Posts Tagged ‘Matt Damon’
The conventional wisdom among people who know a little bit of quantum mechanics is that quantum mechanics is weird.
The conventional wisdom is wrong. Quantum mechanics is not weird. Interpretations of quantum mechanics are weird.
My thinking on this has changed over the years. In high school I read everything I could about the “weirdness” of our universe: Schrödinger’s cat, wave-particle duality, the collapse of the wave function, many-worlds theory, the Heisenberg uncertainty principle.
Then a strange thing happened: I went to college. I studied physics. And guess what? None of that stuff gets more than the briefest mention in the physics classroom. Why?
Because those things are beside the point. Quantum mechanics works. How you interpret quantum mechanics is your problem.
There’s a dichotomy here which is the source of most people’s confusion. Theories are different from interpretations of theories. A theory is a mathematical model that allows us to make predictions. An interpretation is a philosophical construct that allows us to sleep at night; it is a squishy heuristic that helps us unimaginative humans make sense of the math before us. Theories get things done. Interpretations never helped anybody, not really.
Let’s say that in an abandoned shack you discovered a notebook with the word “PHYSICS” written by hand over and over, thousands of times, apparently filling every page. You haven’t looked at the last few pages, but your theory is that these pages will also have the word “PHYSICS” written out. Each time you turn a page, your theory is validated: “PHYSICS” is there, as predicted.
Next to this notebook is another that looks just like it. You open the first page, and are not surprised to see “PHYSICS PHYSICS PHYSICS” again. What’s going on? Did some crazy person live in this shack? Such speculation doesn’t really matter, since you can still hypothesize that “PHYSICS” fills this notebook as well. In fact, you have a stronger theory: every notebook in this shack is filled with “PHYSICS”.
You perform an experiment: you turn the page. “PHYSICS PHYSICS PHYSICS”. The experiment supports your theory. You find more notebooks; same results. Every notebook in the shack is filled, apparently, with “PHYSICS”. But guess what? There are dozens of possible interpretations. And in the absence of further data, you can never know which one is “correct”.
Maybe the shack was once inhabited by a crazy person, who wrote “PHYSICS” precisely 250,001 times in a futile attempt at summoning Cthulhu from his ancient slumber.
Maybe a student misspelled “physics” on a test, and her cruel teacher punished her in the most depraved way possible.
Maybe Matt Damon filled the notebooks, in a method-acting attempt to get into the mindset of an OCD scientist.
Which of these interpretations is the “truth”? Without further data you cannot really say. Arguing about which is right and which is wrong is futile at best, and annoying at worst.
Of course, new data may turn up. We might find out that the notebooks are 75 years old, ruling out our Matt Damon interpretation. That interpretation is no longer a valid interpretation of the data.
Which brings me to my next point: there is no official arbiter of what constitutes a theory versus what constitutes an interpretation. Different philosophers and scientists have used the words differently at different times. All you can hope for is that a particular author is consistent in his/her use of the terms. I personally use the word “interpretation” to describe competing theories that cannot currently be differentiated by any known scientific experiment. If two different interpretations make different, testable predictions, then they are promoted to being totally different theories. (Caveat: others use the words slightly differently. Deal with it.)
So what does this have to do with quantum mechanics?
Quantum mechanics is an entirely mathematical theory. Its postulates are logical, concise, and powerful. We can use quantum mechanics to invent cell phones, computers, lasers, and iPods. Quantum mechanics doesn’t care if you “understand what it really means”, or not. It is arguably the most successful and powerful theory to come out of the 20th century.
Now, the mathematics of quantum mechanics are abstract and hard to visualize. Nevertheless, people insist on trying to visualize anyway. And the result is all kinds of weirdness: Schrödinger’s cat, wave-particle duality, the collapse of the wave function, many-worlds theory, the Heisenberg uncertainty principle. These ideas are all mental hoops that people have jumped through to explain some unambiguous, concrete, abstract linear algebra. The math is just math, and it works; what it means is anyone’s guess.
There’s no crying in baseball, and there’s no philosophy in quantum mechanics.
Don’t like the many-worlds interpretation? Fine. Be a Copenhagenist. Don’t like pilot waves? Great. Stick to your pet idea about superluminal communication. Just remember that all of these competing interpretations make the exact same predictions, so for all practical purposes they are the same. Some people go so far as to say, just shut up and calculate. [Note added 3-19-14: there are problems with pilot wave theories that in my view rule them out as being a valid interpretations of quantum mechanics. But there are hoops people can jump through to try and “force” pilot wave theories to be consistent with, say, Bell’s theorem. My broader point is that there are multiple interpretations of QM and that all have followers to this day, but that none of the interpretations really have any distinct implications for our lives.]
I don’t usually go that far. I actually think that the many-worlds interpretation is a testable theory, not an interpretation (hence the name of this blog). I think many-worlds is falsifiable. (If we ever observe a wave function collapsing, then many-worlds will have to be discarded.) But I don’t think that will happen: many-worlds is too elegant, and too powerful, to not be true.
But we’ll see.
If you think it’s absurd that a cat can be alive and dead at the same time…if you think that it’s crazy to hypothesize other universes…if you think that God does not play dice with the universe…don’t blame quantum mechanics. Blame the philosophers who try to interpret it.
Quantum mechanics works. Otherwise, you’d be reading this on an actual piece of paper.
In an earlier post I talked about events in spacetime, and about how an error in time is usually more grievous than an error in space.
Let’s now talk about the coincidence of spacetime coordinates. Specifically, how significant is it if you share one, two, three, or even four coordinates with a famous person?
First, some preliminary discussion. An event is a point (x,y,z,ct) in spacetime. Technically, you are not an event; you are a series of (unfortunate?) events smoothly snaking its way forward in time. As you sit there, reading this post, your x, y, and z are probably staying constant while ct is continually increasing. (Of course if you are reading this on the bus, then x, y, and z may be changing as well.) Note that I will use a relative coordinate system where x and y are measured with respect to the Earth (they are effectively longitude and latitude) and z is height above sea level. This way, we don’t have to deal with the annoying detail that the Earth is spinning, and orbiting the Sun, and that the solar system is hurtling through space.
Now the act of you reading this is an event; let’s say it has the coordinates (x,y,z,ct) in spacetime. But let’s also suppose that when you read that word, Matt Damon was eating a bagel with cream cheese. That event had the coordinate (X,Y,Z,cT), say. Unless you happened to have been with Matt Damon just then, your spatial coordinates did not coincide. However, it should be obvious that t=T. This means that it is no big deal to share a time coordinate with a celebrity. You currently share a time coordinate with every living celebrity. Right now, as you read this, Quentin Tarantino is doing something. So is cricketer Michael Clarke. So is chess grandmaster Magnus Carlsen.
But how significant is it if one spatial coordinate (x, y, or z) coincides with a celebrity? Or two spatial coordinates? Can we sort this out?
Here are some other possible cases:
x or y (and t) coincide: this is not likely to be true for you at this instant, but it happens with great frequency. It means that either your longitude or latitude is the same as a celebrity, such as Christopher Walken. Let’s say you’re currently in Jacksonville, FL whereas Walken is in Los Angeles. Obviously, your x’s are very different and your y’s, although close, are also different. But you decide to drive to Raleigh, NC for a friend’s wedding. At some point along your drive on I-95 your y-coordinate will be the same as Walken’s, as the line of your latitude sweeps through 34 degrees North. (If you’re curious, it will happen a little before you stop for lunch at Pedro’s South of the Border.) On a flight from Seattle to Miami, your lines of x and y will coincide (at different times) with a majority of celebrities in the USA.
z (and t) coincide: this is also quite common. It means that you and a celebrity (such as chess grandmaster Hikaru Nakamura) share an altitude. I am currently at z = 645 m (2116 ft.) in elevation…well, scratch that, I am three floors up, so it’s closer to z = 657 m. Anyway, if Nakamura drives from Saint Louis (Z = 142 m) to Denver (Z = 1600 m) on I-70 then our elevations will coincide at some point along his drive (presumably a little bit past Hays, KS).
x or y, with z and t: this is much rarer, but does happen. For this to occur, your line of longitude or latitude would have to sweep through a celebrity (such as quarterback Cam Newton), but you would also have to coincidentally be at the same altitude. Now, if you live in the same city as the celebrity (in this case, Charlotte, NC) then a simple trip across town to visit Trader Joe’s would probably be sufficient to achieve x=X (or y=Y) along with z=Z and t=T. However, for someone like me who lives at an arbitrary (and uncommon) elevation such as 645 m, this does not happen often.
x, y, z….but not t: this means that you have visited the exact location that a famous person has visited, but not at the same time. This probably happens hundreds of times in your life. An obvious example is when you go to a famous location: maybe Dealey Plaza in Dallas, maybe the Blarney Stone, maybe the location of Lincoln’s Gettysburg address. (By the way, today is the 150th anniversary of that speech!) A not-so-obvious example (but much more common) is when you drive along a much-used road. I have driven I-95 for huge stretches, for example, and I am sure many celebrities have driven that highway as well. At some point along my drives, I will have “visited” the same location as another celebrity (Tina Fey, let’s say) when she decided to drive down to Savannah for the weekend. I’m sure she stopped at Pedro’s South of the Border, and so have I.
x,y,z and t: this is the holy grail of celebrity coincidence. It means you met the person. Now, of course, humans are not bosons, so the spatial coordinates cannot be exactly the same, but if you meet the person I will say that the coordinates are close enough. My (x,y,z,ct) were once the same as Al Gore. My (x,y,z,ct) were once the same as Alan Dershowitz. My (x,y,z,ct) were once (almost) the same as Hikaru Nakamura. That’s about it.
I have left out several cases (such as x and/or z coinciding, without t) because they are trivial and uninteresting. Imagine the entire world line of a celebrity such as Winston Churchill, who traveled all over the world. If his spatial coordinates were projected onto the ground (painted bright yellow, say) then this looping curvy line would be a huge mess, spanning the globe, and covering huge swaths of England like spaghetti. As I live my life, at any given instant I am pretty sure that one or two of my coordinates match some part of this snaky line. No big deal.
It’s not like he was Matt Damon or anything.
If you enjoyed this post, you may also enjoy my book Why Is There Anything? which is available for the Kindle on Amazon.com.
I am also currently collaborating on a multi-volume novel of speculative hard science fiction and futuristic deep-space horror called Sargasso Nova. Publication of the first installment will be January 2015; further details will be released on Facebook, Twitter, or via email: SargassoNova (at) gmail.com.
I am a formula snob.
We all know about grammar snobs: the ones who complain bitterly about people using who instead of whom. Many people know how to use whom correctly; only grammar snobs care about it. I gave up the whom fight long ago (let’s just let whom die) but I am a grammar snob when it comes to certain words. For example, ‘til is not a word, as I have discussed before.
However, I am almost always a formula snob.
Consider this formula from the text I’m currently using in freshman physics:
x = v0 t + ½ a t2.
To me, looking at this equation is like watching Miley Cyrus twerk with Beetlejuice. I would much, much rather the equation looked like this:
Δx = v0 Δt + ½ a Δt2.
The difference between these two formulas is profound. To understand the difference, we need to talk about positions, clock readings, and intervals.
A position is just a number associated with some “distance” reference point. We use the variable x to denote positions. For example, I can place a meter stick in front of me, and an ant crawling in front of the meter stick can be at the position x=5 cm, x=17 cm, and so on.
A clock reading is just a number associated with some “time” reference point. We use the variable t to denote clock readings. For example, I can start my stopwatch, and events can happen at clock readings t=0 s, t=15 s, and so on.
Here’s the thing: physics doesn’t care about positions and clock readings. Positions and clock readings are, basically, arbitrary. A football run from the 10 yard line to the 15 yard line is a 5 yard run; going from the 25 to the 30 is also a 5 yard run. The physics is the same…I’ve just shifted the coordinate axes. If I watch a movie from 8pm to 10pm (say, a Matt Damon movie) then I’ve used up 2 hours; the same thing goes for a movie from 9:30pm to 11:30pm. Because a position x and a clock reading t ultimately depend on a choice for coordinate axes, the actual values of x and t are of little (physical) importance.
Suppose someone asks me how far I can throw a football. My reply is “I threw a football and it landed on the 40 yard line!” That’s obviously not very helpful. A single x value is about as useful as Kim Kardashian at a barn raising.
Or suppose someone asks, “How long was that movie?” and my response is “it started at 8pm.” Again, this doesn’t say much. Physics, like honey badger, doesn’t care about clock readings.
Most physical problems require two positions, or two clock readings, to say anything useful about the world. This is where the concept of interval comes in. Let’s suppose we have a variable Ω. This variable can stand for anything: space, time, energy, momentum, or the ratio of the number of bad Keanu Reeves movies to the number of good (in this last case, Ω is precisely 18.) We define an interval this way:
ΔΩ = Ωf – Ωi
So defined, ΔΩ represents the change in quantity Ω. It is the difference between two numbers. So Δx = xf – xi is the displacement (how far an object has traveled) and Δt = tf – ti is the duration (how long something takes to happen).
When evaluating how good a football rush was, you need to know where the player started and where he stopped. You need two positions. You need Δx. Similarly, to evaluate how long a movie is, you need the starting and the stopping times. You need two clock readings. You need Δt.
I’ll say it again: most kinematics problems are concerned with Δx and Δt, not x and t. So it’s natural for a physicist to prefer formulas in terms of intervals (Δx = v0 Δt + ½ a Δt2) instead of positions/clock readings (x = v0 t + ½ a t2).
But, you may ask, is the latter formula wrong?
Technically, no. But the author of the textbook has made a choice of coordinate systems without telling the reader. To see this, consider my (preferred) formula again:
Δx = v0 Δt + ½ a Δt2.
The formula says, in English, that if you want to calculate how far something travels Δx, you need to know the object’s initial speed v0, its acceleration a, and the duration of its travel Δt.
From the definition of an interval, this can be rewritten as
xf – xi = v0 (tf – ti) + ½ a (tf – ti) 2.
This formula explicitly shows that two positions and two clock readings are required.
At this point, you can simplify the formula if you make two arbitrary choices: let xi = 0, and let ti = 0. Then, of course, you get the (horrid) expression
x = v0 t + ½ a t2.
I find this horrid because (1) it hides the fact that a particular choice of coordinate system was made; (2) it over-emphasizes the importance of positions/clock readings and undervalues intervals, and (3) it ignores common sense. Not every run in football starts at the end-zone (i.e. x = 0). Not every movie starts at noon (i.e. t = 0). The world is messier than that, and we should strive to have formulas that are as general as possible. My formula is always true (as long as a is constant). The horrid formula is only true some of the time. That is enough of a reason, in my mind, to be a formula snob.
Bonus exercise: show that the product
ΩKeanu Reeves x ΩMatt Damon ≈ 3.0
has stayed roughly constant for the past 15 years.
When I was in elementary school, at some indeterminate age, I made a model of the atom with pipe cleaners and Styrofoam balls. It probably looked something like this:
These models are about as accurate as depicting the Taj Mahal as a decrepit hovel:
Sure, the atom has a nucleus; this nucleus has protons and (usually) neutrons. And electrons “orbit” the atom (although quantum mechanics tells us that this “orbit” is a much more nebulous concept than Bohr would have us believe). But—and here’s the main problem with 5th grade Styrofoam ball models—the scale is completely, totally, massively wrong.
Let’s do a simple calculation. A typical atomic radius is one the order of 0.1 nm. A typical nucleus, about 10 fm. What is the ratio of these two lengths?
About 10,000 to 1.
This bears repeating. A nucleus is something like 10,000 times smaller than an atom, by length. By volume, it’s even more dramatic:
A nucleus is 1,000,000,000,000 times smaller than an atom, by volume.
You don’t really get that impression from the Styrofoam ball model, do you?
A typical football stadium has a radius of maybe 120 m. One ten-thousandth of this is 1.2 cm, about the size of a pea. To get a sense of what an atom really looks like, place a pea at the center of a field in the middle of a football stadium. Then imagine, at the outskirts of the stadium, there are a few no-see-um gnats (biting midges, of the family Ceratopogonidae). These bugs represent the electrons. The atoms are the bugs and the pea. That’s it. The rest of the atom is empty space.
Another way to think about it is this:
In terms of volume, a nucleus is only 0.0000000001% of the volume of the atom.
That means, for those of you scoring at home, that 99.9999999999% of an atom is nothing.
That is, you are mostly nothing. So am I. So is Matt Damon.
So the next time you’d like to help your kids make a model of the atom, just forget it. Whatever model you make will be about as accurate as the physics in The Core. I’d recommend instead getting some nice casu marzu, having a strong red wine, and watching True Grit. You’ll thank me for it.
Posted in Comix, tagged Bryan Smith, Churchill the cat, Edward Cantasano, Helena Bonham Carter, Matt Damon, Stephen King, Violet Beauregarde, Violet Bonham Carter, Winston Churchill on March 5, 2013| Leave a Comment »
Winston Churchill and Violet Bonham Carter now appearing in: Many Worlds Comix #4!
I am hesitant, sometimes, to expound upon the many-worlds interpretation of quantum mechanics, for fear of something I call the Deepak Chopra effect. (I won’t give you a hyperlink to the guy, because I don’t want to increase any traffic to any website he’s associated with.) The Deepak Chopra effect is this:
If you talk about some weird aspect of quantum mechanics, they will come.
Who are “they”?
They are the Deepak Chopras of the world: people who make money by peddling vague new age philosophies.
Suppose you’ve made up some sort of new religion. You want followers, people to buy your books and watch your DVD’s and attend your seminars and drink your Flavor Ade and buy your T-shirts. (Yes, Deepak Chopra sells T-shirts.) What better way to attract attention, to give your puerile ideas a veneer of respectability than to cloak them in the mystique of quantum mechanics? Quantum mechanics is weird—everyone knows that—but almost no one really knows the details. PhD physicists don’t grow on trees, after all. Therefore, if you appeal to quantum mechanics to cover up the stench of your ideology, you will most likely get away with it.
I’m tempted to write some computer code that invents Chopra-esque prose. The output would look like this:
Your [mind] and [eternal light] have been exquisitely formed by [the cosmic warmth] to help you fulfill [your potential matrix] and your [soul capability]. This is because [wave-particle duality] and [the principle of decoherence] prove that your [neo-human consciousness] transcends the [body-mind paradox] to inhabit the [weak nuclear force] under the auspices of [string theory].
Easy, right? Yet Deepak Chopra is the one worth $80 million dollars. Sigh.
So back to the many-worlds interpretation. What could someone like Chopra ever do with such an idea? How could he co-opt the multiverse to scratch out a few more ducats? I shudder to think on it.
People have been using the strange ideas of physics for a long time now, with predictable results. Take this garbage: “What the #$*! Do We Know!?” I wish I had been blogging in 2004 when this farce came out; my review of the movie would have been six words: “Nothing about physics, that’s for sure.” Yet part of the blame rests with physicists themselves: they bandy about strange ideas amongst themselves, with nary a thought about how the public at large will perceive said ideas.
Consider Schrödinger’s cat, for example, the popular notion of which is as follows: a cat can be alive and dead at the same time! Weird! And yet when Schrödinger first proposed this “paradox” his intent was to attack the Copenhagen interpretation of quantum mechanics, by pointing out an obvious absurdity. I know of no physicist on the planet who seriously believes a cat can be alive and dead at the same time. And yet Chopra and others like him point to such quantum weirdness and use it to excuse all manner of hooey.
But what about many worlds? Isn’t it just as crazy, just as loony, as anything Chopra peddles to the masses?
Well, no. It’s weird, sure. But it is based in peer-reviewed science, and is an active topic of investigation to this day. (I doubt anyone’s in a lab somewhere, trying to verify Chopra’s claims.) Many worlds is an interesting mathematical structure to explain our universe, but it doesn’t really affect anyone’s life. It’s not even relevant to how anyone should live their life. It should certainly never be used to prop up a shaky religion.
My advice to you, Dr. Chopra, is to quit using physics to bolster your claims. After all, I don’t use your only field of expertise (endocrinology) to support my idea that Matt Damon is really a cyborg, do I? Then again, maybe I could start a religion—
[Note: my book Why Is There Anything? is now available for download on the Kindle!]
(Photo credit: http://en.wikipedia.org/wiki/File:Schrodingers_cat.svg)