Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: French Bureau of Longitude in 1885
    From: Antoine Couëtte
    Date: 2016 Sep 29, 02:56 -0700

    Dear Paul,

    I think that 1848 was the year when Leverrier discovered Neptun at the tip of his ink-pen, no?

    Lesson learnt from this article on Bureau des Longitudes: you are mainly worth your next contribution, not your last one(s). It also 100% stands true for Airline Pilots too :-) ....

    Yes, the 95T dome worked out very well. That was at the Nice Observatory and this construction and building came as a great technical achievement for that time because one single operator could move these huge Coupole masses with almost no effort .

    Nice Observatory ? ... I knew quite well our regretted Paul Couteau, world renown Astronomer then for Double stars trajectories. Paul Couteau was also the very first one to have exactly discovered and adequately described Neutron stars with their main characteristics, including their huge acceleration on masses. I remember hime telling me "Antoine, imagine dropping a stone from their surface - if you could ... - and after the first second of time, it has already falled down 250 km away" ... That was the main chore of his PhD thesis which he undertook at the Paris Observatory right after WWII and which was released just a few months ahead of the official Anglo-Saxon Neutron Stars Theoricians and Discoverers publications. Paul Couteau was much more interested into deciphering double and triple star apparent orbits, so with his PhD in pocket (he just needed having one, on any subject in Astronomy), he immediately jumped onto an Astronomer position just opening then at the Nice Observatory where he spent the next 40+ years happily working, mostly during nights as you would think, and raising their seven children with his extraordinary Wife. He had totally left Neutron Stars aside, was happy to see that his pioneering results got subsequently confirmed by others and did not ever think of fighting to regain official anteriority on the Neutron Stars theoretical discovery.

    Paul Couteau was the man who put me in contact with Dr. Lerot Dogget then Director of the USNO Nautical Almanach Office in 1980 when I was in the US Naval Carrier Aviation. Then, thanks to Dr. Leroy E. Dogget I could head onto Dr. Pierre Bretagnon from Bureau des Longitudes in Paris. Dr. Pierre Bretagnon had then just published his VSOP82 Planetary Theory. Dr. Pierre Bretagnon was the very first one since Leverrier to have published a new and complete Planetary Theory with all 8 Planets altogether and ay the same time. Although Dr. Pierre Bretagnon intensively relied onto Elctronic computation, and also used the best intergration constants from JPL, his was an absolutely remarkable achievement then. He once told me: "Antoine, since I am sitting securely here (i.e. at BdL), I could afford doing [almost] nothing for the rest of my life". On the contrary he had already undertaken and kept improving an immense task on his own - his amazing 8 Planet simultaneous analytic theories VSOP80, VSOP82 and VSOP87 - equal in this respect to only Leverrier or to Great Simon Newcomb.

    Pierre and I eventually became good Friends. Naval Aviation Aircraft Carrier Pilots wer kind of new to his own Universe.

    On my programming Calculator keep using the main terms of the VSOP2011 Planetary Theory developed by his successors at Bureau des Longitudes.

    Pierre Bretagnon immediately recognized one prominent deficiency of the 1980 IAU Precession theory as early as 1983. This 1980 IAU Precession was directly derived from Simon Newcomb's Tables of the Sun (1895) developed in the Ecliptic/Equinox of Date. Since he had just developed a much better Sun Theory in a fixed plan (Ecliptic/Equinox 2000.0), Pierre had immediately at hand excellent Luni-Solar Precession coefficients aka his "Sun Mean Elements". Pierre Bretagnon at once published in 1983 that the main term in T**3 in the IAU 1980 Theory was definitely in error. It took ten years to the Astronomical Community to be fully convinced and agree to his views.

    In view of new requirements for ever increased Precession and Nutation Theories due to the fast development of VLBI observations, Pierre Bretagnon then undertook on his own to fully developing a totally a new Precession/Nutation Theory based this time upon the use of the sole Euler's Equations. He chose to mainly focus on the Precession terms - much more important for long term - and published a second and improved/corrected new precession theory as SMART98 (Solution du Mouvement de l'Axe de Rotation Terrestre) which immediately became the backbone of the current IAU 2006 / 2000B precession / nutation theorie. In addition to subsequent remarkable improvements, these latter theories differ from SMART98 mainly on one long term coefficient derived from more recent VLBI observations gained meanwhile. Again, in the early 90's Pierre Bretagnon had to humbly counter - Pierre was a very humble man, endowed with an amazingly acute and powerful intelligence - much more prestigious "competitors" (there was a fierce international competition on Precesion then) ... - at least against one of them - through fully "defeating" his method. Pierre Bretagnon had conclusively shown that some important terms of his Colleague's Precession theory had been incorrectly taken in account twice.

    This second "soft battle" took a number of years, and eventually Pierre Bretagnons's views fully prevailed and enabled building up our now current IAU 2006 / 2000B precession / nutation theories on extremely sound, solid and sturdy bases, in particular through the amazingly accurate work of Nicole Capitaine (and al.) from VLBI results and also Agnes Fienga ("Mrs INPOP" Numerical Integration theories), these two Ladies having been among Pierre Bretagnon's extremely bright students.

    As I noted in a recent post, it would be so simple for everybody to just remember and recognize that the most important behavior rule here remains: "what" is right rather than "Who" is right. It could keep avoiding wasting a lot of efforts in a number of areas, e.g. if you keep rudely ignoring this good sense rule as a Captain in an Airplane, you may encounter very bad surprises from your entire Crew - starting from your 1st Officer - if encountering delicate or difficult situations.

    Obviously, such  IAU 2006 / 2000B precession / nutation theories have now become the fruit of international development. But - and by far - the contributions of Pierre Bretagnon first, Nicole Capitaine second (and we could probably inverse that order here) , from Agnès Fienga third, and more generally from Bureau des Longitudes fourth, have been paramount.

    *******

    I regret having to insist on this specific point, because in our current world overwhelmed by the english/american langage, science and publications, the huge prominence of Bureau des Longitudes in this extraordinary story has been consistently diminished and held down if not hidden under the table or even broomed under the carpet.

    This story already happened to Paul Couteau, some 70 years ago: see here-above.

    Well ... the exact same story is currently happening to my own family name: what some 50 years ago was still known in english publications as the "Couette Flow" in hydrodynamics, as invented and pioneered/studied by my Great Grand Father Maurice Couette - which led to his extraordinary and amazing PhD work "Etudes sur le forttement des liquides" published in 1895 -  has meanwhile and widely become known as the "Couette-Taylor Flow" . Here and there this very particular cylindrical flow starts being named the "Taylor-Couette flow" and no need to wait another 50 years until it will be officially recognized and only known as the  "Taylor (only) flow" , although the Great Taylor - who is Great enough for his own extraordinary contributions too - did not study such cylindrical flow invented by Maurice Couette.

    Last lesson learnt: "Quid hoc ad aternitatem ?"

    *******

    As a conclusion, Bureau des Longitudes has again well deserved and gained our full respect. My hat down to them, unreservedly :-)

    Best Regards to all,

    Antoine 

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site