The word "symmetry" comes from the Greek συμμέτρια - proportionality. An object or process is called symmetric if, after some transformation, it coincides with itself.
Instructions
Step 1
If an object subjected to mirror reflection does not change its appearance, then it has bilateral (bilateral) symmetry. For example, the bodies of humans and most vertebrates are bilaterally symmetrical, with the plane of symmetry running along the spine.
Step 2
If an object can be rotated 360 ° around a certain straight line, and after this operation it coincides with itself before the rotation, then such a straight line is called the axis of symmetry of the n-order.
Some geometric bodies, for example, a cylinder and a cone, have an axis of symmetry of infinite order - they can be rotated around this axis at any arbitrary angle, and they will coincide with themselves. This symmetry is called axial.
Step 3
In inanimate nature, symmetry axes of the second, third, fourth, sixth and other orders are often found, but the fifth order symmetry is almost never encountered. In living nature, on the contrary, it is widespread - it is possessed by many plants, as well as animals of the order of echinoderms (starfish, sea urchins, sea cucumbers, etc.).
Step 4
Geometric symmetries can be combined with each other. For example, if an object is symmetrical about two mismatched planes, then these planes must intersect with each other, and the line of their intersection will be the axis of symmetry of the same object.
Observations of combinations of symmetries led the French scientist Évariste Galois to the creation of group theory - one of the important branches of mathematics.
Step 5
In physics, one speaks more often of the symmetry of processes than of objects. A process is called symmetric with respect to a particular transformation if the equation that describes it remains unchanged (invariant) after such a transformation.
Step 6
Noether's theorem, proved in 1918, states that any continuous symmetry of physical processes corresponds to its own conservation law, that is, a certain quantity that does not change in symmetric interactions. For example, symmetry with respect to the shift in time leads to the law of conservation of energy, and symmetry with respect to the shift of space leads to the law of conservation of momentum.
Step 7
Physicists attach particular importance to spontaneous symmetry breaking. Any such violation, when discovered, leads to a deepening of our knowledge of the universe. For example, due to symmetry breaking in one of the experiments with elementary particles, a neutrino was theoretically discovered, and then the existence of this particle was confirmed in practice.