Monday, November 25, 2013

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.

Saturday, November 23, 2013

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!)

Tuesday, November 12, 2013

[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.

Sunday, November 3, 2013

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!!