Nanotechnology and Human Health

Introduction

We are well into the 21 ^st century, and yet, remarkably, in high school physics classes we only teach material that was developed by the end of the 19 ^th century! How can this be true when physics underlies all scientific disciplines? There may be many answers, but a simple answer is that Newtonian mechanics, when dealing with physics on the human scale (the macroscopic world), is considered close enough! As a conceptual and theoretically minded person I don't think that this answer is adequate; we KNOW from modern physics that the world is different than we are used to encountering. However, on large scales the "weird" consequences of quantum mechanics, (which indicates that energy is not continuous but instead comes in small "packets" known as quantum and that the reality is really probabilistic instead of deterministic) are averaged out and, therefore, undetectable. However, at the nanometer (10 ^-9 meters) scale, quantum mechanics cannot be ignored and in fact begins to dominate.

The physics behind quantum mechanics, which has been developed over more than a century now, is essential. We must address these developments in high school physics because science is all about presenting the best current understanding. So I am committed to understanding physics as well as I can and sharing our best CURRENT understanding of physical reality! Nanotechnology literally opens up a world of possibility in that it offers an opportunity to give a tangible explanation and use for quantum mechanics.

In first year physics classes we mostly learn about Newtonian mechanics, which is how macroscopic objects behave in the absence and presence of forces. The underlying assumption is that objects are discrete masses that can be manipulated by forces that can be applied in any amount. There is also a conviction that physical reality is deterministic, which means that we believe that if we measure all of the pertinent information about an object that we can determine its future physical parameters and interactions.

These are assumptions that have been disproven over the past hundred years. Matter is not discrete: instead, it is quantized. This means that it does not have a definite size or shape because it is quantized, which means that energy is not continuous and that there are only certain incremental amounts of energy that are allowable. Zero energy is not an allowable state so all particles must have some vibrational energy. In fact, matter and energy are interchangeable and matter is dualistic, exhibiting characteristics of particles and waves. This has been demonstrated by the dual slit experiments for electrons, which exhibit interference wave properties that result in diffraction and interference, unless the electrons are "observed," in which case their wave function disappears and they act like particles. Now much can be said about the phenomenon of being "observed," but it has been theoretically determined that any and all means of interacting with the electrons (or photons in light, or any type of matter, in fact) causes them to behave like particles.

We have a fundamental lack of understanding about the nature of matter: neither the wave model nor the particle model can explain the essence of matter or radiation. In the macroscopic world, quantum mechanical and Newtonian mechanical predictions of behavior appear to agree. However, at the nanoscale their predictions diverge and it is quantum mechanics that proves to be the most accurate. Consequently, quantum mechanics provides a more comprehensive understanding of how nature really is, so we are compelled as teachers to understand and impart this knowledge. Quantum physics is the best model of reality that we have and I believe that we as teachers are not teaching it because we do not understand it, and are ourselves, unable to fully grasp and engage quantum mechanical implications.

Quantum mechanics is not always consistent with our everyday experience of the macro world and in fundamental ways is contradictory to it. Consequently, it is counter to our intuition. According to J.L Martin, "The basic rules of quantum mechanics are not at all complicated: the main problem is the hurdle of unfamiliarity… it has only been relatively recently that physicists have been forced to accept that 'everyday' mechanics must be modified to deal with phenomena on the cosmological or on the atomic scale. In the main, quantum mechanics is concerned with the atomic scale. Moreover, quantum mechanics is statistical in nature: it deals with questions of probability. This is in itself a psychological barrier for many people: even Albert Einstein was inflexibly opposed to a theoretical scheme which leaves so much to chance." ¹ Einstein was famous for his tremendous success pursuing his intuition, but the success of quantum mechanics over the past century seems to indicate that we must accept that reality is not the way that we would expect, or often, even for which we would hope. We must acclimate to this quantum mechanical world in order to progress in our fundamental understanding of how nature works.

As society delves further into the nanoscale, and as nanotechnology provides more and more opportunities for our students and more challenges for all citizens, it is no longer possible to accept Newtonian mechanics as being "close enough." Quantum mechanics forces us to see reality in fundamentally different and challenging ways, but it is our best understanding and it is imperative as teachers of future scientists and citizens that we impart this knowledge, even though it may be beyond our comfort zone. Nanotechnology, by getting into the scale where quantum mechanics begins to dominate, requires that we address the "weirdness" of quantum mechanics (because it behaves unlike the macroscale world), of REALITY, as best we can comprehend it!

Another important aspect of matter is that it is probabilistic in that there is a defined amount of minimum uncertainty in the product of the momentum and position, as defined by the Planck constant. This observation is called the Heisenberg Uncertainty Principle and it is a fundamental characteristic of matter. Simply stated you can only know the position and the momentum within a given amount, known as the Planck constant. The more accurately you know the position the less you know its momentum and vice versa. A corollary is that we can only know the energy and time within the same limit of maximum accuracy. In fact, we can only know the probability of specific outcomes, so nature is not deterministic!

Quantum mechanics dictates a level of uncertainty and breaks with determinism of classical mechanics. "Uncertainty has entered physics and replaced the determinism of Newtonian mechanics." ² As is usual in quantum mechanics, we must look to experiments for answers, and, "experiment at the atomic level apparently suggests that the physical world is not deterministic… Thus Newtonian mechanics needs to be modified." ³ As scientists faced with the consequences of quantum mechanics, we must reacclimate to an unfamiliar, unexpected and often bizarre new reality.

I will be teaching this subject to a variety of levels of physics classes in the urban Pittsburgh Public School district. I will address this unit to general mainstream first-year physics classes, gifted first-year physics classes and algebra-based Advanced Placement second year physics classes. This represents a broad range of mathematical and conceptual skill levels. However, I believe this unit is accessible on a variety of levels. Conceptually, I believe this unit is accessible to eleventh and twelfth grade students. Some of the specific scientific concepts might be too difficult for the general physics class, but adaptations can be made to the unit by varying the level of explanation of the most difficult concepts. This is also true mathematically. The general physics students will be introduced to the formulas whereas the second year physics students will be expected to manipulate the formulas. This unit is intended to be broad enough to be applicable to any physics course.

Student Demographics

My high school has approximately 1350 students with 400 of them being designated as gifted. The school is roughly 58% Caucasian, 39% African American, 4% Asian and 4% multiracial. There is a range of socioeconomic backgrounds as well, with approximately 35% of the students receiving free or reduced lunch. My classes are more homogeneous with a majority of Caucasian students, a lower percentage of African-American students, and fewer economically disadvantaged students. However, all students are required to take physics and all seniors who have already taken physics are encouraged to consider taking a second year of physics.