Over the past two days, I hosted a conference at Harvard, “To Our Cosmic Horizon and Beyond,” which celebrated 20 years of the Institute for Theory & Computation (ITC) for which I serve as director. It was a great privilege to listen to the brilliant insights on all frontiers of astrophysics from our former postdoctoral fellows as they blossomed into leadership positions at major universities worldwide. In my opening remarks, I welcomed the attendees and noted that the group splits into two parts: those who did not change much over the years and those who aged significantly.
During the banquet, the senior ITC member, Eric Keto, confessed on how much he appreciates the open culture of the ITC which cultivates innovation. I explained that this is no coincidence. When I started my career in astrophysics, I did not know how the Sun shines. The opportunity given to me at the Institute for Advanced Study in Princeton involves a gamble taken by John Bahcall. He paid it forward and I later replicated his generosity to those around me. The ITC is the opposite to an exclusive club. Through the past four decades of my scientific career, I had collaborated with fifty students and hundreds of postdocs and realized that those who make discoveries are not necessarily the ones who look good on paper or leave a good first impression, but rather those who are driven by genuine curiosity and are motivated to learn and contribute. The best way to foster a successful intellectual culture is to welcome everyone and let the fittest survive.
This narrative was repeated at the ITC luncheon forum on the first conference day, which featured four presenters. The last among them, my current postdoc, Juliana Cherston, initiated a wide-ranging discussion on how to cultivate innovation in science. At the end of it, I asked Juliana an open-ended question: “If you had all the money in the world, what would you do?”
At lunch the following day, I gave a speech titled “Anatomy of Paradigm Shifts,” where I discussed paradigm shifts like finding life-as-we-do-not-know-it by fishing in the oceans of methane and ethane on Titan, or discovering interstellar space trash of technological origin. I gave an example of how new ideas bubble up in my head using the example of my latest paper, written a day before the conference. It started with an essay in which I discussed continental drift. This led me to wonder whether the motion of continents by a few centimeters per year could induce systemic effects in pulsar timing arrays which include radio telescopes spread over different continents. This effect appeared to be too small, but it led me to wonder whether pulsar timing arrays can detect interstellar objects from the jitter they induce as they pass through the solar system. This effect again was too small. At that point, I realized that the dark matter carries a larger mass density and wondered if a population of primordial black holes in the asteroid mass range can be constrained by pulsar timing arrays. The numbers were closer but did not work out. To my surprise, I realized that the Main Asteroid Belt in the Solar system can produce a detectable effect. It was 2AM, just a day before the conference started. I realized that if I want to know the answer, I better lose some sleep and start working out the content of a new paper. A few hours later, I completed a 5-page long paper and submitted it for publication in The Astrophysical Journal Letters, along with an essay summarizing my findings. The abstract of my paper was short: “ Recently, Pulsar Timing Arrays (PTAs) reported a signal at nanohertz frequencies consistent with a stochastic gravitational wave background. Here, I show that the Brownian motion of the Sun as a result of its random gravitational interactions with the cluster of thousands of unmodeled Main-belt asteroids of radii ≲ 20 km, not included in the Solar system ephemeris, introduces correlated timing noise for pulsars with the magnitude and frequencies of the reported signal.”
On the morning of the first day of the conference, I received an email from Neil deGrasse Tyson, who read my paper and noted:
“Avi,
A fast and fun paper that is.
Pleased to see you are still capable of a prosaic explanation in place of an extraordinary one instead of an extraordinary explanation in place of a prosaic one.
“Alternatively, a more exotic scenario is that ‘Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.”
p.s. Just attended a talk on solar acoustic oscillations. The frequency spectrum is rich and complicated, leaving me to wonder whether that could be a significant source of noise in your calculations.
-Neil”
to which I replied:
“Indeed. I enjoy the challenge of going against the wind. It is fun. You should try it sometime.
The solar oscillations have a characteristic frequency of order 5 minutes to hours. Their effect would be washed out when averaged over a period of years to which the PTA signal relates.”
At the end of the conference, I compared the ITC community to a family whose children are always welcome back home and said that we are all rooting for the insightful discoveries of our family members.
That evening, I had been approached by many conference participants who personally thanked me. This included late night messages like the one from Professor Mark Vogelsberger at MIT:
“Dear Avi,
I would like to thank you for a wonderful conference.
Also, I would like to thank you for your support during my time at ITC and beyond. Our work on Strongly Interacting Dark Matter has ignited my interest in alternative dark matter and our paper became one of my highest cited works.
Thanks again!
Mark”
to which I replied:
“Dear Mark,
Thank you so much for your kind words. It is my great privilege to have worked with brilliant young scientists like yourself.
Avi”
or another message from Professor Konstantin Batygin at Caltech, who sat at dinner next to my daughter, Lotem Loeb, who finished her first-year at Harvard College not camping in a tent at Harvard Yard:
“Avi — as you could probably tell, I largely lost my voice towards the end of the evening. So I couldn’t fully express in words the deep gratitude I feel for what you have done — not only for me, but for an entire generation+ of people that came through the ITC. I always look back on my time at ITC with profound fondness and gratefulness. And I genuinely appreciate your willingness to strike a contrarian tone in face of an ever-more-inertial academic landscape.
The speech you gave today was moving. Finally, I was impressed with the intellectual maturity and level-headedness of your daughter. It’s easy to get disillusioned with everything that’s happening, but people like her go a way to restore optimism and faith in the next generation.
Thank you for organizing this reunion/conference. I very much look forward to the next time our trajectories intersect in 4D.
Best,
K”
In his conference talk, Konstantin discussed how he copes with nasty criticism about his work on the existence of a new “Planet 9” in the Solar system, by showing a YouTube video titled: “Don’t try it yourself! “Iron Crotch Kong-Fu” master shows skills.” Incidentally, his rock band album titled: “Starlight” just appeared. In reply, I wrote to Konstantin:
“Maintain your exceptional creative work in both the arts and sciences. I am one of your followers on both. Keep rocking the boat, especially when it goes in the wrong direction.”
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 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”, was published in August 2023.
