Zero Shadow day

“I thought the most beautiful thing in the world must be shadow.” - Sylvia Plath, The Bell Jar

When the Sun is right overhead

When the Sun is right overhead.
© A. Paranjpye

The lack of shadow is beautiful too. And it happens twice a year, for places between +23.5 and -23.5 degrees latitude. The Sun is almost never exactly overhead at noon, but usually transits a bit lower in altitude, a bit to the north or a bit to the south. We have all studied in school that the Earth's rotation axis is inclined at 23.5 degrees to the plane of its revolution around the Sun, which is why we have seasons. This also means that the Sun, in its highest point of the day, will move from 23.5 degrees south of the celestial equator to 23.5 degrees north of the equator (Uttarayan), and back again (Dakshinayan), in a year. Of course, the northern most and southern most points are the two solstices, and the crossing of the Sun across the equator are the two equinoxes.

For people living between +23.5 and -23.5 degrees latitude, the Sun's declination will be equal to their latitude twice - once during Uttarayan and once during Dakshinayan. On these two days, the Sun will be exactly overhead at noon and will not cast a shadow of an object on the ground. This Zero Shadow Day will clearly be different for different places on earth.
Scroll down below to find your local ZSD, state-wise maps, resource material, and public ZSD events.

An Android App

You can now download an android app for your phone that was created for our Zero Shadow Day campaign.

The app will tell you the ZSD and local noon for your location or any other place, lets you interactively explore the length of shadows and the position of the Sun for any date, time and place, and also have animations that will help you understand and teach others about the ZSD. The app is coming soon in Tamil, Malayalam, Kannada, Telugu, Marathi and Hindi!

This app was made for ASI POEC by Alok Mandavgane.

When is Zero Shadow Day at your location?

You can find the two Zero Shadow Days at your location using this interactive map made by Alok Mandavgane.

Scroll down to find the nearest place to your location

ZSD Places
6 Apr & 5 Sep Indira Point
10 Apr & 1 Sep Kanyakumari, Nagercoil, Kudankulam, Trinket Island
11 Apr & 31 Aug Kovalam, Trivandrum, Kazhakoottam, Nedumangadu, Sathankulam, Tiruchendur
12 Apr & 30 Aug Varkala, Ponmudai, Paravur, Kollam, Kottarakara, Punalur, Tenkasi, Tirunelveli, Thoothukudi,
13 Apr & 29 Aug Kayankulam, Adoor, Thiruvalla, SankaranKoil, Kovilpatti, Rameshwaram, Ramanathapuram, Car Nicobar
14 Apr & 28 Aug Alappuzha, Kottayam, Vaikom, Pala, Sabarimala, Cumbum, Rajapalayam, Sivakasi, Virudhunagar, Paramakudi
15 Apr & 27 Aug Kochi, Vypin, Thodupuzha, Idukki, Munnar, Theni, Andipatti, Tirumangalam, Madurai, Sivaganga, Karaikudi
16 Apr & 26 Aug Paravur, Aluvag, Chalakudy, Valparai, Kodaikanal, Dindigul, Pudukottai, Pattukottai, Vedaranyam
17 Apr & 25 Aug Guruvayur, Ponnani, Thrissur, Ottapalam, Palakkad, Pollachi, Mettupalayam, Udumalpet, Palani, Trichy, Thanjavur, Thiruvarur, Nagapattinam, Little Andaman
18 Apr & 24 Aug Kottakal, Malappuram, Coimbatore, Gudalur, Palladam, Tiruppur, Kangayam, Karur, Kumbakonam, Mayiladuthurai, Karaikal, Poompuhar
19 Apr & 23 Aug Kozhikode, Koyilandy, Thamarassery, Ooty, Kotagiri, Avinashi, Erode, Tiruchengode, Namakkal, Sirkazhi, Chidambaram
20 Apr & 22 Aug Vadakara, Mahe, Thalassery, Perambra, Wayanad, Mudumalai, Bhavani, Mettur, Salem, Kallakuruchi, Neyveli, Panruti, Cuddalore, Port Blair
21 Apr & 21 Aug Kannur, Payyanur, Taliparamba, Dharmapuri, Sankarapuram, Villupuram, Pondicherry, Havelock Island
22 Apr & 20 Aug Kanhangad, Kasargod, Madikeri, Mysore, Srirangapatna, Shuivanasamudra, Chengam, Tiruvannamalai, Tindivanam, Long Island
23 Apr & 19 Aug Uppala Gate, Puttur, Arakalagud, Krishnarajapete, Melkote, Mandya, Channapatna, Ramanagara, Attibele, Hosur, Krishnagiri, Tirupattur, Vanaiyambadi, Kavalur, Ambur, Arani, Kanchipuram, Chengalpattu, Mahabalipuram, Kelambakkam
24 Apr & 18 Aug Mangalore, Mooadbidri, Bantwal, Sakleshpur, Hassan, Shravanabelagola, Bidadi, Bangaluru, Dasarahalli, Bangarapet, Kolar, Gudiyattam, Vellore, Arcot, Arakkonam, Sriperumbudur, Tiruvallur, Avadi, Chennai, Interview Island, Sound Island
25 Apr & 17 Aug Udupi, Brahmavar, Karkala, Sringeri, Kudremukha, Chickmagaluru, Halebeedu, Arsikere, Tiptur, Tumkur, Doddaballapura, Chickballapura, Chintamani, Chittoor, Thiruthani, Minjur, Pulicat, North Andaman
26 Apr & 16 Aug Kundapura, Trasi, Thirthahalli, Kuppali, Kadur, Tarikere, Sira, Gauribidanur, Peddur, Madanapalle, Tirupati, Srikalahasti, Sriharikota
27 Apr & 15 Aug Bhatkal, Muthala, Shivamogga, Channagiri, Hiriyur, Madakasira, Rayachoty
28 Apr & 14 Aug Honnavar, Kumta, Jog Falls, Shikaripur, Challakere, Kadiri, Nellore
29 Apr & 13 Aug Kumta, Gokarna Sirsi, Ranebennur, Davangere, Anantapur, Cuddapah, Ramathirtham
30 Apr & 12 Aug Karwar, AgondBa, Haveri, Kudigi, Tadipatri. Jammalamadugu, Proddatur, Kavali
1 May & 11 Aug Benaulim, Margao, Dandeli, Hubli, Hospet, Bellary, Guntakal, Gooty
2 May & 10 Aug Panjim. Vasco, Anjuna, Dharwad, Gadag, Gangavathi, Nandyal, Ongole
3 May & 9 Aug Sawantwadi, Belgaum, Sindhanur, Kurnool, Markapur, Chirala, Bapatla
4 May & 8 Aug Malvan, Gokak, Bagalkot, Vinukonda, Chilakaluripet, Machilipatnam
5 May & 7 Aug Devgad, Radhanagari, Mudhol, Raichur, Deosugur, Narasaraopet, Guntur, Mangalagiri, Gudivada
6 May & 6 Aug Ambolgad, Kolhapur, Ichalkaranji, Yadgir, Mahbubnagar, Vijayawada, Eluru, Bhimavaram, Tanuku
7 May & 5 Aug Ratnagiri, Sangli, Miraj, Vijayapura, Nalgonda, Nuzividu, Tadepalligudam, Rajahmundry, Kakinada
8 May & 4 Aug Jaigad, Karad, Afzalpur, Kalburgi, Suryapet, Khammam, Samarlakota
9 May & 3 Aug Chiplun, Mandrup, Akkalkot, Hyderabad, Secunderabad, Kothagudam
10 May & 2 Aug Satara, Pandharpur, Solapur, Basavakalyan, Sangareddy, Jangaon, Palwancha, Visakhapatnam
11 May & 1 Aug Mahabaleshwar, Phaltan, Tuljapur, Medak, Warangal, Vizianagaram
12 May & 31 Jul Mangaon, Baramati, Barshi, Osmanabad, Ausa, Nariapur, Malkangiri, Srikakulam
13 May & 30 Jul Mulshi, Pune, Daund, Latur, Karimnagar, Pamunuru, Sukma, Salur, Bobili
14 May & 29 Jul Alibaug, Lonavla, Talegaon Dabhade, Pimpri Chichwad, Dehu Road, Jamkhed, Ambajogai, Nizamabad, Korutla, Ramagundam, Palakonda
15 May & 28 Jul Mumbai, Navi Mumbai, Karjat, Matheran, Rajgurunagar, Manchar, Ralegan-Siddhi, Beed, Gangakhed, Mancherial, Mandamarri, Dantewada, Jagdalpur, Jeypore
16 May & 27 Jul Borivali, Thane, Dombivili, Kalyan, Bhiwandi, Badlapur, Narayangaon, Khodad, Ahmednagar, Parbhani, Nanded, Nirmal, Mamda, Dudme, Bastar, Nowrangpur, Rayagada, Taptapani, Brahmapur
17 May & 26 Jul Nala Sopara, Virar, Asangaon, Basmat, Kouta, Aheri, Chhota Dongar, Mahulpatna, Pattapur, Ganjam
18 May & 25 Jul Palghar, Kasara Budruk, Sangamner, Shrirampur, Ambad, Hingoli, Adilabad, Mulchera, Koksara, Satapada
19 May & 24 Jul Dahanu, Nashik, Kopargaon, Vaijapur, Aurangabad, Jalna, Pusad, Balharshah, Rowghat, Dharmagarh, Bhawanipatna, Bellaguntha, Puri
20 May & 23 Jul Talasari, Takh, Mehkar, Washim, Wani, Chandrapur, Mul, Keskal, Nayagarh, Motari, Saharabedi
21 May & 22 Jul Bilad, Silvassa, Khedgaon, Manmad, Kannad, Chikhli, Rohna, Wadki, Bhanupratappur, Kanker, Kusuruparaha, Bhubaneswar, Paradeep
22 May & 21 Jul Daman, Vapi, Malegaon, Chalisgaon, Buldana, Khopadi, Yavatmal, Armori, Charama, Saintala, Phulbani, Cuttack
23 May & 20 Jul Diu, Valsad, Bhadgaon, Khamgaon, Akola, Wardha, Kusumkasa, Dhamtari, Balangir, Dhenkanal, Bharcchan
24 May & 19 Jul Somnath, Jafarabad, Navsari, Amalsad, Dhule, Jamner, Shegaon, Nimbora, Wardha, Umred, Kurud, Nuapada, Angul, Bhuban, Jajpur
25 May & 18 Jul Mangrol, Talala, Rajula, Mahuva, Vadoli, Sakri, Amalner, Jalgaon, Bhusawal, Telhara, Amravati, Rajnandgaon, Nawapara Nagar, Padmapur, Bhadrak
26 May & 17 Jul Madhavpur, Datha, Surat, Bardoli, Vyara, Nardana, Chopda, Paratwada, Nagpur, Durg, Bhilai, Bhandara, DOngargarh, Raipur, Barpali, Markona
27 May & 16 Jul Keshod, Savar Kundla, Alang, Nandurbar, Shirpur, Burhanpur, Tumsar, Gondia, Katapali, Chandipur
28 May & 15 Jul Junagadh, Paltana, Ankleshwar, Shahada, Pandhurna, Tilda, Sambalpur, Balasore
29 May & 14 Jul Porbandar, Upleta, Amreli, Bhavnagar, Bharuch, Sendhwa, Chichanda, Bhatapara, Jogal, Digha, Mousuni
30 May & 13 Jul Ghumli, Jamkandorana, Rajpipla, Khargone, Khandwa, Betul, Balaghat, Raigarh, Jharsuguda, Banei, Contai, Pathar Pratima Island
31 May & 12 Jul Bhogat, Bhanvad, Gondal, Gadhada, Amod, Nasvadi, Barwani, Birsa, Kawardha, Champa, Joda, Baripada, Nandigram
1 Jun & 11 Jul Bhatiya, Kamlapur, Sarangpur, Dabhoi, Kasrawad, Sanawad, Chhindwara, Seoni, Mungeli, Bilaspur, Sundargarh, Barbil, Manda, Beida, Haldia, Devasora South
2 Jun & 10 Jul Dwarka, Rajkot, Dholera, Vadodara, Bodeli, Manawar, Sukhtara, Pandaria, Rourkela, Baharagora, Tamluk, Phura
3 Jun & 9 Jul Motikhavdi, Dhandhuka, Borsad, Harda, Chhapara, Korna, Banki Mongra, Lailunga, Jorapokhar, Kharagpur, Medinipur, Debra, Baruipur, South Bungtlang, Kawichaw East
4 Jun & 8 Jul Jamnagar, Petlad, Tutugutu, Chaibasa, Kokpara, Jhargram, Bagnan, Maheshtala, Mothbari, Siaha
5 Jun & 7 Jul Dhrol, Wankaner, Thrangadh, Limbdi, Anand, Mhow, Itarsi, Lakhnadon, Mandla, Pathalgaon, Ghatshila, Howrah, Kolkata, Hasnabad, Chawngte P, Vaumbuk
6-10 Jun & 6-2 Jul Gandhidam, Morbi, Surendranagar, Dhrangadhra, Ahmedabad, Nadiad, Godhra, Dahod, Indore, Dewas, Hoshangabad, Narsingpur, Guthurma, Kunkuri, Jamshedpur, Dhaniakhali, Kalyani, Barrackpore, Bomgain, Basirhat, Lunglei, Lungsen
11-21 Jun & 2 Jul-21 Jun Kothara, Bhuj, Gandhinagar, Ratlam, Ujjain, Tarana, Bhopal, Jabalpur, Shahpura, Chirimiri, Ambikapur, Surajpur, Ranchi, Balarampur, Purulia, Bankura, Burdwan, Hanshkali, Thenzawl, Serchhip, Zokhawthar

You can also download this list as a pdf.

The apparent motion of the Sun in a year, leading to two equinoxes and solstices. © R.L. McNish

Download state-wise maps with the ZSDs marked

These maps are from Alok Mandavgane, with the dates overlaid on top.
Kerala, T.N. & Puducherry
Karnataka & Goa
Telengana & Andhra
Maharashtra
Gujarat, D&D, and D&H
M.P.
Chhattisgarh, Odisha, W.B., Jharkhand
Tripura & Mizoram
Andaman & Nicobar

Resource material on Zero Shadow Day

These resources have been shared by their creators under a non commercial Creative Commons License. If you would like to add your resource to this list, then contact us.

Articles

A page by Paranjpye on the ZSD and many easy ways of observing it (in English)

Information on the ZSD for Karnataka in Kannada, by the Jawaharlal Nehru Planetarium

An article on the ZSD by R. Kavitha in Tamil

An article on the ZSD by Sanjeev Khudshah in Hindi

An article on the ZSD by Umashankar Mishra in Hindi

An article on the ZSD by Vibhu Mishra in Hindi

An article on the ZSD by Sonal Thorve in Marathi

Presentations

Listed below are presentations on ZSD that were created by astronomers and science popularisers. These are for public use (and with modifications if needed), but please do retain the title page that gives due credit to the authors. An introduction to ZSD by Dr. Priya Hasan (1.9 MB, English)

An introduction to ZSD by Rugved Pund of JVP (1.0 MB, English)

An introduction to ZSD by Dr. T.V. Venkateswaran (9.4 MB, English)

An activity guide for ZSD by Dr. T.V. Venkateswaran (0.7 MB, English)

An introduction to positional astronomy by Dr. T.V. Venkateswaran (2.8 MB, English)

An introduction to ZSD by Mr. Madivanane (8.8 MB, English)

Videos

Two videos in Hindi by Alok Mandavgane explaining the theory behind ZSD as well as how we can observe it

More Videos

A video explaining the concept of Zero Shadow Day made by the Arvind Gupta Science Toys group at IUCAA. Pune (in English)

The same video is also available A time-lapse video taken by Ajay Talwar from Dongla, near Ujjain

A time-lapse video taken by Arvind Paranjpye in Pune

and a news report of the ZSD public event organised by Jyotirvidya Parisanstha in Pune ...
See more videos on the ZSD from Mumbai, Puducherry, and Chennai.

6 Comments

  1. So informative page about Positional Astronomy.
    Now I decided to continue to visit this website ones in a week.

  2. Thanks a lot Sir for your Encouragement to observe the Zero Shadow Day Program on 23rd May at Chimnibhati para,Balangir of State Odisha.
    Regards
    Ananda Barpanda, District Coordinator
    Children’s Science Congress of Balangir DIST Odisha

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