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Text 7. EVERY PARTICLE OF MATTER HAS AN ANTIMATTER COUNTERPART
English physicist Paul Dirac is best known today for predicting the existence of antiparticles through mathematics. Dirac was a postgraduate student of the Cambridge University when he read Werner Heisenberg’s groundbreaking paper on matrix mechanics, which described the way how particles jump from one quantum state to another. Dirac was one of the few people capable of grasping the paper’s difficult mathematics, and noticed parallels between Heisenberg’s equations and parts of the classical (pre-quantum) theory of particle motion known as Hamiltonian mechanics. This allowed Dirac to develop a method by which classical systems could be understood on a quantum level. One early result of this work was a derivation of the idea of quantum spin. Dirac figured out a set of rules now known as “FermiDirac statistics” (since they were also independently 17 found by Enrico Fermi). Dirac named particles such as electrons that have a half-integer spin value “fermions,” after Fermi. The rules describe how large numbers of fermions interact with one another.
Quantum field theory
While much of schoolbook physics focuses on the properties and dynamics of individual particles and bodies under the influence of forces, a deeper understanding can be gained by developing field theories. These describe the way that forces make their influence felt across space. The importance of fields as independent entities was first recognized in the mid-19th century by James Clerk Maxwell while he was developing his theory of electromagnetic radiation. Einstein’s general relativity is another example of a field theory. Dirac’s new interpretation of the quantum world was called a quantum field theory. In 1928, it allowed him to produce a relativistic version of Schrodinger’s wave equation for the electron. The so-called Dirac equation also predicted the existence of particles having identical properties to particles of matter but having opposite electric charge. They were dubbed “antimatter” (a term that had been bandied around in wilder speculations since the late 19th century). The existence of antielectron particle, or positron, was experimentally confirmed by US physicist Carl Anderson in 1932, as it was detected first in cosmic rays and in certain types of radioactive decay. Since then, antimatter has become a subject for intense physical research, and also beloved of science-fiction writers - particularly for its property of “annihilating” with a burst of energy on contact with normal matter. Dirac’s quantum field theory laid the foundations for the theory of quantum electrodynamics brought to fruition by a later generation of physicists.
Exercises
1. Read the text again and make the short plan of the text.
2. Retell the text briefly pointing out its key ideas.
3. Translate the following sentences into Russian paying attention to the underlined words:
• English physicist Paul Dirac is best known today for predicting the existence of antiparticles through mathematics
• Dirac was one of the few people capable of grasping the paper’s difficult mathematics, and noticed parallels between Heisenberg’s equations and parts of the classical (pre-quantum) theory of particle motion known as Hamiltonian mechanics
• Dirac figured out a set of rules now known as “FermiDirac statistics”
• In 1928, it allowed him to produce a relativistic version of Schrodinger’s wave equation for the electron.
• Perhaps more importantly, however, Dirac’s quantum field theory laid the foundations for the theory of quantum electrodynamics brought to fruition by a later generation of physicists.
4. Answer the following questions:
• What was Dirac’s status when he read Werner Heisenberg’s paper on matrix mechanics?
• What was the discovery of Werner Heisenberg in matrix mechanics?
• What did the so-called Dirac equation predict?
• Who detected first the antielectron particle?
• What is Paul Dirac generally known for?
• What did Dirac develop?
• What is the difference between schoolbook physics and deeper research?
• Who was the first to recognize the importance of fields?
5. Form adjectives from the following nouns and verbs:
A physicist – mechanics – mathematics – a particle – existence – radioactivity – a norm – a theory 6. Find Russian equivalents to the following words and expressions: Antiparticles – a quantum state - capable of – a spin – to interact – to focus on – to recognize - a field theory - identical properties - electric charge - a subject for – a research - to lay the foundations
7. Finish the following sentences:
• Dirac was a postgraduate student at Cambridge University when …
• Dirac was one of the few people capable of …
• Dirac named particles such as …
• The importance of fields as independent entities was first recognized…
• In 1928, it allowed him to produce …
• Since then, antimatter has become a subject for …