In 1948-49, mathematician, physicist, computer scientist, and engineer John von Neumann introduced the world to his idea of “Universal Assemblers,” a species of self-replicating robots. Von Neumann’s ideas and notes were later compiled in a book titled “Theory of self-reproducing automata,” published in 1966 (after his death). In time, this theory would have implications for the Search for Extraterrestrial Intelligence (SETI), with theorists stating that advanced intelligence must have deployed such probes already.

The reasons and technical challenges of taking the self-replicating probe route are explored in a recent paper by Gregory L. Matloff, an associate professor at the New York City College of Technology (NYCCT). In addition to exploring why an advanced species would opt to explore the galaxy using Von Neumann probes (which could include us someday), he explored possible methods for interstellar travel, strategies for exploration, and where these probes might be found.

His paper, “Von Neumann probes: rational propulsion interstellar transfer timing,” was recently published in the International Journal of Astrobiology, a Cambridge University publication. In addition to being an Adjunct and Emeritus professor of physics at NYCCT, Matloff is a Fellow of the British interplanetary Society (BIS), a Member of the International Academy of Astronautics (IAA), and has been a consultant for the NASA Marshall Space Flight Center.

His pioneering research in solar-sail technology has been utilized by NASA to develop concepts for interstellar probes and diverting potentially-hazardous objects (PHOs) – in other words, asteroids. His writings have helped establish interstellar-propulsion studies as a sub-division of applied physics in academia. He also co-authored books with fellow luminaries like MIT science-writer Dr. Eugene Mallove, noted physicist, author, and NASA technologist Les Johnson, and Italian researcher Dr. Giovanni Vulpetti.

In April 2016, Matloff was appointed an advisor to Yuri Milner’s Breakthrough Starshot alongside fellow astrophysicists like Prof. Abraham Loeb (Harvard Smithsonian Center for Astrophysics) and Dr. Philip Lubin – leader of the Experimental Cosmology Group at UC Santa Barbara. In January 2017, he presented a Frontiers Lecture on interstellar travel at the American Museum of Natural History in Manhattan, where he is also a Hayden Associate.

nybody Out There?

It is essential to address questions about Von Neumann probes, considering their implications for SETI and the Fermi Paradox. For decades, theoretical physicists and researchers have used the possible existence of Von Neumann probes to constrain the search for intelligence beyond Earth. As Matloff told Universe Today via Zoom, the road that brought us to this point was long and winding and went beyond any single person.

As he explained, the connection between Von Neumann’s idea of “Universal Assemblers” and space exploration emerged sometime in the 1970s. This was largely due to interstellar studies like Project Daedalus, a fusion rocket concept developed by the British Interplanetary Society (BIS) between 1973 and 1977. Amid the debate over whether or such missions should be crewed or robotic, the idea of the Von Neumann probe was revived and applied.

In no time at all, the old SETI saw came up, where humanity’s ability to conceive an idea is seen as a possible indication that an older, more advanced species might have done it already! As Michael Hart and Frank Tipler noted in their respective studies, the fact that we see no evidence for extraterrestrial interstellar probes is the most compelling evidence that humanity is alone in the Universe. This is the basis of the Hart-Tipler Conjecture, the earliest-known proposed resolution to Fermi’s Paradox.

According to Tipler, if ETIs did exist, they would have developed the capacity for interstellar travel and explored the Milky Way within ~300 million years:

“What one needs is a self-reproducing universal constructor, which is a machine capable of making any device, given the construction materials and a construction program… In particular, it is capable of making a copy of itself. Von Neumann has shown that such a machine is theoretically possible… As the copies of the space probe were made, they would be launched at the stars nearest the target star. When these probes reached these stars, the process would be repeated, and so on until the probes had covered all the stars of the Galaxy.”