Editing Dyson's eternal intelligence

{{Short description|Hypothetical concept in astrophysics}}

'''Dyson's eternal intelligence''' (the '''Dyson Scenario''') is a hypothetical concept, proposed by [[Freeman Dyson]] in 1979, by which an [[immortality|immortal]] society of [[intelligence (trait)|intelligent]] beings in an [[open universe]] may escape the prospect of the [[heat death of the universe]] by performing an infinite number of computations (as defined below) though expending only a finite amount of energy.

[[Bremermann's limit]] can be invoked to deduce a lower bound on the amount of time required to distinguish two discrete energy levels of a quantum system using a quantum measurement.<ref>Bremermann, H.J. (1965) [http://projecteuclid.org/euclid.bsmsp/1200513783 Quantum noise and information]. 5th Berkeley Symposium on Mathematical Statistics and Probability; Univ. of California Press, Berkeley, California.</ref> One can interpret this measurement as a computation on 1 bit for this system; however, Bremermann's limit is difficult to interpret physically, since there exist quantum Hamiltonians for which this interpretation would give arbitrarily fast computation speeds at arbitrarily low energy.<ref>{{cite journal|last=Jordan|first=Stephen P.|title=Fast quantum computation at arbitrarily low energy|journal = Phys. Rev. A | volume = 95 |issue=3| pages=032305 | year=2017 |arxiv = 1701.01175|bibcode = 2017PhRvA..95c2305J |doi = 10.1103/PhysRevA.95.032305 |s2cid=118953874}}</ref><ref>{{cite journal|last=Sinitsyn|first=Nikolai A.|title=Is there a quantum limit on speed of computation?|journal=Physics Letters A|volume=382|issue=7|pages=477–481|year=2018|arxiv = 1701.05550|bibcode = 2018PhLA..382..477S |doi=10.1016/j.physleta.2017.12.042|s2cid=55887738}}</ref> Following this interpretation, the upper bound on the number of such measurements that can be performed grows over time. Assuming that the energy in the quantum system on which the measurement is performed is lost (while ignoring energy that is lost due to the measurement apparatus itself), the energy available from the mechanism suggested below slows [[logarithm]]ically, but never stops.

The intelligent beings would begin by storing a finite amount of energy. They then use half (or any fraction) of this energy to power their computation. When the energy is used up, they would enter a state of zero-energy-consumption until the universe cooled. Once the universe had cooled sufficiently, half of the remaining half (one quarter of the original energy) of the intelligent beings' fuel reserves would once again be released, powering a brief period of computation once more. This would continue, with smaller and smaller amounts of energy being released. As the universe cooled, the computations would be slower and slower, but there would still be an infinite number of them.<ref>{{cite journal | last=Dyson | first=Freeman J. | title=Time without end: Physics and biology in an open universe | journal=Reviews of Modern Physics | publisher=American Physical Society (APS) | volume=51 | issue=3 | date=1979-07-01 | issn=0034-6861 | doi=10.1103/revmodphys.51.447 | pages=447–460|url=http://www.aleph.se/Trans/Global/Omega/dyson.txt|bibcode=1979RvMP...51..447D}}</ref><ref>{{cite book | last=Dyson | first=Freeman J. |author-link=Freeman Dyson| title=Disturbing the universe | publisher=Harper & Row | publication-place=New York | date=1979 | isbn=0-06-011108-9 | oclc=4956480 | page=}}</ref>

In 1998, it was discovered that the expansion of the universe appears to be accelerating rather than decelerating due to a positive [[cosmological constant]], implying that any two regions of the universe will eventually become permanently separated from one another. Dyson noted that "in an accelerated universe everything is different".<ref>{{cite web|url=https://www.52-insights.com/freeman-dyson-i-kept-quiet-for-30-years-so-maybe-its-time-to-speak-interview-science/|title=Freeman Dyson: "I kept quiet for thirty years, maybe it's time to speak."|date=15 June 2018|work=52 Insights|access-date=18 May 2019}}</ref> However, even if the cosmological constant is <math>0</math>, the matter density in an [[Friedmann–Lemaître–Robertson–Walker metric|FLRW universe]] would converge to <math>0</math> at rate <math> t^{-1/2}</math>,<ref>{{Cite web|url=https://ned.ipac.caltech.edu/level5/Watson/Watson2_4_1.html|title=An Exposition on Inflationary Cosmology - G.S. Watson|website=ned.ipac.caltech.edu}}</ref> suggesting that the stored energy would become unavailable even if it is not used.

==Legacy==
[[Frank J. Tipler]] has cited Dyson's writings, and specifically his writings on the  eternal intelligence, as a major influence on his own highly controversial [[Omega Point]] theory.<ref>Audio interview with Frank Tipler- White Gardenia interview with Frank Tipler, December 2015 https://www.youtube.com/watch?v=kMkp1kZN5n4&t=26s</ref>
Tipler's theory differs from Dyson's theory on several key points, most notable of which is that Dyson's eternal intelligence presupposes an open universe while Tipler's Omega Point presupposes a closed/contracting universe.  Both theories will be invalidated if the observed universal  expansion continues to accelerate.<ref>Q&A with Frank Tipler http://turingchurch.com/2012/09/26/interview-with-frank-j-tipler-nov-2002/ {{Webarchive|url=https://web.archive.org/web/20171003030535/http://turingchurch.com/2012/09/26/interview-with-frank-j-tipler-nov-2002/ |date=2017-10-03 }}</ref>

==See also==
* {{annotated link|Reversible computing}}
* {{annotated link|Supertask}}
* {{annotated link|Zeno's paradoxes}}

==References==
{{reflist}}

[[Category:Physical cosmology]]
[[Category:Freeman Dyson]]