The Incredible Bradley: Why his Aberration Work was so Accurate even Bettering most Modern Renditions ! (Enabling the Extrication of the Diurnal Factor.)
Frank Pio Russo - March 19, 2016.
Abstract: Laying bare to everybody the secret as to James Bradley's fantastically accurate stellar aberration observations and discoveries. And also extrapolating some conclusions regarding my 3 decades of work as direct consequences from Bradley's work.
Today there are many professionals who do not realize the monumentality of Bradley's work which was announced in 1728. For a start in his day there were no reliable longitude clocks because it wasn't till 1764 that the first one was tested after being invented by John Harrison. And secondly it wasn't till 1838 that Bessel was the first to succeed with parallax measurement. Hence Bradley had to do all of his work with measurements of declination only. He actually commented that the stars varied throughout the year and day, such that they were furthest south or furthest north always at about 6 am or 6 pm (1). It is just common sense: look at the globe of Earth and project the inferred diurnal motion of celestial East from the ecliptic pole, and realize that at 6 am the stars would appear to move southwards and at 6 pm they would appear to go northwards.
The latter actually fits in well with his declination measurements, because it is at both 6am and 6 pm that he would have lined-up with the orbital speed of the earth - so no mystery there ! Now it is generally acknowledged that it was the fantastic accuracy of his instruments which allowed Bradley to make his discoveries... they were made by the famous George Graham. However regardless of this, "A History of Astronomy" implies that in Bradley's day the error of measurement should have been no greater than 2 arc seconds (2) . However the latter revelation does not fit in very well with the incredible acumen and skill displayed by Bradley - although it is consistent with what I have noticed myself - so much so that there must be another explanation for Bradley's excellence! I mean, a few days ago I went to see this beautiful 18 inch telescope at the "Shell-Lap Supplies" store... it is extremely well made and almost 3 centuries to the future of Bradley's instruments, and yet I think I read somewhere that it has a pointing error of about two and a half arc seconds. YES THERE MUST BE ANOTHER EXPLANATION FOR BRADLEY'S GREATNESS !
Well, after putting my full IQ at 'shouldering' the problem, I have come up 'trumps' ! Bradley's phenomenal success was due to what most people would consider an act of stupidity by his predecessor Samuel Molineux: most people would show very low esteem to one who would fix his telescope to his chimney, such that he can only mainly observe one star i.e. Gamma Draconis ! Most people would want to be able to point their telescope at whatever they wish, e.g. Mars, the Moon , Sirius or the rings of Saturn... not to mention the moons of Jupiter of course! But there was some method in Molineux's 'madness': he was trying to discover stellar parallax which was to become invaluable to sea travellers. Naturally Molineux was wealthy and a member of parliament so "waste" was not an issue. Molineux went on to employ and work together with Bradley because of Bradley's superior astronomical skills not to mention the fact that he was also a fellow of the prestigious "Royal Society".
Yes ! It may have appeared as a 'stupid' act to fix the telescope to the chimney, but it was actually a stroke of 'genius' ! For one could virtually assume that the central position of Gamma Draconis was correct to 10 decimal figures of an arc second ! With any oscillations and variations being actual and real rather than being due to any inherent pointing error !
This actually goes a long way in explaining why, in the following centuries there was so much variability in attempting to define the 'aberration constant' till eventually all effort was abandoned and a theoretical rendition was adopted. The incredible accuracy of Bradley could not be replicated as its secret had not been exposed and realized by anybody till now !
In view of the foregoing there are many new features of my nearly 29 years of work on stellar aberration and the speed of light. For a start, my absolute - (or aberration) - speed of light of 304,476 km/sec plus or minus 125 km ( 3 ) now becomes incredibly accurate because the bulk of the error was attributable to the then considered imprecise 'polar' aberration constant of 20.18 or 'ecliptic' of 20.47 (arc seconds). In other words, if one were to assume that the aberration constant is 'beyond reproach', the then derived 'absolute' or aberration speed of light ends up having a plus and minus error of only 10 kilometres... that's certainly both a massive and drastic improvement on the previous error level.
Furthermore, it is clear that the diurnal considerations can easily be extricated from the system. With most of Bradley's early observations - which were sort of referenced to 6 am or 6 pm - the rotation of the earth of 465.10 m/sec or its ecliptic vector of 426.6 m/sec did not affect the aberration observed, simply because of the respective geometrical orientations... in other words Bradley would have seen a 'polar' observation of 20.2 arc seconds (my value today is 20.18).
In conclusion, I must say that I've greatly enjoyed my intricate detective work that I've carried out in regards to Bradley over the past now nearly 30 years... hopefully this last article polishes up my work somewhat so that it's more palatable and more easily understood... things have stagnated for far too long languishing in the now surpassed shadow of Einstein.
Frank Pio Russo.
1. Bradley James. 1727-8. Philosophical Transactions. Vol. 35 p.649-654. Royal Society, London.
2. Pannekoek A. 1961. A History of Astronomy. p.209. Interscience New York.
3. Russo F.P. 1995. Analysis of stellar aberration yields the 'real' speed of light. Speculations in Science and Technology. 18:200-204.