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The Electron's Antimatter Opponent: How Was the Positron Discovered?
In the fascinating world of quantum physics, positrons, antimatter particles with a positive charge, are the opposite of electrons. Since the first positron was discovered in 1932, this important discovery has not only opened a whole new chapter in particle physics, but also has profound implications for our understanding of the composition of the universe.
Origins of the theory
The theoretical basis of positrons can be traced back to the Dirac equation proposed by Paul Dirac in 1928. This equation combines quantum mechanics with relativity and the concept of electron spin, and explains the Zemann effect. Although Dirac's paper did not explicitly predict a new particle, the layout provided the possibility of two solutions for the electron having positive and negative energies.
Dirac stated in his subsequent paper: "...an electron with negative energy moves in an external electromagnetic field as if it had a positive charge."
Dirac's model sparked debate with scholars such as Constantin Oppenheimer, who opposed the assumption that the proton was a negative-energy electron. In 1931, Dirac creatively predicted an undiscovered particle, the "anti-electron", which is what we later called the positron. Over time, various physicists proposed theories that viewed positrons as electrons traveling in reverse time, and these theories eventually became widely accepted.
Experimental clues and discoveries
In the early days of the positron exploration, some researchers claimed that Dmitri Skobelts had first discovered the positron through careful observation. Although experimental results in 1913 showed that there were particles bending in opposite directions in a magnetic field, he himself was skeptical about the discovery of positrons at a 1928 conference.
Skobelts stressed that these early claims were "just pure nonsense."
The actual discovery of the positron was finally confirmed in 1932 by Carl David Anderson while conducting research on cosmic rays. He used the characteristics of the magnetic field to further analyze the cosmic rays and successfully identified the existence of positrons. Anderson won the Nobel Prize in Physics in 1936 for this. It is worth noting that Anderson did not coin the term "positron" but accepted the suggestion of the editors of Physical Review.
Natural Occurrence and Observation
Positrons are naturally produced during radioactive decay processes such as beta+ decay, and from the interaction of gamma rays with matter. Positrons and neutrinos are produced naturally during the decay of certain heavy atoms, such as potassium-40. Positrons have also been observed in gamma-ray flashes from thunderstorm clouds, according to a 2011 study by the American Astronomical Society.
Artificial Generation and Applications
Today, physicists have established a variety of methods to artificially produce positrons. Lawrence Liverpool National Laboratory in California used ultra-intense lasers to irradiate metal targets, generating more than 10 billion positrons. In addition, the European Organization for Nuclear Research (CERN) and the University of Oxford have also shown that they have successfully produced tens of trillions of electron-positron pairs in experiments.
These further experiments will not only help us understand physical phenomena in extreme astronomical environments, but also promote further exploration of antimatter research.
Among current medical imaging technologies, techniques such as positron emission tomography (PET) are widely used for tumor diagnosis and observing the fuel uptake of internal diseases. Whether in basic physics or applied science, the discovery of the positron marks a small but significant step in humanity's understanding of the world of particles.
With the advancement of science and technology, the application and research of positrons are still continuing to deepen. Will it bring more subversion and enlightenment to our view of the universe in the future?
