2010-04-27 17:46:03
Love, hate, indifference… these are the essential forces of nature, although in physics books they are named as attraction, repulsion or neutrality. Regardless of the name by which they are identified, the truth is that Nature moves thanks to them even in its smallest components.
Before Enrico Fermi, our protagonist today, decided to investigate the phenomena that occur inside atoms, many others had tried their luck. Lord Rutherford had experimented with hatred, his most famous experiment: it consisted of launching alpha particles, with a positive electrical charge, first against a sheet of mica and then gold. He discovered that some of these particles bounced off a dense object, also positively charged because electric charges of the same sign show an antipathy that translates into repulsion. That experiment served to demonstrate the existence of the atomic nucleus.
After Rutherford’s discovery, physics laboratories became accustomed to bombarding atoms with alpha particles and observing what happened. They verified that this recalcitrant hatred that particles of the same sign have for each other was a barrier that, despite everything, some managed to overcome. Rutherford himself discovered that some particles, when collided with enough energy against the nucleus of an atom, managed to overcome their mutual repulsion and become attached to it. Thus, beyond the hatred that objects with an electrical charge of the same sign profess, when the proximity between particle and nucleus exceeds a certain value, another feeling of nuclear attraction appears that only works at short distances and allows us to overcome their differences.
Of course everything has a price. The artificially fattened nucleus after the union usually suffers from indigestion that leads it to transform into a different chemical element from the original. With these games, the chimera of matter transmutation had been achieved. They demonstrated it in 1933 Juliot and Irene Curíe (daughter of Madame Curíe) by bombarding atoms of boron, magnesium and aluminum with alpha particles and converting them into nitrogen, silicon and phosphorus.
Enrico Fermi, opted for indifference. Like Rutherford, he bombarded substances but instead of using electrically charged particles he opted for uncharged bullets: neutrons. There is nothing like indifference to go unnoticed, and neutrons, carrying no charge, could pass through the outer shell of electrons and approach the atomic nucleus without arousing suspicion. In his experiments, Fermi verified that neutrons managed to penetrate the nuclei of atoms but their incorporation did not go unnoticed. Some nuclei reacted by emitting radioactive particles of very different types.
For these experiments, Fermi received the Nobel Prize in Physics in 1938. But, contrary to what usually happens to laureates, the most interesting part of his research work was yet to come.
Fermi had bombarded the heaviest element known up to then, uranium, with neutrons. As a result of the bombardment, different radioactive substances were created that the researcher and his colleagues had not been able to identify. Despite everything, in his Nobel acceptance speech, he stated that they must be new elements heavier than uranium, even assigning names such as ausenium and Hesperium. But among the products of the bombing there was something else that would be revealed in 1939 thanks to the work of the German researchers Otto Hahn and Lise Meitner.
Hahn and Meitner studied the elements obtained during Fermi’s experiments and discovered that there were elements much lighter than uranium, substances that could only be produced thanks to a process that no one had suspected: nuclear fission. After catching a neutron, some uranium atoms would pop and break into much smaller pieces, releasing several neutrons and a large amount of energy.
The history of this discovery is not without controversy, Hahn received the Nobel Prize in Chemistry in 1944, while Lisa Meitner, who had to flee Germany because of her Jewish status, was left without it. Hahn and Meitner, who had worked as a team for years, were separated due to the intolerance, fanaticism and prejudices of the time. Meitner’s flight at the crucial moment of the investigation forced them both to publish the discovery in separate papers, Hahn published it first in Germany and could not list Lisa as an author for fear of Nazi reprisals and Meitner did so for several weeks. later in Nature. After each of them followed their careers separately, Hahn took the honors and Meitner’s contribution was forgotten, another example of the power of the forces that govern the Universe: hate, love and indifference.
Listen to the biography of Enrico Fermi.
#Cienciaes.com #Enrico #Fermi #nuclear #energy