Pendon Museum Updated 2025-07-16
Video 2.
The History of Pendon Museum by World of Railways (2012)
Source. The founder was Australian. His family was wealthy, and he liked cycled around the Vale.
Skelet machine #1 is infinite Updated 2025-07-16
The proof uses Turing machine acceleration to show that Skelet machine #1 is a Translated cycler Turing machine with humongous cycle paramters:
  • start between 50-200 M steps, not calculated precisely on the original post
  • period: ~8 billion steps
This could refer to several more specific courses, see the tagged articles for a list.
Intuitively we see that the situation is fundamentally different from the Turing machine that halts if and only if the Goldbach conjecture is false because for Collatz the counter example must go off into infinity, while in Goldbach conjecture we can finitely check any failures.
Amazing.
Marxen-Buntrock machine Updated 2025-07-16
Best busy beaver machine known since 1989 as of 2023, before a full proof of all 5 state machines had been carried out.
Paper extracted to HTML by Heiner Marxen: turbotm.de/~heiner/BB/mabu90.html
Turing machine acceleration Updated 2025-07-16
Turing machine acceleration refers to using high level understanding of specific properties of specific Turing machines to be able to simulate them much fatser than naively running the simulation as usual.
Acceleration allows one to use simulation to find infinite loops that might be very long, and would not be otherwise spotted without acceleration.
bbchallenge.org/story#what-is-known-about-bb lists some (all?) cool examples,
wiki.bbchallenge.org/wiki/Cryptids contains a larger list. In June 2024 it was discovered that BB(6) is hard.

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