"Quantum mechanics tells us that the vacuum is not empty but is filled with virtual particles that pop into and out of existence. Normally these particles are hidden from our view, but now a team of physicists has used the electrical equivalent of an ultrafast mirror to convert virtual photons into real electromagnetic radiation. Known as the dynamical Casimir effect, it was first predicted more than 40 years ago. The static Casimir effect ... 1948, involves two perfectly reflecting parallel mirrors that, when placed in a vacuum, will be attracted to one another. This attractive force is caused by the radiation pressure exerted by virtual photons outside the mirrors and the fact that this pressure exceeds the pressure between the mirrors because of the limited number of modes of electromagnetic vibration that are permitted within this gap. In other words, the force results from a mismatch of electromagnetic modes in space. The dynamical effect was proposed by Gerald Moore in 1970 and is caused by a mismatch of modes in time. The phase of an electromagnetic wave goes to zero at the surface of a mirror, if that mirror is a perfect electrical conductor. When the mirror is moved slowly through a vacuum, this zero point can move with the mirror. However, if the mirror is moved at a significant fraction of the speed of light, then the electromagnetic field does not have time to adjust but instead becomes excited and as a result generates real photons. Put another way, the mirror prises virtual photons (always produced in pairs) apart so that instead of rapidly annihilating, the particles are free to remain as real photons."
Friday, November 18, 2011
Thursday, November 17, 2011
Earth's close encounter of asteroids
"After yet another narrow encounter with an asteroid the size of an airship earlier this week, do we need to pay more attention to technology that could protect our planet and its inhabitants from these turbo-charged cosmic fireworks?"
Should Earth's close encounter trigger asteroid avoidance research? | Opinion | The Engineer
Should Earth's close encounter trigger asteroid avoidance research? | Opinion | The Engineer
Tuesday, November 15, 2011
Leonardo, Genio e Mito
Alla Venaria Reale (Torino) si apre la mostra su Leonardo da Vinci. Il titolo è "Leonardo, il Genio, il Mito".
http://www.lavenaria.it/mostre/ita/mostre/archivio/2011/leonardo.shtml
In esposizione vi è l'autoritratto della Biblioteca Reale e il Codice del Volo.
In una pagina del codice, sotto la scrittora di Leonardo, vi è un ritratto, forse un suo autoritratto da giovane.
Vedi http://staff.polito.it/amelia.sparavigna/da-vinci-portrait.html
http://www.lavenaria.it/mostre/ita/mostre/archivio/2011/leonardo.shtml
In esposizione vi è l'autoritratto della Biblioteca Reale e il Codice del Volo.
In una pagina del codice, sotto la scrittora di Leonardo, vi è un ritratto, forse un suo autoritratto da giovane.
Vedi http://staff.polito.it/amelia.sparavigna/da-vinci-portrait.html
Image processing della pagina del codice, A.C. Sparavigna
Tuesday, November 8, 2011
Bee rescue
Stingless bee rescue, by Wendy Pyper
http://www.abc.net.au/science/articles/2003/05/08/2045526.htm#artBookmarks
"Of the 1600 species of wild bees native to Australia, about 14 species are stingless. As stingless bees are harmless to humans, they have become an increasingly attractive addition to the suburban backyard or verandah.
Most stingless bee keepers are not after honey. Rather, they enjoy the sense of conserving a native species whose original habitat is being increasingly cleared and developed. In return, the bees pollinate crops, garden flowers and bushland during their search for nectar and pollen."
http://www.abc.net.au/science/articles/2003/05/08/2045526.htm#artBookmarks
"Of the 1600 species of wild bees native to Australia, about 14 species are stingless. As stingless bees are harmless to humans, they have become an increasingly attractive addition to the suburban backyard or verandah.
Most stingless bee keepers are not after honey. Rather, they enjoy the sense of conserving a native species whose original habitat is being increasingly cleared and developed. In return, the bees pollinate crops, garden flowers and bushland during their search for nectar and pollen."
¿Un Futuro Sin Abejas?
s"Misteriosamente, las abejas mueren o se extravían y no pueden volver a su reducto, por lo que sus poblaciones se diezman inexplicablemente. Si ellas desaparecieran, alimentar a los 7 mil millones de habitantes de la Tierra, será muy difícil."
Especial Abejas: ¿Un Futuro Sin Abejas?
Especial Abejas: ¿Un Futuro Sin Abejas?
Thursday, October 27, 2011
Giant Waterworld Around Naked Eye Star
Giant Waterworld Confirmed Around Naked Eye Star - Technology Review
"55 Cancri A is a Sun-like star some 40 light years away. It has an apparent magnitude of about 6 and so is visible to the naked eye in the constellation of Cancer.
This star is unusual in that it is just one of a handful that are known to have at least 5 planets. The innermost of these planets--55 Cancri e--was discovered in 2004 and has since had plenty of attention from astronomers. Various groups have observed the the changes in radial velocity that it causes its parent star. This tells them about that it orbits its star every 18 hours and that its mass is about 8 times Earth's or about half Neptune's."
"55 Cancri A is a Sun-like star some 40 light years away. It has an apparent magnitude of about 6 and so is visible to the naked eye in the constellation of Cancer.
This star is unusual in that it is just one of a handful that are known to have at least 5 planets. The innermost of these planets--55 Cancri e--was discovered in 2004 and has since had plenty of attention from astronomers. Various groups have observed the the changes in radial velocity that it causes its parent star. This tells them about that it orbits its star every 18 hours and that its mass is about 8 times Earth's or about half Neptune's."
"The innermost planet around 55 Cancri A is almost certainly an exotic waterworld with a radius about twice Earth's, say astronomers"
Friday, October 14, 2011
Mela, Pomponius
"Pomponius Mela, who wrote around AD 43, was the earliest Roman geographer. He was born in Tingentera (Algeciras) and died c 45 CE. His short work (De situ orbis libri III.) occupies less than one hundred pages of ordinary print. It is laconic in style and deficient in method, but of pure Latinity, and occasionally relieved by pleasing word-pictures. Excepting the geographical parts of Pliny's Historia naturalis (where Mela is cited as an important authority) the De situ orbis is the only formal treatise on the subject in Classical Latin."
Munich Digitization Center
http://www.digital-collections.de/index.html?c=autoren_index&l=en&ab=Mela%2C+Pomponius
Munich Digitization Center
Digitised works/ Author: Mela, Pomponius
http://www.digital-collections.de/index.html?c=autoren_index&l=en&ab=Mela%2C+Pomponius
Thursday, October 13, 2011
Indos
"Sed praeter physicos Homerumque qui universum orbem mari circumfusum esse dixerunt, Cornelius Nepos ut recentior, auctoritate sic certior; testem autem rei Quintum Metellum Celerem adicit, eumque ita rettulisse commemorat: cum Galliae pro consule praeesset, Indos quosdam a rege Botorum dono sibi datos; unde in eas terras devenissent requirendo cognosse, vi tempestatium ex Indicis aequoribus abreptos, emensosque quae intererant, tandem in Germaniae litora exisse. Restat ergo pelagus, sed reliqua lateris eiusdem adsiduo gelu durantur et ideo deserta sunt."Pomponius Mela
De chorographia, Liber III
"Mais à l'autorité des anciens philosophes et d'Homère, qui ont prétendu que la terre était de tous côtés environnée par la mer, on peut ajouter celle de Cornélius Nepos, qui, étant plus moderne, est par conséquent plus sûr. Or, cet auteur rapporte, à l'appui de cette opinion , le témoignage de Q. Metellus Celer, auquel il fait dire qu'étant proconsul dans la Gaule, le roi des Botos lui fit présent de quelques Indiens , et que, s'étant informé d'où ils étaient venus, il apprit que, les tempêtes les ayant emportés loin de la mer des Indes, ils avaient été jetés, après un long trajet, sur les rivages de la Germanie. Le reste de la côte asiatique est donc baigné au nord par une mer sans bornes; mais cette partie est couverte de glaces éternelles, et par conséquent déserte."
Louis Baudet translation
To the ancient philosophers and Homer, who claimed that the land was surrounded on all sides by the sea, we may add Cornelius Nepos, who, being more modern, is therefore more reliable. However, this author reports in supporting this fact, the witness of Q. Metellus Celer: when he was proconsul in Gaul, the king of Botos made him a present of a few Indians, and that, being informed of where they came from, he learned that the storms have swept away them of the Indian Ocean. They were thrown, after a long journey, on the shores of Germania. The rest of the northern Asian shores are surrounded by the sea, but this part is covered with eternal ice, and therefore deserted.
De chorographia, Liber III
"Mais à l'autorité des anciens philosophes et d'Homère, qui ont prétendu que la terre était de tous côtés environnée par la mer, on peut ajouter celle de Cornélius Nepos, qui, étant plus moderne, est par conséquent plus sûr. Or, cet auteur rapporte, à l'appui de cette opinion , le témoignage de Q. Metellus Celer, auquel il fait dire qu'étant proconsul dans la Gaule, le roi des Botos lui fit présent de quelques Indiens , et que, s'étant informé d'où ils étaient venus, il apprit que, les tempêtes les ayant emportés loin de la mer des Indes, ils avaient été jetés, après un long trajet, sur les rivages de la Germanie. Le reste de la côte asiatique est donc baigné au nord par une mer sans bornes; mais cette partie est couverte de glaces éternelles, et par conséquent déserte."
Louis Baudet translation
To the ancient philosophers and Homer, who claimed that the land was surrounded on all sides by the sea, we may add Cornelius Nepos, who, being more modern, is therefore more reliable. However, this author reports in supporting this fact, the witness of Q. Metellus Celer: when he was proconsul in Gaul, the king of Botos made him a present of a few Indians, and that, being informed of where they came from, he learned that the storms have swept away them of the Indian Ocean. They were thrown, after a long journey, on the shores of Germania. The rest of the northern Asian shores are surrounded by the sea, but this part is covered with eternal ice, and therefore deserted.
King Arthur's round table
According to Telegraph, http://www.telegraph.co.uk/news/uknews/8724183/King-Arthurs-round-table-may-have-been-found-by-archaeologists-in-Scotland.html, 26 Aug 2011, King Arthur's round table may have been found by archaeologists in Scotland. In fact, the archaeologists have found a "circular feature" beneath the historic King's Knot in Stirling. The King's Knot is a geometrical earthwork in the gardens below Stirling Castle. The design of the Knot that we see today dates from the 1620s, but its central mound could be much older. It seems that some writers going back more than six centuries have linked the landmark to King Arthur. Archaeologists from Glasgow University, working with the local Archaeological Society, found that the round feature on the site pre-dates the visible earthworks.
For a discussion on the King's Knot
see please "The orientation of the King's Knot of Stirling Castel" at