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Ask an experimental physicist

35 RolfAndreassen 08 June 2012 11:43PM

In response to falenas108's "Ask an X" thread. I have a PhD in experimental particle physics; I'm currently working as a postdoc at the University of Cincinnati. Ask me anything, as the saying goes.

This is an experiment. There's nothing I like better than talking about what I do; but I usually find that even quite well-informed people don't know enough to ask questions sufficiently specific that I can answer any better than the next guy. What goes through most people's heads when they hear "particle physics" is, judging by experience, string theory. Well, I dunno nuffin' about string theory - at least not any more than the average layman who has read Brian Greene's book. (Admittedly, neither do string theorists.) I'm equally ignorant about quantum gravity, dark energy, quantum computing, and the Higgs boson - in other words, the big theory stuff that shows up in popular-science articles. For that sort of thing you want a theorist, and not just any theorist at that, but one who works specifically on that problem. On the other hand I'm reasonably well informed about production, decay, and mixing of the charm quark and charmed mesons, but who has heard of that? (Well, now you have.) I know a little about CP violation, a bit about detectors, something about reconstructing and simulating events, a fair amount about how we extract signal from background, and quite a lot about fitting distributions in multiple dimensions. 

Cryonics Wants To Be Big

28 lsparrish 05 July 2010 07:50AM

Cryonics scales very well. People who argue from the perspective that cryonics is costly are probably not aware of this fact. Even assuming you needed to come up with the lump sum all at once rather than steadily pay into life insurance, the fact is that most people would be able to afford it if most people wanted it. There are some basic physical reasons why this is the case.

So long as you keep the shape constant, for any given container the surface area is based on a square law while the volume is calculated as a cube law. For example with a simple cube shaped object, one side squared times 6 is the surface area; one side cubed is the volume. Spheres, domes, and cylinders are just more efficient variants on this theme. For any constant shape, if volume is multiplied by 1000, surface area only goes up by 100 times.

Surface area is where heat gains entry. Thus if you have a huge container holding cryogenic goods (humans in this case) it costs less per unit volume (human) than is the case with a smaller container that is equally well insulated. A way to understand why this works is to realize that you only have to insulate and cool the outside edge -- the inside does not collect any new heat. In short, by multiplying by a thousand patients, you can have a tenth of the thermal transfer to overcome per patient with no change in r-value.

But you aren't limited to using equal thickness of insulation. You can use thicker insulation, but get a much smaller proportional effect on total surface area when you use bigger container volumes. Imagine the difference between a marble sized freezer and a house-sized freezer. What happens when you add an extra foot of insulation to the surface of each? Surface area is impacted much as diameter is -- i.e. more significantly in the case of the smaller freezer than the larger one. The outer edge of the insulation is where it begins collecting heat. With a truly gigantic freezer, you could add an entire meter (or more) of insulation without it having a significant proportional impact on surface area, compared to how much surface area it already has. (This is one reason cheaper materials can be used to construct large tanks -- they can be applied in thicker layers.)

Another factor to take into account is that liquid nitrogen, the super-cheap coolant used by cryonics facilities around the world, is vastly cheaper (more than a factor of 10) when purchased in huge quantities of several tons. The scaling factors for storage tanks and high-capacity tanker trucks are a big part of the reason for this. CI has used bulk purchasing as a mechanism for getting their prices down to $100 per patient per year for their newer tanks. They are actually storing 3,000 gallons of the stuff and using it slowly over time, which implies there is a boiloff rate associated with the 3,000 gallon tank in addition to the tanks.

The conclusion I get from this is that there is a very strong self-interested case (as well as the altruistic case) to be made for the promotion of megascale cryonics towards the mainstream, as opposed to small independently run units for a few of us die-hard futurists. People who say they won't sign up for cost reasons may actually (if they are sincere) be reachable at a later date. To deal with such people's objections and make sure they remain reachable, it might be smart to get them to agree with some particular hypothetical price point at which they would feel it is justified. In large enough quantities, it is conceivable that indefinite storage costs would be as low as $50 per person, or 50 cents per year.

That is much cheaper than saving a life any other way. Of course there's still the risk that it might not work. However, given a sufficient chance of it working it could still be morally superior to other life saving strategies that cost more money. It also has inherent ecological advantages over other forms of life-saving in that it temporarily reduces the active population, giving the environment a chance to recover and green tech more time to take hold so that they can be supported sustainably and comfortably. And we might consider the advent of life-health extension in the future to be a reason to think  it a qualitatively better form of life-saving.

Note: This article only looks directly at cooling energy costs; construction and ongoing maintenance do not necessarily scale as dramatically. The same goes for stabilization (which I view as a separate though indispensable enterprise). Both of these do have obvious scaling factors however. Other issues to consider are defense and reliability. Given the large storage mass involved, preventing temperature fluctuations without being at the exact boiling temperature of LN2 is feasible; it could be both highly failsafe and use the ideal cryonics temperature of -135C rather than the -196C that LN2 boiloff as a temperature regulation mechanism requires. Feel free to raise further issues in the comments.

The two insights of materialism

18 Academian 24 March 2010 02:47PM

Preceded by:  There just has to be something more, you know?  Followed by:  Physicalism: consciousness as the last sense.

Contents:  1. An epistemic difficulty  2. How and why to be a materialist

An epistemic difficulty

Like many readers of this blog, I am a materialist.  Like many still, I was not always.  Long ago, the now-rhetorical ponderings in the preceding post in fact delivered the fatal blow to my nagging suspicion that somehow, materialism just isn't enough.

By materialism, I mean the belief that the world and people are composed entirely of something called matter (a.k.a.  energy), which physics currently best understands as consisting of particles (a.k.a.  waves).  If physics reformulates these notions, materialism can adjust with it, leading some to prefer the term "physicalism".

Now, I encounter people all the time who, because of education or disillusionment, have abandoned most aspects of religion, yet still believe in more than one than one kind of reality.  It's often called "being spiritual".  People often think it feels better than the alternative (see Joy in the merely real), but it also persists for what people experience as an epistemic concern:

The inability to reconcile the "experiencing self" concept with one's notion of physical reality.

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There just has to be something more, you know?

13 Academian 24 March 2010 12:38AM

A non-materialist thought experiment.

Okay, so you don't exactly believe in the God of the Abrahamic scriptures verbatim who punishes and sets things on fire and lives in the sky.  But still, there just has to be something more than just matter and energy, doesn't there?  You just feel it.  If you don't, try to remember when you did, or at least empathize with someone you know who does.  After all, you have a mind, you think, you feel — you feel for crying out loud — and you must realize that can't be made entirely of things like carbon and hydrogen atoms, which are basically just dots with other dots swirling around them.  Okay, maybe they're waves, but at least sometimes they act like dots.  Start with a few swirling dots… now add more… keep going, until it equals love.  It just doesn't seem to capture it.

In fact, now that you think about it, you know your mind exists.  It's right there: it's you.  Your "experiencing self".  Maybe you call it a spirit or soul; I don't want to fix too rigid a description in case it wouldn't quite match your own.  But cogito-ergo-sum, it's definitely there!  By contrast, this particle business is just a mathematical concept — a very smart one, of course — thought of by scientists to explain and predict a bunch of carefully designed and important measurements.  Yes, it does that extremely well, and you're not downplaying that.  But that doesn't explain how you see blue, or taste strawberry — something you have direct access to.  Particles might not even exist, if that means anything to say.  It might just be that observation itself follows a mathematical pattern that we can understand better by visualizing dots and waves.  They might not be real.

So actually, your mind or spirit — that thing you feel, that you — is much more certain an extant than scientific "matter".  That must be something very important to understand!  Certainly you can tell your mind has different parts to it: hearing, seeing, reasoning, moving, remembering, empathizing, picturing, yearning… When you think of all the things you can remember alone — or could remember — the complexity of all that data is mindbogglingly vast.  Imagine the task of actually having to take it all apart and describe it completely… it could take aeons…

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