Free Astronomy Magazine March-April 2024

13 MARCH-APRIL 2024 ASTRO PUBLISHING years ago, the Muscovite astrophysi- cist Nikolai Kardashev invented a method to measure the level of technological advancement of a civ- ilization, based on the amount of energy it can exploit. The scientist proposed a short scale composed of only three levels (which others later extended up to six levels), in the lowest of which we find Type I civi- lizations, those capable of accessing all the energy available on their planet and storing it for consump- tion. Hypothetically, they should also be able to control natural events such as lightning, earthquakes, vol- canic activities, etc. In the middle are Type II civilizations, capable of di- rectly consuming the energy of a other stars, as far as we know. On the opposite front, a Type I civiliza- tion is approximately as developed as ours, therefore still far from being able to snoop through a hyper-pow- erful telescope onto the surfaces of planets thousands of light years away. Consequently, it is by exclusion that Osmanov refers to Type II. Based on our current knowledge, is it pos- sible that such a civilization exists within the distance of 3000 light years indicated by Osmanov himself? In the sphere of space that surrounds us and which has that value as its ra- dius, there are 350-400 million stars, a non-negligible quantity, but still lit- tle more than a thousandth of the total of the Milky Way. Regardless of anyone’s opinions, we cannot a pri- ori exclude that one of those stars hosts a Type II civilization. Osmanov calculated that if there were 650 such civilizations in the Milky Way and they were uniformly distributed on the galactic plane, one of them could be between 1000 and 3000 light years away from Earth, and therefore could observe our build- ings built 1000 to 3000 years ago, G iordano Bruno was one of the most avid supporters of the infinity of the universe and the existence of in- finite worlds. For his theories, judged hereti- cal by the tribunal of the Inquisition of the Papal State, he was condemned and burned at the stake in Rome on 17 February 1600. E dward Teller (on the left) together with Enrico Fermi, at the time when, conversing with some of their colleagues during a lunch break, they gave rise to the paradox on the con- trast between the statement that we are most likely not alone in the uni- verse and the observational data that are not favorable to this hypothesis. star, probably building a Dyson sphere. At the top of the scale, there are Type III civilizations, ca- pable of capturing all the energy emitted by their galaxy and every object within it, includ- ing degenerate stars and therefore also black holes! This last, hyperbolic level can be ex- cluded in the case of the Milky Way, for the simple reason that there are no alien megastructures placed to collect the energy emitted by the Sun, nor anything similar around