Why Physists Lie: The Language of Physics

In every academic field, an absolutely essential component is to create a set of “technical terms” (i.e., jargon) so that those outside the field don’t understand what you are saying but you still sound impressive. Physicists, however, have been faking all their experiments since around 1927 (alternatively, physicists and those of us who might be called mathematical physicists, are all insane; as I am insane from the study and use of physics I can’t tell which is true). We have cleverly hidden this not just using jargon, but by using both (more or less) “normal” language to mean things that have little or no relation to the normal meanings AND by taking technical terms from classical physics and using them to mean bizarre things.

Example 1: Most people have heard of Heisenberg’s uncertainty principle. Simplistically, it is a sort of a set of mathematical ratios that tell us the more certain we are when we measure something like spin, position, momentum, or any other “observable” property of a quantum system, the less certain we are of related “observable” properties of the system. The common example is position and direction: the more we know about the position of e.g., an electron, the less we know about its direction.

Fewer know the small set of basic postulates of quantum mechanics, one of which says something like everything there is to know (or all the information about) a quantum system is contained in our mathematical representation of its state. By “mathematical representation”, I mean something like the way we use numbers and math to describe values like speed, velocity, mass, position, etc.

Intuitively, this seems to say that we can write down a description of a quantum system such that we know everything about that system. However, the (in)famous uncertainty principle tells us we can never know anything exactly about any property of a quantum system, and the more we know about some property the less we know about others. What gives?

Example 2: An extremely important property of particles is what physicists call “spin”. Now, this would seem to be intuitive. Better still, we often refer to spin with phrases like “spin up” and “spin down” or “spin along the x-axis”, making it more obvious that by “spin” we really do mean rotation of the particle. But we don’t. In fact, we refer to another property of such systems (orbital angular momentum) which in classical physics is equivalent to spin: the “orbit” of something like a planet or a bullet along its axis. When something “orbits” along its own axis, this would seem to mean (and in classical physics it does) “spinning”. In quantum mechanics, these two ways of describing how something can spin correspond to very different things, and the seemingly more intuitive term “spin” is almost impossible to mentally visualize.

Example 3: I used the term “observable” above. In quantum physics, one finds references to “observables”, and these are defined as measurable properties of systems in quantum mechanics. And, as the observables are things like position and momentum, it would seem that we wouldn’t need such a term. After all, in classical physics we don’t refer to the position of an arrow or the momentum of a car as “observables”. These and other properties of physical systems are observed, and we have names for them (mass, speed, velocity, momentum, etc.) that we use to represent the values of our measurements/observations. Why would we need a term for the things we measure rather than, as in classical physics, just use the darn names of the properties we measure? Because “observables” in quantum mechanics are mathematical operators/functions, not values. They’re Hermitian matrices.

Example 4: Why on earth do we represent so-called “observables” by the mathematical functions? Because when, in quantum physics, we refer to the “state” of our system, the system we are referring to has no physical existence. It isn’t real. It’s a mathematical entity that dwells in an abstract mathematical space that isn’t 3-dimensional, or 4-dimensional, or 10-dimensional, but usually infinite-dimensional. So, when we “measure” these systems, we have to use mathematical functions because there is only a mathematical system to “measure”.

Example 5: What do we mean by “measure”? Answer: don’t ask.

This entry was posted in Uncategorized and tagged , , , , , , . Bookmark the permalink.

4 Responses to Why Physists Lie: The Language of Physics

  1. Jeff says:

    Example 1: I think quantum systems are like studying DNA without a quantifiable theory to study it. You will always have a constant, giving a particular instance, within that instance however, you might have a particular state for a given period of time that doesn’t change, and will remain a constant theoretically, unless something is done to change it. Think of two fan blades, one moving clockwise and the other counter clockwise, they will have points where they intersect, but they will not remain at a constant point of intersection forever, only for given point of time, but that given state (as it can be referred to as) where they intersect might occur X amount of times in a 10 second interval. You could then later make predictions if you come up with a formula for it and could essentially narrow down the time so your predictions are nearly flawless unless someone comes along with a better hypothesis or theory I suppose, but if you have superb formula or hypothesis there wouldn’t be any need for anyone to create one, unless they think there are some possible flaws in the logic, or choose to improve it. Which is how theories get developed.

    To expand on it further, there is no sigma standard for quantum mechanics like there is for other methodologies. So being able to pinpoint an observable quantum model would be kind of difficult without thinking about the system in its totally given its point of reference, or in this case what is being observed, which could probably be classified as a dynamic system imo.

  2. Thanks for the comment!

    One issue is that the example you gave (while very clear, concise, and illustrative) is that it describes classical physics. In particular, the state/phase space for (or, for simplicity, a model of) a “system” consisting of two fans rotating as you describe has a one-to-one correspondence between parameters or variables that define the state of the system at any time t and the system. To illustrate, imagine we construct a model of a fan with blades moving clockwise and another in which they move counter-clockwise. We can construct rather easily a model that tells us things like the position of every blade of both fans arbitrarily into the future. More importantly, if we wish to do this, our model contains components that correspond to things like a blade’s position, its momentum, it’s position relative to other blades, etc.

    In quantum physics, when we speak of the state of a system there is no system that exists which has that state. Ever. This is because we have “prepared” the system by disturbing physical systems like electrons repeatedly in order to give use a mathematical entity that is (very, very simplistically) an average of the magnitude of various ways in which we disturbed the electrons. We start with a bunch of electrons and some equipment. We “prepare” the system by messing around with the electrons until we really have no idea what’s going on with any of the individual electrons, but we know something about the average (or simply combined) disturbances which allow us to derive a mathematical entity that describes this average of sorts. It DOES NOT describe any of the electrons or anything else that we “prepared”. That mathematical entity is probabilistic: it allows us to say that given certain measurements of whatever it is we disturbed in order to derive our mathematical “system”, we can predict the outcomes of those measurements.

    Basically (and this is the standard understanding of quantum mechanics), a system in quantum mechanics is a probability function, not a real/physical system. It is no more a physical system than is the constant pi or the normal distribution from probability theory.

    We can’t think of the system in terms of its totality because it exists only as a statistical totality and only as such.

  3. Jeff says:

    True, but in this case would the system be disturbed or are we simply making predictions about the state that system might be in once it is setup without knowing how it started?

    Let’s even say they both start from rest (each fan with 5 blades) and we don’t know either of their initial positions. It would eventually have to reach a point of equilibrium (they wouldn’t be working against each other). Once it reaches that point, it would be possible to make predictions about the current state the system is in, because it is actually two systems, in this example it is just being combined to make one; much like Heisenberg’s uncertainty principle.

    I probably should have elaborated a little more.

  4. Jeff says:

    From ( I know its wiki ): http://en.wikipedia.org/wiki/Uncertainty_principle
    “Historically, the uncertainty principle has been confused[4][5] with a somewhat similar effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the systems.”

    There is also a good paper on this which gets into Schrodinger’s cat, Copenhagen’s interpretation and the Einstein-Podolsky-Rosen argument. It also talks about creating thought experiments and is definitely worth reading.

    Interpretation Of Quantum Mechanics. By: French, Steven R. D., Salem Press Encyclopedia of Science, 2011

    I came across it when I was reading up on Quantum Computation, which is how I eventually came up with the two-fan thought experiment, because I was trying to figure out what would be the best way to determine the position a qubit might be in. Which led me to looking into Quantum Dots, that I have been wanting to do more research on, but haven’t had time.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s