Enrico Fermi on Einstein's theory of special relativity

Yesterday I came across some fantastic notes by a young Enrico Fermi on Einstein's special relativity, which were included in "Asimmetrie", an outreach magazine issued by the Italian Institute for Nuclear Physics (INFN). After some search I found an English translation (by Robert Jantzen, I think).

The reading is really mind-blowing (well, at least for me...) and even more so considering Fermi was 21 at the time...

Enjoy!

Apparently, there are no pictures of Fermi and Einstein together, so I turned down to this one...

Recommended by us: "MicroBooNE, in 3-D"

Tingjun Yang (left) and Wesley Ketchum lead the effort to develop new 3-D reconstruction 
software for the MicroBooNE experiment. Here they stand inside the MicroBooNE 
time projection chamber.Photo: Reidar Hahn

“ 

Imagine your job is to analyze the data coming from Fermilab's MicroBooNE experiment. 

It wouldn't be an easy task. MicroBooNE has been designed specifically to follow up on the MiniBooNE experiment, which may have seen hints of a fourth type of neutrino, one that does not interact with matter in the same way as the three types we know about. The big clue to the possible existence of these particles is low-energy electrons.

But that experiment could not adequately separate the production of electrons from the production of photons, which would not indicate a new particle. MicroBooNE's detector, an 89-ton active volume liquid-argon time projection chamber, will be able to. To take advantage of this, every neutrino interaction in the chamber will have to be examined to determine if it created an electron or a photon.

And there will be a lot of interactions to study — the MicroBooNE collaboration expects to see activity in their detector once every 20 seconds, including nearly 150 neutrino interactions each day.

If all goes to plan, human operators won't have to worry about any of that. When MicroBooNE switches on next summer, it will sport one of the most sophisticated 3-D reconstruction software programs ever designed for a neutrino experiment.

According to Wesley Ketchum and Tingjun Yang, two postdocs leading the software development team at Fermilab, MicroBooNE's computers will be able to accurately reconstruct neutrino interactions and automatically filter the ones that create electrons. The key to accomplishing this lies in the design of the time projection chamber.

Continue to read on Fermilab Today 

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La sezione d'urto "plettro-bicchiere"

In questo post volevo parlarvi di un fatto curioso capitatomi questo fine settimana durante un concerto del gruppo scozzese dei Biffy Clyro al Live Music Club di Trezzo sull'Adda (MI). 

Naturalmente il fatto accaduto ha un rilevanza, seppur marginale, con la fisica nel raccontarvelo c’è quindi l’intento di comunicare come, la quasi totalità dei fenomeni che ci accadono, possono essere analizzati con un approccio scientifico e razionale. Ma entriamo nel vivo del racconto: durante l’esibizione del “gruppo spalla” i Walking papers, io e il mio amico ci siamo recati al bancone del bar, situato su un lato del locale, per acquistare da bere. Appena ricevute le bevande, un bicchiere di birra da 0.40L (e un bicchiere di Montenegro), ci siamo apprestati a ritornare approssimativamente al centro del locale dove ci aspettavano gli altri nostri due amici. Contemporaneamente all’atto dell’acquisto delle bevande il gruppo spalla finiva la sua esibizione e procedeva ai classici saluti e all’usuale lancio dei plettri per la chitarra* quando ad un certo punto sentiamo un rumore nelle nostre vicinanze e riceviamo alcuni schizzi di birra o qualche altro liquido.  Un po’ confusi ci guardiamo e ci chiediamo che cosa mai fosse accaduto, personalmente non avevo compreso la situazione, avevo sentito un colpo nel mio bicchiere di plastica** (di Montenegro) e poi avevo ricevuto degli schizzi ed ho pensato subito che esso fosse attribuibile al quel “balzetto” indotto da un bicchiere deformato che  ritorna nella sua configurazione originale e produce uno schizzo a seguito della agitazione della superficie del liquido contenuto al suo interno. Ho comunicato tempestivamente la mia interpretazione del fenomeno al mio amico il quale tuttavia mi ha guardato e mi ha riferito: “no! ti dico che è entrato un plettro nel mio bicchiere”; io l’ho guardato stranito e un po’ incredulo perché avevo sentito una botta nel mio bicchiere ed ero convinto dipendesse quindi dal mio e non che gli schizzi provenissero dal suo bicchiere o da un altro, quando però egli ha recuperato con le sue stesse mani il plettro all’interno del suo bicchiere mi son dovuto “arrendere” all’evidenza. Ebbene si, un plettro lanciato dal palco da alcuni componenti del gruppo, aveva dapprima colpito il mio bicchiere per poi dirigersi all’interno del bicchiere di birra del mio amico producendo degli schizzi. Tutto questo ci ha lasciato abbastanza perplessi e abbiamo riso dell’accaduto, passando subito al vaglio i parametri coinvolti per valutare una prima stima della probabilità del fatto e classificandolo in maniere affrettata quantomeno come “poco probabile”, ma dal momento che la situazione non permetteva un approfondimento “serio”, mi son ripromesso di valutare meglio la questione in separata sede, ed eccomi qui a fare un po’ di stime :)

Highlights of Classical and Quantum Gravity

Good news today, the paper Tidal acceleration of black holes and superradiance by Vitor (Cardoso) and myself was selected by the Editorial Board of Classical and Quantum Gravity (CQG) to be one of the journal’s Highlights of 2012-2013!

Besides being now free to download, the Highlights will be promoted in a number of campaigns over the next year  as a representation of some of the most interesting and high-quality work in gravitational physics.

But what makes the paper really worth a reading is the first paragraph, where we managed to refer to both Italian novelist Italo Calvino and mighty rock band Pink Floyd... that's quite an impressive achievement for a scientific paper!

If you wish to know what Pink Floyd's masterpiece "The Dark Side of the Moon" has to
 do with black holes, read the (not-very-technical) paper here.

Visit to the Maryland Center for Fundamental Physics

This week I was invited at the Center for Fundamental Physics in Maryland, where I gave a talk about black holes and fundamental light fields beyond the Standard Model. On the way back to the airport in Washington DC, I stopped by the Air & Space museum. Here is a picture of me before the Hubble Space Telescope.
BTW, in The Mall in DC all museums belong to the Smithsonian Institute and they are free, amazing!)

[Recommended by us] Why Hot Water Freezes Faster Than Cold—Physicists Solve the Mpemba Effect

Aristotle first noticed that hot water freezes faster than cold, but chemists have always struggled to explain the paradox. Until now.

Water may be one of the most abundant compounds on Earth, but it is also one of more mysterious. For example, like most liquids it becomes denser as it cools. But unlike them, it reaches a state of maximum density at 4°C and then becomes less dense before it freezes.

In solid form, it is less dense still, which is why standard ice floats on water. That’s one reason why life on Earth has flourished— if ice were denser than water, lakes and oceans would freeze from the bottom up, almost certainly preventing the kind of chemistry that makes life possible.

Then there is the strange Mpemba effect, named after a Tanzanian student who discovered that a hot ice cream mix freezes faster than a cold mix in cookery classes in the early 1960s. (In fact, the effect has been noted by many scientists throughout history including Aristotle, Francis Bacon and René Descartes.)

The Mpemba effect is the observation that warm water freezes more quickly than cold water. The effect has been measured on many occasions with many explanations put forward. One idea is that warm containers make better thermal contact with a refrigerator and so conduct heat more efficiently. Hence the faster freezing. Another is that warm water evaporates rapidly and since this is an endothermic process, it cools the water making it freeze more quickly.

None of these explanations are entirely convincing, which is why the true explanation is still up for grabs.

Today Xi Zhang at the Nanyang Technological University in Singapore and a few pals provide one. These guys say that the Mpemba paradox is the result of the unique properties of the different bonds that hold water together.

What’s so odd about the bonds in water? Discover it HERE.

La passione per lo studio delle stelle raccontata dall'astrofisica Marta Burgay

Ecco l'intervento nellla trasmissione di Rai Tre "Che tempo che fa" all'astrofisica Marta Burgay dell'osservatorio astronomico di Cagliari, dove si parla di radiotelescopi, pulsar, pulsar doppie, relatività generale e del lavoro e della passione dei ricercatori in generale :) Buona visione!!