(Gravity has been a wonder for humans for a very long time and still it is for its complex and universal nature. The design of a number of machines become possible after understanding the laws of gravity. It is one of the four fundamental laws of nature in our universe. But it is a very long and interesting journey to understand that the gravity is one of the fundamental laws of this universe. In this series, we try to present some important historical efforts and human’s struggle to understand it.)
Capsule- 1: Galileo’s pendulum experiments
Although, numerous attempts have been made to understand the free fall of objects on the earth by different people worldwide, but Galileo’s efforts are considered as the first scientific attempt to understand the free fall of objects on earth.
At that time, people could find that the planets are moving around a star in a circular or elliptical path. Kepler and Tycho Brahe tried to formulate some laws for the motion of terrestrial objects. But it was not clear that there is a strong and long range force which is binding the solar system in a shape. When it was understood that the earth is spherical like a ball, a group of people used laugh saying that why don’t the things and people fall down when earth is round. There exists many flat earth supporters till now in the 21th century when we see our earth from satellites and international space station daily. But, at that time there were no satellites, even to do experiments there were no sophisticates equipments, even no accurate stop watches. The good part is people were coming out of middle ages’ dark sleep and they become interested in natural processes. It was the time of 16th century.
It was much before the apple hit Newton’s head. A candelabrum in a cathedral kept Galileo swing with it.
So, the story starts like this. A young man named Galileo Galilei (1564-1642) was sitting in the cathedral of Pisa, Italy for a prayer. During the rituals, he observed that there is a big candelabrum which is hanging from the roof with the support of a long wooden rood. It was decorated very beautifully and they have lit candles on it. The candelabrum was freely hanging, and somebody disturbed it so started swinging. Out of curiosity, Galileo observed that the time taken in the oscillations is same until it came to rest. The scientific minds just don’t see things, they observe.
Galileo was very perplexed to observe that the time taken in the oscillations by the candelabrum was same, but he wanted to check again. Because, at that time there was not even a stopwatch. So, he waited for some more time in cathedral that somebody again disturbs the candelabrum and he again try to observe the time taken in one oscillation, but nobody did so, everybody was busy in prayers.
There was some fire which started burning in Galileo. After coming to home, he took a heavy stone and suspended with a string. Then, he started verifying again the time in the oscillations. Interestingly, he had nothing to measure the time, not even a good watch. So, he started measuring time with his pulses and heartbeats. It was a great wonder that his observation in cathedral was correct. The time taken in the different oscillations was same. Then, he tried stones of different weights and different length of strings. He was thrilled to find that the time taken in the different oscillations was same for each set of length of string and weight of stone. He could also figure out that the time take in the different oscillations is different for different length of strings but it was same for different weights of stones. And it was amazing. People at that time generally thought that the heavy bodies fall faster than the light ones, and it became a type of dogma. So, Galileo found something which was in contradiction to general belief. He was excited to find that.
He arranged two stones, one of light weight and one of high weight. He made a plan to check his findings. He requested his friend to help him in the plan. His friend climbed on the highest possible floor of tower of Pisa and dropped the two stones (a heavy and a light one) at the same time and Galileo could find that the stones were reaching ground at the same time. It was unexpected and exciting.
Galileo came home with a new set of questions in his mind. Can there be a mathematical formulation for the time taken by a body in covering a certain distance during a free fall. Or in other words, what is the mathematical relation between time and distance in the case of free fall?
Galileo then started a few more experiments, which are more interestingly explained in this video.
In his experiments, Galileo found that the speed of the falling or moving bodies under gravity increases with time. He wanted to understand the rate of change of velocity with time. In his book Dialogue Concerning Two New Sciences Galileo writes that Distance travelled is proportional to square of time taken.
This was the remarkable relation came from Galileo’s work. Galileo was not satisfied here. He was ready for some new experiments to understand the gravitation and formulate the mathematical equations for to establish the laws of gravitation. He was eager to understand the force earth applied on the falling objects. Or in other words, he wanted to know the gravitational acceleration.
The details of other experiments in next capsule. Keep reading.
Science Backyard 