Hillwoods academy, preet vihar SPACE club celebrated the winter solstice in a different way! This year we decided to do eratosthenes experiment and local noon experiment in tandem with another brach of our school in Gandhinagar, Gujrat where the school happens to be very close to tropic of Cancer! We planned to do the local noon finding at both the places of winter solstice day with gnomons of different shapes and sizes to make it more interesting. Mr. C B Devgun, President SPACE was invited on 20thDecember to give a talk on the winter solstice day and what students can do on that day. He interacted with students of SPACE club and other students and suggested them to find local noon with shadow formation of various objects.
On the day of winter solstice, around 6 teams from Hillwoods preet Vihar and 4 teams from Hillwoods Gandhinagar took the readings of the local noon. Hillwoods academy preet vihar team was under the guidance of Babita Kundalia, Coordinator, SPACE club. Various gnomons like gnomon stick provided by SPACE, basket ball pole, statue of liberty model, cricket stumps, road sighs were used to take the shadow measurements and students really enjoyed doing the shadow experiment! Hillwoods academy teams found the sunangle to be 52 degrees and Gandhinagar students found it to be 47 degrees as reported by them in evening. That turns out to be a difference of 5 degrees in latitude in both the schools (which was later verified from google earth)!! Local noon timings between both the schools were found to be around 18 minutes which converts to 4.5 degrees in longitude difference. Earth circumference was also measured taking these readings into consideration. A detailed report with readings will be soon made and sent.
We are attaching the images from the activity in the Hillwoods academy preet vihar. Pictures from the Gandhinagar branch are awaited. Students really enjoyed doing the experiment and will repeat the same again during equinox days and summer solstice day. We would like to thank SPACE for providing the technical support for the event.
STEPL (Space Technology and Education Pvt. Ltd.) conducted an experiment for school children as part of the Winter Solstice Day celebrations at Jantar Mantar on 22nd Dec by SPACE.
The competition titled 'Scientist of the Day' involved measuring the shadow of a long stick over a period of time and using the shortest shadow to find the Circumference of the Earth. This uses the concept that the sun rays shine directly overhead on the Tropic of Capricorn (the latitude line at 23.5° south, passing through Brazil, South Africa, and Australia) on the day of Winter Solstice. Younger students participated in a competition "Measuring the Sun Angle" which was a smaller part of the original one.
About 150 students from 21 schools from Delhi NCR participated in this competition, including schools such as The Airforce School, Subroto Park; DPS Sonepat; Ryan International School, Rohini; Step by Step, Noida; Apeejay School, Saket, etc. The students sat in groups amidst the green lawns surrounded by the ancient monuments and measured away for a couple of hours. It was a great experience for the teachers and students to be involved in such a project.
All the groups did a great job and attended to the measurements with attention and diligence. I am proud to announce the winners of these two competitions:
In Senior Section Ryan International School, Vasant Kunj won the first prize where as team 8 and team 7 from Ryan International School, Rohini got second and third prize respectively.
In Junior Section team 5 from The Air Force School, Subrato Park won the first prize where as team 15 and team 16 from Step By Step Greater Noida stood second and third prize respectively.
SPACE celebrated Winter Solstice with public outreach and with a large group of school students at Jantar Mantar, New Delhi22nd December was the shortest day of the winter, i.e. the Winter Solstice when the Earth's axis in the Northern Hemisphere was tilted furthest away from the sun. After this day, the day lengths slowly increase again. This day is celebrated over the world in different cultures, the most famous celebrations being at Stonehenge. SPACE observed this day in Jantar Mantar in New Delhi.
SPACE conducted public outreach at Jantar Mantar. Thankfully, although Winter Solstice indicates the peak of winter unofficially, it turned out to be a glorious sunny day. A lot of tourists and general wanderers walked through and were happy to find out what the ancient 'Jantar's (Yantras- meaning Machines) or structures were actually used for and how they were used to measure locations and time using the sun's shadow or by observing celestial objects.SPACE conducted tours of the various instruments and explained their workings.
STEPL (Space Technology and Education Pvt. Ltd.), i.e. the education wing of SPACE conducted an experiment for school children. The competition titled 'Scientist of the Day' involved measuring the shadow of a long stick over a period of time and using the shortest shadow to find the Circumference of the Earth. This uses the concept that the sun rays shine directly overhead on the Tropic of Capricorn (the latitude line at 23.5° south, passing through Brazil, South Africa, and Australia) on the day of Winter Solstice. About 200 students from 15 schools from Delhi NCR participated in this competition, including schools such as The Airforce School, Subroto Park; DPS Sonepat; Ryan International School, Rohini; Step by Step, Noida; Apeejay School, Saket, etc. The students sat in groups amidst the green lawns surrounded by the ancient monuments and measured away for a couple of hours. It was a great experience for the teachers and students to be involved in such a project.
Experimental material such as Telescopes, Binoculars and Astrokits were provided by SPACE Arcade www.spacearcade.in.
SPACE will celebrate Winter Solstice at Jantar Mantar
22nd Dec, 11:00am - 3:00 pm
SPACE will celebrate Winter Solstice with Public Outreach at Jantar Mantar, New Delhi.
Learn about all the Jantar Mantar instruments and see how they are used.
STEPL will conduct competitions on 'Measuring the Sun Angle' (Primary students) and 'Measuring the Circumference of the Earth' (Middle and Senior school students)
A solstice is an astronomical event that happens twice each year, when the tilt of the Earth's axis is most inclined toward or away from the Sun, causing the Sun's apparent position in the sky to reach its northernmost or southernmost extreme.
On the day of Winter Solstice, North Pole tilts away from the Sun and South Pole tilts towards the Sun. The Winter Solstice occurs exactly when the earth's axial tilt is farthest away from the sun at its maximum of 23° 26'. So the Sun shines at lowest heights in Northern skies and at maximum heights at Southern skies. It results in the shortest day in the Northern Hemisphere but at the same time it’s the longest day in Southern Hemisphere. So for people in Southern Hemisphere it’s a Summer Solstice.
Winter Solstice indicates winter at its peak. After this, the length of the day starts increasing and it reaches a point where day and night becomes equal in length at Vernal or Spring Equinox. The day continues to grow longer till Summer Solstice, the longest day.
The Winter Solstice will take place at 23:38 UT on 21st Dec (5:08 am IST on 22nd Dec) . In New Delhi, sunrise on winter solstice day is at 7:10 am and sunset is at 5:29 pm making it a day which is about 10 hours in duration.
On Dec 22nd, SPACE will conduct a Public Outreach in collaboration with Nehru Planetarium at Jantar Mantar, New Delhi. The students from various schools of Delhi will be performing activities tracking the shadow created by the sun using the Jai Prakash Yantra, and participating in competitions.
Since ancient times people were curious about the place they were living on ….The mother planet- Earth. After discovering the shape of earth, i.e. round, there were very few people who could think of measuring its size. Eratosthenes was one who first measured the circumference of the earth quite accurately.
Eratosthenes Background and his Experiment
Eratosthenes was a Greek living in Alexandria, Egypt, in the third century, BC. He knew that on a certain day at noon in Syene, a town a considerable distance to the south of Alaxandria, the sun shone straight down a deep well. This observation meant that the sun was then directly overhead in Syene, as shown in Figure 1. Eratosthenes also knew that when the sun was directly overhead in Syene, it was not directly overhead in Alexandria, as shown in Figure 2. Notice in both drawings, the sun’s rays are shown as parallel.
Figure 1 Figure 2
How Eratosthenes Found the Circumference of Earth
He was the first person to actually execute the idea of measuring circumference of earth and give the radius of the earth quantitatively. His idea was very simple.
He first made some simple assumptions:
·The earth is spherical
·The distance to the sun is very large compared to the size of the earth
·So the rays of the Sun falling on the earth are all parallel to each other
How did he do it, more than two thousand years ago? Take a look at Figure 3. Syene is represented by point “S,” and Alexandria by point “A”. In Figure 3, the arc length between S and A is d, and the angle corresponding to the arc SA is angle Q. The radius of Earth is R.
Eratosthenes perform the experiment at noon time. As he knew about the amazing fact about the zero shadow happening at Syene. It was very clear in his mind that the shadow can be zero only at the noon time. At other timings of the day we will certainly find some or the other shadow because of the daily movement of the sun. So, to find out whether the shadow becomes zero at Alexandria as well one had to observe it only at the noon time.
He observe at point S (in Syene) sun rayis perpendicular to the surface of Earth so casting no shadow and the sun is directly overhead there as shown in figure 4.
Therefore :
Noon shadow length at Syene on summer solstice day = 0 and sun is overhead.
He also measured the shadow of a tower A in Alexandria at noon shown in Figure 4.
The tower at A, which is perpendicular to Earth’s surface, and the ray of sunlight at point S both point to the center of Earth, and the rays of sunlight are parallel. So the angle between the sunlight and the tower is equal to Q (Alternate interior angles are equal.) Therefore: Q = Angle between Gnomon and Sun ray
Eratosthenes hired a person who walked from Alexandria till Syene and measured the distance, which cames out to be 718 km. Therefore :
d = Distance from the place where sun is overhead
If he had walked around the whole earth this curve would be 360 0 and the length he walked would be the circumference of the earth.
Therefore one can easily find out circumference of earth by using simple unitary method. According to this method if angle between Alexandria and Syene is 7º which is 50th part of the total angle at the centre of the earth…then the distance between the above two places is also just 50th of the total circumference. This can be written as the following formula:
Circumference of earth(C)/distance between two places(d)= 360º / angle between Gnomon and sunray(angle Q)
Rearranging for the circumference C, C = 360/Q X d
Measuring the Circumference of Earth by you at Jantar Mantar
You will also measure the circumference of the earth using the same method as Eratosthenes did. He measured it on the day of summer solstice but you will be measuring circumference of our planet on the day of equinox using the same technique.
So far you must have understood that, Eratosthenes used unitary method which is quite simple to implement. You only need to know the angle between place where you are doing the experiment and the place where sun is overhead and distance between these two places. Putting these values in the following formula will give us circumference of earth:
C = 360/Q X d
Let us now see how you will find he circumference of earth at Jantar Mantar -
Experiment
Material needed
Gnomon with base X 1
A plumb line (tie a nut with a thin thread) X 1
Drawing board X 1
White chart paper, sharp pencil, fine thread, board pins, protector, meter scale
Spirit Level X 1
India Map X 1(along with the scale mentioned on it)
PREPARATION:
Fix the chart paper on drawing board with the help of board pins
Unscrew the gnomon stick from the base and measure the full length of Gnomon stick several times. Record the Average length in millimetres. This is the height of the gnomon, H
Stick the gnomon base (yellow colored plastic piece) on the board using board pins in such a way that it should not move throughout the observations.
Mark with pencil, the centre of the hole where you are going to screw in the gnomon.
Screw the gnomon stick back in base.
Make a plumb line by attaching weight to the end of a string and try to make the gnomon stick as vertical as possible. For this you may stick some paper padding under base of the gnomon.
Position the board under the sun in such a way that the shadow of the tip of the gnomon is falling on the chart paper only and has plenty of space to move around without going off the chart paper.
Marking the shadow
1. Between 11:30am to 1pm mark the tip the shadow formed by the gnomon every 5 minutes.
2. Remove Gnomon from board.
3. Measure the shortest distance from the curve to the base of the pencil in millimetres several times. Record the average. This is the length L of the shadow
Measuring the Sun Angle ‘a’:
It is very simple to measure the sun angle.After conducting the experiment and measuring the length of shortest shadow you need to draw a right angle triangle with sides proportional to the Gnomon height H and shadow length L. For this draw a horizontal line CP=L; Draw a line AC perpendicular to it at one end, of length H. Join AP.
Measure the angle CAP i.e. ‘a’. This is the angle between your location and the place where sun is overhead on equator.
Measuring the Distance ‘d’
As you will be doing this experiment on the day of equinox, you already know that the sun is traveling above the equator, which means you need to find the distance between your place and equator along the longitude.
Finding this distance is also very simple as you just need an Indian map along with its scale (All maps carry a scale written on it which vary from map to map, e.g. 1cm = 150Km). You need to find the distance between Delhi and equator along with the same longitude and then multiply that to the map scale. This will give you the value of ‘d’
Alternatively you may also measure it before hand with the help of ‘Google Earth’ or any other map. One map will also be given as a reference.
* We will provide you the facility of both, google map and a large map showing India and equator on the competition site as well.
Measuring Circumference:
Using the following formula you will measure the circumference of the earth:
C/d = 360/a
C = 360/a X d
Where C – circumference, a- sun angle, d- distance between Delhi and place where sun is overhead.
June 21 is a very important day for our planet in its relationship with the sun. June 21 marks the beginning of summer in the northern hemisphere and is called the summer solstice. It simultaneously heralds the beginning of winter in the southern hemisphere. It is the longest day for peopleliving in the northern hemisphere.In 2010, the solstice occurs in the Northern Hemisphere on June 21, at 11:28 UT, i.e. at 16:58 IST. The name is derived from Latin sol (sun) and sistere (to stand still), because at the solstice, the Sun appears to stands still in its movement during its motion (it appears to travel slowly).
The earth spins around its axis, an imaginary line going right through the planet between the north and south poles. The axis is tilted somewhat off the plane of the earth's revolution around the sun. The tilt of the axis is 23.5 degrees; and thanks to this tilt, we enjoy the four seasons. For several months of the year, one half of the earth receives more direct rays of the sun than the other half. Days are longer in the summer for the northern hemisphere due to the tilt of the Earth's axis allowing for more sunlight to be projected onto the surface.
At the June solstice, Earth is positioned in its orbit so that the North Pole is leaning 23-and-a-half degrees toward the sun. As seen from Earth, the sun is directly overhead at noon 23-and-a-half degrees north of the equator, at an imaginary line encircling the globe known as the Tropic of Cancer. The sun's rays are directly overhead along the Tropic of Cancer (the latitude line at 23.5° north, passing through Mexico, Saharan Africa, and India).This is as far north as the sun ever gets. This results in the longest day of the year. For example in New Delhi, sunrise on summer solstice day in 2010 is at 5:24 am and sunset is at 7:22 pm making it a day which is almost 14 hours duration.
When the axis tilts towards the sun, as it does between June and September, it is summer in the northern hemisphere but winter in the southern hemisphere. Alternatively, when the axis points away from the sun from December to March, the southern hemisphere enjoys the direct rays of the sun during their summer months. All locations north of the equator have day lengths greater than 12 hours at the June solstice. Meanwhile, all locations south of the equator have day lengths less than 12 hours.
June 21 is called the summer solstice in the Northern Hemisphere and simultaneously the winter solstice in the Southern Hemisphere. Around December 21 the solstices are reversed and winter begins in the Northern hemisphere.
Summer Solstice Event conducted by SPACE:
To celebrate summer solstice, SPACE will be performing public outreach at Jantar Mantar, New Delhi on Monday, 21st June. Educators from SPACE will be measuring the sun angle and the sun’s declination using the Ram Yantra and the Jai Prakash Yantra instruments. They will also explain the various instruments at Jantar Mantar to the public. All media and public are invited to attend this event.
Details:
Summer Solstice:June 21, at 11:28 UT, i.e. at 16:58 IST
Event: SPACE will conduct Public Outreach and Activities
Location: Jantar Mantar, New Delhi
Date and Time: Monday, 21st June, 2010 from 11:00 AM to 1:00 PM
For more information about the article/event contact Jaishree at SPACE at 9212669934.
