# Stellar Exploratory Data Analysis or How to create the HR Diagram with R

I recently have started to refresh my skills with R programming language. I am doing the  Harvard Course on Data Science on EdX. I am using R Studio for doing all the exercises. In the second part of the course, Visualisation, which is an area of research interest for me, there is an exercise on stars dataset. But this exercise was available only to those who were crediting the course. Since I was not crediting, but only auditing I left the exercise as it is. But after a week or so I looked at the stars dataset. And thought I should do some explorations on this. For this we have to load the R package dslabs specially designed for this course. This post is detailing the exploratory data analysis with this dataset. (Disclaimer: I have used help from ChatGPT in writing this post for both content and code.)

> library(dslabs)

Once this is loaded, we load the stars dataset

data(stars)

## Structure of the dataset

To understand what is the data contained in this data set and how is it structured we can use several ways. The head(stars) command will give use first few lines of the data set.

> head(stars) star magnitude temp type 1 Sun 4.8 5840 G 2 SiriusA 1.4 9620 A 3 Canopus -3.1 7400 F 4 Arcturus -0.4 4590 K 5 AlphaCentauriA 4.3 5840 G 6 Vega 0.5 9900 A

While the  tail(stars) gives last few lines of the data set

tail(stars) star magnitude temp type 91 *40EridaniA 6.0 4900 K 92 *40EridaniB 11.1 10000 DA 93 *40EridaniC 12.8 2940 M 94 *70OphiuchiA 5.8 4950 K 95 *70OphiuchiB 7.5 3870 K 96 EVLacertae 11.7 2800 M

To understand structure further we can use the str(stars) command

> str(stars) 'data.frame': 96 obs. of 4 variables: $star : Factor w/ 95 levels "*40EridaniA",..: 87 85 48 38 33 92 49 79 77 47 ...$ magnitude: num 4.8 1.4 -3.1 -0.4 4.3 0.5 -0.6 -7.2 2.6 -5.7 ... $temp : int 5840 9620 7400 4590 5840 9900 5150 12140 6580 3200 ...$ type : chr "G" "A" "F" "K" ...

In RStudio we can also see the data with View(Stars) function in a much nicer (tabular) way. It opens up the data in another frame as shown below.

Thus we see that it has 96 observations with four variables, namely star, magnitude, temp and type. The str(stars) command also tells use the datatype of the columns, they are all different: factor, num, int, chr. Let us understand what each of the column represents.

## Name of stars

The star variable has the names of the stars as seen in the table above. Many of the names are of ancient and mythological origins, while some are modern. Most are of Arabic origin, while few are from Latin. Have a look at Star Lore of All Ages by William Olcott to know some of the mythologies associated with these names. Typically the alphabets after the star names indicate them being part of a stellar system, for example Alpha Centauri is a triple star system. The nomenclature is such that A represents the brightest member of the system, B the second brightest and so on. Also notice that some names have Greek pre-fixes, as in the case of of Alpha Centauri. This Greek letter scheme was introduced by Bayer in 1603 and is known as Bayer Designation. The Greek letters  denote the visual magnitude or brightness (we will come to the meaning of this next) of the stars in a given constellation. So Alpha Centuari would mean the brightest star in the Centaurus constellation. Before invention of the telescope the number of stars that are observable were limited by the limits of human visual magnitude which is about +6. With invention of telescope and their continuous evolution with increasing light gathering power, we discovered more and more stars. Galileo is the first one to view new stars and publish them in his Sidereal Messenger. He shows us that seen through the telescope, there are many more stars in the Pleiades constellation than can be seen via naked eyes (~+6 to max +7 with about 4200 stars possibly visible).

Soon, so many new stars were discovered that it was not possible to name them all. So coding of the names begun. The large telescopes which were constructed would do a sweep of the sky using big and powerful lenses and would create catalogue of stars. Some of the names in the data set indicate these data sets, for example HD denotes Henry Draper Catalogue.

## Magnitudes of stars

Now let us look at the other three columns present us with observations of these stars. Let us understand what they mean. The second column represents magnitude of the stars. The stellar magnitude is of two types: apparent and absolute. The apparent magnitude is a measure of the brightness of the star and depends on its actual brightness, distance from us and any loss of the brightness due to intervening media. The magnitude scale was devised by Claudius Ptolemy in second century. The first magnitude stars were the brightest in the sky with sixth being the dimmest. The modern scale follows this classification and has made it mathematical. The scale is reverse logarithmic, meaning that lower the magnitude, brighter is the object. A magnitude difference of 1.0 corresponds to a brightness ratio of $\sqrt[5]{100}$ or about 2.512. Now if you are wondering why the magnitude scale is logarithmic, the answer lies in the physiology of our visual system. As with the auditory system, our visual system is not linear but logarithmic. What this means is that if we perceive an object to be of double brightness of another object, then their actual brightness (as measured by a photometer) are about 2.5. This fact is encapsulated well in the Weber-Fechnar law. The apparent magnitude of the Sun is about -26.7, it is after all the brightest object in the sky for us. Venus, when it is brightest is about -4.9. The apparent magnitude of Neptune is +7.7 which explains why it was undiscovered till the invention of the telescope.

But looking at the table about the very first entry lists Sun’s magnitude as +4.8. This is because the dataset contains the absolute magnitude and not the apparent magnitude. Absolute magnitude is defined as “apparent magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs (32.6 light-years), without dimming by interstellar matter and cosmic dust.” As we know, the brightness of an object is inversely proportional to square of the distance (inverse square law). Due to this fact very bright objects can appear very dim if they are very far away, and vice versa. Thus if we place the Sun at a distance of about 32.6 light years it will be not-so-bright and will be an “average” star with magnitude +4.8. The difference in these two magnitudes is -31.57 and this translates to huge brightness difference of 3.839 $\times$ 1012. And of course this  definition does not take into account the interstellar matter which further dims the stars. Thus to find the absolute magnitude of the stars we also need to know their distance. This is possible for some nearby stars for which the parallax has been detected. But for a vast majority of stars, the parallax is too small to be detected because they are too faraway. The distance measure parsec we saw earlier is defined on basis of parallax, one parsec is the distance at which 1 AU (astronomical unit: distance between Earth and Sun) subtends an angle of one arcsecond or 1/3600 of a degree.

Thus finding distance to the stars is crucial if we want to know their actual magnitudes. For finding the cosmic distances various techniques are used, we will not go into their details. But for our current purpose, we know that the stars dataset has absolute magnitudes of stars. The range of magnitudes in the dataset is

> range(stars$magnitude) [1] -8 17 Thus stars in the dataset have a difference of 25 magnitudes, that is a brightness ratio of 105! Which are these brightest and dimmest stars? And how many stars of each magnitude are there in the data set? We can answer these type of questions with simple queries to our dataset. For starters let us find out the brightest and dimmest stars in the dataset. Each row in the dataset has an index, which is the first column in the table from RStudio above. Thus if we were to write: > stars[1] it will give us all the entries of the first column, star 1 Sun 2 SiriusA 3 Canopus 4 Arcturus 5 AlphaCentauriA 6 Vega 7 Capella 8 Rigel 9 ProcyonA 10 Betelgeuse ... ... But if we want only a single row, instead of a column, we have to tell that by keeping a , in the index 1. Thus for the first row we write  > stars[1,] > star magnitude temp type 1 Sun 4.8 5840 G Thus to find the brightest or dimmest star we will have to find its index and then we can find its name from the corresponding column. So how do we do that? For this we have functions which.max and which.min, we use them thus: > which.max(stars$magnitude) [1] 76

We feed this to the dataset and get
 > stars[76,] star magnitude temp type 76 G51-I5 17 2500 M

This can also be done in a single line

> stars[which.min(stars$magnitude), ] star magnitude temp type 45 DeltaCanisMajoris -8 6100 F Now let us check the distribution of these magnitudes. The simplest way to do this is to create a histogram using the hist function. hist(stars$magnitude)

This gives the following output

As we can see it has by default binned the magnitudes in bins of 5 units and the distribution here is bimodal with one peak between -5 and 0 and another peak between 10 and 15. We can tweak the width of the bars to get a much finer picture of the distribution. For this hist function has option to add breaks manually. We have used the seq function here ranging from -10 to 20 in steps of 1.

> hist(stars$magnitude, breaks = seq(-10, 20, by = 1)) And this gives us: Thus we see that the maximum number of stars (9) are at -1 magnitude and three magnitudes have one star each while +3 magnitude doesn’t have any stars. This histogram could be made more reader friendly if we can add the count on the bars. For this we need to get some coordinates and numbers. We first get the counts mag_data <- hist(stars$magnitude, breaks = seq(-10,20, 1), plot = FALSE)

This will give us the actual number of counts

> [1] 0 1 2 1 7 6 4 3 3 9 6 4 4 0 2 5 2 2 2 1 5 7 3 7 5 3 2 0 0 0

Now to place them at the middle of the bars of histogram we need midpoints of the bars, we use mag_data$mids to find them and mag_data_counts for the count for labels. > text(mag_data$mids, mag_data$counts, labels = mag_data$counts, pos = 3, cex = 0.8, col = "black")

To get the desired graph

Thus we have a fairly large distribution of stellar magnitudes.

Now if we ask ourselves this question How many stars in this dataset are visible to the naked eye? What can we say? We know that limiting magnitude for naked eye is +6. So, a simple query should suffice:

count(stars %>% filter(magnitude <= 6)) n 1 57

(Here we have used the pipe function  %>%  to pass on data from one argument to another from the dplyr pacakge. This query shows that we have 57 stars which have magnitude less than or equal to 6. Hence these many should be visible… But wait it is the absolute magnitude that we have in this dataset, so this question itself cannot be answered unless we have the apparent magnitudes of the stars. Though computationally correct, this answer has no meaning as it is cannot be treated same as the one with apparent magnitude which we experience while watching the stars.

## Temperature of Stars

The third column in the data set is the temp or the temperature. Now, at one point in the history of astronomy people believed that we would never be able to understand the structure or the content of the stars. But the invention of spectroscopy as a discipline and its application to astronomy made this possible. With the spectroscope applied to the end of the telescope (astronomical spectroscopy), we could now understand the composition of the stars, their speed and their temperature. The information for the composition came from the various emission and absorption lines in the spectra of the stars, which were then compared with similar lines produced in the laboratory by heating various elements. Helium was first discovered in this manner: first in the spectrum of the Sun and then in the laboratory. For detailed story of stellar spectroscopy one can see the book Astronomical Spectrographs and Their History by John Hearnshaw. Though an exact understanding of the origin of the spectral line came only after the advent of quantum mechanics in early part of 20th century.

But the spectrum also tells us about the surface temperature of the stars. How this is so? For this we need to invoke one of the fundamental ideas in physics: the blackbody radiation. Now if we find the intensity of radiation from a body at different wavelengths (or frequencies) we get a curve. This curve is typical and for different temperatures we get unique curves (they don’t intersect). Of course this is true for an ideal blackbody which is an idealized opaque, non-reflective body. Stellar spectrum is like that of an ideal blackbody,  this continuous spectrum is punctuated with absorption and emission lines as shown in the book cover above.

The frequency or wavelength at which the radiation has maximum intensity (brightness/luminosity) is related to the temperature of the body, typical curves are shown as above. Stars behave almost as ideal black bodies. Notice that as the temperature of the body increases the peak radiation wavelength increases (frequency is reduced) as shown in the diagram above. These relationships are given by the formula

$$L = 4 \pi R^{2} \sigma T^{4}$$

where $L$ is the luminosity, $R$ is the radius, $\sigma$ is Stephan’s constant and $T$ is the temperature. This equation tells us that $L$ is much more dependent on the $T$, so hotter stars would be more brighter.

It was failure of the classical ideas of radiation and thermodynamics to explain the nature of blackbody radiation that led to formulation of quantum mechanics by Max Planck in the form of Planck’s law for quantisation of energy. For a detailed look at the history of this path breaking episode in history of science one of the classics is Thomas Kuhn’s Black-Body Theory and the Quantum Discontinuity, 1894—1912.

That is to say hotter bodies have shorter peak frequencies. In other words, blue stars are hotter than the red ones. (Our hot and cold symbolic colours on the plumbing peripherals needs to change: we have it completely wrong!) Thus the spectrum of the stars gives as its absolute temperature, along with all other information that we can obtain from the stars. The spectrum is our only source of information for stars. This is what is represented in the third column of our data. For our dataset the range of stellar temperatures we have a wide range of temperatures.

range(stars$temp) [1] 2500 33600 Let us explore this column a bit. If we plot a histogram with default options we get: > hist(stars$temp)

This is showing maximum stars have a temperature below 10000. We can bin at 1000 and add labels to get a much better sense. Which star has 0 temperature??

hist(stars$temp, breaks = seq(0,35000, 1000)) > temp_data <- hist(stars$temp, breaks = seq(0,35000, 1000), plot = FALSE) > text(temp_data$mids, temp_data$counts, labels = temp_data$counts, pos = 3, cex = 0.8, col = "black") This plot gives us much better sense of the distribution of stellar temperatures. With most of the temperatures being in 2000-3000 degrees Kelvin range. The table()  function also provides useful information about distribution of temperatures in the column. > table(stars$temp)

2500 2670 2800 2940 3070 3200 3340 3480 3750 3870 4130 4590 1 10 7 5 1 3 4 1 1 2 3 3 4730 4900 4950 5150 5840 6100 6580 6600 7400 7700 8060 9060 1 5 1 2 2 2 1 1 2 1 2 1 9300 9340 9620 9700 9900 10000 11000 12140 12400 13000 13260 14800 1 2 3 1 4 1 1 1 1 1 1 1 15550 20500 23000 25500 26950 28000 33600 1 4 2 5 1 2 1

While the summary() function provides the basic statistics:

> summary(stars$temp) Min. 1st Qu. Median Mean 3rd Qu. Max. 2500 3168 5050 8752 9900 33600    ## Type of Stars The fourth and final column of our data is type. This category of data is again based on the spectral data of stars and is type of spectral classification of stars. “The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere’s temperature. ” The categories of the type of stars and their physical properties are summarised in the table below. The type of stars and their temperature is related, with “O” type stars being the hottest, while “M” type stars are the coolest. The Sun is an average “G” type star. There are several mnemonics that can help one remember the ordering of the stars in this classification. One that I still remember from by Astrophysics class is Oh Be A Fine Girl/Guy Kiss Me Right Now. Also notice that this “type” classification is also related to size of the stars in terms of solar radius. In our dataset, we can see what type of stars we have by > stars$type [1] "G" "A" "F" "K" "G" "A" "G" "B" "F" "M" "B" "B" "A" "K" [15] "B" "M" "A" "K" "A" "B" "B" "B" "B" "B" "B" "A" "M" "B" [29] "K" "B" "A" "B" "B" "F" "O" "K" "A" "B" "B" "F" "K" "B" [43] "B" "K" "F" "A" "A" "F" "B" "A" "M" "K" "M" "M" "M" "M" [57] "M" "A" "DA" "M" "M" "K" "M" "M" "M" "M" "K" "K" "K" "M" [71] "M" "G" "F" "DF" "M" "M" "M" "M" "K" "M" "M" "M" "M" "M" [85] "M" "DB" "M" "M" "A" "M" "K" "DA" "M" "K" "K" "M"

Our Sun is G-type star in this classification (first entry). If we use the table() function on this column we get the frequency of each type of star in the dataset.

> table(stars$type) A B DA DB DF F G K M O 13 19 2 1 1 7 4 16 32 1 And to see a barplot of this table we will use ggplot2() package. Load the package using library using library(ggplot2) and then > stars %>% ggplot(aes(type)) + geom_bar() + geom_text(stat = "count", aes(label = after_stat(count)), vjust = -0.5, size = 4) Thus we see that “M” type stars are the maximum in our dataset. But we can do better, we can sort this data according the frequency of the types. For this we use the code: > type_count <- table(stars$type) > # count the frequencies > sorted_type <- names(sort(type_count)) > # sort them > stars$type <- factor(stars$type, levels = sorted_type) > # reorder them with levels and plot them > stars %>% ggplot(aes(type)) + geom_bar(fill = "darkgray") + geom_text(stat = "count", aes(label = after_stat(count)), vjust = -0.5, size = 4)

And we get

## To plot HR Diagram

Now, given my training in astronomy and astrophysics, the first reaction that came to my mind after seeing this data was this is the data for the HR Diagram! The HR diagram presents us with the fundamental relationship of types and temperature of stars. This was an crucial step in understanding stellar evolution. The intials HR stand for the two astronomers who independently found this relationship: The diagram was created independently in 1911 by Ejnar Hertzsprung and by Henry Norris Russell in 1913.

By early part of 20th century several star catalogues had been around, but nothing stellar evolution or structure was known. The stellar spectrographs revealed what elements were present in the stars, but the energy source of the stars was still an unresolved question. Classical physics had no answer to this fundamental question about how stars were able to create so much energy (for example, see Stars A Very Short Introduction by James Kaler on the idea that charcoal powers the Sun by Lord Kelvin). Added to this was the age of the stars, from geological data and idea of geological deep time, the Sun was estimated to be 4 billion years old as was the Earth. So stars had been producing so much energy for such a long time! But that is not the point of this post, the HR diagram definitely helped the astronomers think about the idea that stars might not be static but evolve in time. The International Astronomical Union conducted a special symposium titled The HR Diagram in 1977. The proceedings of the symposium have several articles of interest on the history of creation and interpretation of the HR Diagram.

I think it was but natural that astronomers tried to find correlations between various properties of thousands of stars in these catalogues. And when they did they find a (co-)relationship between them. The HR diagram exists in many versions, but the basic idea is to plot the absolute magnitude and temperature (or colour index). Let us plot these two  to see the co-relation, for this we again use the ggplot2() pacakge and its scatterplot function geom_point().

> stars %>% ggplot(aes(temp, magnitude)) + geom_point()

This gives us the basic plot of HR diagram.

Immediately we can see that the stars are not randomly scattered on this plot, but are grouped in clusters. And most of them lie in a “band”. Though there are outliers at the lower temperature and magnitude range and high magnitude and temperature around 10-15 thousand range. We see that most stars lie in a band which is called the “Main Sequence”. We can try to fit a function here in this plot using some options in the ggplot() library, we use geom_smooth() function for this and get:

stars %>% ggplot(aes(temp, magnitude)) + geom_point() + geom_smooth( se = FALSE, color = “red”)

Of course this smooth curve is a very crude (perhaps wrong?) approximation of the data, but it certainly points us towards some sort of correlation between the two quantities for most of the stars. But wait, we have another categorical variable in our dataset, the type of stars. How are the different types of stars distributed on this curve? For this we introduce type variable in the aesthetics argument of ggplot() to colour the stars on our plot according to this category:

> stars %>% ggplot(aes(temp, magnitude, color = type)) + geom_smooth( se = FALSE, color = "red") + geom_point()

This produces the plot

Thus we see there is a grouping of stars by the type. Of course the colours in the palette here are not the true representatives of the star colours. The HR diagram was first published around 1911-13, when quantum mechanics was in its nascent stages. The ideas of Rutherford’s model were still extant and was just out. The fact that this diagram indicated a relationship between the magnitude and temperature, led to thinking about stellar structure itself and its ways of producing energy with fundamentally new ideas about matter and energy from quantum mechanics and their transformation from relativistic physics. But that is a story in future. For now, let us come to our HR diagram. From the dataset we have one more variable, the star name which could be used in this plot. We can name all the stars in the plot (there are only 96). For this we use the geom_text() function in ggplot()

> stars %>% ggplot(aes(temp, magnitude, color = type), label = star) + geom_smooth( se = FALSE, color = "red") + geom_point() + geom_text((aes( label = star)), nudge_y = 0.5, size = 3)

This produces a rather messy plot, where most of the starnames are on top of each other and not readable:

To overcome this clutter we use another package ggrepel() with the following code:

> stars %>% ggplot(aes(temp, magnitude, color = type), label = star) + geom_smooth( se = FALSE, color = "red") + geom_text_repel(aes(label = star))

This produces the plot with the warning "Warning message: ggrepel: 13 unlabeled data points (too many overlaps). Consider increasing max.overlaps ". To overcome this we increase the max.overlaps to 50.

> stars %>% ggplot(aes(temp, magnitude, color = type), label = star) + geom_point() + geom_smooth( se = FALSE, color = "red") + geom_text_repel(aes(label = star), max.overlaps = 50)

This still appears cluttered a bit, scaling the plot while exporting gives this plot, though one would need to zoom in to read the labels.

Of course with a different data set, with larger number and type of stars we would see slightly different clustering, but the general pattern is the same.

We thus see that starting from the basic data wrangling we can generate one of the most important diagrams in astrophysics. I learned a lot of R in the process of creating this diagram. Next task is to

# A Short History of Initial Development of Quantum Mechanics

A timeline created using h5p. The reference book used is Lev Tarasov – Basic Concepts of Quantum Mechanics.

# Galileo’s Experiments on Accelerated Motion

A short account of Galileo’s description of his own experiment on accelerated motion — a short account of it, the apparatus he used and the results he got.
The first argument that Salviati proves is that in accelerated motion the change in velocity is in proportion to the time (𝑣 ∝ 𝑡) since the motion began, and not in proportion to the distance covered (𝑣 ∝ 𝑠) as is believed by Sargedo.

“But for one and the same body to fall eight feet and four feet in the same time is possible only in the case of instantaneous (discontinuous) motion; but observation shows us that the motion of a falling body occupies time, and less of it in covering a distance of four feet than of eight feet; therefore it is not true that its velocity increases in proportion to the space. (Salviati)

Also, he proves that the increase in proportion is not of simple doubling but larger. They agree upon a definition of uniformly accelerated motion,

“A motion is said to be equally or uniformly accelerated when, starting from rest, its momentum receives equal increments in equal times. (Sargedo)

To this definition Salviati adds an assumption about inclined planes, this assumption is that for a given body, the increase in speed while moving down the planes of difference inclinations is equal to the height of the plane. This also includes the case if the body is dropped vertically down, it will still gain the same speed at end of the fall as it would gain from rolling on the incline This assumption makes the final speed independent on the profile of the incline. For example, in the figure below, the body falling along𝐶 → 𝐵, 𝐶 → 𝐷 and 𝐶 → 𝐴 will attain the same final speed.

This result is also proved via a thought experiment (though it might be feasible to do this experiment) for a pendulum. The pendulum rises to the height it was released from and not more.
After stating this theorem, Galileo then suggests the experimental verification of the theorem. of The actual apparatus that Galileo uses is an wooden inclined slope of following dimensions: length 12 cubits (≈ 5.5 m, 1 cubit ≈ 45.7 cm), width half-cubit and three-finger breadths thick . In this plank of wood, he creates a very smooth groove which is about a finger thick. (What was the thickness of Galileo’s fingers?) The incline of this plank are changed by lifting one end. A bronze ball is rolled in this groove and time taken for descent is noted.

“We repeated this experiment more than once in order to measure the time with an accuracy such that the deviation between two observations never exceeded one- tenth of a pulse-beat.

Then Galileo performed variations in the experiment by letting the ball go different lengths (not full) of the incline and “found that the spaces traversed were to each other as the squares of the times, and this was true for all inclinations of the plane”. Each variation was repeated hundreds of times so as to rule out any errors. Also, the fact that for different inclines the times of descent were in noted and were in agreement with the predictions.
Since there were no second resolution clocks to measure time, Galileo devised a method to measure time using water. This was not new, water clocks were used earlier also.

The basic idea was to the measure the amount of water that was collected from the start of the motion to its end. The water thus collected was weighed on a good balance.This weight of water was used as a measure of the time. A sort of calibration without actually measuring the quantity itself: “the differences and ratios of these weights gave us the differences and ratios of the times”

Galileo used a long incline, so that he could measure the time of descent with device he had. If a shorted incline was used, it would have been difficult to measure the shorter interval of time with the resolution he had. Measuring the free fall directly was next to impossible with the technology he had. Thus the extrapolation to the free fall was made continuing the pattern that was observed for the “diluted” gravity.

“You present these recondite matters with too much evidence and ease; this great facility makes them less appreciated than they would be had they been presented in a more abstruse manner. For, in my opinion, people esteem more lightly that knowledge which they acquire with so little labor than that acquired through long and obscure discussion. (Sargedo)

### Reference

Dialogues Concerning Two New Sciences

# An account of Nagpur state from 1790

This is an interesting account of Nagpur state from late eighteenth century. It is part of a small book titled Journal Of A Route To Nagpore by Daniel Robinson Leckie. I have taken some liberty to replace the long s typeset as f with regular s. For example, coft is cost. Some of the names are in archaic English but one can make sense of the them. For example Peshwa is Paishwah. This account shows the extent of the Rajah of Nagpore’s territories as well as some peculiarities of the region. Some of the places that are mentioned are the fortifications, palace, Jumma Talao, Sakkardarah etc. The account also has a short, somewhat incorrect, history of the house of the Bhoslas. Leckie says the Nagpur Bhoslas were descended from Shivaji’s house which clearly was not the case. Also there are remarks on the current affairs of the Nagpur state with the Peshwa in Pune and Chatrapati in Satara.

ACCOUNT OF NAGPORE,

&c. &c.

NAGPORE, situated in 79º 46′ east longitude from Greenwich, and 21º 49′ north latitude, is the present capital of Gondwauna1, a name little known to Europeans, perhaps owing to the remote situation of it from our settlements, and the Rauj2 of that name having been dismembered before we possessed any territory in India, at which time the comparatively confined state of the affairs of the Company did not lead to geographical inquiries.

I have taken no small degree of pains to ascertain the boundaries of Gondwauna; and though I will not pretend to say that the information I have procured is in every respect: exact, yet it may serve to give a general idea of the extent of the country.

It is not amiss to observe, that the people of this place are by no means communicative, and very circumspedt in giving information, particularly to Europeans, and it has cost me no small degree of trouble to collect what trifling information this account contains.

Gondwauna is bounded on the north-east; by an imaginary line, drawn from the town of Belhare to the city of Ruttunpoor; on the south-east by such another imaginary line, drawn from Ruttunpoor through the village of Soormul (situated about five coss to the north-east of Nurrah, which last is laid down in the map), to the junction of the Oordah and Beingunga rivers; on the south-wedt by the Oordah (Wadha) river; and pn the north-east by that chain of mountains which separates it from Malwa.

When Gondwauna was partly reduced by Aulumgwer, he obliged a great number of the natives together with the Rajah, to embrace the Mahomedan religion ; and the country remained for a series of years in this situation, the Rajah paying a fort of homage to the Moghul, as lord paramount : when, in the beginning of the present century, Ragojee Bhooshla, descended from the great Sevagi, reduced the greatest part of Gondwauna, to the south of the Nurbudda, with the province of Berar. The lenity with which he treated the Gonde Rajah deserves particular mention, as it shows a trait of humanity in the Merhattahs worthy of the highest pitch of civilization. He not only abstained from all forts of personal violence, but allotted three lachs of rupees annually for the Gonde Rajah’s maintenance, and the fort for him to live in, by no means as a confinement. Burhaun Shah, the son of the conquered Rajah, has still handsome allowances, and the fort to live in ; and the confidence which the late Moodajee placed in him was great: for what could be a greater mark of it in the East, than putting his family and women under his charge when he went upon any warlike expedition? which he constantly did.

Ragojee was the founder of Nagpore, which he surrounded with a rampart, it being only an insignificant village appertaining to the fort prior to his capture of it. It is situated oh a high plain, is richly cultivated, and produces fine wheat, and bounded by hills to the north- west and south. The Nag Nudde, a rivulet running to the southward, gives name to the town.

The houses are generally meanly built and covered with tiles, and the streets are narrow and filthy. The only good building is the palace, begun by the late Moodajee, and now finishing by his fon, the present Rajah ; it is built of a blue done dug out of a quarry in large blocks on the western skirts of the town. The present Rajah, however, has destroyed the grand effect which would have been produced by the stone alone, by intermixing brick-work in the building. There is a very large and deep3 tank near the west gate, called Jumma Tallow, three sides of which are handsomely built up with masonry ; and the Rajah has a foundery to the southward of the town, called Shukerderri, where he calls tolerably good brass guns. There, with some few gardens of the Rajah’s, neatly laid out in walks planted with cypress-trees, and interspersed with fountains, are the only places of note at Nagpore.

It should appear that Major Rennell (Memoir, second edition, 4to. page 12) is not perfectly clear with regard to the idea he has formed of the Merhattah state, that all the chiefs owe a fort of obedience to the Paishwah, resembling that of the German Princes to the Emperor. The account I heard from the Dewaun4 in the Durbar5 was,

But the fine extensive country which the Paishwah occupies, together with the advantage of playing the Sattarah puppet, will always give him influence with the other chiefs.

“That there is a person whom they call the representative of the Rauj, who is kept in the fort of Sattarah, and he is treated with all imaginable respect when he makes his appearance at Poonah, which is only upon particular occassions ; and when at Sattarah he is supplied with every luxury, and magnificently attended. On the demise of this image of government the handsome son of some poor man is chosen to supply his room. The Paishwah is prime minister to the Merhattah state; the Rajah of Nagpore, &c. commander in chief of the armies ; and they, as well as the rest of the chiefs, call themselves. servants of the Rauj; and none acknowledges the least immediate authority of the Paishwah, but they are all bound in cafes of necessity to render mutual assistance to each other, for the public good of the constitution.’’

The present Rajah, Rogojee Bhooshla, the grandson of the Conqueror (Ragojee the first was succeeded by his eldest son, Jannojee who was succeeded by his brother Sabage, who was slain in battle by Moodajee, the father of the. present Rajah. I have not the particulars their histories) does not seem to be either adapted to civil or military business ; he is generally dressed plainly in white, but wears costly diamonds and pearls; his behaviour is courteous to strangers. His great penchant is for elephants and mares. He has about 200 of the former, the finest; I ever beheld; and they are fed so sumptuously with sugar-cane, treacle, ghee, &c.. and not unfrequently fowl pallow, that they become almost mad with lust, breaking their chains and doing great mischief, which is considered by the Merhattahs as fine sport. The principal people about the Rajah are, his brother, Munnea Bapoo, a very quiet young man; Bhowaunny Caulloo, the Dewaun, a shrewd old fellow, and his nephew, Pondrang, the commander and paymaster of the army; Siree Dhur, the Monshee; and Mahadajee Leshkery, the Rajah’s confident, who is consulted on all occasions.

The Rajah does not keep up above 10,000 horse, the pay of which, as is the custom among all native princes, is irregularly distributed. He has two battalions of Sepoys, armed and clothed like ours ; and although they have been drilled by black officers, formerly belonging either to the Nabob of Lucknow, or our service, yet they go through their exercise very badly, and I do not think they will be able to make a stand against any body of native Sepoys disciplined by European officers.

I have heard that the total collections of the Rajah’s dominions, including Ruttunpore and Cuttae, only amount to seventy lacks of rupees per annum. I will not, however, pretend to affirm that this is exact though I do not think it can much exceed that sum; for the Rajah’s country, notwithstanding the great extent of it, does not contain a proportionable quantity of cultivated land to that which is waste and occupied by forests.

It is generally supposed that Nagpore is the capital of Berar. This is evidently a mistake. The inhabitants of Nagpore talk relatively of Berar as an adjoining province, as we do of Bahar to Bengal; and it has been shown that Nagpore is a city of late date. Elichpour is the capital of Berar, by the accounts I have received from the natives, who represent it as a very ancient city, and much larger than Nagpore.

A custom prevails in this town, which I cannot forbear taking notice of, because it serves to prove that long usage will give a plausibility to things seemingly the most preposterous. The bramins and best people at Nagpore have women attendants upon their families, whom they breed up from their childhood, and are called Butkies, or Slauls. They attend on their masters and mistresses during the day-time, and are permitted to go to any man they please in the night; some of them become very rich, and they are in general very handsome, fine women.

Nagpore,

August 20, 1790.

(Daniel Robinson Leckie)

Journal Of A Route To Nagpore

1The three ancient capitals of Gondwauna were Gurry Mudlah, Gurry *****, and Deogur.

2The dominion of a Raujah is called a Rauj, that of a King is denominated a kingdom.

3Pond

4Minister

5Court

# Book Review: Ages in Chaos by Stephen Baxter

Ages in Chaos is a scientific biography of James Hutton by Stephen Baxter. Hutton was a Scottish scientist who also played his part in Scottish enlightenment. Hutton was the first to speculate on the idea deep time required for geological processes at the end of 1700s arguing with evidence he collected. He was trained as a medical doctor, practiced farming for 10 odd years and had continued his explorations of geology throughout. The prevalent theories of geology, called Neptunists, posited that water was the change agent. Hutton on the other hand posited that it was heat which was responsible for changes, hence Vulcanists. Also, another thing was that of time needed for this change. As others of his era, Hutton was deeply religious, like Newton, wanted to find evidence for creation as per bible.
During his time, especially popular was the idea of flood as per Bible, while the Earth was literally considered to be 6000 years old. This created a problem for Hutton, who was labelled to be atheist and heretic for suggesting that Earth is much older and that there was no design. But Hutton was a conformist and wanted to find a uniform evidence for all observable aspects. He was not like a modern scientist, as he is painted many times. The ideas were vehemently attacked on each point. Though he went to the field to find geological examples for this theory. James Watt, Black and John Playfair were his friends and provided him with evidence in the form of rock samples. During his lifetime, Hutton’s ideas will not find much audience. But due to his friends, his ideas sustained a a barrage of criticisms. Only in the next generation with Lyell this work would find acceptance. This idea of a deep time was crucial in formation Darwin’s theory.
https://www.goodreads.com/book/show/157978.Ages_in_Chaos
The book reads well mostly, but at times a complete lack of illustrations in the forms of geological artefacats and maps (of Scotland) makes it difficult to read well.

# Book Review: Pendulum: Léon Foucault and the Triumph of Science by Amir D. Aczel

The book traces Leon Foucault’s ingenious approach to solving the problem of providing a terrestrial proof of rotation of the Earth. The pendulum he devised oscillates in a constant plane, and if properly engineered (as he did) can actually show the rotation of the Earth. The demonstration is one the most visually impressive scientific experiments. Also, Foucault gave prediction, an equation which would tell us how the pendulum will behave at different parts of the Earth. The pure mathematicians and physicists alike were taken aback at this simple yet powerful demonstration of the proof which eluded some of the most brilliant minds, which includes likes of Galileo and Newton. Rushed mathematical proofs were generated, some of the mathematicians earlier had claimed that no such movement was possible. That being said, Foucault was seen as an outsider by the elite French Academy due to his lack of training and degree. Yet he was good in designign things and making connections to science. This was presented to the public in 1851, and the very next year in 1852 he created another proof for rotation of the Earth. This was done by him inventing the gyroscope.. Gyroscope now plays immense role in navigation and other technologies. Yet he was denied membership to the Academy, only due to interest of the Emperor Napolean III in his work in 1864. The pendulum is his most famous work, but other works are also of fundamental significance.

• He was first person to do photomicrography using Daguerreotype
• Accurate measurment of speed of light using rotating mirrors –
• Devised carbon arc electric lamp for lighting of micrcoscope
• One of the first to Daguerreotype the Sun
• Designed the tracking systems used in telescopes
• also designed many motors, regulators to control electrical devices

There are a couple of places in the book where Aczel seems to be confused, at one point he states parallax as a proof for rotation of Earth around its axis, whearas it is more of a proof of Earths motion around the Sun. At another place he states that steel was invented in 1800s which perhaps he means to say that it was introduced in the west at the time. Apart from this the parallels between the rise of Napoleon III, a Nephew of Napolean, to form the second Empire in France and Foucault’s own struggle for recognition of his work and worth is brought out nicely.

# Review of Laal Kaptaan

Recently I saw the movie Laal Kaptaan (लाल कप्तान, literal translation Red Captain). Though I had seen the trailer when it was released sometime back this year, I did not see the movie. The visuals in the trailer were quite good, so I decided to finally watch it. And I was not disappointed. This is one of the few movies in recent times that I have managed to see in one shot. Or rather the movie managed to make me do it.

The major part of the movie is set in the region of Bundelkhand (literally the dominion of the Bundelas). This region which falls South-East of Agra and Delhi has historical places like Jhansi, Gwalior, Panna, Chhatarpur, Banda and Orchha within its folds has been historically important. The province of Awadh (Oudh) lies to the east of Bundelkhand and Ganges marks the boundary to the East, while the Rajputana lies to the West. The Yamuna divides the region into two, with the majority of the part lying to the West of Yamuna. The region between the two mighty rivers is known as a doab (marked yellow in the map below). Many of these were erstwhile princely states, which also existed until 1947, when they were merged with the Indian republic.

The era when the Mughal empire was disintegrating post the death of Aurangazeb in 1707, was especially tumultuous for this region. With the power vacuum created by the decaying Mughal empire being filled by the Marathas, by this time the Chatrapati was only a titular head and real power rested with the Peshwas and the various great houses of the Marathas (Shinde, Holkar, Bhosle, Gaikwad). The Marathas laid waste to large tracts and levied chauth ( collection of one-fourth of income ) on these regions mercilessly. But in general, they were hated in this region for their bullishness and general havoc they perpetrated on the public and places. For example, they looted the Red Fort in Delhi with impunity, scrapping off precious and semi-precious stones from the Diwan-e-Khaas to do a vasuli. (I might make a dedicated post for this later.)
If the Battle of Plassey (1757) was the founding stone of the British in India, then the battle of Buxar (1764) was the first real fortification of this foundation, and the British really established themselves in India as a potent force. Though the Marathas were the most powerful, the British did not engage with them directly until the end of the century. The third Battle of Panipat (1761), a few years before the battle of Buxar limited the Maratha presence in the North severely and was one of the major reasons that led to its full demise as a political and military power by the start of the next century. Though, this enabled the houses of Shinde, Holkar, Bhosle and Gaikwad to establish their own semi-independence over the Peshwas. Eventually, everyone became under the British. But the time in which the movie is set, the Marathas were still a force to reckon with and the EIC has just established itself as a millitary and political power in much of the region from Bengal to North India along the Gangetic plains.
The movie starts just after the Battle of Buxar (1764) when a large number of people are hanged outside the fortress of Shergarh (most probably a fictional place, as I could not find it anywhere in the sources). after the British win the battle. One of the persons who sides with the British named Rehmat Khan is especially despised upon, with him being called a gaddar (traitor) by the hanged. The accused are hanged on a huge banyan tree, with their bodies hanging like overgrown fruits along its branches. It is raining and in this scene, a young teenage boy promises Rehmat Khan that one day he will also hang on the same tree.
Fast forward 25 years (1789), we are taken to the den of a dacoit (डकैत /डाकू ) where the Bairagi called by another generic name Gossain (this term I had not heard before this film). He comes in and asks for fire for his chillam. Mayhem ensues and the hunter takes his prey. The entire scene starts with dark of the night and ends in the early morning.
The horde of warrior ascetics (of which were the Gossain/Naga) came to prominence in the resulting political instability and shifting sands post the fall of the Mughal empire.

…these orders became politically significant only after the collapse of the Mughal Empire, and more particularly after British activities created political and economic chaos in the second half of the eighteenth century.

Going forward, the hunter goes on to take his reward, where the local chieftain mocks him and doesn’t want to pay. He is made to pay by the Gossain. The film then follows the Gossain on his quest to locate and kill Rehmat Khan. Though there are hints that there is a link between the Gossain and the teenage boy who is hanged in the beginning, we are not sure how they are connected. I won’t go into the plot of the film, but will instead focus on some of the characters and background of the film.
Though some of the other reviews have portrayed the character of Rehmat Khan (played by Manav Vij) as just grunting. But I think he played the role very well, perhaps these reviewers are used to seeing villains as people who yell and show a lot of emosions on their faces. He subtly played the act of a cold-blooded, calculating and cruel character quite well and was never out of character. Rehmat Khan is a Rohilla. Now, the Rohillas were of an Afghan ethnicity, and they sided against the Marathas (led by Najib ad-Dawlah) with Ahemdshah Abdali during the third battle of Panipat. The Marathas were very enraged by this and Mahadji Shinde did collect his revenge on them a few years in 1772 after Panipat by destroying Rohilkhand and scattering bones of Najib ad-Dawlah. After this defeat, the First Rohilla war happened in which the British siding with the Nawab of Oudh defeated the Rohillas and the state of Rampur of established. The second Rohilla war, in 1794, between British and the Rohillas ended their supremacy in the region. Now, the time between the two wars, there was lot of guerilla activity carried out by the Rohillas, which led them to be set as Nawabs of Rampur. Given all this chaos and uncertainty,  there were no permanent alliances or allegiances. The main part of Laal Kaptaan (c. 1789) is set in this era for the Rohillas. So, Rehmat Khan, a prominent Rohilla, defecting over to British was noteworthy, but not out of the line.
Pindaris

Pindaris were not a tribe, but a military system of bandits of all races and religions. They fluctuated in numbers, being augumented from time to timeby military adventurer from every State, and frequently amounted to as many as 30,000 men.

Pindaris present an episode in history of India, which is quite extraordinary, though skimmed upon in the history texts. Here we are witnessing a rise of a band of people whose existence was based on terrorising and looting people in distant provinces.  The Pindaris were roughly active in the last three decades of eighteenth century to the first two decades of nineteenth. Earlier they were under tutelage of Maratha cheiftains who used them as militias to wreck havoc on supply lines of the enemies and disrupt civilian peace. So them accompanying the Maratha camp is completely normal. The depiction of the Pindari lust for the loot (tum log lo khazana, mai chala lene zanana) is well done in the film. In fact, the comedy of errors that the bunch sent to hunt down Rehmat Khan is something to relish. The frustration of the little Maratha knight in being unable to  control them is well worth seeing.
But as the Maratha power came to a decline, the Pindaris in the nineteenth century became a force of their own, without masters. They would raid far, and were viscious and cruel in their tactics to make people pay. There are reports that people even committed suicides when they came to know that a Pindari raid was imminent.
Another thing worth mentioning in the film is the settings in which the film is shot. The cinematography is par excellence, set amongst fantastic fort ruins. I cannot identify the actual locations used in the film, so any information on that would be welcome.

The other character in the film worth mentioning is the Dog Walker played by Deepak Dobriyal. He has a pair of very fine Mudhol hounds (also known as Caravan hounds) named Sukhiram and Dukhiram.
The character has no name in the film, but he finds people who are wanted for a price. That is how he makes his living. He refuses a horse mount saying it interferes with  His character has many layers and he shares a special relationship with the Gossain, they respect each other. It was a treat to watch Dobriyal play this character with English hat and his greeting of:

Howde do…

The two female characters in the film, one played by Zoya and other by Heena are in their niche. Zoya as a courtesan who is neglected, while Heena playing the wife of a chieftain carries herself well. Their characters are in emotional turmoil with maternal love and the surrounding situation.

The clothing, the artefacts are all era-appropriate and so are the languages used. A lot of work must have gone in background research and it shows in the quality of the film. Kudos to the production team for that. Just that the look of Saif has a semblance to Depp’s Jack Sparrow, that could have been avoided.
Overall a very watchable film, if you have not, do watch it.

PS: A special ode to Saif Ali Khan.
In my personal opinion, Saif Ali Khan has really matured as an actor over the years and has earned my respect for it. You can’t really compare his role in Yeh Dillagi and lets say his depiction of Langda Tyagi in Omkara. It is as if you are watching two completely different actors. The variety of roles he has done in recent times, and with grace is just amazing. He has done roles which many of the mainstream actors would shy away from. Hope that we see his good form in the future also.

References

Lorenzen, D. (1978). Warrior Ascetics in Indian History. Journal of the American Oriental Society, 98(1), 61-75.

# Rotating Earth: the proofs or significance of Leon Foucault’s pendulum – Part 1

In an earlier post, we had discussed proofs of the round shape of the Earth. This included some ancient and some modern proofs. There was, in general, a consensus that the shape of the Earth was spherical and not flat and the proofs were given since the time of ancient Greeks. Only in the middle ages, there seems to have been some doubt regarding the shape of the Earth. But amongst the learned people, there was never a doubt about the shape of the Earth. Counter-intuitive it may seem when you look at the near horizon, it is not that counter-intuitive. We can find direct proofs about it by looking around and observing keenly.
But the rotation of Earth proved to be a more difficult beast to tame and is highly counter-intuitive. Your daily experience does not tell you the Earth is rotating, rather intuition tells you that it is fixed and stationary. Though the idea of a moving Earth is not new, the general acceptance of the idea took a very long time. And even almost 350 years after Copernicus’ heliocentric model was accepted, a direct proof of Earth’s rotation was lacking. And this absence of definitive proof was not due to a lack of trying. Some of the greatest minds in science, mathematics and astronomy worked on this problem since Copernicus but were unable to solve it. This included likes of Galileo, Newton, Descartes, and host of incredibly talented mathematicians since the scientific revolution. Until Leon Foucaultin the mid-1800s provided not one but two direct proofs of the rotation of the Earth. In this series of posts, we will see how this happened.
When we say the movement of the Earth, we also have to distinguish between two motions that it has: first its motion about its orbit around the Sun, and second its rotational motion about its own axis. So what possible observational proofs or direct evidence will allow us to detect the two motions? In this post, we will explore how our ideas regarding these two motions of the Earth evolved over time and what type of proofs were given for and against it.

Even more, there was a simple geometrical fact directly opposed to the Earth’s annual motion around the Sun and there was nothing that could directly prove its diurnal rotation. (Mikhailov, 1975)

Let us consider the two components of Earth’s motion. The first is the movement around the Sun along the orbit. The simplest proof for this component of Earth’s motion is from the parallax that we can observe for distant stars. Parallax is the relative change in position of objects when they are viewed from different locations. The simplest example of this can be seen with our own eyes.
Straighten your hand, and hold your thumb out. Observe the thumb with both the eyes open. You will see your thumb at a specific location with respect to the background objects. Now close your left eye, and look at how the position of the thumb has changed with respect to the background objects. Now open the right eye, and close the left one. What we will see is a shift in the background of the thumb. This shift is related by simple geometry to the distance between our eyes, called the baseline in astronomical parlance. Thus even a distance of the order of a few centimetres causes parallax, then if it is assumed that Earth is moving around the Sun, it should definitely cause an observable parallax in the fixed stars. And this was precisely one of the major roadblock

Earth moving around an orbit raised mechanical objections that seemed even more serious in later ages; and it raised a great astronomical difficulty immediately. If the Earth moves in a vast orbit, the pattern of fixed stars should show parallax changes during the year. (Rogers, 1960)

The history of cosmic theories … may without exaggeration be called a history of collective obsessions and controlled schizophrenias.
– Arthur Koestler, The Sleepwalkers

Though it is widely believed that Copernicus was the first to suggest a moving Earth, it is not the case. One of the earliest proponents of the rotating Earth was a Greek philosopher named Aristarchus. One of the books by Heath on Aristarchus is indeed titled Copernicus of Antiquity (Aristarchus of Samos). A longer version of the book is Aristarchus of Samos: The Ancient Copernicus. In his model of the cosmos, Aristarchus imagined the Sun at the centre and the Earth and other planets revolving around it. At the time it was proposed, it was not received well. There were philosophical and scientific reasons for rejecting the model.

First, let us look at the philosophical reasons. In ancient Greek cosmology, there was a clear and insurmountable distinction between the celestial and the terrestrial. The celestial order and bodies were believed to be perfect, as opposed to the imperfect terrestrial. After watching and recording the uninterrupted waltz of the sky over many millennia, it was believed that the heavens were unchangeable and perfect. The observations revealed that there are two types of “stars”. First the so-called “fixed stars” do not change their positions relative to each other. That is to say, their angular separation remains the same. They move together as a group across the sky. Imagination coupled with a group of stars led to the conceiving of constellations. Different civilizations imagined different heroes, animals, objects in the sky. They formed stories about the constellations. These became entwined with cultures and their myths.

The second type of stars did change their positions with respect to other “fixed stars”. That is to say, they changed their angular distances with “fixed stars”. These stars, the planets, came to be called as “wandering stars” as opposed to the “fixed stars”.

Ancient Greeks called these lights πλάνητες ἀστέρες (planētes asteres, “wandering stars”) or simply πλανῆται (planētai, “wanderers”),from which today’s word “planet” was derived.
Planet

So how does one make sense of these observations? For the fixed stars, the solution is simple and elegant. One observes the set of stars rising from the east and setting to the west. And this set of stars changes across the year (which can be evidenced by changing seasons around us). And this change was found to be cyclical. Year after year, with observations spanning centuries, we found that the stars seem to be embedded on inside of a sphere, and this sphere rotates at a constant speed. This “model” explains the observed phenomena of fixed stars very well.
The unchanging nature of this cyclical process observed, as opposed to the chaotic nature on Earth, perhaps led to the idea that celestial phenomena are perfect. Also, the religious notion of associating the heavens with gods, perhaps added to them being perfect. So, in the case of perfect unchanging heavens, the speeds of celestial bodies, as evidenced by observing the celestial sphere consisting of “fixed stars” was also to be constant. And since celestial objects were considered as perfect, the two geometrical objects that were regarded as perfect the sphere and the circle were included in the scheme of heavens. To explain the observation of motion of stars through the sky, their rising from the east and setting to the west, it was hypothesized that the stars are embedded on the inside of a sphere, and this sphere rotates at a constant speed. We being fixed on the Earth, observe this rotating sphere as the rising and setting of stars. This model of the world works perfectly and formed the template for explaining the “wandering stars” also.
These two ideas, namely celestial objects placed on a circle/sphere rotating with constant speed, formed the philosophical basis of Greek cosmology which would dominate the Western world for nearly two thousand years. And why would one consider the Earth to be stationary? This is perhaps because the idea is highly counter-intuitive. All our experience tells us that the Earth is stationary. The metaphors that we use like rock-solid refer to an idea of immovable and rigid Earth. Even speculating about movement of Earth, there is no need for something that is so obviously not there. But as the history of science shows us, most of the scientific ideas, with a few exceptions, are highly counter-intuitive. And that the Earth seems to move and rotate is one of the most counter-intuitive thing that we experience in nature.
The celestial observations were correlated with happenings on the Earth. One could, for example, predict seasons as per the rising of certain stars, as was done by ancient Egyptians. Tables containing continuous observations of stars and planets covering several centuries were created and maintained by the Babylonian astronomers. It was this wealth of astronomical data, continuously covering several centuries, that became available to the ancient Greek astronomers as a result of Alexander’s conquest of Persia. Having such a wealth of data led to the formation of better theories, but with the two constraints of circles/spheres and constant speeds mentioned above.
With this background, next, we will consider the progress in these ideas.
A stabilised image of the Milky Way as seen from a moving Earth.

# Why did not scientific revolution occur in India?

If one wonders why did not the scientific revolution happen in India some aspects of how knowledge was limited might have an implication. I present here a comparative study of conditions prevailing in the two societies, and how the presence of the printing press disrupted the traditional balance of knowledge and its sharing in the society. Unfortunately, in India, we have no counterpart to this event which could have lead to the spread of knowledge amongst the masses. Even if it were, the rigid caste system would have made it almost impossible for knowledge to be so freely transferred. In an era of a global village, we still feel strong repercussions of caste-based discrimination today.
Consider this about how knowledge was restricted to apprenticeship and was often lost in transition amongst the traditional Indian craftsmen.

The secret of perfection in art and crafts resided in individuals
and was never widely publicized. Master-craftsmen trained their
apprentices from a very tender age but they did not teach them the
more subtle aspects of their craft. Neither did they write books
revealing the secrets of their perfection. These points were revealed
by the master-craftsman only towards the end of his life and only to
a favoured apprentice. Their secrets often died with them. p. 211
(Rizvi - Wonder that Was India Part 2)


This was compounded by the fact that the profession that one could practice was decided by the caste one was born in. In addition to this, the mostly oral nature of the Hindu theology in Sanskrit and exclusive rights to Brahmins as custodians of this knowledge played a huge role in stifling any societal or scientific progress. The extant books (both theological and scientific, mathematical) were mostly in Sanskrit, which again restricted their readership. And as they were reproduced by hand the copies and access to them was limited. The mobility between castes was strictly forbidden. Thus we have both theological as well as scientific, mathematical and technological knowledge bound by tradition which was not available to the general public by its design. Any leakage of such a knowledge to people who were not intended to know it was met with severe punishments.
In contrast to this, consider the situation in Europe. The church did have an control over the knowledge that was taught in the universities. The Bible was in Latin, which can be seen as European counterpart of Sanskrit in terms of its functions and reach, and the Church held authority over its interpretation and usage. The impact of movable type on the spread of the Bible is well known. The translation of the Bible to publicly spoken languages and its subsequent spread to the general public is seen as a major event in the renaissance and subsequently that of the scientific revolution. This was only possible due to the struggle between Catholics and Protestants, again this did not have any counterpart in the Indian context. But as with any subversive technology the printing press did not only print the Bible. Soon, it was put to use to create materials for all types of readership.

First appearing around 1450 in the German city of Mainz, printing
rapidly spread from Johann Gutenberg's original press throughout
the German territories and northern Italy, most notably Venice.
This establishment, during the second half of the century, of
scores of print shops corresponds to two related features of
European, especially Western European, society at that time.
The first is the fairly high rate of literacy on which the market
for books and pamphlets was based. The second is the quite sudden
wide availability of a multitude oE philosophical and general
intellectual options. Together, these two features created a
situation in which knowledge for very many people was no longer
so chained to the texts of the university curriculum. This was a
new situation practically without parallel. p. 24
(Dear - Revolutionizing the Sciences)


This spread led to the creation of books in areas of knowledge where it was guarded or passed through apprenticeship.

In 1531 and 1532 there first appeared a  group of small booklets,
known as Kunstbüchlein ("Iittle craft-books"), on a variety of
practical craft and technical subjects. These anonymous books were
produced from the shops of printers in a number of German cities,
and catered to what they revealed as an eager appetite for such
things not just among German craftsmen, but among literate people of
the middling sort in general. They broke the perceived monopoly of
the craft guilds over possession of such practical knowledge as made
up metallurgy, dyeing or other chemical recipes, pottery or any of
a multitude of potential household requisites. p. 26
(Dear - Revolutionizing the Sciences)


Though, as Dear rightly points in the next paragraph just having access to information of paper about a craft does not necessarily lead to practice as experts, it nonetheless helped to overcome a belief about the fact that knowledge indeed can be transferred in the form of books via the printing press.
In the coming century, the presence of the printing press helped the spread of knowledge to all parts of Europe in all subjects of inquiry. There is no parallel to this in the Indian context. Neither the technology (in the form of a printing press) nor the drive to spread the knowledge to the general masses was present in India. In this post, I have glossed over many details but I believe there were two main reasons for a scientific revolution to not happen in India are, first the connection of caste with profession and non-availability of a technology to spread knowledge to the general public. As a result, though earlier we had a better technology and scientific knowledge we did not have a Scientific Revolution. In the current era, with the connected devices, and also with caste not being a barrier to one’s profession, who knows we might be on the doorsteps of a revolution.

# Hymn of Creation from Rig Veda

This wonderful Hymn of Creation one of the oldest surviving records of philosophic doubt in the history of the world, marks the development of a high stage of abstract thinking, and it is the work of a very great poet, whose vision of the mysterious chaos before creation, and of mighty ineffable forces working in the depths of the primaeval void, is portrayed with impressive economy of language.

“Then even nothingness was not, nor existence.
There was no air then, nor the heavens beyond it
What covered it? Where was it? In whose keeping?
Was there then cosmic water, in depths unfathomed?
“Then there were neither death nor immortality,
nor was there then the torch of night and day.
The One breathed windlessly and self-sustaining.
There was that One then, and there was no other.
“At first there was only darkness wrapped in darkness.
All this was only unillumined water.
That One which came to be, enclosed in nothing,
arose at last, bom of the power of heat.
“In the beginning desire descended on it
that was the primal seed, bom of the mind.
The sages who have searched their hearts with wisdom
know that which is is kin to that which is not.
“And they have stretched their cord across the void,
and know what was above, and what below.
Seminal powers made fertile mighty forces.
Below was strength, and over it was impulse,
“But, after all, who knows, and who can say
whence it all came, and how creation happened?
The gods themselves are later than creation,
so who knows truly whence it has arisen?
“Whence all creation had its origin,
he, whether he fashioned it or whether he did not,
he, who surveys it all from highest heaven,
he knows— or maybe even he does not know.

From – The Wonder That Was India – A. L. Basham