. Present perfect vs past simple ** Complete the exchanger with the verbs in the present perfect or the past simple (Laura / ever / run) a marathon before? B: Yes, she (run) one two years ago. A: 1 (not eat) pizza for ages! B: Really? We (have) one last night. A: Zhaniya (go) on holiday twice this year. B: She's lucky. 1 (not / have) a holiday for three years A: (try) ice - skating? B: Yes, actually! (go) ice - skating lots of times. A: Oh no! Askar (break) Mum's new vase. B: She only (buy) it yesterday! A: (you / see) Ann at the party? B: No, she (not / be) there. She (be) ill since last week.
Serendipnost characteristic of a true scientist. In science, they are often looking for one thing, and due to chance, a happy coincidence of circumstances and insight, they find something completely different, sometimes even more important. True, the history of science testifies that this gift, as in the ancient fairy tale, inspired and deep minds are rewarded, that only brilliant insight and excellent preparation make it possible not to indifferently pass by a happy event, but to translate it into a discovery. Thus, the case, as it were, is no longer a case, and the serendipnost is not just a happy coincidence ...
There is an ancient oriental tale about three smart, beloved by fate, lucky princes, wandering around the world and sometimes by chance, and more often due to their intelligence, dexterity and ingenuity, they found wonderful and useful things that they, in general, were not looking for. The princes came from the Serendip principality (as the Arabs in ancient times called the island Ceylon). There was even the term "serendipnost" - the gift of finding valuable or pleasant things that are not looking for.
In science, they are often looking for one thing, and due to chance, a happy coincidence of circumstances and insight, they find something completely different, sometimes even more important. Truly, the history of science, that it is a gift, as in the ancient tale, inspired and deep minds are rewarded, that only brilliant insight and excellent preparation do not indifferently pass by a happy event, but turn it into a discovery. Thus, the case, as it were, is no longer a case, and the is not just a happy coincidence ...
We will not give examples about a falling apple, a “eureka” about the water that has been pushed out of the bath, a strange blue glow that suddenly flickered in the darkness of a laboratory closet and marked the beginning of a whole section in science. Suffice it to recall the fascinating history of the discovery and study of elements heavier than the heaviest, "closing" leaf of Mendeleev uranium, the history of the first created human synthetic elements that long ago disappeared from the face of the Earth or did not exist at all.
Actually it all started with serendipness on that sunny morning of 1935. Under the low cool arches of the ancient building of the University of Rome, young Enrico Fermi, already then a world-renowned physicist, with four closest friends and collaborators Edoardo Amaldi, Oscar d'Agostino, Franca Rasetti and Emilio Segre, frozen with amazement, contemplated the “handiwork” of a simple experimental chamber, in which, as it seemed, they had succeeded in creating new elements heavier than uranium as a result of bombardment with neutrons.
A small hermetic glass tube served as a neutron gun. It contained beryllium powder and radioactive gas — radon, which emits, like radium, alpha particles (helium nuclei), which are necessary to produce the components of neutrons. Alpha particles, about one in a hundred thousand, getting into the nucleus of the beryllium atom, combine with it, generating the nucleus of the carbon atom and releasing the neutron. Free neutrons require assistance in the training mode, allowing to penetrate into the main citadel of nature - the atomic nucleus.
Farms and other physicists by then already knew very well that the atom - the main building material of nature - is 99.999999999 percent free space. In a neutral atom, negatively charged light particles - electrons - move in external orbits around a positively charged nucleus, the volume of which is about one trillion parts of the atom and less.
In the nucleus, almost the entire mass of the atom is concentrated, and the density of its block is of colossal size (240 trillion grams per cubic centimeter) A cubic millimeter of matter with a density of life of matter would weigh approximately 100 thousand tons. If ordinary houses consisted of only atomic nuclei, then fifteen standard ten-storey houses would weigh as much as the entire globe.
It is known that the atomic nucleus consists of positive charged heavy objects of particles and prototypes. The number of protons in the nucleus determines its charge, as well as the number and arrangement of orbital electrons, which compensate for the positive charge of the nucleus, and the atom as a whole remains neutral. The number and arrangement of electrons in orbit completely determine all chemical properties of an atom, all innumerable combinations of elements, all chemical reactions that underlie an infinite variety of the living and nonliving world. These electrons and the place of the chemical element in the periodic table. The periodic system has ceased to be an empirical law of chemistry. Having obtained a reliable basis in the theory of the structure of atoms, it acquired a simple but very essential physical meaning and became the basis of the law of atomic physics. On the basis of the scientific data known today, it is perhaps not an exaggeration to assert that this is the only universal and simple enough to be universal, law of the structure of a substance discovered by man.
Even mushrooms should be sought, guided by some rule, ”the founder of the periodic law, D.I.Mendeleev, joked. The found principles of the structure of matter open up dozens of ways for people to search for and create at will new building materials of the Universe, opened the door to the magical kitchen of nature.