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Exercises. 1) Sum up the main ideas of the text using the following vocabular. 2) Translate the text in writing. Popular Information
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Exercises
1) Sum up the main ideas of the text using the following vocabular
deviations from symmetry at the microscopic level, prove to be extremely useful, permeate the Standard Model, spontaneous occurrences, come as a complete surprise, fully confirm the explanations, to explain broken symmetry within the framework of, to extend the model, to detect broken symmetry independently of each other, to lie behind the very origin of the cosmos, to remain unanswered, unravel new mysteries
2) Translate the text in writing
Popular Information
Unravelling the hidden symmetries of nature
Nature’s laws of symmetry are at the heart of this subject: or rather, broken symmetries, both those that seem to have existed in our universe from the very beginning and those that have spontaneously lost their original symmetry somewhere along the road.
In fact, we are all the children of broken symmetry. It must have occurred immediately after the Big Bang some 14 billion years ago when as much antimatter as matter was created. The meeting between the two is fatal for both; they annihilate each other and all that is left is radiation. Evidently, however, matter won against antimatter, otherwise we would not be here. But we are here, and just a tiny deviation from perfect symmetry seems to have been enough — one extraparticle of matter for every ten billion particles of antimatter was enough to make our world survive. This excess of matter was the seed of our whole universe, which filled with galaxies, stars and planets — and eventually life. But what lies behind this symmetry violation in the cosmos is still a major mystery and an active field of research.
Through the looking glass
For many years physics has focused on finding the natural laws that are hidden deep within the wide range of phenomena we see around us. Natural laws should be perfectly symmetrical and absolute; they should be valid throughout the whole of the universe. This approach seems true for most situations, but not always. That is why broken symmetries became the subject of physics research as much as symmetries themselves, which is not so remarkable considering our lopsided world where perfect symmetry is a rare ideal.
Various types of symmetries and broken symmetries are part of our everyday life; the letter A does not change when we look at it in a mirror, while the letter Z breaks this symmetry. On the other hand, Z looks the same when you turn it upside down, but if you do the same with the letter A, the symmetry will be broken.
The basic theory for elementary particles describes three different principles of symmetry: mirror symmetry, charge symmetry and time symmetry (in the language of physics, mirror symmetry is called P, from parity, C stands for charge symmetry and T for time symmetry).
In mirror symmetry, all events should occur in exactly the same way whether they are seen directly or in a mirror. There should not be any difference between left and right and nobody should be able to decide whether they are in their own world or in a looking glass world. Charge symmetry states that particles should behave exactly like their alter egos, antiparticles, which have exactly the same properties but the opposite charge. And according to time symmetry, physical events at the microlevel should be equally independent whether they occur forwards or backwards in time.
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Symmetries do not just have an aesthetic value in physics. They simplify many awkward calculations and therefore play a decisive role for the mathematical description of the microworld. An even more important fact is that these symmetries implicate a large number of conservation laws at the particle level. For example, there is a law that energy cannot be lost in collisions between elementary particles, it must remain the same before and after the collision, which is evident in the symmetry of equations that describe particle collisions. Or there is the law of the conservation of electrical charges that is related to symmetry in electromagnetic theory.
The pattern emerges more clearly
It was around the middle of the 20th century that broken symmetry first appeared in studies of the basic principles of matter. At this time physics was thoroughly involved in achieving its greatest dream – to unite all nature’s smallest building blocks and all forces in one unified theory. But to begin with, particle physics only became more and more complicated. New accelerators built after the Second World War produced a constant stream of particles that had never been seen before. Most of them did not fit into the models physicists had at that time, that matter consisted of atoms with neutrons and protons in the nucleus and electrons round it. Deeper investigations into the innermost regions of matter revealed that protons and neutrons each concealed a trio of quarks. The particles that had already been discovered also were shown to consist of quarks.
Now, almost all the pieces of the puzzle have fallen into place; a Standard Model for the indivisible parts of matter comprises three families of particles. These families resemble each other, but only the particles in the first and lightest family are sufficiently stable to build up the cosmos. The particles in the two heavier families live under very unstable conditions and disintegrate immediately into lighter kinds of particles.
Everything is controlled by forces. The Standard Model, at least for the time being, includes three of nature’s four fundamental forces along with their messengers, particles that convey the interaction between the elementary particles. The messenger of the electromagnetic force is the photon with zero mass; the weak force that accounts for radioactive disintegration and causes the sun and the stars to shine is carried by the heavy W and Z boson particles; while the strong force is carried by gluon particles, which see to it that the atom nuclei hold together. Gravity, the fourth force, which makes sure we keep our feet on the ground, has not yet been incorporated into the model and poses a colossal challenge for physicists today.
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