Great party yesterday December 22, 2006
Posted by dorigo in food, personal, social life.2 comments
Yesterday’s party began in the worse possible way, with a phone call from Dario, the big boss of our group, who announced he would not make it, being stuck at the Fiumicino airport due to a lost connection.
Despite that initial setback, things got merry very soon as people started flowing in. I was especially pleased to see Elisa and Michele, and Chiara and Giulio. Both these couples had been invited quite late for different reasons: Elisa, who did her thesis with me four years ago, had not read my messages of invitation; Chiara, a summer student at Fermilab 10 years ago, lives in Grenoble and it was only by chance that I met her in the basement of the physics department this Tuesday.
It was also nice to have at the party a few people I did not know: Federica, Julien’s new girlfriend, and Diana, Mia’s cousin - especially since they are both young and pretty.
In the end we had about 30 guests, as predicted. There was a huge amount of food, because many had brought a contribution. And very good wines too, some of which has stayed with me. I am in fact presently serving myself an appetizer as I write these lines, and along with the appetizer an exquisite Sylvaner 2004 by Gruss.
Especially appreciated were the tartines (my concoction) which disappeared in the first five minutes, the pasticcio with mushrooms, the calamari, and the roast-beef. And of course, two large bowls of Tiramisu, a dessert made with coffee-dipped savoiardi (a particular kind of cookie), mascarpone cream, and a cocoa topping.
Below are a couple of pictures I took during the party.
The closest book game December 21, 2006
Posted by dorigo in Blogroll, books, games, internet, italian blogs, language, personal.6 comments
By monitoring incoming links today, I found 10 from http://backreaction.blogspot.com/ , and had a look. She had indeed linked me, and I found out it was an invitation to act on a game posted by clifford first.
So the game is, take the closest book to you right now, go to the fifth sentence on page 123, write the following three sentences in the blog, and tag three people.
The closest book to me in English (also visible from the picture in the previous post, if you have good eyes) is “Late Roman Painting” by my father, the late Wladimiro Dorigo. I’m quite happy to post three sentences from my father here.
“In the crypt of the Five Saints, in the Cemetery of Callistus, the only portrait of a praying figure which remains almost intact (though damaged) for inspection is that of ‘Dionysas’, so called from the inscription Dionysas in pace. It may well be affirmed, with De Walt, that every specific trace of impressionism has disappeared from this countenance. Its facial planes are so separated from the physiognomical lines of eyes, nose or mouth as to amount to a formal dissociation which is wholly expressionist.”
Wow that was long! Three sentences in pure Dorigo style. Now who should I tag ? Let’s see.
Ok, let’s take Gordon ( http://gordonwatts.wordpress.com ), Zerocold ( http://zerocold.wordpress.com ), and gattostanco ( http://gattostanco.diludovico.it/) .
This was fun!
Waiting for you December 21, 2006
Posted by dorigo in food, personal, social life.8 comments
The three large pans of lasagne (one containing bucatini with mushrooms and meat sauce, one with pine nuts and ham, and a third “regular” one) are ready to go. The calamary are done. The tuna steaks with olives are baked. Polenta is on its way. The large chunk of roast-beef is waiting to be sliced. An obnoxious amount of tartines with caviar, salmon, crevettes are all set in their trays. Some 20 liters of good to very good wine are waiting, either on the table (the reds) or out of the window (the whites and the cartizze).
All we are still missing is the guests! In 20 minutes they will start coming. You sure you cannot make it tonight ?
Radon contamination and Poisson statistics December 21, 2006
Posted by dorigo in games, mathematics, personal, physics, science, travel.1 comment so far
Two weeks ago I was coming back from a trip to Chicago and I was carrying my pocket digital gamma dosimeter, something I still do when I travel on a plane. Upon walking through the corridor leading to the stairs to my apartment, I noticed that the thing beeped three times in the matter of 20 seconds or so, and the other day I decided I would investigate whether there is Radon contamination in my basement.
Radon is a inert gas emitted by the decay of Thorium, a radioactive material contained in traces in the ground. Radon is heavy and mildly radioactive itself. It accumulates over time in poorly ventilated areas such as basements, and it can stick to plastic surfaces quite easily.
My digital dosimeter records x-ray radiation and has a window of sensitivity roughly in the right region to detect decay products of radionuclides such as Radon. If set at the maximum sensitivity, it beeps every 100 nanoRems of integrated gamma dose. That means about 20+-6 seconds of exposure, under normal conditions (but beware, background radiation depends on the region of the world where you are, as well as on your latitude). By beeping three times in 20 seconds it was giving a signal, or was it a statistical fluctuation ?
I investigated the matter by going back to the basement, and taking notes of the number of beeps given in 5 minutes. The count was 22 (2.2 microRems), while outdoors it counts 15 (1.5 microRems) in the same time interval. Now the question arises, is the measurement indicating a significant contamination of Radon or just another fluke ?
If you just followed Statistics 101 and are thinking at Christmas presents with the other side of your brain, you might come out with “22 is not significantly different from 15, after all these are random counts and they are subjected to Poisson statistics, so 22 is really 22+-sqrt(22), 15 is 15+-sqrt(15), and 22+-4.6 is not so different from 15+-3.9″. Wrong.
Sure, gamma collection is a random process, but the counter does not beep every time it sees a gamma. Rather, it beeps once it collects a certain dose. For what you know, a 100 nanoRem beep could arise from one photon, or 100. In the former case you would be right in your error estimates, in the latter you would be off by a factor of 10. Further, not every photon will release the same amount of energy in your counter – but that is a unnecessary detail and I’ll neglect it here.
What we know, as I stated at the beginning, is that in normal conditions a beep occurs every 20+-6 seconds (yes, I did construct a histogram of timings to get that information). What that means is a 30% relative uncertainty on 20 seconds. That must imply that 20 seconds, or 100 nanoRems, are integrated with an equivalent number of counts which fluctuates by 30%. The number whose square root is 30% of its value is, of course, 10. So we can eyeball that 100 nanoRems are on average obtained by 10 photon counts.
Equipped with that information, we can now evaluate the significance of our 2.2 microRem/1.5 microRem difference. If 100 nanoRems are 10 counts, then on average 2.2 microRems are 220 counts. So we are really talking about 220+-15, and 150+-12. These two numbers are incompatible at almost 4-sigma level. We conclude that my basement indeed has Radon contamination, and that the radiation level in it is 1.5+-0.1 times larger than it is outdoors.
Did I know 5 minutes would have been enough to detect a significant signal before performing the experiment ? No, since I did not know how much of a signal I would be observing. But I did know that I would have been sensitive to a 20-30% increase with a 5′ exposure. Knowledge is power…
NGC1514 from urban skies December 20, 2006
Posted by dorigo in astronomy, personal, science.3 comments
After washing the mirror, later today I made some fine adjustments to the collimating screws of my telescope, which had a problem connected to a poor design. I fixed it with the addition of washers. Then I removed a counterweight in lead that is utterly unnecessary – a rubber band properly anchored does the same thing and weighs a hundredth.
Tonight the sky was clear, and I was able to set the telescope up on my terrace and properly collimate it. After playing around for a while with the rubber band, I started looking at a few familiar objects of the autumn sky. Of course, I did not expect much – from my terrace, which is surrounded by all sorts of lights and immersed in the damp city center of Venice, I can hardly see Mv=5 stars. And still…
Still, with a light pollution filter (the IDAS LPS) I found out I could still see the shape and size of M1 easily, and even a couple of faint stars inside it.
M77, the giant galaxy I mentioned in another post today, was still discernible and although no spiral arms were even guessable, there was a distinct decrease in luminosity from the nucleus to the halo.
M42 was glorious as ever, and I had no trouble seeing the fifth and sixth components of the trapezium, as well as the usual incredible details of the nebulosity. Of course, seeing it from the dolomites two moons ago was another matter…
But I was very happy when I decided I would give a look at a planetary nebula I had never tried observing, NGC1514 (see picture on the left), which lies only a few degrees north of the Pleiades. It took me two or three minutes to star-hop to the place where it was supposed to be, and I was happy to see I could make out the size and shape of that fuzzball, lying around a ninth magnitude star. The nebula is not a hard object at Mv=10 or so, but having seen it tonight from Venice means something to me… It means I can still have fun from my terrace, even in the absence of the gas giants – Jupiter and Saturn will become easy targets only in the winter and spring.
Washing a 16″ mirror December 20, 2006
Posted by dorigo in astronomy, personal, science.add a comment
Yes, that’s right. Every once in a while, even telescope mirrors require washing.
True, most of the dust that over time deposits on the surface does not do too much harm, either in terms of reflectivity or in terms of resolution. The dirtiest ones I’ve seen were abominable, but they still delivered at above 95% of their nominal light-collection power.
Nevertheless, a clean mirror is better than a dusty one, especially if you need that extra bit of contrast and luminosity that gives you a tad better glimpse of a galaxy far away. So today, being home for several reasons, I decided to take some time to do my own very special laundry.
My mirror does not have a quartz coating on top of the aluminum layer. It is a choice dictated by wanting the most reflectivity possible: the quartz coating takes away some 1-2% of the possible photons that your eyepiece collects. On the other hand, the protective effect of the quartz over the very thin aluminum treatment is overestimated: pure aluminum will produce by itself a thin oxide layer at contact with air, which is very strong and is enough protection, especially if you are going to make a fresh aluminum coating every couple of years or so – which is my case, since Romano Zen does it at an affordable price.
So, is it dangerous to wash your mirror ? Yes and no. You have certainly to be very careful to use tools which are perfectly clean, lest you damage the surface. But water and soap will do with a soft sponge.
That is what I did this morning: I placed the mirror on the floor of my shower box, and gently brushed it with the water-dripping sponge and a little soap. Then I rinsed and let it dry at a small tilt angle. The result ? All the dust is gone, and most of a bad oil stain as well. I estimate that the reflectivity is back to some 99.995% of its original value (since about 6 mm^2 of the 125600 of the surface are still affected by stain or black dots), while before washing it the non-reflective surface had brought that number down to 99% or so.
Big deal ? Well, not really, but when you own an instrument that allows you to travel through space like a big dobsonian reflector, you want to squeeze the most out of it. Every photon counts! Last week, as I was observing M77, a giant galaxy which is about 60 million light years away from us, I thought that the 70x magnification power and 4000x light gathering power provided by the optical system I was using was effectively allowing me to be looking at the galaxy as if I had traveled for 59 million years at light speed toward the galaxy. I was looking at it as if I had been only 1 million light years away!
So, a 1% increase in light gathering power might seem ridiculous, but think about it: it means getting a light increase as if going from 1 million light years away to 0.9999 light years of distance. That means having traveled in space for one light-hour, or about a billion kilometers closer!
Are one’s ntuples like one’s genitals ? December 18, 2006
Posted by dorigo in Blogroll, computers, humor, internet, personal, physics, science.1 comment so far
A post by Chad Orzel, over at Uncertain Principles (http://scienceblogs.com/principles/2006/12/you_cant_cook_a_cow_the_proble.php) inspired me and I left a comment there, which I wish to reproduce here.
The topic is free access to raw data used to produce scientific results. Of course, a very much debated issue, on which I have my own stand, but do not pretend to be Right.
Here’s what I had to say to Chad, answering his point that it is unclear what level of detail the accessible data should include (he made the example of particle collisions):
I agree that the level of abstraction of particle collider data needs to be agreed upon, but I still find it fascinating the idea that one might, one day, click on a figure – wherever it is posted on the web – and get access to the data used to produce it, and the code needed to make sense of it. To stick with D0’s single top signal, it is based on detailed analysis of some 600 events. To characterize these in a very detailed way, one could just refer to a high-level root ntuple, containing not particles, but jets, electrons, neutrinos (from missing Et), b-tag information. I am thinking of sort of 100 variables per event – not far from what we deal with in most analyses, after the primary reconstruction and a selection of the information we want to study in detail.
Think about it – in the future, you might just cut that information and paste into a web-based neural network or some other fancy algorithm, and then do all sort of tricks.
People like Tony Smith, who has interesting ideas about the top quark at the tevatron but no access to the data – or to details about how the results were obtained, for that matter – would be able to touch ball. Many people playing with our ntuples would just create background noise, but a few could come up with interesting new leads.
Once I heard Melissa Franklin come up with an amusing sentence, quite in her own witty-upsetting-punch-line style: “One’s [high-level] ntuples are just like one’s genitals. You may be allowed to play with them every now and then, but not too much.” I disagree with that both ways
On the chest of a barmaid in Sale… December 18, 2006
Posted by dorigo in games, humor, language.1 comment so far
“On the chest of a barmaid in Sale
were tattoed all the prices of ale.
And, on her behind,
for the sake of the blind,
there was the same list in braille.”
Working on meta-string theory December 18, 2006
Posted by dorigo in humor, mathematics, physics, science.8 comments
A comment by Alejandro made me ponder over the need for a meta-string theory.
Sure, we were blessed with two best-selling books about the failures of string theory quite recently: so, asking 2006 to bring more to the just cause of allowing non-string theoretical work in particle physics to get their due share of attention in physical departments throughout the world seems a bit over the top.
However, think about it for a second. How do you kill a theory ? By showing it is internally flawed to an irreparable level, or by showing it is utterly inconsistent with the data. They tell me that both of these avenues appear impossible with string theory these days, because of the theory’s own shortcomings: the lack of a well-defined internal structure (say a lagrangian function or a usable symmetry group as its basis), and the lack of any prediction for experimentally measurable observables. [I know, I am getting flamed for this...]
However, one could conceive a meta-string theory even in the absence of a well-defined string theory. Whatever string theory is, we can formally give it a name: S. One can then imagine to work on S with suitable operators E[] which modify S, namely E[S] = S’. What E does is to provide S with an experimental input which influences the theory in such a way to make it change form. For instance, imagine we discover a fourth generation set of particles: it is quite likely that S will change into S’ in order to accommodate -or even post-dict- the set. Easy to do, since S was not hindered by a precise pre-defined structure.
We can also imagine new mathematical developments M[]: their action on S is formally the same: M[S]=S”. For instance, maybe if M[] provided an indication of which, among the zillions of vacua of the theory, is to be preferred for some specific reason, that could make S very different from what it is right now.
Of course, all E[] and M[] are by definition idempotent. That is, E[E[S]]=E[S]. They also should commute, E[M[S]]=M[E[S]], in order for the formal system to make sense: in other words, the theory one develops should not depend on the order by which theoretical and experimental input is used in its construction. Discussing other properties would take us too far.
Given this very basic formal system, one is direly looking for an example of a suitable operator N[] which, applied to string theory in its present form, produces the null element: no theory.
So what could such a N[] be ? Would N[]== no SUSY work ? No, not enough unfortunately, as far as I understand. SUSY is generally appreciated by string theorists as a step in the right direction, but no proof – and no SUSY is therefore not a show stopper. Maybe N is the combination of several experimental and theoretical inputs ? Unlikely.
The search for N is on. But let’s make a point here: having designed our formal system of operators acting on theories, we can well say we already are half-way through: we do not need to prove anything, just saying we hypothesize the existence of a N[] such that N[S]=0 should suffice. It is now up to string theorists to demonstrate that the set of N[] is null.
