In the last blog we learnt some early descriptions of nature and how they were widely accepted by the people. But in the course of history, there has been certain moments which is worth mentioning here, say for example the discovery that there was force called gravity which pulls everything down and also restricts everything from going up! , the famous Theory of Relativity by Albert Einstein which changed forever our understanding of science.
The Theory of Relativity is a new theoretical concept on which I am currently doing my research. So we will talk about it later. In this blog let us consider the contributions made by greats like Tycho Brahe, Johannes Kepler, Galileo Galilei and Sir Isaac Newton.
I am trying my level best not to include the mathematical element in my blogs, since it would make many (I guess) sleepy and uninterested.
EARLY MEDIEVAL YEARS
TYCHO BRAHE AND JOHANNES KEPLER
Portrait 1: Tycho Brahe
Tycho Brahe was a very influential figure in the course of scientific history. He made pioneering works in the field of astronomy. He is well known for his precise data collection and recorded his observations accurately.
The great German astronomer Johannes Kepler worked under him for a brief period. After his death, Kepler used Tycho Brahe's data to carry out his astronomical observations.
Whenever I talk about Brahe, I cannot omit saying a task that he single handedly did out of his shear passion for astronomical science. The story goes like this, King Frederick II granted Tycho Brahe an estate on the island on Hven. Tycho used this land for developing his own astronomical observatory which in turn provided him with very useful data about planetary motions.
As I already mentioned Johannes Kepler used these observations for developing his Laws on Planetary Motion. In one way Tycho really influenced Kepler a lot in his work...
Portrait 2: Johannes Kepler
Johannes Kepler is famously known for his laws of planetary motions, which became highly influential in field of space science. His laws of planetary motions were later explained by Isaac Newton in his famous book, 'The Principia'. These three influential laws are given below,
LAW 1:
'Planets move in elliptical orbits with the sun at one end of the foci.'
Explanation: Copernicus believed that planets and other celestial bodies moved in circular orbits around the sun, but Kepler modified his theory by stating that they move in elliptical orbits as shown below.
Figure 1: Depiction of Kepler's First Law. The two black dots that you can see inside the ellipse accounts for the two foci and sun is placed at one of the foci.
Now there is a reason why they have elliptical orbits, however I am not going to explain that part here because it needs the use of mathematics. So to put it simply, this phenomenon is because of 'eccentricity', a term associated with ellipse ( a special type of conic section), which is a very interesting concept in Mathematics (and quite easy too!). I will deal with eccentricity and its applications in another blog.
LAW 2:
The line between the planet and the sun sweeps out equal areas in equal intervals of time.
Explanation: First consider two positions (the two green dots associated with A) representing the initial and final positions of the planet and find the area traversed by the planet(the red region). Now consider initial and final positions of the same planet (the two green dots associated with B) after a time interval say, one or two weeks, and find the area traversed by the planet in this case (the blue region). The final inference is,
area (Red region)= area (Blue region)
Figure 2: Kepler's Second law of Planetary Motion.
It is quite easy to write this in words but we must appreciate the work done by our ancestors, in carefully observing the movements of planets and postulating laws which has tremendous applications even today, more than five hundred years after it was originally postulated!
LAW 3:
The square of the time period of revolution of a planet is directly proportional to the cube of the semi-major axis of the ellipse traced out by the planet.
Explanation: Kepler's Third law can be mathematically expressed as follows,
T ² ∝ r³
Now in order to remove the proportionality sign we introduce a constant, 'K' which is called the Kepler Constant.
This implies that,
K= r³/ T²
Now let us go further and meet one influential figure in the scientific revolution, this man played a major role in the development of modern science but had to suffer a lot of criticism and torture for going against the then widely accepted Aristotelian notions of Science. He is Galileo Galilei...
YEARS OF GALILEO
Galileo was a passionate scientist and was a real experimenter. His love for mathematics helped him to achieve great breakthroughs in the field of scientific research but he had to pay a harsh price...
Galileo's father wanted him to be a doctor, however Galileo didn't like the profession because of his real interest in mathematics. He was a sought of a rebel...and openly criticised some of the well-known science concepts prevailing at that time.
Galileo was very interested in the motion of rolling bodies, his experiments on smooth, inclined, double inclined planes are very famous and are examples of some of the early experiments to analyse motion of bodies. Based on his experiments he formulated a law, now known as the 'Galileo's Law of Inertia'. The inability of a change its state of rest or uniform motion in a right line is called the 'inertia'.
Galileo's Law of Inertia can be stated as follows,
'' Every body continues to be in a state of rest or of uniform motion in a straight line unless compelled to change that change by forces impressed there on''
This statement is in fact, 'Newton's First Law of Motion'. From this statement we can clearly understand that a body, say, a ball continues to move without hindrance in a straight line if the ground is devoid of friction. However we must understand that this is just an ideal situation, such a condition is never possible unless we are provided with a perfect, frictionless plane.
The year 1589 changed Galileo's life forever. It was in 1589 that Galileo climbed the Leaning Tower of Pisa and carried out the famous 'Pisa Tower Experiment'. He threw many objects from the top of the tower to the ground ranging from wood to cannon balls!
According to Aristotle, heavier objects fell faster than lighter ones in proportion to their weights. But Galileo deposed this idea by stating that the descent of a heavy and light object is independent of their masses. Galileo postulated,
''Bodies of the same material falling through the same medium would fall at the same speed.''
He developed a new device to observe the sky now called a telescope, He found that Jupiter was surrounded by four bodies (moons) namely, Ganymede (the largest moon in our solar system), Europa (the smoothest moon in our solar system), Callisto (one of the brightest moon in our solar system) and IO. These moons are now called the 'Galilean moons'. His findings were truly remarkable. Backed by his discoveries he questioned the Geocentric model of Universe.
But the 'school of thought' that existed then was that everything revolved around the Earth, and Galileo's findings sharply questioned this idea. People began criticising him and even filed cases against him in the court for going against an age-old belief. Galileo was not ready to yield to such lame criticisms and filed his astronomical observations to a higher authority stating that he was right. But even they were not ready to accept his findings, probably because of the increasing public support to the old idea.
''You cannot teach a man anything, you can only help him find it within himself.''
- Galileo Galilei
Galileo won the permission to write a book on his observations with strict restrictions. This one book also won him a lot enemies and changed his life for the worse. He wrote the book in the form of a dialogue and it was titled, 'Dialogues Concerning Two New Sciences'. In this book he criticised the people who supported the old school. A person who has ever had a chance to read this dialogue would discover who is the 'greater person'...Albert Einstein read this dialogue and was so moved by it that he called Galileo the 'Father of Modern Physics'.
The contents of the book worried the authorities as a result Galileo was tried for heresy and was sentenced to house arrest for the rest of his life. Galileo's greatest ambition was to mathematise motion and he did it during his final years by writing a book which summarised most of his mathematical notions of motion. It is said during his years under house arrest, he used to store his mathematical and scientific papers inside a globe that he possessed.
Ironically the year Galileo died, a boy was born in Woolsthorpe, London who would bring Galileo's ideas to a grand completion...
THE NEWTON YEARS
The 'boy', I mentioned in the last line is none other than Isaac Newton, an inventive successor for Galileo. Newton was greatly influenced by the writings of Galileo. He went on to prove Galileo's ideas mathematically. We cannot criticise an idea if its expressed mathematically, for it is the language of nature and is the perfect tool for proving or discarding a theoretical concept.
Since I have already made a blog on Sir Isaac Newton, I am not going deep into his life once again. Let us consider some of his greatest scientific achievements.
Newton published his landmark work, 'The Principia' in the year 1687. 'The Principia' is considered as the single-most important scientific work ever written. In this book Newton clearly lays down his famous laws of motion and his theory of Universal gravitation.
NEWTON'S LAWS OF MOTION:
NEWTON'S FIRST LAW:
''Every body preserves in its state of rest or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon''
Explanation: Consider a body at rest. This body will be continue to be in the state of rest until an external force acts on it. Now consider a ball rolling on the ground, in an ideal situation this ball will continue its uniform motion in a straight line till infinity.
NEWTON'S SECOND LAW:
''The alteration of motion is ever proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed''
Explanation: It simply means that the force acting on a body is directly proportional to the product of its mass and acceleration.
Mathematically,
Consider a body with initial velocity 'u', and final velocity 'v' having a mass 'm'.
Momentum = mass ✖ velocity
Initial momentum: mu
Final momentum: mv
Change in momentum: mv-mu
= m(v-u)
Rate of change of momentum: m(v-u)/t
According to Newton's Second Law, Force ∝ rate of change of momentum
⇒ F∝ m(v-u)/t
We know rate of change of velocity is acceleration (a)
⇒ F∝ ma
⇒ F=kma, where 'k' is the constant of proportionality
when k=1
F=ma
This is how we mathematically derive Newton's Second Law of Motion.
NEWTON'S THIRD LAW:
''To every action there is always opposed an equal reaction''
Explanation: This is perhaps the only 'law' which does not require an explanation. It must be kept in mind that the action and reaction forces always act on different bodies and are equal in magnitude. Newton's Third Law of Motion has huge applications in rocket science.
NEWTON'S THEORY OF COLOURS
Sir Isaac Newton was fascinated by colours and he made seminal contributions to optics, a branch of Physics. Newton's masterpiece, 'Opticks' established many of the ideas and concepts that we learn today.
WHITE LIGHT SPECTRUM
It is said that Newton made a small hole in his room through which he allowed the entry of a light beam which was in turn passed through a prism. The incident white light or sun light was split into its seven constituent colours by the prism.
Newton went a step ahead by keeping an inverted prism P₂ next to P₁ to see what happens when the light rays which escaped P₁ entered P₂. His observation made him speechless. He found that all the seven colours which exited P₁ combined to form the initial white light after passing through P₂, this phenomenon is known as the 'recombination'.
Picture credits:
1. Wikimedia Commons- portraits of Tycho Brahe, Johannes Kepler, Galileo Galilei and Isaac Newton, images depicting Kepler's laws of planetary motion, Leaning Tower Experiment, copy of Principia, depiction of Newton's Third Law of Motion, dispersion of light by glass prism.
2. NCERT Textbook: Recombination phenomenon.
Information credits:
1. Wikipedia: some information regarding place and time (Tycho Brahe and Galileo Galilei)
Well done!
ReplyDeleteThank you so much Sir 😊
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