1874 Transit of Venus Observations of Samanta Chandrasekhar
By - N. Rathnasree, Nehru Planetarium, New Delhi (submitted to Dream 2047, a Vigyan Prasar Publication - 29th February 2004)
Samanta
Chandrasekhar, of Orissa, is a poignant figure of a classical Siddhantic
Astronomer of India, who survived into the 20th century (he died in
1904).
The year 2004 is a
very appropriate year to remember his work and, in particular, to put together
his observations of the 1874 Transit of Venus. Not just observations –
predictions too, as he was a Siddhantic Astronomer, completely un-influenced by
the western schools of Astronomy, and to some extent – unaware of it, during
the early phases of his Astronomical efforts.
Samanta Chandrasekhar was born on the 13th of December 1835, at Khandapara, in Orissa. His full name was Mahamahopadhaya Chandrasekhar Singh Harichandan Mohapatra Samant, but he was better known as Pathani Samanta. His lifetime Astronomy efforts were summarized by him in ‘Sidhanta Darpana’, which was published in 1899, by Calcutta University. The original manuscript of 2500 Sanskrit shlokas was written in Oriya script, on palm leaves, by Samanta Chandrasekhar.
Samanta
Chandrasekhar did not have a formal University education and his interest and
efforts in Astronomy were completely self taught, from manuscripts of Siddhantic
Astronomical treatises, that he had access to. It is very evident that he had no
exposure to the revolutionary advances in Astronomy between the 17thand
19th centuries, until rather late in his Astronomical career, and
very little, even towards the end of that. He remained a complete Siddhantic
Astronomer in the classical mould, uninfluenced by more recent developments.
Chandrasekhar was a
keen observer and made meticulous observations of celestial objects with
instruments that he had made himself. He was deeply perturbed on finding that
the ephemeral elements calculated from classical siddhantic principles did not
agree with his observations. The same perplexity had also been faced by Swai
Jaisingh, early in the 18th century, and had given rise to the
construction of his gigantic masonry observatories for the correction of
ephemeral elements. One underlying factor that had been responsible for these
perplexities was the freezing of classical Indian astronomical calculations away
from observational verifications. The precession of equinoxes (Ayanamasa) had
been noticed as far back as the Vedic times, by Indian Astronomers and had been
entering the calculation of ephemeral elements as bija corrections – ad hoc
corrections that needed to be applied with the passage of time, to incorporate
the changes in ephemeral elements arising from precession. For about a thousand
years before the time of Swai Jai Singh or Pathani Samanta – the emphasis had
shifted away from observational verifications and ephemeral elements had
remained uncorrected.
These perplexities
led Samanta to make a life time of observations with simple handmade
instruments, correct the ephemeral elements from these, and create predicted
ephemeral elements in the classical Siddhantic format for future observations.
The resulting ephemeral elements were amazingly accurate. Samanta’s work was
in the classical mould – with the assumption of a geocentric Universe,
although his own model included the planets other than Earth, as revolving
around the Sun.
Equivalent
mathematical formulations exist for calculation of ephemeral elements in the two
different world systems – Geocentric or Heliocentric – and many observed
phenomena require only the appropriate framework of calculations in order to
accurately predict possible celestial events.
Thus, Samanta’s inability to envisage or accept the Copernican
revolution, did not prevent him from making many accurate calculations of
contemporary celestial events in his lifetime and observing them. The most
interesting of the celestial phenomena in his life time was the December 9 1874
Transit of Venus.
This rare and
inspiring event was visible from India and many other parts of the world. The
Transit of Venus 8 years following that, in 1882, was not visible from India.
Such an event will again be visible on the 8th of June 2004, from
India and other parts of the world, and is creating a lot of excitement amongst
the amateur astronomers and educators. The underlying excitement of this event,
being the possibility of recreating historical
measurements of the Earth-Sun distance by students world wide, through
observations of the timings of this transit.
Going back to the
year 1874 – there must have been considerable excitement at that time too,
with efforts from Astronomers worldwide, making expeditions to India, as one of
the locations from where, the event was visible. There were also efforts by
Observaotories under the then British Government in India, to study this event.
And then, there were observatories
built by private individuals and princely states where activities were intense,
for the observations of this event. Some popularizations efforts also seem to
have been in evidence. Chintaman Raghunathachary, of Madras observatory, for
instance, had made a popular
booklet on this event, that had been translated into many languages, including
Urdu. In all probability, none of this excitement reached the remote Khandapara
regions of Orissa, where Samanta could have heard of this event.
Pathani Samanta observed the 1874 Transit of Venus – and reported it in his Siddhanta Darpana as -
Arun Kumar Upadhyaya, in his translation of the Siddhanta Darpana – interprets this Shloka as –
“Solar eclipse due to Sukra (Venus) – To find the eclipse of the Sun due to Sukra, their bimba (angular diameter) and size of other tara graha (stars and planets nearby?) is stated. In Kali year 4975 (1874 AD) there was a Solar Eclipse due to Sukra in Vrischika Rasi (Scorpio). Then Sukra bimba was seen as 1/32 of solar bimba which is equal to 650 yojana. Thus it is well proved that bimba of Sukra and planets is much smaller than the Sun.”
Did Samanta hear
that there was going to be a transit and set out to observe it – or did he
find that there was to be such an occurrence from his lifetime work of creating
accurate ephemeral elements? Most probably, the latter, as there seems no
evidence that there was any European Astronomical activity in the regions of
Orissa, at that time. The Italian expedition from the Palermo Observatory was to
Muddapur in Bengal a neighbouring state to Orissa and could there have been some
information that reached to Kandapara? It is not certain and there seems no
evidence of it. Even if the information did reach, Samanta would not have
accepted it without his own calculations agreeing with that.
All in all, it
seems possible that not only did Samanta observe this Transit, but, he predicted
it from his own calculations, unaware, of the excitement in the rest of the
world arising from the Transits of Venus – in the 17th, 18th
and 19th centuries.
The mention of the
ratio of the bimba or apparent angular diameters of Venus and Sun as 1/32 is
very interesting.
On the date of
these observations – the 9th of December 1874, the apparent angular
diameters of Sun and Venus, respectively, were – 32 minutes, 29 seconds of arc
and 1 minute, 3 seconds of arc. The ratio then would have been discernable as 1:
30.93.
This ratio would
have small variations from one transit to another due to the ellipticity of
orbits involved. In the year 2004, for instance, the apparent diameters
are – 31 minutes, 31 seconds for Sun and 58 seconds of arc, for Venus
so that the ratio discernable, would be 1:32.6 for the coming Transit of Venus.
Pathani Samanta’s
observations were completely non telescopic, and made with handmade instruments
– and the accuracy achieved seems extra ordinary. In theoretical calculations
and observations of the Transit of Venus, Samanta’s achivement would be
considered comparable to that of Jeremiah Horrocks, though poignantly
anachronistic.