Editing Freeman Dyson (section)

==Concepts==
===Biotechnology and genetic engineering===
{{see also|The Sun, the Genome and the Internet}}
Dyson admitted his record as a prophet was mixed, but thought it is better to be wrong than vague, and that in meeting the world's material needs, technology must be beautiful and cheap.

{{Blockquote | style=font-size:100% | My book ''The Sun, the Genome, and the Internet'' (1999) describes a vision of green technology enriching villages all over the world and halting the migration from villages to megacities. The three components of the vision are all essential: the sun to provide energy where it is needed, the genome to provide plants that can convert sunlight into chemical fuels cheaply and efficiently, the Internet to end the intellectual and economic isolation of rural populations. With all three components in place, every village in Africa could enjoy its fair share of the blessings of civilization.|source={{harvnb|Dyson|2007}} }}

Dyson coined the term "green technologies", based on [[biology]] instead of [[physics]] or [[chemistry]], to describe new species of [[microorganism]]s and [[plant]]s designed to meet human needs. He argued that such technologies would be based on [[solar power]] rather than the [[fossil fuel]]s whose use he saw as part of what he calls "gray technologies" of industry. He believed that [[Genetic engineering|genetically engineered]] crops, which he described as green, can help end [[rural poverty]], with a movement based in [[ethics]] to end the inequitable [[distribution of wealth]] on the planet.{{sfn|Shwartz|2001}}

===''The Origin of Life''===
{{Main|Abiogenesis}}
Dyson favoured the dual origin theory: that life first formed as [[Cell (biology)|cells]], then [[enzyme]]s, and finally, much later, [[gene]]s. This was first propounded by the Russian biochemist, [[Alexander Oparin]].{{sfn|Oparin|1924}} [[J. B. S. Haldane]] developed the same theory independently.{{sfn|Haldane|1929}} In Dyson's version of the theory, life evolved in two stages, widely separated in time. Because of the biochemistry, he regards it as too unlikely that genes could have developed fully blown in one process. Current cells contain [[adenosine triphosphate]] or ATP and [[adenosine 5'-monophosphate]] or AMP, which greatly resemble each other but have completely different functions. ATP transports energy around the cell, and AMP is part of RNA and the genetic apparatus. Dyson proposed that in a primitive early cell containing ATP and AMP, RNA and replication came into existence only because of the similarity between AMP and RNA. He suggested that AMP was produced when ATP molecules lost two of their phosphate radicals, and then one cell somewhere performed [[Manfred Eigen|Eigen]]'s experiment and produced RNA.{{sfn|Schewe|2014|pp=222–223}}

There is no direct evidence for the dual origin theory, because once genes developed, they took over, obliterating all traces of the earlier forms of life. In the first origin, the cells were probably just drops of water held together by surface tension, teeming with enzymes and chemical reactions, and having a primitive kind of growth or replication. When the liquid drop became too big, it split into two drops. Many complex molecules formed in these "little city economies" and the probability that genes would eventually develop in them was much greater than in the prebiotic environment.{{sfn|Dyson|1985|p=}}
[[File:Dyson rings.PNG|thumb|Artist's concept of Dyson rings, forming a stable [[Dyson swarm]], or "Dyson sphere"]]

=== Dyson sphere ===
{{Main|Dyson sphere}}
In 1960 Dyson wrote a short paper for the journal ''[[Science (journal)|Science]]'' titled "Search for Artificial Stellar Sources of Infrared Radiation".{{sfn|Dyson|1960|pp=1667-1668}} In it he speculated that a technologically advanced [[Extraterrestrial life|extraterrestrial]] [[civilization]] might surround its native star with artificial structures to maximize the capture of the star's energy. Eventually, the civilization would enclose the star, intercepting [[electromagnetic radiation]] with [[wavelength]]s from visible light downward and radiating waste heat outward as [[infrared]] radiation. One method of [[Search for extraterrestrial intelligence|searching for extraterrestrial civilizations]] would be to look for large objects radiating in the infrared range of the [[electromagnetic spectrum]].

{{Blockquote | style=font-size:100% | One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which surrounds its parent star. |source={{harvnb|Davis|1978}}}}

Dyson conceived that such structures would be clouds of [[asteroid]]-sized [[space habitat]]s, though [[science fiction]] writers have preferred a solid structure: either way, such an artifact is often called a [[Dyson sphere]], although Dyson used the term "shell". Dyson said that he used the term "artificial biosphere" in the article to mean a habitat, not a shape. The general concept of such an energy-transferring shell had been created decades earlier by science fiction writer [[Olaf Stapledon]] in his 1937 novel ''[[Star Maker]]'', a source which Dyson credited publicly.<ref name=perimeterinstitute.ca />{{efn|name=Dyson1979p211}}

===Dyson tree===
{{Main|Dyson tree}}
Dyson also proposed the creation of a ''Dyson tree'', a [[genetic engineering|genetically engineered]] plant capable of growing inside a [[comet]]. He suggested that comets could be engineered to contain hollow spaces filled with a breathable atmosphere, thus providing self-sustaining habitats for humanity in the outer [[Solar System]].

{{Blockquote | style=font-size:100% | Plants could grow greenhouses… just as turtles grow shells and polar bears grow fur and polyps build coral reefs in tropical seas. These plants could keep warm by the light from a distant Sun and conserve the oxygen that they produce by photosynthesis. The greenhouse would consist of a thick skin providing thermal insulation, with small transparent windows to admit sunlight. Outside the skin would be an array of simple lenses, focusing sunlight through the windows into the interior…  Groups of greenhouses could grow together to form extended habitats for other species of plants and animals. |source={{harvnb|Dyson|1997}} }}

===Space colonies===
{{Blockquote | style=font-size:100% | I've done some historical research on the costs of the Mayflower's voyage, and on the Mormons' emigration to Utah, and I think it's possible to go into space on a much smaller scale. A cost on the order of $40,000 per person [1978 dollars, $181,600 in 2022 dollars] would be the target to shoot for; in terms of real wages, that would make it comparable to the colonization of America. Unless it's brought down to that level it's not really interesting to me, because otherwise, it would be a luxury that only governments could afford. |source= {{harvnb|Davis|1978}}}}

Dyson was interested in space travel since he was a child, reading such science fiction classics as [[Olaf Stapledon]]'s ''[[Star Maker]]''. As a young man, he worked for [[General Atomics]] on the nuclear-powered [[Project Orion (nuclear propulsion)|Orion]] spacecraft. He hoped Project Orion would put men on Mars by 1965, and Saturn by 1970. For a quarter-century, Dyson was unhappy about how the government conducted space travel:
{{Blockquote | style=font-size:100% | The problem is, of course, that they can't afford to fail. The rules of the game are that you don't take a chance, because if you fail, then probably your whole program gets wiped out. |source= {{harvnb|Davis|1978}}}}

Dyson still hoped for cheap space travel, but was resigned to waiting for private entrepreneurs to develop something new and inexpensive.

{{Blockquote | style=font-size:100% | No law of physics or biology forbids cheap travel and settlement all over the solar system and beyond. But it is impossible to predict how long this will take. Predictions of the dates of future achievements are notoriously fallible. My guess is that the era of cheap unmanned missions will be the next fifty years, and the era of cheap manned missions will start sometime late in the twenty-first century.

Any affordable program of manned exploration must be centred in biology, and its time frame tied to the time frame of biotechnology; a hundred years, roughly the time it will take us to learn to grow warm-blooded plants, is probably reasonable. |source={{harvnb|Dyson|1997}} }}
<!-- Dyson also proposed the use of bioengineered space colonies to colonize the Kuiper Belt on the outer edge of our Solar System. He proposed that habitats could be grown from space hardened spores. The colonies could then be warmed by large reflector plant leaves that could focus the dim, distant sunlight back on the growing colony. This was illustrated by [[Pat Rawlings]] on the cover of the National Space Society's ''Ad Astra'' magazine. -->

===Space exploration===
{{Blockquote | style=font-size:100% | A direct search for life in Europa's ocean would today be prohibitively expensive. Impacts on Europa give us an easier way to look for evidence of life there. Every time a major impact occurs on Europa, a vast quantity of water is splashed from the ocean into the space around Jupiter. Some of the water evaporates, and some condenses into snow. Creatures living in the water far enough from the impact have a chance of being splashed intact into space and quickly freeze-dried. Therefore, an easy way to look for evidence of life in Europa's ocean is to look for freeze-dried fish in the ring of space debris orbiting Jupiter.

Freeze-dried fish orbiting Jupiter is a fanciful notion, but nature in the biological realm has a tendency to be fanciful. Nature is usually more imaginative than we are.  …To have the best chance of success, we should keep our eyes open for all possibilities. |source={{harvnb|Dyson|1997}} }}

===Dyson's eternal intelligence===
{{Main|Dyson's eternal intelligence}}
Dyson proposed that an [[immortality|immortal]] group of intelligent beings could escape the prospect of [[Heat death of the universe|heat death]] by extending time to infinity while expending only a finite amount of energy.{{sfn|Dyson|1979a|pp=447-460}} This is also known as the Dyson scenario.{{sfn|Cendes|2019}}

===Dyson's transform===
{{Main|Dyson's transform}}
His concept "Dyson's transform" led to one of the most important [[lemma (mathematics)|lemmas]] of [[Olivier Ramaré]]'s theorem: that every even integer can be written as a sum of no more than six primes.{{sfn|Ramaré|1995|pp=645–706}}

===Dyson series===
{{Main|Dyson series}}
The Dyson series, the formal solution of an explicitly time-dependent [[Schrödinger equation]] by iteration, and the corresponding Dyson time-ordering operator <math>\mathcal T\,,</math> an entity of basic importance in the [[mathematical formulation of quantum mechanics]], are also named after Dyson.<ref name=ocw.mit.edu />
[[File:Freeman dyson.jpg|thumb|upright=1.1|Freeman Dyson in 2007 at the [[Institute for Advanced Study]] ]]

===Quantum physics and prime numbers===
Dyson and [[Hugh Montgomery (mathematician)|Hugh Montgomery]] discovered an intriguing connection between quantum physics and [[Montgomery's pair correlation conjecture]] about the zeros of the zeta function. The primes 2, 3, 5, 7, 11, 13, 17, 19,... are described by the [[Riemann zeta function]], and Dyson had previously developed a description of quantum physics based on m by m arrays of totally random numbers.{{sfn|Dyson|1962|p=1191}} Montgomery and Dyson discovered that the ''[[eigenvalues]]'' of these matrices are spaced apart in exactly the same manner as Montgomery conjectured for the nontrivial zeros of the zeta function. [[Andrew Odlyzko]] has verified the conjecture on a computer, using his [[Odlyzko–Schönhage algorithm]] to calculate many zeros.{{sfn|Odlyzko|Schonhage|1988|p=797}}

There are in nature one, two, and three-dimensional [[quasicrystals]]. Mathematicians define a quasicrystal as a set of discrete points whose [[Fourier transform]] is also a set of discrete points. Odlyzko has done extensive computations of the Fourier transform of the nontrivial zeros of the zeta function, and they seem to form a one-dimensional quasicrystal. This would in fact follow from the [[Riemann hypothesis]].{{sfn|Dyson|2015|pp=41–42}}

===Rank of a partition===
[[File:Rank of a partition.svg|thumb|upright=1.5|The rank of a partition, shown as its [[Young diagram]]]]
{{Main|Rank of a partition}}
In [[number theory]] and [[combinatorics]], the rank of an [[integer partition]] is a certain [[integer]] associated with the partition. Dyson introduced the concept in a paper published in the journal [[Eureka (University of Cambridge magazine)|''Eureka'']]. It was presented in the context of a study of certain [[Congruence relation|congruence]] properties of the [[Partition function (number theory)|partition function]] discovered by the mathematician [[Srinivasa Ramanujan]].{{sfn|Dyson|1944|pp=10–15}}

===Crank of a partition===
{{Main|Crank of a partition}}
In [[number theory]], the crank of a partition is a certain [[integer]] associated with the partition. Dyson first introduced the term without a definition in a 1944 paper in a journal published by the Mathematics Society of [[Cambridge University]].{{sfn|Dyson|1996|p=51}} He then gave a list of properties this yet-to-be-defined quantity should have. In 1988, [[George E. Andrews]] and [[Frank Garvan]] discovered a definition for the crank satisfying the properties Dyson had hypothesized.{{sfn|Andrews|Garvan|1988|pp=167–72}}

===Astrochicken===
{{Main|Astrochicken}}
[[File:JohnvonNeumann-LosAlamos.gif|thumb|upright|John von Neumann]]

Astrochicken is the name given to a [[thought experiment]] Dyson expounded in his book ''Disturbing the Universe'' (1979). He contemplated how humanity could build a small, [[Self-replication|self-replicating]] automaton that could [[space exploration|explore space]] more efficiently than a crewed craft could. He attributed the general idea to [[John von Neumann]], based on a lecture von Neumann gave in 1948 titled ''The General and Logical Theory of Automata''. Dyson expanded on von Neumann's [[Automata theory|automata theories]] and added a biological component.{{sfn|Schewe|2014|pp=230–31}}

===Lumpers and splitters===
{{Main|Lumpers and splitters}}

Dyson suggested that philosophers can be broadly if simplistically, divided into lumpers and splitters. These roughly correspond to [[Platonism|Platonists]], who regard the world as made up of ideas, and [[materialism|materialists]], who imagine it divided into atoms.{{sfn|Dyson|2015a|p=238}}