Does the Sun rise from the East?

If the answer is an unqualified yes, then this story would not be worth reading. And if it is in the negative, it fouls with our primary school teaching. Permit me to mention that direction of the Sunrise and the Sunset varies with the latitude and changes with the seasons. The extreme deviations are observed during what is called the Solstice days. This year (2013) the winter solstice was on 21st December. If this issue attracts your attention, get up in the morning and point a compass towards the East. If you are located in or around Delhi, you will observe that the Sunrise will be at an angle 28.8 degrees to the South of East. If you are a late riser, watch the Sunset. Once again you will see the Sun going into the horizon at an angle of about 26.4 degrees South of the West. These inputs, amongst many others have come to me from my old friend, Joseph Thomas.

Azimuth Angles

These angles are called azimuth angles. At the Equator, the angle remains nearly constant all through the year. On the rest of the Earth, it swings from South East to North East. Indeed, during the Equinox (21 March and 21 September) it becomes due East. For those interested in this subject, I am giving below, the pictures of how these angles are measured. It is customary to treat due North as zero, and then we count it clockwise. Thus East is 90 degrees, South is 180 and West is 270 degrees, as shown below:

In the Southern Hemisphere, the counting is the opposite: there, South is zero, as given below:

 

 Thomas surfed through the Internet and has sent the following figures related with the Latitude of Delhi, which is approximately 29 degrees North. In addition to the azimuth angles he has also given us ‘the noon angles’ about which we will talk a little later.

Date	Noon Elevation(Deg)	Sunrise(Hrs Local)	Sunrise(Hrs IST)	Azimuth Angle(Sunrise)	Sunset(Hrs Local)	SunsetHrs (IST)	Azimuth Angle(Sunset	Declination(Deg)	Remarks
20 Mar 13	61.00	0600	0622	090.2	1759.5	1821.5	270.1	0.000	Equinox at 1602 hrs
21 Jun 13	84.27	0458	0520	063.2	1849	1911	298.2	+23.437	Solstice at 1000 hrs
23 Sep 13	60.60	0545	0607	091.9	1744	1806	271.7	0.000	Equinox at 0146 hrs
21 Dec 13	36.43	0646	0708	118.8	1654	1716	243.6	-23.437	Winter solstice at 2230 hrs

 You may now choose your own method to determine the East and the West and observe the Sunset or the Sunrise, as you like it. The Golfers will appreciate this phenomenon more, because they see the Sun emerging through the different seasons, and watch it in all its glory. Here is a picture which I took at the Chandigarh Lake a few days back.

 

Part Two – The Story of Sundials

In the digital age, the process of telling time during day or night, is a simple process. It is on the cell phones, computers, television sets and there are clocks all around. All this is a recent phenomenon. Just a hundred years ago, very few people had a watch of their own. There were clock towers in prominent places and the Churches, which struck the hour. Go back in the history and you find that these clocks are no more than seven hundred years old. Before that, there was ONLY one method of telling time, and that was by observing the shadow cast by the Sun. Given below is a picture of a typical clock tower. It is in the Golden Temple, Amritsar. And exists even thought no one looks at it to tell time any more.

Have you ever wondered how people told time before the invention of the clock? It was through Sundial. They were created in several forms. But in all cases, there is one thing in common. Every Sundial has a surface known as the ‘gnomon’ It is inclined at an angle equal to the latitude of the place where the Sundial is located and it points towards the North. The shadow cast by the ‘gnomon’ on the dial tells the time of the day. The Sundial in the Golden temple has survived till the present day. It is located on bridge which joins the outer walkway (called ‘parkarma’) with the Sanctum Santorum. As one passes over the bridge, it is located on the left side, and is almost half way down the bridge. Given below are a couple of pictures of the instrument.

 And here is a close up of the Sundial

 The above simple Sundial has one disadvantage: at around the noon the resolution is very little, while at sunrise and the sunset, you can tell time with much greater precision. Maharaja Jai Singh of Jaipur improved upon this  and created a Large circular sundial at the Jantar Mantar in Jaipur, which was later repeated in Delhi and it continues to exist till this date as a solar observatory.

To commemorate the Golden Jubilee of our joining the National Defence Academy, Kharakvasla,  the XIX Course association erected a Sundial near the Gole Market. A picture of this dial is given below:

  

Vice Admiral Krishnan was the principal architect of this 25 feet tall monument and you see him walking on the left, with his back facing the camera. Our Pune based  friends Sooraj Sriram and Vivek Sapatnekar made valuable contribution in this project. George Poonen who came from the USA had this event covered by having a postage stamp issued by the US postal department. A picture is given below:

 While conceptualizing the model and as a memento for this two models were made in Delhi. Pictures of these models are given below. In these models we also added two vertical ‘pins’ which can measure the ‘azimuth’ angle and the ‘noon elevation’ You can see these angles marked on the model. Here are the pictures:

This model was made of stainless steel, since in the beginning we intended to use it in the final version. However, we noticed that steel shines, and therefore it does not produce sharp shadows. In the other model (made of wood) we used a anodized aluminum, which proved to be a more appropriate material. Notice the angle markings for determining solar angles.

 Sundial Time and the Clock Hour

An interesting observation we made was that the Sundial reads the solar time. It divides the daylight period into the desired number of fragments. In India, the day was conventionally divided into eight “Pahers” Four during the day and four at night. The word ‘dopaher’ (which coincides with the noon) marks the end of the second ‘paher’ The ‘paher’ was sub-divided into three ‘gharhis’ and the smaller units of time were known in India as ‘pal’ and ‘kshana’ The point to note is that during the summer when the length of the day increases, the paher became longer, and in the winter it became shorter. For a long time there was a debate amongst the intellectual on this issue. Indeed, at the end of the day, the clock hour was accepted as the universal standard, which divides the solar ‘day’ into 24 equal parts regardless of the season.

The Noon Angle

The importance of the ‘noon angle’ can hardly be over-emphasized. This is the angle which the Sun makes with the horizontal plane at the Noon time. Whenever the noon angle is closer to 90 degrees, the solar radiations have to traverse the smallest distance through our atmosphere, and so we get more light and heat. At Sunset, Sunrise and during the winter, the Sun is at a low angle, and therefore, its radiation gets attenuated. The following pictures show this phenomenon.

This is hot Sun, which we receive in the tropics. The evening Sun looks this: 

 From Which Direction Does the Sun Rise at the North Pole?

Just shoot this question at a few of your friends. And see them trying to find the answer. Some will, indeed, hit back and say that the Sun does not rise at the North Pole! This is only partially true. The Sun does rise ONCE a year in March and it sets in September. And since the ONLY direction at the North Pole is the South, the Sun rises and sets in the south!

A Tailpiece.

When I was talking about the Sundials to the children of a school, a smart child asked me, “Sir, how will you tell time with the Sundial at night?” I shot the question back at them. They came out with a number of answers including the use of the shadow of the moon, during the moonlit nights. But the smartest answer was,

               “I will ring up my cousin in the USA!!!”

AN ADDENDUM

A few days after I had uploaded this piece on the blog, my friend Ashwani told  me that he had seen a Sundial in the church at  Kasauli. He also brought two pictures which I am inserting below:

  You see Ashwani standing next to the Sundial

 And this is a close up of the Sundial

He observed the time shown by the Sundial very meticulously. And when he met me next he told me that there was a difference in the time on his watch and the one shown by the sundial. In the post above, I had mentioned that the time shown by these two techniques is INHERENTLY different. This difference is on two counts:

• A fixed difference caused by the longitude. During the days of the Sundials, the concept of ‘Standard time’ did not exist. Each Sundial goes by the local noon, which varies with our longitude. In India, IST line passes through somewhere near Allahabad. The solar noon in the East occurs before the IST while in places located West of the place it occurs after that time. We are all familiar with the fact that the Sun rises in Kolkata much earlier than Mumbai. Therefore, if the Sundial need to be used now they need a correction table.
• The other correction is related with the seasonal variation. The Sundial works by the shadow. In the winter, the days are short, so the shadow moves faster. In the summer the reverse occurs.

It needs to be remembered that ‘time’ is essentially needed to coordinate human activity. During the days of the Sundials, there were no trains, aircraft and radio programmes. Therefore no coordination was needed with people located away from the town or the village. On the basis of the shadow, the Church or the Municipality struck the hour by means of a bell or a gong, and that was enough for workers and students to reach their places of activity.

I am grateful to Mr PPS Hariprasad (e-mail hariprasadpps@gmail.com) for some very useful information he has sent. He has studied the subject in great depth. He has also informed me that a Sundial has been erected in EME Centre at Secunderabad.

TEXT AND PICTURES RECEIVED FROM Maj Gen Prabal Sen, VSM (Retd)

Veteran Maj Gen PC Sen is Director MDC, Ashok Leyland at Hosur (TN) He has sent in the following text as an addendum to this Post

Gordon Sanderson’s Sundial, New Delhi

  

I saw this Sundial for the first time when I was about 4 years old (circa 1958). We as a family of four had gone for a picnic to the Minar. It was quite far from Delhi and a favourite  picnic spot only for the adventurers.   The structure of the Sundial was small ( perhaps so as not to challenge the might and beauty of Qutb Minar in any way – British sensibility or sheer economy or maybe both?). It is tucked in a corner and one is quite likely to miss it – I still remember that it had overgrown grass around it and was very cool to the touch. It had no railings around it, it was intact (I notice from the photographs that an edge now has got damaged) and was standing in solitary splendor. There was something quite regal about it.

I remember my father reading some inscription near the sundial (please recall  that the Brits had left only 11 years back), that it was erected by his wife,  (The photograph on top and the following photograph and article downloaded from  the Internet does not mention that although). The garish and lurid railings  around the structure (and  the blue steel notice board stand) are in sharp contrast to the marble structure  quite upsetting and affronting  to one’s eyes.

The Sundial is a small specimen, made of marble & fitted with a sleek blade ( not copper as in Harmandar Sahab) to form a shadow that rotates with time. It isn’t very stylish, or stunning either, but is inscribed with a simple inscription in Latin that reads “Transit umbra; Lux permanent” (“The shadow passes, the light remains”). Constructed as a tribute to Gordon Sanderson, a former Superintendent with the Archaeological Survey of India (A.S.I.), the Sundial stands testimony to the achievements & illustrious career of Sanderson in a country where archaeologists & historians are forgotten & considered with unconcern.

Sanderson carried out extensive excavations & restoration work within the Qutb Complex, now a World Heritage Site. He also documented & researched about the structures present within the Red Fort Complex, another World Heritage Site in Delhi. Sanderson is credited with authoring several books about Indian architectural marvels & heritage sites, & this line-drawing supposedly sketched by Sanderson showing what the Qutb Complex might have looked like had all the emperors who initiated several projects here had completed them.

Please note the massive Minar  on the right , started as the Alai Minar ( Allauddin  Khilji). Khilji died before it could be completed, the Qwwatul Islam mosque is on the left corner.