euros 14

Measuring the shadow of the black hole

Goethe University is participating in international Event Horizon Telescope (EHT) Collaboration via the ERC-project Black Hole Cam

The international Event Horizon Telescope (EHT) Collaboration, which is imaging for the first time the black-hole candidate at the center of our Milky Way, has a major research focus in Germany. A significant contribution to this experiment is part of “BlackHoleCam”, a German-Dutch experiment founded in 2014. The research group of Prof. Rezzolla at the Institute for Theoretical Physics at the Goethe University Frankfurt is part of the collaboration. BlackHoleCam is supported by the European Research Council via an ERC Synergy Grant of 14 Million Euros.

Due to the strong pull of gravity, not even light can escape from black holes, whose surface, i.e., the event horizon, cannot be observed directly. However, the boundary which separates photons that are trapped from those that can escape from the incredible gravitational pull is called the black-hole “shadow”, because it would appear as a shadow against a bright lit background. It is such a shadow that is the target of series of observations presently ongoing of Sgr A*, the name of the black-hole candidate in our Milky Way. During the observations, the researchers will analyze the radio emission emitted by Sgr A*, whose mass is 4.5 million times that of our Sun and whose shadow is about half of the size of the distance between the Sun and the Earth.

Despite being so massive, Sgr A* is also very far from us, at a 26,000 light years, making the angular size of the shadow extremely small. Measuring the emission from this surface is therefore equivalent to imaging an apple on the surface of the Moon. To accomplish this ambitious project several radio telescopes across the globe are connected and thus form a virtual telescope with a diameter comparable to the Earth. This technique is called Long Baseline Interferometry (VLBI).

The work of BlackHoleCam is lead by Prof. Luciano Rezzolla (ITP, Frankfurt), Prof. Michael Kramer (Max Planck Institute for Radio Astronomy, Bonn), and by Prof. Heino Falcke (Radboud-University Nijmegen, Netherlands); all of them are important contributors of the EHT collaboration. In the current observations of Sgr A*, network of radiotelescopes from Europe, the United States of America, Middle- and South America, and the South Pole telescope are participating at the same time. During the observations, each telescope records the data on hard disks which are shipped after the end of the campaign to one of the high-performance computer centers in the US or to Bonn. In these centers the individual data of the telescopes are combined by supercomputers and an image can be reconstructed.

This shadow image can be regarded as the starting point for the theoretical research of Prof. Rezzolla’s group. Besides predicting theoretically what type of image scientists is expected to observe, the group in Frankfurt is also working on determining whether it will be possible to establish if Einstein’s theory of general relativity is the correct theory of gravity. There are several other theories of gravity besides the well-known one by Einstein and the observations of the black-hole shadow may help to identify the true one. Because of this, scientists in Frankfurt analyze the size and the geometry of the shadow and compare them to synthetic images generated on supercomputers which model accretion flows onto black holes..

These images are computed by solving the equations of relativistic magneto-hydrodynamics and tracing the orbit of photons around black holes in different theories of gravity using state-of-the art numerical tools developed in the group of Prof. Rezzolla. Comparing the synthetic shadow to the observed one may shed light on the existence of one of the most extreme predictions of Einstein’s theory of gravity: the existence of black holes. However, as Prof. Rezzolla remarks, “These observations represent a major step forward in the international attempt of understanding the nature of the dark and compact object at the centre of our Galaxy. However, they are just the first step and it is likely that many more observations of increasing precision will be necessary for finally settling this fundamental issue”.

Tempo fa decisi di non rispondere ai post e alle battute dei romani sull'apertura della Esselunga nella capitale. Sono milanese, dentro, e dunque di parte. Inoltre, diciamolo, difendere un supermercato è forse più stupido che attaccarlo per il solo fatto di essere milanese. In una città con Lidl e Eurospin a ogni angolo, solo l'Esselunga minaccia l'urbe e la romanità, con i suoi commessi lanzichenecchi e lo store manager vestito da generale napoleonico. Oggi, che mi ritrovo a Milano e in un Esselunga, voglio spiegare cosa significa per me, e credo per tutti quelli nati qui, fare la spesa all'Esselunga. Età prescolare - Il primo luogo dove, tenendo la mano alla mamma, mostri un interesse non ludico verso un prodotto. Punti il dito indicando la crema pronta della Centrale del Latte, o i Kellog’s, o le patatine con la sorpresa. Per la prima volta realizzi che la vita non è solo gioco, pastelli e album da colorare, bisogna anche nutrirsi e ci sono cose buone, come i Loaker, e cose che fanno schifo al cazzo, come i broccoli. E il fatto che nei broccoli surgelati abbiano messo le figurine di Popeye non ne migliora il gusto. Hai voluto la figurina, ti mangi i broccoli lessi. La prima grande cazzata della tua vita. All'Esselunga. Età scolare - Oramai non vai più con la mamma, vai da solo. La mamma non ti ha affidato solo la lista della spesa e dei soldi, ma la tua prima responsabilità. Il nutrimento della famiglia, la sua igiene e la sua armonia dipendono da te, non puoi fallire. Fallisci. C'è sempre qualcosa che manca, hai scordato, non c'era, non l'hai trovata, sei troppo piccolo per raggiungere lo scaffale, troppo timido per chiedere aiuto, non si può mai fare affidamento su di te, ora tocca ritornarci. All'Esselunga. La prima grande rottura di cazzo. Adolescenza - Con i tuoi ci parli a malapena, ora il tuo riferimento sociale sono gli amici. Buste di Coca cola, Fanta, Sprite e patatine San Carlo, senza sorpresa, la sorpresa sarebbe un limone con la bionda della 3°B, ma per te sarebbe più facile trovare un Fantic 125 nel fustino del Dixan che baciare una ragazza a una festa. Specie se alle feste non ti invitano mai. Con le patatine, le bibite e i tuoi amici sfigatissimi passerai il pomeriggio guardando le nuvole al parco di Trenno. Forse, se sarai fortunato, una assomiglierà alla bionda della 3°B. No, sembra la cassiera dell'Esselunga, ma tu comunque ci vedi la bionda della 3°B. Età adulta - Sei un drogato di merda. Ti aggiri tra i corridoi dell'Esselunga come uno zombie dagli occhi rossi. I due salsiccia e peperoni fatti la notte prima sono solo un ricordo evanescente, la fame chimica bussa al portone del tuo cervello come un mendicante al monastero la notte di Natale, gli devi aprire. E così lasci che ti accompagni tra gli scaffali prendendo le decisioni al posto tuo: tutta roba inutile e carissima. Con la scusa che non ti va di cucinare opti per la vaschetta carpaccio, grana e rucola, 100 grammi, 14 euro, 140 euro al chilo. Pensi a quanto ti costerebbe un chilo di afgano nero… No, di più, meglio il carpaccio, anche se da solo non basta, ci vuole del pane. Il pane, così, non dice molto. Tre etti di pizza rossa biologica, due pacchi di grissini piemontesi artigianali stirati a mano dalla pronipote del fornaio di Casa Savoia e per finire una confezione di brioche del Mulino bianco e una di merendine Fiesta per farcire le brioche, ché da sole sono un po’ vuote. Totale spesa: 60 euro. Totale calorie: il fabbisogno annuale di un bambino eritreo. Totale valore nutrizionale: Ghandi. Considerazioni finali: sei un cretino. Vai alla cassa fiero e conscio che da lì a poco riempirai lo stomaco con le peggio schifezze sul mercato. Non hai il sacchetto, ma sei ecologista, ne farai a meno. Al momento di pagare finalmenti alzi gli occhi gonfi di notti pesanti e droghe leggere e finalmente la vedi, è lei: la bionda della 3°B, ora lavora all’Esselunga. Sei strafatto, ma uomo, oggi finalmente le rivolgerai la parola. “Hey, io ti conosco, tu sei… la nuvola del parco di Trenno!” Vecchiaia – Quando ci arrivo ve lo dico. Non manca molto.

8

HOUSE OF ESCHER

When coal is brought to the surface, it has to be separated from possible debris, such as pieces of rock. To do this a system was developed that is called “washing”. In this washing installation the dug up coal is put into large silos that have grids at the bottom through which water is added in pulsating movements. On the grid there was a bed of felspar. Due to the pulsating movements the coal moved over the felspar bed while heavier pieces of stone sank through it onto the grid.

This washery was built in the fifties and stayed in service of the surrounding mines for almost twenty years. The building was protected as heritage and the outside already got a makeover in light of the plans to turn it into a public building. After having invested 13 million euros (almost 14 million dollars) the renovation stopped because the necessary funds were no longer available…

Upon entering the building it becomes instantly clear why this location is called ‘House of Escher’. The building has stairs that seem to be going everywhere, while leading nowhere. The association with the renowned lithograph by M.C. Escher “Ascending and Descending” (1960) is easily made…

On this impossiblee staircase it seems you can walk up (or down) the stairs all the way round and always end up on the same step. In three dimensions this is an impossible object. It only exists in two dimensions by toying with the perspectives.

10

Hello friends ! 

Uni starts again soon and I’m in desperate need of some extra income, so I’m opening commissions. 

Check the captions if you’re confused about prices, I added some precisions.I’ll draw for any fandoms but if I’m not familiar with yours I will need some guidance. And I draw nudity but not explicit porn, basically my limit is erotism, I’m not comfortable with drawing erect members or body fluids. Don’t hesitate to ask for more informations, my askbox is open ! 

I’ll be taking all payments through paypal.

IF THIS SOUNDS COOL TO YOU, you can email me at busylilblop@gmail.com to set up a commission !

If you can’t it’s cool but could you signal boost this post please ?

Thank you again, I love you all !

@ tourists in paris :

here’s some advice

  • see those authentic cafés with checkered tablecloth and well-dressed waiters? it’s a scam. always check the prices before sitting down – and if they try to force you to order something, just get up and leave, don’t stay because you feel bad
  • if it’s a bistro-style restaurant, look at the price of the burgers and tartare steak to judge. a burger should be under 14 euros a steak tartare under 16. my favorite is rue de l’arbre sec (ask for the gratin dauphinois)
  • water is always free in restaurants, so don’t order that expensive bottle of wine. if you want to drink some, buy it at a monoprix at a lower price and go drink it on the banks of the seine ; and buy muscat because it’s better than red wine okay
  • don’t hold the bar in the metro if you can lean again the doors, you’ll have more balance, less germs and you can keep your belongings safe by trapping them against you and the door
  • if you’re site-seeing, you’re gonna take the metro 1 and it’s full of thieves. hide your valued objects on the bottom of your bag and put it at your feet. the thieves are likely to be children who will circle around you, so stay aware of them
  • you’ll get a more aesthetic picture of the eiffel tower from the pont neuf, alongside a nice view of the seine and you can actually sit there, it’s perf
  • bus stations can be tricky to find but it’s the best transport cause you can actually see the outside ; take the bus 29 if you want to see pretty buildings, the opera and the galeries lafayette
  • you’re surely gonna go see the beaubourg museum : take a break at the bakery 50m away called Topaze and eat a st. honoré there (also i saw mika eat next to it once so it’s a historical landmark)
  • eat the baguette if it’s hot, just do it
  • the RER station may be called “Châtelet les Halles” but it’s actually two different stations, you’ll be arriving at les halles and you’ll have to walk to reach châtelet and take other metros and you will get lost (don’t worry, everybody does)