Newton's Discovery of the Refraction of Light

Episode Eleven – Achievements of Newton

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Today we go over the achievements of Isaac Newton, focusing on his many hugely important contributions to science.

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Episode Transcript

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Introduction

Hi everyone! This is episode eleven of the Metaphysics of Physics podcast.

I am Ashna, your host and guide through the hallowed halls of the philosophy of science. Thanks for tuning in!

With this show, we are fighting for a more rational world, mostly by looking through the lens of the philosophy of science. We raise awareness of issues within the philosophy of science and present alternative and rational approaches.

You can find all the episodes, transcripts and subscription options on the website at metaphysicsofphysics.com.

Today we are providing an overview of the achievements of the great Isaac Newton, focusing on his contributions to science. At a later stage we will go over what made him such a great scientist.

Newton

My favorite portrait of Isaac Newton.

This will be the first of our coverage of great figures in the history of science. With some more coming later this year. But, without further ado, let us start our discussion of the achievements of Isaac Newton.

We have a lot to cover, so we cannot cover any one aspect of his work in great detail. Nor can we cover all of his extensive contributions.

Some of them we will not go into detail on. Some we will not cover at all. Such as his work on cubic functions, infinite series, harmonic systems, Diophantine equations, finite differences and more.

We will cover some of the more influential aspects of his work. Starting with calculus, working our way to his other mathematical contributions and then working forward from there.

Calculus

One of his greatest works for which he is best known, is his invention of calculus.

Now, I am aware that many people debate whether Newton or Leibniz developed calculus first. While I believe that in fact Newton may have developed it first, I am not sure whether this will ever be known with complete certainty.

And really, it does not matter much. It seems quite likely that Newton and Leibniz developed calculus independently, although Newton seems to have begun his work first.

It would not be the first time two different people independently developed important and major scientific advances at much the same time. Another classic example would be Wallace and Darwin. Both of whom developed somewhat similar theories of evolution.

Regardless of which of them developed it first or if they each discovered it independently, Newton certainly developed calculus and so he deserves great credit for that.

What is calculus? It is a branch of mathematics which is essentially composed of two aspects.

Differential calculus, which studies patterns of continuous change.

And integration, which amounts to adding up infinitesimally small values and is the mathematical reverse of differentiation. Calculus is the underpinning of much of modern mathematics and without it much of modern mathematics would not be possible.

As differential calculus studies things in motion, it is a fundamental underpinning of the physics of moving objects. Or indeed any quantity which changes continuously over time.

Principia Mathematica

The original calculus textbook.

In fact, much of Newton’s physics depends on and was derived using differential calculus. For instance, you can use calculus to derive an equation for acceleration from an equation for velocity.

Now, just how important is calculus? Well, it is very hard to overstate the importance of calculus. It is one of the most important, widely applicable branches of mathematics ever invented.

Why is this? Because it can be used to describe the behaviour of virtually anything that moves or changes over time. Which is to say, virtually anything at all.

You can use calculus to describe the velocity of a space rocket. Or how stock markets change over time. It can be used to study the equations and or graphs that describe phenomena. You can use calculus to find various properties of these equations and graphs. Such as the rates of change and optimal values and the list goes on.

Calculus is used in countless optimization problems. In such problems you take equations that describe relationships between certain variables and you find the value or values of those variables that give you the optimal results.

Suppose you have an equation that describes the amount of material used to create containers of a certain volume. You can use calculus to find the dimensions of a container that will hold 1.5 litres but which will minimize the amount of material used.

That’s litres (leeters) not litters, though I guess you could find out how many litters of kittens you can fit in a container, using calculus too!

A great variety of problems where you want to maximize or minimize some quantity can be solved using calculus. For example, problems which are very frequent in business and/or design where efficiency must be maximized and cost minimized.

That is differential calculus.

Integral calculus also has many applications. One of them is finding areas or volumes. For instance, if you want to find the volume of an irregular shape such as a Coke bottle, you can use integration to do so.

Many properties in physics are calculated as integrals. For instance, finding the coordinates of the centre of mass of an object, studying magnetic flux and so forth.

And then there is the fact that since integration is the reverse of differentiation, you can use it to derive many equations, just as you can using differential calculus.

The applications of calculus are far too numerous to mention all but a few of the most general applications. Suffice to say that every branch of higher mathematics uses it and calculus is applicable to almost any field of knowledge known to man.

Which is true of mathematics in general, right? Mathematics is all about describing and deriving the various relationships between entities and their properties.

Well, calculus is a fundamental technique used to find many of these. Without which much of higher mathematics would not be possible.

Pythagoras

Pythagoras was among the first to catch on to the general practicability of math. But, he took it a bit too far …

Newton-Raphson Method

This is a method of numerical analysis which allows one to find approximate solutions for real-valued functions. That is, mathematical functions with solutions that are real numbers.

Yes, it has been generalized to complex values, but we will not go into that here.

Let us suppose that you have the equation x3 + 5x – 3 = zero. What value of x satisfies this equation? The Newton-Raphson method allows an approximate value to be found.

It is an iterative process, requiring repeated cycles through the Newton-Raphson formula in order to get increasingly accurate results.

This is not the only such method used to solve functions. But, it is a commonly used one and some computer algorithms use it to solve functions.

But why should we care? Well, many equations where you need to solve for x can be solved with the Newton-Raphson method. In fact, many equations where we have no known method for finding exact solutions can have this method applied. This allows approximate values to be found.

You can also use it for optimization problems, similar to the optimization described when we discussed calculus. In fact, the Newton-Raphson method itself uses calculus, differentiation in particular.

Its applications are many and varied. It is frequently used in the analysis of flow in large networks. Such as water distribution networks or electrical flow through electrical grids.

It also has various uses in numerical analysis and other areas of mathematics, but we will not go into that. Suffice to say that it is an extremely important tool in solving and analysing a great many equations.

Binomial Theorem

This mathematical theorem involves the expansion of powers of binomials. A binomial is something like “X squared plus 2”. Basically, the binomial theorem deals with some variable plus something else, all to the power of something.

These powers of binomials can be written in their full form as a polynomial. Such as x squared plus 5x + 3.

Let us suppose you have something like “2x +3”. And you want to multiply it by itself, you have this:

(2x+3)2

You get a polynomial like this:

4x2 + 12x + 9

The binomial theorem lets you find these polynomials.

So, if you want to multiply (2x + 3) by itself 5 times, what do you get? Well, the binomial theorem will tell you that.

Pascal's Triangle

The Binomial Theorem uses Pascal’s Triangle, which was known to ancient mathematicians.

Which is good, because the polynomial will look something like 32x5 + Nx4….etc. Calculating this by hand would take a while.

Now, it should be noted that others, including Euclid and Al-Karaji had developed less generalized methods for doing this kind of thing. However, Newton’s method was more general. It could also be applied to all real numbers, as opposed to only nonnegative integers.

But, so what? Of what importance or application is this to the real world? Well, quite a lot as it turns out.

Every computer on most networks, including the internet, has an IP address. This is essentially a unique number that is used to identify your particular computer on the network (I am over-simplifying a bit but the fine details do not matter that much).

Well, these are often automatically assigned and the binomial theorem helps to do that. The binomial theorem can deal with other such network problems.

It is also used in estimating probabilities in fields like economics and weather forecasts.. It is used to help design infrastructure to help find the proper amount of materials to use. As well as that, it also helps rank things. And so on….

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