is a campaign. The purpose of this campaign is to take scientific thinking
wherever the sun shines, to take doing and discovering wherever the
a.A new and strange
phenomenon, outside of everyday experience.
We started working on a cheap telescope kit, trying to replicate what Galileo had done in 1610 to first discover sunspots. We did succeed in designing a low cost simple telescope.
More interestingly, we found out, by doing and discovering , that telescopes are not necessary to see and study sunspots. We discovered the ‘Very Long Focal Length’ lens approach for projecting sunspots with a single lens. We experimented with mirrors and succeeded beyond our expectations. In March 2000, we discovered that CST Railway Station is a giant pinhole camera where anyone can see sunspots for the price of a platform ticket. Aiming at low cost sunspot viewing, we overshot and reached no cost sunspots. Now, a mass campaign really was possible.
One question arose. Why had it taken so long in history to discover sunspots ? Haven’t there been tall buildings with leaking roofs for thousands of years ? Didn’t our ancestors realise that the circular patches formed are images of the sun? Didn’t they look closely at those images ? We will not be surprised if some historical scientific texts are discovered which show that Galileo was not the first to discover sunspots. Many questions about the history of science are thrown up by the simplicity of sunspots.
It remains a fact that as of today (Feb 2001),very few people have actually seen sunspots with their own eyes. We hope that by the end of 2001 very few people will not have seen sunspots. Because, stubbornly countering the prevailing economic trend to confine and package knowledge and education , which can then be sold to those with sufficient purchasing power, the sun is available to everyone. With the methods in this workshop, it will be possible
to perform non-trivial scientific experiments and see sunspots at no cost even with a little piece of broken mirror.
As we write these words the sunspots have become so big that on some days you can actually see them with your own eyes, without magnification, if you look carefully at the sun with a good quality solar filter , tested for safety.***
Duncan Steel in his recent book ‘Eclipse’, writes : “ For centuries large sunspots had been observed with the naked eye by the Chinese when dust storms blew in from Central Asia, blanketing parts of northern China. They had similarly been noticed in Europe, but it was only when telescopes appeared in the seventeenth century that continuous monitoring of these dark markings on the solar surface was feasible.”
We disagree. Observation and continuous monitoring of sunspots is possible without a telescope by a number of low cost/ no cost (LCNC) methods. You can see sunspots on the railway platform at CST, without any telesope. (The image at CST railway station is the result of the principle of the pinhole camera)
A telescope is an instrument to gather and concentrate the light reaching us from astronomical objects like the planets and stars which is extremely faint. But the sun is different . Its light reaching us is not too faint but too strong. It does not need to be gathered and concentrated . If anything, its intensity needs to be reduced .We can study and understand many wonderful things about the sun without using a telescope.
6. GETTING STARTED :
A Black box viewer which can be easily made out of a cardboard carton is a most useful device for observing the sun outdoors. To begin with, intriguing problems can immediately be posed to the students about the shapes of images from differently shaped apertures. Why do these become circular when the distance is increased. The shapes of the images cast by mirrors of different shapes also makes a fine introductory experiment. The kids can learn about angles, inverse square law, etc. by doing and discover experiments with this simple apparatus.
7. VERY LONG FOCAL LENGTH CONVEX LENS:
To view sunspots the VLFL lens method is both elegant and simple.
It is commonly believed that a convex lens concentrates the light from the sun. This however is true only if the focal length of the lens is not too large. As the focal length of the lens increases the size of the sun’s image increases. For a very long focal length (VLFL), the diameter of the sun’s image disc can be quite large, larger than the lens itself.( In a pinhole camera also, the size of the image depends on the distance of the screen from the pinhole).
In general the following formula is true :
diameter of the
sun’s image disc = ½ degree
From this we deduce
For a 50 mm diameter lens with a focal length of 6 metres, the image of the sun will be larger than the lens itself, showing that a convex lens doesn’t necessarily concentrate light. Using a VLFL (very long focal length) convex lens, along with a cardboard shade with a hole cut in the centre , you can get a nice big image of the sun on which sunspots are clearly visible, if the lens is of reasonably good quality.
This is by far the cheapest, but not the easiest, method to project sunspots, which works because the sunlight intensity is so strong. This experiment can be done in any room which has a window or door opening outside, and which can be sufficiently darkened by putting cloth over the apertures from where light enters. Complete darkness is not necessary. Just how much darkness is needed you can discover for yourself by trial and error.
Take any available small mirror (like a face mirror selling on the footpaths for Rs 10) and keep it on a stool outside the room in a place where the sun shines on it. Adjust the angle of the mirror so that the sunlight is reflected in a bright patch on a wall of the darkened room. Increase the distance of the mirror so that it is about 20-25 metres from the wall. As you increase the distance the light patch will become more and more circular. This is the sun’s image with the mirror acting like a large ‘pin hole’. At this stage the sun’s image will be bright and diffuse, i.e. not sharp.
The next stage is to take an opaque piece of card paper and punch a hole in it of around 2-3mm diameter with an ordinary paper punch. Now hold this paper about 30 cm in front of the mirror so that the punched hole is in the centre of the light patch which now forms on the card paper. What happens to the image on the wall 20 metres away ?
Surprisingly, the image does not decrease in size. It becomes dimmer and sharper. Cut off as much light as possible in the room(except of course the light coming from the mirror) so that the image looks clearer. Now keep a white piece of paper on the wall so that the image forms on this white screen. The sunspots should be clearly visible on this image during this period of sunspot maximum.
9. HOW SUNSPOTS MOVE.
You can study how sunspots move by taping the white paper screen to the wall and tracing the outline of the suns disc. Mark the position of the sunspots and write the date next to it. Next day again form the image of the sun so that it exactly fits the circular outline. Again mark the date and position of the sunspots, which will have moved. Do this experiment every day for several weeks.
You will discover that after about four weeks the large sunspots return to their original locations. Some of the smaller sunspots may not last four weeks. You will discover the rotation of the sun, that the sun has a tilted axis of rotation, an equator and poles just like the earth. (Remember however that the direction of rotation is changed by reflection in the mirror, and the image is again inverted by the pinhole camera effect. Figure out the real direction of rotation.)
10. SUNSPOTS WITH AN LC TELESCOPE
You can make a simple
telescope with which to project sunspots. Though you can look directly
at the sun through the telescope with a proper filter, we do not recommend
this method as most common filters are not safe, and a telescope concentrates
light making eye damage more likely. Galileo, in later life, became
The magnifying power of the telescope is given by the following formula :
focal length of
the objective i.e. for 1 metre and 5 cm., the magnification is 20.
Here are some questions that we can pose for the Sunderstanding campaign. Many of these questions can be answered by experiments with everyday materials. Some experiments may require the cooperation of friends and colleagues in different states and countries. But today with internet communication reaching every district and taluka this can be done easily and quickly. Some questions have not yet been answered by LCNC methods. But maybe if we think and work hard at it, we will discover new LCNC methods to answer questions that have hitherto required expensive and sophisticated equipment.
1. How big is the
THE BRAINBOW CUBES PROBLEM …. OR…. THE NINE COLOUR PROBLEM.
What is a Brainbow ?
A rainbow is caused by the bending of light by raindrops.
The brainbow is caused by the stretching of your brain and the bending of your mind by the following problem :
There are twenty seven cubes consisting of nine sets of three, each set of a different colour. Arrange these cubes into a 3x3x3 cube such that on each of the six faces, all the nine squares are of a different colour i.e. no two squares have the same colour. Is this possible ? If not, why not ? If yes, then show how.