A Brief History of the Catapult

A catapult can be as small as an elastic band slingshot used to hurl small stones or as large as the
90 metre (300 feet) long units used to launch fighter jets from an aircraft carrier. Let us see how
the humble catapult made its journey over the millennia. Like many scientific inventions, which are
now thankfully used for peaceful purposes, its origins are ensnared in the history of violent war.

The catapult was invented around 400 BC in the ancient Greek town of Syracus. But what was the need to invent it and what difference did it make? During those times, the only way you could
inflict damage in a battle was by getting very close to the opponent’s army or fort, which would
obviously result in high casualties for the aggressor. Even arrows could not hit enough of something
more than 100 metres away to disable them. Catapults allowed warriors to inflict damage without
risking themselves. They were frighteningly accurate, could cover a distance that no bow could
ever propel an arrow – say up to 700 metres – and they could target soldiers guarding the forts from
a long distance. The defenders too could do an even better job by placing the catapults where they
wanted, say on the ramparts of the fort, and taking down the enemies before they could use their



After the catapult came the ballista, which could hurl projectiles even further; and this was followed
in quick succession by the trebuchet, which could throw heavier projectiles over a larger distance. It was a major siege warfare weapon, used to inflict damage on forts.

These three types of catapults ruled the roost for centuries, with lighter and more powerful itera-
tions being developed throughout that time, until gunpowder was invented in the second millenni-
um by the Chinese… However, it was not until the Europeans accessed gunpowder in the early 14th century that more powerful weapons such as cannons were built.

Due to the energy of the gunpowder hurling projectiles, such as stones or iron balls with great
speed and force, they were far more devastating than catapults and its ilk ever were. However, a
cannon had its own limitations. A newer type of fort, called a bastion, was built with sloped walls
and filled with earth (mud) and bricks and the thick forts were hard to crack (instead of the earlier
ones that had flat wall of stones, watch towers and so on). The attackers were still looking for
newer siege weapons to bring down forts.

A more evolved artillery known as mortars and howitzers were developed in the late 16th century.
Howitzers were developed as a medium-trajectory weapon between that of the flat trajectory
(direct fire) of cannon and the high trajectory (indirect fire) of mortars. Originally intended for use
in siege warfare (the forts were besieged and were expected to fall after a prolonged siege), they
were particularly useful for delivering cast iron shells filled with gunpowder or incendiary materials
into the interior of fortifications. Howitzers could be fired at a wide variety of angles. Then folks
across the world stopped building traditional forts that took decades to complete and consumed humongous building material and labour. And thus came an end to these more traditional weapons of warfare.

Let’s also be thankful that catapults and their derivatives are confined to the science classroom and ThinkTac TACtivities these days….

Albert Einstein

Albert Einstein: the name itself conjures up an image of awe and admiration, for perhaps any person on Earth. By far one of the greatest and most famous scientists of all time, Einstein created an iconic image of a scientist with his tousled hairstyle, his moustache and that naughty twinkling of his eye as he was wont to say `now I will a little think’ . He was perhaps the first celebrity or ‘superstar’ scientist, establishing himself during an era when mass communication, television, radio etc were all technologies that were coming to the fore. He was also incredibly witty, charismatic and a great humanist, that makes his quotes some of the most popular ones around. His name is synonymous with “genius”, and is used endearingly to anyone who seems to be “smart” or precocious, or makes a witty comment. While his genius is unquestionable, Einstein also led a very colourful life.

Born into a Jewish family in 1879 Germany, Einstein grew up as any normal child would. Popular belief has it that he was “weak in mathematics”, at school. But if you read more about him, you realise that he had mastered differential and integral calculus by the age of 14! He excelled in physics too, and obviously showed an inclination towards it very early in his life. Growing up in Munich, he also got seriously interested in philosophy and music, both of which would remain life-long passions. Einstein played the violin, and could fiddle away a Bach or Beethoven violin sonata with ease! When Einstein was 13, his family moved to Italy. After completing his schooling in Munich, Einstein also joined them a year later. In 1895, he enrolled into a secondary school in Switzerland, a country that soon became his adopted home. Study at the Zurich Polytechnic was followed by a job in the Swiss patent office, in Bern, which he got after waiting for a job for more than two years after he had graduated. It is incredible how a lot of Einstein’s most profound discoveries were made while he worked at the patent office, at his “boring job”. I guess it shouldn’t surprise too many of us in India: our most famous scientist, Sir C V Raman, also made several scientific breakthroughs while working as an accountant in the Accountant-General’s office in Calcutta’s central business district!

Nevertheless, Einstein started publishing scientific papers while continuing for a few years at his day job at the patent office. This resulted in him being conferred a PhD (distance learning at its best!) by the University of Zurich, and by 1908 he was already considered a leading scientist. Over the next several years, Einstein was on the faculty of universities in Bern, Prague, Zurich and Berlin. Meanwhile, Einstein had a tumultuous, and often controversial, personal life. Several famous books  have been written on the subject, especially with new correspondence having come to light over the last few decades. His treatment of his first wife, Mileva Maric, and family is well-documented and notorious – a disowned first child born out of wedlock was abandoned; marriage brought two more children, and divorce destroyed the family: one of his sons ended up being a schizophrenic and killed himself at the age of 20. Einstein already had an affair with his first cousin, Elsa, during his first marriage. After divorce from Mileva in 1919, he married Elsa. She tragically died in 1936, after they had already moved to the United States. Einstein left Europe for good of his own accord in 1933, because by 1932 he had been convinced that things were going to get worse in Germany and detesting anti-Jewish propaganda and totalitarian politics, he did not want to stay there any more. He had a visiting position at the California Institute of Technology (Caltech) and also an offer of a professorship at the Institute for Advanced Study (IAS), Princeton, a fledgling institution then, which gave him an opportunity to leave his native land without causing any flutter. Einstein relinquished his German citizenship and settled in America: first at Caltech, and then IAS, Princeton for the rest of his life.

And during all these personal upheavals, Einstein’s scientific output of very high quality continued at a mind-boggling pace. His work was unprecedented and remains unsurpassed; its quality unparalleled! It had all started with a bang in 1905, termed “Einstein’s Miracle Year”. He wrote three path-breaking papers that year (among many more): on Brownian Motion, the Photoelectric Effect (for which he won the Nobel Prize in 1921; this is the Centenary Year to celebrate his Award) and the Special Theory of Relativity, that remarkable piece of work that shows how the speed of light cannot be bettered, and hence how time can dilate and mass can increase as objects move closer to the speed of light. This led to perhaps the most famous equation in the world, E = mc2, thereby creating an equivalence between mass and energy, which theoretically unshackled the energy contained within an atom, and explained to us how stars burn and produce energy. This also led to the eventual invention of the atom and hydrogen bombs, which altered history forever, as the former was used on humans by the USA at the end of World War II, when it bombed the Japanese cities of Hiroshima and Nagasaki, killing hundreds of thousands and maiming millions. The scars of that act will last till humans live on this planet. Einstein, as a great pacifist, was also scarred by these horrific acts of war and violence. He implored the US government to never use the bomb and his personal letter to FD Roosevelt, beseeching him to refrain from using the weapon, reached the White House as FDR was dying and the cover remained unopened. Unfortunately, Roosevelt’s hawkish successor, Harry Truman, ordered the first and only use so far of a weapon of mass destruction as soon as he became the President.

Coming back to Einstein, by 1911 he had formulated the basic tenets of the General Theory of Relativity (GR, or GTR), arguably the greatest ever achievement of the human mind. Einstein postulated that gravity can warp “space-time”, which he thought of as a continuum pervading throughout the Universe. Not only was the idea revolutionary and hard to comprehend, most scientists of the day had a hard time believing it. In 1919, the famous British astronomer, Arthur Eddington, conducted observations during the solar eclipse that proved that aspect of the theory: that gravity distorts space-time. He did so by looking at the position of stars directly behind the Sun during an eclipse, and found that their apparent position in the sky was marginally different from when the same stars are seen during the night. And the predictions of GR matched exactly with the observations. The Sun’s gravity had actually bent light! Today, the same principle is used to image faraway galaxies, which are obscured by nearer massive galaxies. This has allowed us to measure distances to some extremely faraway galaxies very accurately, and the phenomenon is known as “Gravitational Lensing”. Today, GR corrections are used in day-to-day applications, e.g. GPS satellites, without which we wouldn’t be able to use our Google Maps or satellite communication systems accurately and adequately. Most brilliantly, GR also predicts the presence of Gravitational Waves, and only over the last few decades has technology reached a level where it has been able to build gravitational wave detectors. In the last 6-8 years, these most sophisticated detectors (read about “LIGO”) have actually detected these predicted waves, which have emerged from massive cosmic events, like the merger of two black holes or neutron stars, billions of light years away!

So Einstein’s impact on our daily life and on our imagination, is MASSIVE, no pun intended! He always had a love for Eastern cultures and civilisations, and had close interactions with many famous Indians. His letters to Gandhi are famous, and although they never met, they had a great admiration for each other. Einstein helped SN Bose publish his famous papers in Europe, and that led to an immediate recognition of Bose to the world and created a great partnership and friendship, for which “Bose” and “Einstein” are often uttered in the same breath: “Bose-Einstein Condensate” and “Bose- Einstein Statistics”. Particles that obey the latter are of course known as bosons, and how ubiquitous that word has become thanks again to the discovery of the Higgs Boson a few years ago. Einstein’s meetings with Tagore remain close to the heart of most Indians, as they too shared a great respect for each other. And while Einstein’s theories and discoveries will last for all time, some questions remain unanswered, e.g. a unified theory to describe all forces: he could never reconcile gravity with the other three forces, he never accepted the breakdown of causality as in quantum uncertainty; or what really is happening inside a Black Hole and is all its mass really concentrated in zero volume, a singularity?

Let me end this with a few of my favourite quotes of Einstein:

“Great spirits have always encountered violent opposition from mediocre minds”

“Nothing will benefit human health and increase the chances for survival of life on Earth as much
as the evolution to a vegetarian diet.”

About Gandhi: “Generations to come will scarce believe that such a one as this ever in flesh and
blood walked upon this Earth.”

Long live the spirit of this remarkable man!


Around 200 years back in the early 19th century, in a city of Switzerland, there was a system for businessmen from around the country to meet once in a year to showcase their new products and services. This conference was a place for making and breaking of deals and new businesses getting started as well as destroyed. Those days we had clocks but no wrist watches. A small group of 5 artists had come up with an idea of adding a chain to a clock and making it small enough to look elegant on soft wrists. They showcased 10 wrist watches as jewellery articles for women in the annual conference with the hope that the design would be bought by one of the clock making businessmen. Instead, those who made clocks saw them as a threat. As soon as they realised that the artists took 2 months to design one wrist watch, they came up with a plan to consume their product instead of promoting it. They purchased all the 10 watches at a healthy price and hid them by gifting them to ladies they were related to. However, the artists came with 20 watches next year. The clock making businessmen repeated what they did the previous year. The trend continued for another two years. By the fourth year, the clock making businessmen (now converted to registered companies) started coming with a pre-approved budget and arrangement for consuming the watches made by the artists. However they were caught by a surprise in the fifth year when the artists displayed ten thousand watches. The clock making companies ran out of their capacity to consume the watches. On the contrary, they had unknowingly created enough buzz about wrist watches by selectively gifting it to some eminent women in Switzerland, which helped the artists sell the 10k watches at a healthy price.

This imaginary story is an example of what is known as Biomimicry, where you adapt a phenomenon exhibited by nature for solving a problem in human life. Velcro is one of the most popular examples of Biomimicry, where George de Mistral (also a Swiss Engineer) found some seeds stuck on himself and his dog after one of his walks. As he dug deeper, he noticed the special design of the seeds, which allowed them to get stuck not just to George’s dog, but to any animal that has a little hair on its body. While this digging deeper led George to come up with the design of what is used in multiple consumer products as a fastener, it is also interesting to dig deeper into why trees do this. Since trees cannot walk, they use animals, wind and water to send their seeds to long distances. Unlike humans and many other animals, plants want their off-spring to grow as far from themselves as possible. This avoids competition for resources between the parent and child plant. Different plants adopt different strategies to achieve this distant dispersal of seeds. Some make their seeds light enough to be easily carried by the wind while some add unique design features (like the helicopter seed), which make the seeds spin, thereby maximising the time for which they stay in the air. This enables them to travel long distances via wind. On the other hand, some trees lure the animals by producing tasty fruits, which the animals consume. The fruits contain the seeds, which get excreted by the animals at a place away from the parent plant. Some seeds, like chestnuts and acorns, are consumed directly by the animals like the squirrels. If the seeds get eaten up, why do trees make them that way? Well! The squirrel eats some of the seeds and hides the extra ones. It often forgets some of the hidden ones. However, the hidden and forgotten seeds are only promos from the trees. These trees give a surprise during one of the years by increasing the number of seeds produced by 10x. Typically you have one squirrel living on one tree. Though it is a treat for the squirrels, there is a limit to what they can consume. This mechanism of producing more seeds as a surprise is called masting. The business model adopted by the wrist watch artists mimics masting. Have you seen other businesses following this model? Though humans may mimic the model, can we figure out and mimic the communication and collaboration shown by these trees? It is nothing less than magic how all the trees in a region synchronise so as to perfectly time the masting event simultaneously!

Scientific Literacy

The purpose of education is to replace an empty mind with an open one. Through the constant development of human civilisation, the value associated with intellectual coherence has only increased. As the importance of an enriching education has been understood and realised, the demands from it have evolved.

In the 21 st century, the responsibility to provide everyone with the background skills to cope with the fast paced changes of the present and future has been shouldered by scientists and educators. In this regard, the World Economic Forum (WEF) (in a report analysing the New Vision for Education) has listed a set of 16 skills that students must inculcate to assert their character and competency. Scientific literacy features among the foundational subset of the same.

(WEF report: https://www3.weforum.org/docs/WEF_New_Vision_for_Education.pdf )

Scientific literacy is rooted in the most general principles and broad knowledge of science. It requires one to observe, question, test, evaluate and revise our opinions as needed. Science is about continually acquiring new knowledge but more importantly, it’s about keeping an open and curious mind. Developing scientific literacy should be a priority at every stage of a child’s education—both inside and outside of the classroom.

At ThinkTac, we recognise the wonders that an engaging approach to learning science can have. We encourage children to explore and question the world around them, as well as continue with their science education. Our programmes let young students have fun while they master science with our Hands-on, Experiential Science programmes even from the comfort of their home. The study of science and maths are originally like games – with rules but no objectives and that is essentially how they must be treated.

(Link: https://www.thinktac.com/ )

Scientific literacy is paramount to the 21 st Century society. UNESCO provided a universal goal by the name of STL –Scientific and Technological Literacy to reaffirm the same. In India, the fight for the universalisation of education is still very much on, and the implementation of STL is impossible to envision in the near future.

The way to create an impact, is then to attempt amends at a grassroots level. Science-education strategies should focus on increasing the scientific literacy of the general public. Educators have simplified the basic methodology to implement the same, and fit it into a sentence plug with acronyms to make it easier to recollect. It goes as follows-
Peter Right Has Excellent Apple Cakes”
Here the letters expand as:
P- Purpose
R- Reasoning
H- Hypothesis
E- Experimentation
A- Analysis
C- Conclusion

The sole purpose of introducing this at the grassroot level is to breakdown the complexity that experimentation is associated with. It can be done by integrating experiential learning aids like cards, tactile boxes and natural findings into the syllabus. It helps students get a feel of how scientists think in real time and could ignite the seed of innovation in their minds. This method makes them think cogently and view the world with a keen eye for concept and detail. This approach will also foster interdisciplinary cooperation.

Ultimately, scientific literacy has 3 objectives – to help people understand day to day issues of global pertinence, to appreciate how the natural laws of science influence their lives and to gain perspective on the intellectual climate of their time. All of this, in turn, will improve their chances of lifetime success. As American astrophysicist Neil deGrasse Tyson said, “If you’re scientifically literate, the world looks very different to you, and that understanding empowers you.”

Experiential learning

  1. Correlation

Have you ever baked a cake? 

If you have, you know that binge watching YouTube tutorials and re-reading the recipe till you can recite it in your sleep are sure shot ways of prepping yourself for the actual event. But what you also might know is that until you don the mitts and take in the heat of the oven, you don’t know what you’re in for.

It is going to take you not one, not even two but quite a good number of attempts to bake the perfect treat for yourself.

The phrase ‘Old habits die hard’ is quite true in experimentally every case. When you are exposed to something routinely, withdrawal from it is an uphill task. Now, some genius sitting with his thoughts in some corner of the world thought to himself—What if we made things we needed to learn a habit? Chances are that they wouldn’t ever escape one’s memory.

This is a probable thought from which experiential learning found its existence. Experiencing theoretical concepts through real world simulations of the same is what this system encompasses.

  1. Definition

A more technically accepted definition of experiential learning would be a hands-on experience of concepts which are aimed at inculcating critical thinking and problem-solving abilities. One could also make sense of it as repeated cycles involving experience, reflection, conceptualization and experimentation in any order.

  1. Food for thought

Aristotle famously said, “For the things we have to learn: Before we can do them, we learn by doing them.”, this is merely the essence on which the larger dream of the inclusion of experiential learning in every realm of academics is based.

Experiential learning as a term could invoke a sense of complexity, but truth to be told, it can be as simple as making a paper-boat. Everyone is surrounded by science. As generic as this statement is, looking at the world around you- your routinely tasks or items lying around you and integrating them with basic science concepts can itself pave the way for greater understandings that are more often self-taught. Each one of us can have our own Newton and the apple moment if we paid enough attention. The possibilities are endless and the learnings are limitless. 

  1. The need

Today is truly a good time for the enthusiasts of science and technology. Opportunities are knocking many doors and the world is more accepting than ever. It is no more a society that rigidly upholds its ideals of the earth being flat. Yet, it is sad to see that top graduates and academically progressed individuals find themselves at the hands of monotony and are far from the liberation of innovation. To propel the fuel that innovators need, experiential learning is a sure shot go-to.

Click here to get your own experiential science kit from ThinkTac.

The Science Behind Transpiration: Do plants sweat?

Transpiration in plants

Transpiration in Plants

Transpiration is the loss of water from plants in the form of water vapour.

Imagine, during your summer vacations, you go to play football outside. The Sun is scorching hot. One thing you need right now, more than scoring a goal, is a bottle of water! Any living being for that matter needs the same. Do you think plants also need the same?

Yes, they do.



In fact, the water does not magically disappear from a plant. Plants lose water from them through a process called transpiration. 

Transpiration happens in part because plants need to breathe. Plants need to take in carbon dioxide and to do this, they need to open their stomata. When this happens, water comes out


Transpiration is the process by which moisture is carried through plants from the roots to small pores on the underside of leaves, where it evapourates to vapour and is released to the atmosphere.

Transpiration Water Cycle

This release of water vapour into the atmosphere, through transpiration, creates a water cycle. It is called the transpiration water cycle. It occurs when:


  • The water from the nearby soil is absorbed into the roots due to the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil.
  • The water flows from the roots to the leaves. This is driven by capillary action (Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules).
  • The water from the leaves enters the atmosphere. The water potential in the surrounding air is lower than the water potential in the leaf airspace of the stomatal pore. Due to this, water vapour from the cells in the leaves enters the atmosphere as water vapuor. This process is known as transpiration.
  • The water vapour in the atmosphere now forms clouds through the process of condensation. 
  • And these clouds of water vapour turn into water droplets and fall back on earth through the process of precipitation
  • This water that falls on the land, is then absorbed by the soil and is used to nourish the plants. 

This cycle keeps repeating and hence, is called the transpiration water cycle.


You will hardly need anything for this tactivity. If you have a broad leaved plant in your garden, then it is well and good, otherwise you can always head to the nearest park and look for the same.

All you need to do is wrap a plastic sheet around the leaf and close it tightly. Wait for a few hours and you will see water droplets inside the plastic sheet, as though the leaf has “sweat” – or  TRANSPIRED – as  shown in the video below:

To learn more about the applications and important concepts, enroll for your course on ThinkTac, where you can get to do live experiments using the materials that come with your package, to understand the concepts better.

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