Classical vs. Modern Physics: Classical Physics

Hello, and welcome back to MPC! Last week, I got you all excited about modern physics (well, at least I hope I did). However, you may still not even know what modern physics is! The goal of today and next week’s post is to provide you with a better understanding of what exactly we will be talking about on MPC. Before we get started with “Modern Physics,” let’s discuss a little bit of the history behind “Classical Physics”!

If I were to ask you to name a physicist, who would you name? Well, I guess there could be a lot of answers. What if I asked you to name a physicists that you associate with an apple? I would venture to say that the most popular answer to this question would be Sir Isaac Newton. Almost everyone knows Isaac Newton — he masterfully summarized the complexities of motion into three laws and wrote the law of gravitation (if you are not sure what those are, do not worry!). More importantly, Newton’s work laid the foundations for “Classical Physics.”

Classical Physics is the era of physics lasting from the 17th century to the 19th century. Classical physics is the type of physics that you may have studied in school: mechanics (forces, Newton’s Laws of Motion), electromagnetism (current, voltage, Ohm’s Law, Faraday’s Law), optics (concave/convex lenses, mirrors), etc. (once again, if you have never heard of any of these things, do not worry — they are not needed for the modern physics that we will be discussing). Some of the most well-known classical physicists are Isaac Newton, Christiaan Huygens, Michael Faraday, and James Clerk Maxwell.

Classical physicists had a simple goal: describe the world and predict physical phenomena. In fact, many people would describe classical physics with one word, “deterministic.” In context, this word essentially means that classical physicists strove to develop formulas/equations that would enable humans to completely describe any scenario. In other words, classical physicists wanted to develop physics to a point such that, if someone could somehow record the position of every person, every object, and every particle in the universe, he/she would be able to describe exactly where all of the particles would be at any given time in the future. As an analogy, imagine a classical physicist were watching a movie: his/her goal would be to, given just the first frame of the movie, apply laws and principles to deduce exactly how the movie ends.

How did classical physicists go about making predictions? Formulas, of course! A formula is just a mathematical relationship between various quantities. For instance, Newton’s second law of motion can be stated with one of the most famous formulas of all time: force is equivalent to mass times acceleration (F = ma). It should be noted that the concept of a force allows one to predict how quickly an object will be accelerating just by figuring out the force acting on that object (if F = ma, a = F / m). In other words, given the force acting on an object, one can determine, with “certainty,” what that object’s acceleration is.

For anyone who has experience in classical physics, these ideas probably make complete sense. What may not make too much sense (yet) is how modern physics deviates from this deterministic approach to physical phenomena. Do not worry though — that’s what we will be discussing next week. See you then!


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