Freeman Dyson (1923-2020)

With great sadness, we received the message that Freeman Dyson has passed away. He was 96 years old. A distinguished physicist, Freeman Dyson was a member of the i4is Advisory Council for many years. Many obituaries have already appeared. In the following, I would like to honour Freeman by presenting his contributions to interstellar studies.

A master of exploratory thinking, his contributions to the field of interstellar studies are numerous. It is safe to say that he is one of the founders of our field. His contributions will remain a source of inspiration, a treasure trove of scientific creativity. Freeman was not afraid of entering into new domains, taking ideas, and combining them to generate novel concepts; audacious, but firmly grounded in existing physics, courageously extrapolating existing engineering. The back-of-the-envelope calculation as a showcase of human ingenuity. Just to mention a few:

– Orion interstellar spacecraft: In a landmark paper, he made the, to my knowledge, first detailed calculations on a crewed, nuclear bomb-driven spacecraft, capable of reaching other stars. The paper “Interstellar Transport” is a mandatory read for everybody interested in interstellar travel and a masterpiece in first-order feasibility analysis. Based on technologies of the 1960s, it includes even a possible date when we might be capable of developing such a spacecraft from an economic standpoint (He estimates 2168):
Dyson, F. J. (1968). Interstellar transport. Physics Today, 21(10), 41-45.

– Dyson Sphere: The megastructure, first proposed by Olaf Stapledon but turned into science by Dyson, encloses a star in order to harvest its energy. Speculative at first, the concept has stimulated subsequent research on looking for alien megastructures in our galaxy but even in millions of other galaxies. So far, no Dyson Spheres were discovered. But it shows how exploratory thinking can stimulate and guide observational science.
Dyson, F. J. (1960). Search for artificial stellar sources of infrared radiation. Science, 131(3414), 1667-1668

– Astrochicken: The idea of a kg-scale biological, self-replicating interstellar probe is again demonstrating how he combines ideas from different domains to create a new concept. The astrochicken blends microelectronics, biology, and artificial intelligence. It “would be launched by a conventional spacecraft into space, like an egg being laid into space. Astrochicken would then hatch and start growing a solar-energy collector. The solar collector would feed an ion drive engine that would power the craft. Once Astrochicken entered a planet’s vicinity, it would collect material from the moons and rings of the planet, taking in nutrients. It could land and take off using an auxiliary chemical rocket similar to that used by bombardier beetles. It would periodically transmit details of its journey when it could make radio contact with Earth.”

The seeds he has planted will continue to grow into futures, one day to the stars.
He will be greatly missed.

Andreas Hein, i4is

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