Depending on the solar cycle, in space,around the earth, one could detect about 10 heavy particles per second per cubic cm. I have no idea how it translates to a number of secondary gammas. This may look like a small fluence, but bear in mind that our imaginary detector has 3,5 m in diameter.

No way!

Inverse square law makes it practically impossible. Typical activity of the (fresh!) cobalt teletherapy unit is ~300 TBq. Lets say that your gamma telescope is so efficient that it collects 1/3 of all the gamma rays emitted if placed 1 m from the source (in other words its inlet aperture is about 3.46 m in diameter and the detector has 100% quantum efficiency). That gives you 1,000 billion counts per second. Now put your telescope in a (very low!) orbit, say 500 km. Due to the inverse square law you now detect 4 counts per second. Because you want some spacial resolution to get your "pixels", the detector needs to be segmented. If you want 100x100 matrix, the count rate per segment is now 10 000 times lower. In order for your pixel to emerge from the background (which is orders of magnitude higher), you would have to count for years.

This is all assuming that your field of view is ideally covering the area you want to search. Your orbit is not geostationary and your telescope is is above the target area only once in a while. Oh, BTW, I completely forgot the atmosphere attenuation for the 1.33 MeV Co60 photons (half value layer for air is about 9 m). That alone kills it completely.

It would be a nice stunt in a Hollywood movie, but in reality it simply does not work.

Every once in a while, I find myself in a position to debunk the merits of astrology. As you can imagine, the people who are believers are next to impossible to be persuaded otherwise. However, one of the arguments seem to be more convincing and at least make some of these people think. If the position of stars at the moment of one's birth really influence one's destiny and (say) one's life expectancy, wouldn't insurance companies pay a top dollar for astrological natal charts? Insurance companies do not give two bits for the moral and ideological implications of the formulae they are using to determine their rates. They will use satanic rituals providing they improve their bottom line.

In order to get a better bang for their dollar, Serbian government made some radical changes regarding the pay grades of researchers in state universities and institutes. The most important metrics is now the number of publications in the high impact factor journals.

In principle, the idea is not terribly bad. Academic success is being measured by some quantitative objective criteria.

Unfortunately, in practice the system is far from ideal. The problem begins with "impact factor". Too many journals are gaming the system. This is a global international phenomenon.

Upon the introduction of the new system, few unscrupulous Serbian researchers began exploiting the obvious loophole. Namely, there are tons of journals worldwide, who will happily take one's money and publish whatever junk one sends. For whatever reason they carry high impact factor. Few of these "scientists" built entire carriers using this shameful practice.

The prank has been widely publicized in Serbian news outlets and more than served its purpose.

I am sorry but you are plain wrong! "Enough energy to vapourize a ship" can be achieved with an infrared laser (photons of energy below 1 eV). Even if you allow for multiphoton interactions it is orders of magnitude below the threshold for the pair creation (1.02 MeV for electron-positron) . There aro no lasers that produce photons in MeV range. Also, the annihilation of electron and positron, which is the lowest energy particle-antiparticle anihilation, produces gama photons ~.51 MeV which are quite invisible to humans.

I could not agree more save for your last point. You are an exception, not a rule. Unfortunately, people are "sheeple" and one should never underestimate their capacity for being fed crap. It is mind-boggling what percentage of population would tweet (or discuss over Facebook) the latest plot of their favorite reality show.

Well, I AM a scientist and the AC post above me, perfectly explains that INDEED burning coal decreases mass, albeit very slightly. For precise numbers see e,g, this.
We are talking about power generation, so a GWhr generated from fossil fuel reduces the resultant mass by the same amount as a GWhr generated from nuclear reaction. E=mc^2 holds.

Ok, let me give it a shot.

Notice the sensor for the experiment? It's a camera, probably a CCD array. Even at the quantum efficiency of 100% a single photon will register as a hit at certain pixel. One is effectively measuring a position. No other information is extracted from the measuring of the SINGLE photon. As far as the experiment goes, the image is reconstructed from many photons.

So why mentioning single photons at all? Apparently, you can obtain the image even if you shoot the photons one at the time. In terms of the fancy quantum mechanics lingo one is performing measurements on a "time ensemble".

The interesting question is: does the single photon contain the image information after it passes the stencil. Well, its wave function does! It is conceptually impossible to devise an experiment that will extract this information from the measurement of one particular photon though. It's the basic quantum mechanical principle. At the detection plane the choice of basis in Hilbert space (fancy way of saying choosing what to measure) for our measurement is such that the photon is a particle localized as a hit on a particular pixel. It is the fact that we performed measurement on a prepared quantum ENSEMBLE that gives us spatial probability distribution. The more photons hit our detector the better statistics and less noisy our image is. But the fact remains, every single photon contained ALL the information about the stencil. My point is: Don't expect to shoot a single photon of Encyclopedia Britannica and expect to reconstruct it at the receiver end.

Many people here correctly pointed that this is equivalent to the Young's double slit experiment. What is novel is the introduction of a smart optical delay line which preserves the information contained in photon's wave function.