At a time when so much hype surrounds advances in modern physics, it is important to recognize how much potential the physics we learn in school still has.
“It seems probable that most of the grand underlying principles have been firmly established [. . . .]. An eminent physicist has remarked that the future truths of physical science are to be looked for in the sixth place of decimals,” claimed Albert A. Michelson . He is best known for his role in the Michelson-Morley experiment, which disproved the idea of a luminiferous ether, a hypothetical substance through which everything — people, light, planets, and stars — traveled. Ironically, it would take another man, Albert Einstein, to interpret and extend the results of this experiment — that the speed of light was constant in any reference frame — in order to disprove the quoted claims of Michelson . With the discovery of general relativity and quantum mechanics, the limits of human knowledge became apparent. This perspective will first outline our current state of knowledge in modern physics and then shift towards recent research and developments in classical physics.
A significant portion of the latest research occurring in physics is within the field of quantum mechanics, which deals with extremely small-scale and subatomic interactions. Much of this research focuses on making incremental advances in specific sub-fields of quantum mechanics to gain a better understanding of the fundamental physical mechanisms at play. One of the major drivers of this research is its sheer number of applications. A better understanding of quantum mechanics can lead to improvements in computer chip design, laser technology, microscopy, and GPS . In fact, we have already been able to develop technologies such as magnetic resonance imaging (MRI) due to our increased understanding of the spin property of subatomic particles . Ultimately, small advances in the roots of quantum mechanics can propagate and lead to not just an improved theoretical understanding but also practical applications.
|MRI scanners are a prime example of how our growing understanding of quantum mechanics can lead to innovations that can help humans.|
|(Image: Stanford University. (2018). Stanford Health Care’s PET/MRI scanner [Image]. Retrieved from https://stanfordhealthcare.org/content/dam/SHC/diagnosis/p/images/pet-mri.jpg)|
Albert Einstein established a solid foundation for relativity, the branch of physics that deals with objects moving at high speeds, long-range gravitational interactions and large masses, and the fabric of spacetime. Many studies we hear about pertain to confirmations of his predictions, such as LIGO’s detection of gravitational waves or observations of gravitational lensing. There are also important consequences of relativity that humans can’t escape; for example, satellites’ clocks need to be tuned to tick at a different rate due to the effects that gravity has on the rate time passes. Research in this branch of physics is closely tied to astronomy because it involves high velocities and the long-distance and large-scale interactions of gravitation, both of which certainly exist in outer space much more than on Earth.
In a sense, most humans have the capability to deal with the “very small” (quantum), simply because everything we interact with is made out of atoms but not the “very fast” (relativity), since nothing we can see on earth, other than light itself, moves at speeds even close to the speed of light: 3×108 m/s. This is one way of explaining why there might be more research in quantum mechanics as opposed to relativity as it is both easier to conduct on earth and also may yield more relevant results for us.
The “holy grail” of modern physics is finding a theory of everything, a single model that characterizes and unifies the four forces: gravity, strong nuclear, weak nuclear, and electromagnetism. Theories like quantum gravity and string theory are all attempts to unify physics, but no theory has been fully successful. But any foundational work in physics is mostly likely occurring in quantum mechanics, general relativity, or the unification of the theories, fields we don’t yet know enough about.
Now, we transition to classical mechanics, electromagnetism, and thermodynamics, fields mostly established before the 20th century rise of modern physics. Here, we aren’t seeking fundamental, governing equations — we already have them (e.g., Newton’s laws). But science doesn’t stop at the equations! Equations can be combined, interpreted, and applied to solve challenging problems, develop devices, and answer questions. Most research in classical physics centers around its employment to answer questions that have relevant applications, often through numerical simulations and experimental verification, rather than identifying the fundamental mechanisms at play, like in modern physics. Nonetheless, classical physics is still developing, albeit in different ways from modern physics.
Take, for instance, a Utah State University study that investigated techniques to reduce the impact forces on objects entering water. This research, focusing on fluid dynamics, could have been carried out before the discovery of modern physics and produced the same results. This is not to diminish the importance of the work conducted but rather to place it in the category of research that does not incorporate the quantum or relativistic worlds. The researchers approached their problem empirically, dropping spheres into a tank and monitoring the peak impact force through accelerometers attached to the projectiles. They found various approaches, including dropping a dummy sphere beforehand and placing the sphere inside a jet of water falling alongside it, which reduced the peak impact force. This study has applications in a variety of areas, including softening rocket water landings, which can in turn lead to cost savings and improved reusable space launch technologies .
At MIT, a recent study discovered a way to solve the extremely difficult task of breaking spaghetti into exactly two pieces when snapping it by holding the ends. On the surface, it seems like a quirky piece of research, but knowing the fracture properties of materials has important consequences for mechanical engineering and material science. By numerically modeling the fracturing of a rod caused by bending and twisting, the researchers found a way of snapping of spaghetti (twisting 270º, then bending) that both theoretically and experimentally results in just one fracture . Like the water entry study, this research was conducted without involving any modern physics because it simply isn’t necessary to accurately explain the fracture of the spaghetti. Regardless, both studies are prime examples of how we are still using our understanding of classical physics to draw novel and interesting conclusions.
|A recent study at MIT modeled the way in which spaghetti fractures . This figure from the study shows the similarities between the numerical model and the experiment. Work like this heavily leans upon our understanding of classical, not quantum, physics.|
|(Chu, J. (2018). MIT mathematicians solve age-old spaghetti mystery. Retrieved from http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813)|
There are still areas of classical physics that we don’t know much about but still have the toolkits to address. For example, we don’t know if the Navier-Stokes equations of fluid flow have solutions in all cases (this is one of the Millennium prize problems), but at least we have these underlying differential equations, and these can be used to model and predict the flow of fluids, through numerical methods and computer simulations. Finding a closed-form solution would definitely be helpful, but currently, the groundwork has been laid, and much of the underlying physics has been understood with some level of intuition, certainly more than we can say about modern physics.
Classical physics has a plethora of practical applications, providing businesses fuel for innovation. For example, the Dyson vacuum cleaner company was the first to successfully create, market, and sell a bagless vacuum cleaner by using a technique called cyclonic separation — a technique invented a century earlier, in 1885 — but just cleverly applied to an everyday problem . Another example is in aircraft design: extensive computational and real-world wind tunnel testing based on a thorough understanding of fluid dynamics is always conducted before the creation of new aircraft, and engineering innovations such as winglets come about because of our ability to harness physics.
|The Dyson vacuum cleaner  and aircraft winglets  are both examples of how a detailed understanding of classical physics is incredibly useful to humans.|
|(Airbus Group, Inc. (2012). A320 Sharklet close up [Image]. Retrieved from https://www.airbus.com/newsroom/press-releases/en/2012/04/first-new-build-sharklet-equipped-a320-completed-in-toulouse.html)|
It would be hard to understate the benefits of a solid understanding of quantum mechanics, which could and already is beginning to open up vast frontiers like in quantum computing, general relativity, and astrophysics, which can help unravel the secrets of the universe and satiate the fundamental human thirst for knowledge. However, much of the underlying physics in these fields has yet to be understood. But we do not need quantum mechanics and general relativity to continue doing what we have been doing for decades and even centuries — that is, developing a greater understanding of natural phenomena and utilizing physics to advance human civilization and make the world a better place. We still have much to extract from our existing understanding of classical physics, which will continue having an impact on our lives for decades and even centuries to come.
References  Airbus Group, Inc. (2012). A320 Sharklet close up [Image]. Retrieved from https://www.airbus.com/newsroom/press-releases/en/2012/04/first-new-build-sharklet-equipped-a320-completed-in-toulouse.html
 Beck, R. (1997). Seeing The Invisible. Chemical & Engineering News, 75(27), 41-42. doi: 10.1021/cen-v075n027.p041
 Chu, J. (2018). MIT mathematicians solve age-old spaghetti mystery. Retrieved from http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813
 In the eye of the vortex that keeps Dyson’s world spinning. (2018). Retrieved from https://medium.com/dyson/in-the-eye-of-the-vortex-that-keeps-dysons-world-spinning-3ab390cf0363
 Michelson, Morley and the speed of light. From Einstein Light. (2018). Retrieved from https://newt.phys.unsw.edu.au/einsteinlight/jw/module3_is_it_true.htm
 Orzel, C. (2018). What Has Quantum Mechanics Ever Done For Us?. Retrieved from https://www.forbes.com/sites/chadorzel/2015/08/13/what-has-quantum-mechanics-ever-done-for-us/#c47805340468
 Reducing the impact forces of water entry. (2018). Retrieved from https://phys.org/news/2018-11-impact-entry.html
 Science, L. (2018). What is an MRI (Magnetic Resonance Imaging)?. Retrieved from https://www.livescience.com/39074-what-is-an-mri.html
 Stanford University. (2018). Stanford Health Care’s PET/MRI scanner [Image]. Retrieved from https://stanfordhealthcare.org/content/dam/SHC/diagnosis/p/images/pet-mri.jpg