If you don’t plan to become a scientist or an engineer, is there a good reason to study physics? I say, “Yes,” because knowing just a little bit can be quite rewarding in ordinary life. For example, I have been enjoying just one little bit of physics for more than 55 years. I even earned my living applying that one little bit. Which bit is that? Namely, that energy is conserved. You don’t even need an elementary physics course to learn that. You don’t need to know Newton’s Laws. Just three words, energy is conserved. There; now you know it. I call it CE, for Conservation of Energy.
What can you do with CE? Well, right now I’m sitting near a lake watching the waves break on the beach. Far from the shore, the waves are hard to see. It seems like they have very little energy. But as the water gets shallow, the waves rise, they curl and they break, expending their energy. Wait, what does that mean? Because I know about CE, I can say with certainty that the wave’s energy does not disappear. The wave’s energy must be converted to some combination of kinetic energy, potential energy, heat energy, probably chemical energy, conceivably even a tiny bit of nuclear energy too small to measure. That’s something else you should learn; energy can be readily converted to many other forms of energy.
On the other hand, to determine how much of the wave’s energy is converted to which forms, and where it goes, is not at all simple. That is a very difficult problem requiring much tedious bookkeeping. I could devote my whole life to detailed investigation of just one wave, and still never finish. But because I truly understand CE, I know the answer in advance. If all my liftime’s bookkeeping is correct, the answer will show that energy is conserved. Wow! That’s very empowering. I know the answer with certainty without doing the work.
As I look around, I see CE everywhere. It applies to the waves on my lake, or ripples in a Japanese tea garden, or to giant waves crashing on the coast of France. It applies to the core of the sun. It applies to the national power grid. It applies to adding cream to coffee. It applies to biology. In all those examples, I know what is happening without the need for detailed calculations. Energy is conserved.
I read a PF Insights article, LHC Part 4: Searching for New Particles and Decays about the cutting edge of science happening at CERN. The article discussed how hard it was to extract useful information from the raw data, and how the scientists had to devise non-obvious strategies. It said, “Deviations are called “missing transverse energy”. As an example, if some high-energetic particle goes upwards, but nothing visible goes downwards, the measured sum is not zero, and some invisible particle escaped in downwards direction. This is a powerful tool: if a collision has a large missing transverse energy, then either a neutrino or a new particle got produced.” Aha! I certainly don’t understand all that, but I know what they’re doing … CE! Their task is to figure out how much energy is missing and where it went. I could help those CERN scientists strategize, you could help them strategize. You don’t need a PhD in particle physics; to creatively apply CE. [Note @mfb says that this passage from the LHC article actually talks about a cousin of CE, conservation of momentum. But the point remains.]
Perpetual motion is a forbidden topic on PF because it wastes our time talking about it. Nevertheless, almost every day someone posts a question of the form: If I start with some energy, then transform it to A, then to B, then to C (and so on), then feed it back to the start, then won’t it be perpetual? If you simply apply CE to the question, it becomes almost trivially easy to provide the answer, “No”, without even reading the details of A, B or C. Here’s how.
If any one of the steps, A, B, C, … is imperfect it will leak some energy and have an efficiency <100%. In real life, probably every step has efficiency <100%. To achieve 100% efficiency for the whole loop, some other step must compensate by bringing in energy from outside, or have an efficiency >100%, and that would violate CE. Therefore the loop efficiency must be <100% and motion is not perpetual. (See Perpetual Motion, for a better explanation.)
There you go. The next time you hear someone trying to describe a perpetual motion scheme, you already know that it can’t work without needing to look at the details. That empowers you to sound like a science guru.
Making a Career
In college, I had to learn a lot of things. But after graduation, I paired CE with DE (Differential Equations) to make CEDE my specialty. I spent my entire career either controlling the flow of energy or predicting the flow of energy and transformations of energy. My first big project was to model everything about a nuclear power plant. All the way from the atoms splitting in the core, to the turbines and generators, to the controls and instruments, to the most trivial of details down to (but not including) rest room plumbing. The model became a simulator used to train operators of nuclear power plants. Of course, I had to use knowledge other than CE, but CEDE was 90% of the job.
Simulation is mostly CEDE. Control systems are mostly applications of CEDE. Power plants, and power grids, are elaborate applications of CEDE. Energy futures markets are primarily applications of CEDE.
I’m not alone. Thousands of people earn a living as CEDE experts. CEDE is a profession not threatened with obsolescence by automation. In tomorrow’s world, thousands of CEDE experts will still be needed. You too could make CEDE a career.
The More Physics You Learn, The More Fun It Becomes
You can learn CE in your first 60 seconds of studying physics, but don’t stop there. There are pleasures learning more.
I took a course in classical physics. I learned why energy is conserved. It is a consequence of something called time translation symmetry. It seems that a very clever mathematician, Emily Noether, discovered a fabulous theorem that ties those things together. Call me a geek, but I thought that learning about Noether’s theorem was great fun.
I took a course in general relativity (GR). There I learned that on cosmological scales where things are described by GR, that energy is not conserved (in some cases depending on how you define energy and conserved.) “Oh no,” was my first reaction. But upon reflection, I see that I’m better off knowing there is a ceiling to my beloved CE.
I took a course in quantum mechanics (QM). There I learned that at very small scales, things behave in bizarre ways. One bizarre thing is energy-time uncertainty. That does not violate CE, but it limits what we can observe about the tiny details of what happens. Once again I’m better off knowing that there is also a floor to my understanding of CE.
You can spend a lifetime studying aspects of physics. If you do, I wager that not a single day would pass when CE does not play an important role in the subject you’re learning.