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Botanicult Fiction: The Dyson Tree – Spreading Leaf on a Comet

July 22, 2020

By Dr. David Galbraith, Head of Science, Royal Botanical Gardens.

In early 2020 the world lost Dr. Freeman Dyson (15 December 1923 – 28 February 2020), a brilliant and controversial American physicist. Dyson was a polymath involved in astronomy, nuclear engineering, and even quantum electronics. He was also known for startling thought inventions, the most famous of which was the Dyson sphere. This was a proposed spherical enclosure for an entire star that could provide an inhabitable inner surface equivalent to the area of thousands or millions of Earths. A Dyson sphere would allow its builders to collect most of the energy being emitted from its star, too. They have caught many peoples’ imaginations and are now staples in science fiction.

It’s an amazing coincidence that this year we are also being treated to a wonderful comet, C/2020 F3 (NEOWISE) visible in much of Canada in mid-July after sunset. Why is this a coincidence? Because one of Dyson’s most imaginative theoretical inventions was the Dyson tree, an engineered plant that could live on, or in, a comet.

Freeman Dyson’s tree would be planted on a comet to take advantage of gasses coming off it. It would produce chemical energy from sunlight through photosynthesis. Like the Dyson sphere, the engineering knowledge necessary to produce a Dyson tree lies far in our future, if we are ever able to create such a thing at all. And like the Dyson sphere, the Dyson tree has taken off into science fiction with a life of its own. Writers such as Rachel Pollack, Dan Simmons, Stephen Baxter, and Reid Malenfant have built Dyson trees into their science fiction universes. The concept has appeared in video games and was also taken on in Carl Sagan and Ann Druyan’s non-fiction book “Comet” in 1985.

What would life be like on a comet? For one thing there’s little gravity as comets are small objects. This could lend itself to large structures. One of the reasons Dyson’s astronomical arboreal invention isn’t completely mad is that comets are “dirty snowballs,” containing significant amounts of water and carbon. In the vicinity of the sun they lose gasses, including water vapour, giving them the visible tails we can see from Earth. Perhaps in this rarefied, strange, and temporary environment life could be planted and survive, at least for a while. If a Dyson tree was able to capture some cometary atmosphere perhaps it could function like a greenhouse too, enabling life to spread into the more remote corners of our solar system.

Botanicult Fiction is an affectionate review of plants in pop culture viewed through the lens of plant nerds and curated for your reading or viewing pleasure during this challenging time of self isolation

comet in a night sky
Comet C/2020 5 (NEOWISE) photographed by author David Galbraith north of Guelph, Ontario, on 17 July 2020. Thirty second exposure taken with a Nikon D7000 camera and 18 mm lens.

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