoid groupthink and find the missing light.
Seeking scientific evidence is the method by which we can recover missing light in our worldview. After my recent interview with Zac Bayly for the fashion magazine Numéro, he resonated with my comments about the distinction between scientific evidence and unsubstantiated beliefs, and said: “I would love to believe that the Loch Ness monster exists (because that would be really fascinating and exciting!), but I have no interest in it when there is no clear evidence for it. However, if there was evidence that a large creature of some type was swimming around in there (there doesn’t seem to be, of course), I wouldn’t close my eyes and sing a song really loud with my fingers in my ears rather than listen to the evidence, for fear of seeming silly. (I’m also in fashion, rather than science, so perhaps I’m especially immune to the fear of seeming frivolous.)” I replied that being immune to the fear of seeming frivolous is a prerequisite for making new discoveries.
A day later, I had the h3 podcast on YouTube with Ethan Klein, which received 300,000 views within a day. Ethan asked: “Many scientists are skeptical of the extraterrestrial technological interpretation of `Oumuamua. What do you say about that?” I replied: “In science we do not have the luxury of ignoring evidence. This is the realm of politics.” Ethan immediately jumped in: “… So are you saying that other scientists ignore the evidence?”. I clarified: “No, I am not saying that at all. Scientists are not allowed to ignore evidence. Mainstream experts on space rocks wrote scientific papers to explain the anomalous properties of `Oumuamua. These explanations suggested that `Oumuamua was a natural object of a type that we had never seen before, like a hydrogen iceberg or a nitrogen iceberg or a fluffy dust cloud which is a hundred times more rarefied than air. These interpretations face major challenges regarding the survival of such objects in interstellar space or near the Sun, as well as the global mass budget that is required to account for them. Three years later, the same telescope in Hawaii discovered another object, 2020 SO, which exhibited a push away from the Sun by reflecting sunlight without a cometary tail, just like `Oumuamua. It was later identified as a known rocket booster made of stainless steel from a 1966 launch by NASA. Clearly, 2020 SO was artificial. Was `Oumuamua manufactured by a NASA-like agency on another planet?”
The richness of our view of the Universe depends on our willingness to stay open minded and seek “missing light”. Just like in the “missing light” case of dark matter and dark energy, perhaps there are artificial probes from interstellar space that we did not anticipate. Using intriguing evidence to motivate gathering of new data is a prerequisite for expanding our “photon sphere” to display the full splendor of the Universe. Aside from its poetic beauty, this practice also has practical consequences. It is key for the long-term survival of humanity.
In this context, Ethan added: “NASA recently launched the DART spacecraft that successfully deflected the asteroid Dimorphous by crashing into it. Are there other methods to deflect asteroids away from a collision course with Earth?” I replied: “If we discover a dangerous Earth-crossing asteroid early enough along its path towards us, we only need to give it a small kick. A gentle nudge at a large distance would translate to a large miss as it comes closer to Earth. Aside from the Bruce Willis approach in the film Armageddon, this task can be accomplished by shining a laser on the asteroid and ablating some of it, thus creating the rocket effect of an artificially-induced cometary tail. Or we can paint one side of the asteroid so that it absorbs or reflects sunlight differently, and the Solar radiation pressure would do the job for us. We must keep in mind that 66 million years ago, the dinosaurs were killed by a meteor. They were very proud of their physical dominance but lacked the human brain. The lesson from history is simple: “Never bully the frivolous nerds in your class. They may be the mavericks who notice the missing light and save humanity!”
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, is scheduled for publication in June 2023.