Classical vs. Modern Physics: Modern Physics

Hello, and welcome back to MPC! Last week, we spoke about classical physics and its deterministic nature. This week we will be talking about the other major branch of physics: modern physics. Get ready, because this is where things get really cool!

At the end of the 19th century, most physicists assumed that physics was essentially complete — that is, almost everything that could be discovered in physics had been discovered. According to Lord Kelvin, there were only two major problems remaining: issues surrounding the speed of light and issues surrounding the energy of light. Now, Lord Kelvin’s claim was quite bold — he seemed to think that once the previously mentioned issues were ironed out, physics would be complete and physicists would have achieved full determinism of the world. So, physicists were able to solve these major problems and we can now determine anything and everything (provided we have all of the required data of the present), right?

Well, not exactly. Yes, solutions to these problems were eventually found, but, quite ironically, these solutions opened doorways to even more problems. Specifically, they would serve as the foundations for two of physic’s largest fields: relativity and quantum mechanics. So, while physicists of the late-19th century may have been right to assume that classical physics was nearly complete, no scientist anticipated this wave of new physics — known as modern physics — that was about to turn physics on its head.

The transition from classical physics to modern physics was by no means simple. Modern physics provides an entirely different perspective of the world than classical physics does, and it would take Max Planck and Albert Einstein (two famous physicists that we will be discussing in great detail in the future) to discover this new angle from which the world could be interpreted. What makes modern physics so different from classical physics? Well, first and foremost, that whole deterministic view of the world from classical physics is invalid within the realm of modern physics. Indeed, with modern physics, it is impossible for one to determine what exactly will happen in the future, regardless of how much information he/she has about the present. You may be wondering, “If modern physics is not deterministic, what is it?” The answer: probabilistic. You may notice the root word of probability in probabilistic, and that is no coincidence. Just how flipping a coin is all about probability (there is a 50% chance the coin lands on heads and a 50% chance it lands on tails, but there is no way you can be sure about which side it will land on), everything about our world depends on probability and has a certain degree of uncertainty.

But, who cares? How about an example to pique your interest? Let’s just say you have a rock and you throw it at your neighbor’s window (let’s call your neighbor “John”). What will happen?

“Well, you are going to break John’s window and he is going to come outside and yell at you, of course.”

What’s wrong with that statement? Look at the use of that phrase “of course.” The problem is, of course implies that you know for certain what the outcome of the aforementioned event will be; in other words, of course implies that you were able determine the outcome of your shenanigans. This is a problem — modern physics says our world is not deterministic, there must be some uncertainty. Let’s think of an alternative outcome:

“You break John’s window, but he is not home and does not notice the broken glass for a few days.”

Is this possible? Of course it is! Yes, it is a more unlikely than the first outcome that was proposed, but it is a possibility nonetheless. How about another possible outcome?:

The rock is about to hit John’s window when it suddenly teleports to the opposite side of the window, without damaging it. John does not notice anything.

You may be laughing now, but this is actually a valid possibility. As a matter of fact, physicists have shown that this can actually occur, although it is extremely unlikely. Yes, it is crazy, but it fits the modern physics model (you cannot say for certain whether this outcome will happen, or one of the other two will occur, or a completely different outcome will occur — there is uncertainty). You may be surprised to know that this “teleportation,” known as quantum tunneling, happens very frequently (on the scale of atoms, though). Believe it or not, we would not be alive without it!

We have only scratched the surface of modern physics (yes, it gets even cooler). I hope that you now have an idea of the content we will be talking about on MPC and why you should stick around! Next week, we will dive into some actual physics. See you then!


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