There might be a more immediate threat than black holes at the LHC… ninjas working for shady arms dealers intent on a new world order!
A ninja at the LHC. No... really. Image from the GI Joe Movie fankit.
Ok, I’m being facetious. I just got back from watching the new action movie, G.I. Joe: The Rise of Cobra. As someone who grew up watching the G.I. Joe cartoon in the 80s and reading the many iterations of G.I. Joe comic books, I couldn’t help but go out to watch the film despite my low (i.e. nonexistent) expectations for anything academy award-worthy.
What I felt like sharing with the US LHC blogosphere, however, was an oblique mention of the LHC in the middle of the movie. There’s technically some small spoilers ahead… but look, I don’t think anybody is going to watch this movie for its plot, so I’ll spill the beans.
One of the movie bad-girls, the Baroness — because she’s married to a French baron — forces her physicist husband to activate some nano-bot missiles using a “particle accelerator in France.“ Did I mention that the French baron is also a particle physicist? Yeah, it’s that kind of movie. Anyway, the scene involves the ninja assassin Storm Shadow (pictured above) slicing up some innocent particle physicists (experimentalists, no doubt*). In the background of all this is a big machine that looks very similar to the ATLAS detector.
Those of you who have attended one of the “Science of Angels & Demons” talks will be familiar with the misrepresentations of particle physics labs. (Lab coats, windows to the interaction point, …) But like the many liberties in science, technology, and plausibility that the movie takes, one is just asked to take these in stride; this isn’t meant to be a `cerebral’ film, it’s a movie about action figures.
By the way, how should you know that the premise of “activating” nano-bots using the LHC is silly? The energy scales at the LHC can be converted into length scale**. If one does a back-of-the-envelope calculation, one finds that the TeV-scale energies probed by the LHC corresponds to length of roughly 10^{-19} meters. This is way smaller than a “nanobot” or anything that would be built out of atoms. For a concrete comparison, Cornell’s `nanoguitar‘ is only on the order of 10^{-5} meters.
So trying to use the LHC to ‘activate’ nanobots would be like trying to use a toothbrush to wash your kitchen floor… only your toothbrush would be the width of a DNA molecule and your kitchen floor would be the size of Jupiter.
While we’re at it, here are a few other priceless particle physics ‘moments’ in recent blockbusters:
- Star Trek (2009): Vulcans in the future work with ‘red matter,’ a fictional substance that can warp space and is presumably named to mimic ‘dark matter.’
- Spiderman 3 (2007): While fleeing the police, Flint Marko accidentally falls into a particle accelerator (apparently a chain-link fence is a sufficient barrier to synchrotron radiation in the Marvel universe), turning him into the supervillain The Sandman.
- The World is Not Enough (1999): Okay, this movie is now a decade old, but I’ll never forget the ridiculous scene where Denise Richardson pulls herself out of some large service pipe, peels off a tight-fitting jumpsuit, and introduces herself as “Christmas Jones, I’m a theoretical physicist.” (At least I remember her saying that, it was so long ago.)
Anyway, to all my experimental colleagues: keep an eye out for ninjas!
-Flip (“… I’m a theoretical physicist.”)
* — I say this because it’s a well-known fact that most theorists posses crazy ninja abilities.
** — The idea of converting energy scales to length scales comes from the observation that nature appears to have ‘fundamental’ dimensionful constants. For example, the speed (=length / time) of light is constant which sets an `equality’ between length and time. Similarly, Planck’s constant (h-bar) sets an equality between energy and rate (inverse time). Thus one can convert an energy (TeV) into a length scale by dividing by the speed of light, dividing by the Planck constant and then taking the inverse of the result. This isn’t an exact relation since sometimes the constants are defined with factors of pi floating around, but it gives an order of magnitude estimate for the relation between length and energy scales.
Mr Tancredo, surely you don’t think that attractive women physicists are as ridiculous as red matter or supervillain inducing accelerators, do you?
Vulcans “red matter” is a cross between dark matter and “red mercury” – mythical substance of urban legends connected with nuclear and ballotechnic weapon, stealth and medieval alchemy
http://en.wikipedia.org/wiki/Red_mercury
Apologies, I got your last name mixed up with one I see frequently in emails!
[...] US LHC Blog » Forget black holes… ninjas at the LHC?There might be a more immediate threat than black holes at the LHC… ninjas working for shady arms dealers intent on a new world order! A ninja at the LHC. No… really. Image from the GI Joe Movie fankit. Ok, I’m being facetious. …Read More [...]
[...] “One of the movie bad-girls, the Baroness — because she’s married to a French baron — forces her physicist husband to activate some nano-bot missiles using a “particle accelerator in France” … anyway, the scene involves the ninja assassin Storm Shadow slicing up some innocent particle physicists (experimentalists, no doubt).” Particle physicist grad student Flip Tanedo assesses the role of the Large Hadron Collider in G.I. Joe, the latest big-screen summer blockbuster (US/LHC blogs). [...]
But what does the “length” /mean/? Sorry, I have experimentalist or even engineering leanings [SHOCK!]
Hi Lauren — my apologies! Don’t misunderstand me: I never, ever, never-ever-ever said that it was ‘ridiculous’ that an attractive woman would be a physicist, nor would I ever believe such a thing. I meant that it was ridiculous that a theoretical physicist would be pulling him/herself out of a some sort of glorified sewer, much less wearing anything other than sandals and a comfy t-shirt. (This is an extension of the `why do all movie physicists wear lab coats?’ phenomenon.)
The idea of any of my theory colleagues having to roto-rooter work as part of their research is, indeed, up there on my list of silly thoughts. (The only `heavy machinery’ theorists regularly use is an espresso machine.)
[For the record, Vittoria Vetra was an `attractive woman physicist' in the movie Angels & Demons. Neither I nor anyone else listed her gender as implausible during our many `physics of Angels & Demons' discussions here!]
So no, it bears repeating that there is nothing silly with the idea that women —- or ethnic/religious/gender-identity minorities, or people with underprivileged backgrounds —- becoming physicists, despite the stereotype of the white male scientist from an upper-middle class background. (And regardless of whether or not they are attractive!)
As someone who doesn’t fit the description of a stereotypical physicist myself, I can attest to the importance of having role models that also ‘break the mold,’ so to speak. Fortunately, over the past seven years I’ve noticed that this really is something that’s changing: not from movies, but actual real-life young researchers who act as mentors for undergrads and graduate students.
Cheers,
F
PS — if you’re getting lots of e-mails about a ‘Mr. Tancredo’ I can see why you’d be quick to point out potentially discriminatory remarks…
PPS — the reason why I’m amused by this comment is that there was a big hullabaloo on the blogosphere not-too-long ago about a famous blogger making a comment about the attractiveness of a famous female physicist. I have to admit that when I made my post I was curious if people would misinterpret it and imply that I was sexist. I hope I’ve cleared up the fact that I am not!
Serge — thanks for clarifying the origin of “red matter!” That makes a lot more sense now.
Cheers,
F
Hi Michael — excellent question! I think an analogy would be the best answer. Consider how a microwave works.
A microwave cooks things by having standing electromagnetic waves that happen to resonate with the dipole moment of a water molecule. In other words, the frequency is such that it’s really good at jiggling water molecules (the jiggling is where the thermal energy comes from that cooks the food).
So what’s happened here? The energy of a photon (a quantum of the electromagnetic field) is hf, where h is the Planck constant and f is the frequency of the electromagnetic wave. Thus the photons of ‘just the right frequency to excite water molecules’ are photons of definite energy. The energy scale is thus converted into a length scale (the scale of the water molecule) that is probed by the photon.
This was very hand-wavy and certainly it’s only an order of magnitude estimate, but this is really how we like to think about higher energies probing smaller length scales. This is why the LHC is the world’s best microscope.
As another example, people didn’t realize that protons had a substructure (i.e. the proton is made up of smaller stuff) until the famous deep inelastic scattering experiments at SLAC. There they shot high-energy electrons into a core of protons. They found that while most reactions were elastic (e.g. an electron grazing off the electric field of the proton), some were inelastic (smashing into the proton). The particular distribution of inelastic electrons was a strong hint that the electrons weren’t really interacting with the proton as a whole, but rather just the constituent quarks and gluons. This meant that the electrons were probing length scales smaller than the scale of the proton size. (This is the analog to the Rutherford experiment bombarding alpha particles into gold leaf to show that atoms had a positively charged nucleus.)
Hope that helps!
F
I took my wife to see “GI Joe: Rise of the Cobra” last weekend. It was not an optimal choice.
Hi Filip, I didn’t think you meant the comment in a discriminatory way, but some more context was necessary to show that since these stereotypes, as you mentioned, are so pervasive even though overt discrimination is very rare. In some ways it was nice for Hollywood to show a physicist who didn’t fit that stereotype (also, wasn’t she a nuclear physicist?) although she did not play the part very convincingly. In any case, the physicist-as-bond-girl was the ridiculous part about it; i think we lady scientists definitely know better than that!
ps: Despite my objection to that list, I like your posts, keep up the good work!
Hi Flip,
I found my way to these LHC blogs from a quote on a British newspaper site.
http://www.guardian.co.uk/science/blog/2009/aug/12/lhc-shutdown-higgs-boson-cern
It’s really good seeing you all posting stuff. I’m particularly impressed that you aren’t talking down to us and that you assume we can understand quite complex stuff if it’s explained right.
If you don’t mind, can I just ask you about the microwave example. You say the energy of a photon is hf. I’m ok that far: that says energy is proportional to frequency and the constant that relates the two is a simple constant of proportionality (named after Planck). I don’t understand WHY the two relate in this way but maybe it’s just one of those things you have to accept because that’s what you see when you measure it. What I don’t understand then is, how do you get from knowing that energy to a length? You seem to do some hand-wavy stuff and then state that the result, the fact that the water molecules jiggle, shows that this equates to a distance (ta-da!). But that’s kind of cheating, going to the end and then working back, leaving a hole in the middle. Could you do it in a forward direction, starting with the frequency of the microwaves and deriving a distance that matches the scale of the water molecules?
JC
Hi JC — the easiest way to fluster a physicist is to insist that they connect the dots between their waving hands!
But indeed you are asking exactly the right question and I should have made the logic more explicit. To restate the question: it’s not clear why the electromagnetic fields in the microwave (of some energy E and hence some frequency f) correspond to some natural length scale, namely the length scale of the water molecule’s dipole.
The main idea here is resonance. (This is another one of those underrated themes in physics that I should perhaps write a separate post about.) The frequency of the oscillation f tells us about the time scale in which the electric polarity flips back and forth. This back and forth of the electric field is precisely what pulls and pushes the water molecules to jiggle.
In order for the microwaves to cause the maximum ‘jiggle’ in the water molecule, it needs to allow just enough time for the polar molecule to rotate in response to the polarity before it flips polarity again. If it flips polarity much too quickly, then the water molecule won’t have time to start rotating and it won’t jiggle. If it flips polarity much too slowly, then the water molecule’s motion doesn’t produce any appreciable thermal energy (there’s no resonance).
Thus there is a ‘just right’ frequency that corresponds to the right time scale to to get water molecules (of a given length scale) to jiggle in resonance. Energy scales, time scales, and length scales are all related.
Perhaps a much better analogy is a swing. On a swing we have a characteristic frequency in which we kick our legs to keep the swing going and increase the amplitude. If we kick at a higher frequency then the kicks only cancel each other out leading to no net push. If we kick at a lower frequency then we’re not efficiently depositing energy and the swing’s amplitude is damped.
Again — this isn’t a rigorous derivation, but sometimes a good analogy is an even more elegant tool. (Hopefully this was a good analogy.)
Hi Flip,
I realise that two analogies for the price of none is a pretty good offer, but could we stay with the microwave one for a few moments. It raises some interesting questions in my understanding of these things (and they are pertinent to what you are doing here in introducing people to the theoretical side of the LHC).
Where did I start with your example? Like many people, I think of photons as electromagnetic waves, so I naturally think of frequency and/or wavelength as their measure. What is unnatural is thinking of them as particles of energy. (I’m throwing this in so you get some feedback from us readers: it seems to me that what you’re doing with this blogging is like running a particle experiment and then trying to piece the results together from chance remarks you hear afterwards in the canteen.) When I tune a radio the scale is either length (the shortwave band would be marked out in tens of meters) or frequency (an FM radio station might be 94 million cycles per second). What I never see is a scale marked out in energy. Why, I don’t know? Maybe the figures look a bit silly and the pioneers of radio chose the sensible looking ones. Or perhaps, early on, they wanted to give people an idea of just how much antenna wire they were going to need to buy.
Anyway, to get back to the example, if I work out the wavelength for the microwaves I get 12.5cm. Now that causes me to pause. It doesn’t look anything like the natural scale of a water molecule. I’m not sure, off hand, how big a water molecule is, but it isn’t so big that you measure it in centimetres (that would be really heavy rain!). But it’s ok, because that’s not what you’re saying. You give me a further clue by mentioning the water molecule’s dipole. I know what a dipole is. But hang on, a dipole could be magnetic or electric, so which do you mean? Ah, the “electric field … pulls and pushes”, so it must be an electrical dipole. So why does a water molecule have an electrical dipole? Isn’t it neutral, with the same number of positive and negative charges? Ok, a bit of rummaging around produces the answer: it’s to do with the shape it folds itself into. It leaves part of the molecule a fraction positive and the rest, therefore, a fraction negative. (Somebody correct me if I’ve got that wrong.)
So, what you’re saying is that the time for one wavelength, which for the microwave photon is 417pS, corresponds to the time it takes for the molecule to move itself around in the electric field. I don’t have any feel at all for how molecules like this behave, but it sounds as though it might be plausible and I’ll take your word for it that this is about right.
Now to the follow-on question. The bit I’m hazy about.
How does the interaction between the photon and the molecule occur? How do you, as a theoretical physicist, look at it?
Does the photon still exist after the interaction, with a much reduced amount of energy (and, hence, a lower frequency)? Or does it cease to exist?
How do we visualise what is happening? Is it a fly past, or an ‘impact’? Or is it more like the sea lifting and dropping a ship?
How is the force exerted by the photon? I think what worries me is how a kind of smeared-out photon gathers together all its energy to give it up to the molecule.
And, a really tricky one I’ve just thought of: since a photon can have any amount of energy, can it have zero energy, or is that disallowed because the wavelength would be infinite? Or is that just saying it ceases to exist? (Maybe the universe is chock-a-block with old energy-free photons that we can’t see!)
Sorry so many questions, but it is interesting.
P.S. Only answer if you feel it’s useful on the blog – I don’t really expect you to teach me ALL of theoretical physics and you’ve probably got real work you should be getting on with anyhow.
JC
Hi JC!
I’ll have to admit right off the bat that I didn’t crunch the numbers myself, so kudos to you for doing so! I’ll try to get to all of your points, but several of them warrant whole posts that I hope to be able to write up in the not-too-distant future.
At the quantum level, you are indeed correct that one should wonder if it’s correct to think about waves vs. particles. This system, however, is just macroscopic enough to be thought of in a classical way. I would say that the quantum effects (waves or particles — I’ll get to this in a later post) conspire to set up a classical electromagnetic field, so we’re justified in thinking in terms of classical electromagnetic waves and not mentioning photons anywhere.
Going to your next point about why we mark off our radios in frequency rather than energy, indeed, using E = hf for photons one could convert wavelength to energy so that one could mark off ones radio in electron volts (or joules, etc). This would be a little misleading since E = hf is the energy of a single photon of a given frequency. The electromagnetic waves that travel to your radio station, however, are really classical macroscopic electromagnetic waves which are composed of many many many such photons. The energy of the entire wave would be calculated using classical electrodynamics (insert fancy words here like “Poynting vector” and such) and would represent the sum of a large number of photons, each with energy roughly E=hf.
So now it seems I’m telling you something inconsistent: the whole point was that E = hf allows us to trade units of (inverse) time and energy, but now I’m telling you that microwaves (and certainly radio waves) are essentially classical and E=hf doesn’t really hold. The microwave was meant to be an analogy, so indeed the analogy breaks down at some point. In particle physics we usually are only talking about single quanta (single particles), so the E=hf conversion is more sensible. Even then it’s still sort of a ‘rule of thumb.’
Regarding your calculation about the wavelength of microwaves: you did some excellent thinking on your feet and your suspicions are indeed correct. There’s another scale in the problem: the scale of the water molecule’s electric dipole. The entire water molecule is electrically neutral, but it’s composed of + and – charges which are a bit separated (sort of like a bar magnet). When the electric field oscillates, then, the + and – want to swap positions so the molecule rotates. This dipole sets another scale to the problem and so the calculation is a little bit more complicated. (It just went from being an undergraduate level homework problem to a graduate level homework problem!) There’s a short discussion on Wikipedia about this:
http://en.wikipedia.org/wiki/Microwave_oven#Principles
Ok, so your follow-up questions:
How do I view the interaction between the photon and the molecule? So as mentioned above, I would think about this classically. There are electromagnetic waves that are wobbling about. What the molecule (dipole) sees is an electric potential which is changing, so the molecule wants to follow the minimum of the potential. (A changing potential -> force.)
I think what you want to ask, though, is how I view the interactions of photons quantum mechanically. The short answer is that I think about them in terms of Feynman Diagrams. These are a whole long digression in themselves which I’ll try to get to another time, but in short the Feynman Diagrams (Google them to see what they look like) are pictures of how quantum particle interact. They’re easy to put together, but the genius behind them is that they represent surprisingly complicated mathematical formulae. [Learning to draw Feynman diagrams is an undergraduate task whose essence can be taught to enterprising children, learning to *calculate* Feynman diagrams is a graduate student's job.]
To answer that question more qualitatively: I think about photons and other particles interacting quantum mechanically as particles being created and destroyed as they pass their momentum along to each other. In words it’s not a very helpful image, but it’s much more powerful than it sounds. You could ask if this is *actually* what’s happening or if this is just a tool: this, also, is a much deeper question than I can really answer. The reason is that it boils down to “if a tree falls down in the woods and there’s nobody there to hear it, does it make a sound?”
For some interactions of photons with, e.g., electrons, the photon essentially bounces off. (e.g. look up “Compton scattering.”) In other interactions the photon is completely absorbed (or annihilated), such as when a particle and antiparticle annihilate into a photon, and the photon itself splits into another particle-antiparticle pair.
Your analogies for visualizing the interaction are nice: The classical interaction of a charged object in a changing electric field (like the water molecule dipole in the microwave) is like the sea lifting and dropping a ship. The interactions of quantum photons with other quantum particles are better thought of as ‘impacts.’
When it comes down to thinking about forces exerted by the photon the classical notion of ‘force’ breaks down a little. The photon itself *is* the mediator of the electromagnetic force. (That’s a bit of a deep statement if you’re not used to it!) What the photon does is impart its momentum to the thing that it’s hitting. That thing changes its momentum, and we say that it was acted on by a force.
Finally, the question of a zero-energy photon is again a question of “if a tree falls in the woods and nobody is there to hear it…” I’m not trying to be evasive with this, but one of the principles of quantum mechanics is that one can really only make definite statements about observable quantities. Things that we cannot observe (like a zero energy photon, or even a very very very small energy photon) are things that we cannot make reasonable statements about. Really.
Let me try to spice up that last answer a little with some history: One of the huge mysteries in quantum physics 60 or so years ago was how to deal with apparent nonsensical answers coming out of our calculations. The predictions for the probability for a photon to be produced in a process were coming out infinite. (A probability doesn’t make sense if its larger than one, let alone infinity!) It turns out that the problem was that people were including the possibility of making very small (e.g. zero) energy photons. These photons were completely spoiling the equations. By rephrasing the question they were asking (“probability of producing photons of a measurable energy”) and taking into account the appropriate quantum effects, the calculations started giving precisely the correct results. (I still find this rather amazing.)
These were some really, really great questions and I hope to spin them off into some dedicated blog posts in the future. Thanks for the contributions!
-F