# Left and right

Left and right

Left (also left-hand ) and right (also right-hand ) is an assignment description of the two sides separated by the vertical from the perspective of the viewer . Associated with this are two opposite location or directional information with the same name .

In addition to above and below and in front and behind, they form one of the three dimensions of Euclidean space and thus serve people in egocentric (as opposed to allocentric ) societies for spatial orientation .

Deviating in the connotation , the name of fabrics usually means the outside (right) and inside (left) (see clothing, textiles, perforation ).

## Handedness

The right and left hands are not identical, even if they are the same size. They differ in their handedness , they are chiral .

The laws of physics are largely, but not completely, symmetrical about left and right. One can conduct a physical experiment in which differences between the two directions in the measurement can be used to determine left and right. This mirror symmetry is known as a parity violation . It only occurs in connection with the weak interaction .

## Objects

A left and a right side can be defined for objects. The question often arises whether this is seen from the point of view of the observer or from another point of view.

### Creature

from behind
from the front

Left and right half of the body and right and left body parts are anatomically from the perspective of the individual described . The distinction between right and left must be learned in childhood. Technically, one speaks of the "egocentric" view. Transferring this view to other people's bodies requires another learning step.

With the snails there are, mostly species-specific, left- and right-handed snail shells . The winding of the housing is viewed from the tip (apex): a counterclockwise direction of rotation - then the opening of the housing facing the viewer is on the left - is left-handed (sinistral), a clockwise direction is right-handed (dextral). The shell of the vast majority of snail species is right-handed. A so-called snail king is a single snail whose shell is wound in the mirror-image, atypical direction. The spotted Roman snail, for example, is right-wound, a "snail king" occurs in this species with a frequency of 1: 20,000.

The vast majority of animals belong to the Bilateria (bilateral animals) with a left and a right half of the body that are largely mirror-symmetrical to each other . However, this bilateral symmetry is not perfect - there are asymmetries in the arrangement of unpaired (simply formed) internal organs such as the heart and liver, with slight deviations in relation to the position, shape and size of the eyes, ears, limbs and so on.

### Rivers

The direction of view down the valley, i.e. downstream, in the direction of flow from the source to the mouth , defines the left and right banks of a river .

### Documents, pictures and cards

With documents , pictures and maps , the viewer's point of view defines the left and right sides. So people or objects in pictures in the German speaking mostly ( "left to right" v. L. N. R. ) Named.

In many languages , like in German , you write from left to right. In other languages, such as Hebrew and Arabic , the writing is done from right to left. The Indian numerals are written in scripts in both writing directions with the units digit to the right and each additional digit to the left.

On a map is usually located above the north , down south , left the West and right East . Maps of the North Pole region or the Antarctic are oriented in such a way that the prime meridian starting from the central pole points vertically downwards or - from the South Pole - upwards. Thus, on each of these pole maps, the western hemisphere is on the left and the eastern hemisphere is on the right.

Floor plans of buildings are usually drawn so that the long sides are drawn parallel to the paper. The northerly direction is then drawn in with an appropriately aligned north arrow .

Orientation plans on boards, for example of building corridors, exhibition grounds, shopping centers, housing developments, are conveniently oriented as a vertical board in such a way that the right of the plan with a parallel view over or next to the board also corresponds to the right in nature - a north arrow on the plan then generally does not point up.

### X-rays, photographic film

In the case of medical treatment on the human body, there must be no confusion of the sides with a high degree of certainty. In principle, it is marked on each X-ray image which side of the body or which side of the extremities is shown. Due to the chirality of the initials L and R - in German - they are graphically ideal for displaying both the (part) side of the body and the correct viewing direction of the X-ray image, which is available on film coated on both sides. The X-ray cone runs from above through a hand or a lung onto a (light-tight) X-ray film cassette, on which the marking letter ( lead mark , made of brass or NiRo ) for the corresponding side of the body is placed. This letter is then graphically legible from the viewing direction (like exposure direction from above). When the lungs of the standing person are transilluminated, i.e. irradiation from behind and simultaneous viewing on the fluorescent screen from the front, the image is viewed from the opposite direction. If an X-ray image is made in this type of projection, the letter must be turned around or a slip-on letter in mirror writing must be used so that it appears the right way round when viewed "against the X-ray beam".

35mm film is exposed through the lens on the layer side and projected ("enlarged") as a slide or negative, precisely in the reverse beam path, onto canvas or paper. Left and right, as well as above and below, are interchanged in nature and on film, or film and canvas (image), from the perspective of the photographer behind the camera or the projector operator. This figure corresponds to a rotation of 180 ° in the optical axis. 35mm films are sometimes provided with frame numbers on the edge strips so that they can be read with the negative the right way round, unless the direction of the film is unusually oriented, as is the case with Rollei 35 .

### vehicles

With vehicles , the main direction of travel defines the left and right side, for example in continental Europe and many other parts of the world you drive on the right-hand side of the road ( right-hand drive ), the steering wheel of motor vehicles is on the left (around the oncoming traffic easier to judge; only trucks of the mid-20th century had the steering wheel on the right in countries driving on the right, so that they could orient themselves on the right side of the road), priority is given to right over left .

In the case of watercraft , the right is referred to as starboard (because the steering rudder of the galley was originally right, in the middle of the stern is a newer invention) and left as port , although a rule of right-of-way applies only to motorized watercraft between each other, starboard over port .

### people

In the case of people, the point of view of the person described defines the left and right sides. The left eye is thus the left eye in the direction of the person described, although this is on the right for an opposing observer. This also applies to all other organs; z. B. is the human liver on the right side, although this is shown in anatomical representations on the left side.

In medicine, the Latin names dexter (right) and sinister (left) are used for this.

### Mirrors, video telephony, self-portrait, reflex camera

If I see myself in the mirror , I can also see the right side of my face in the virtual mirror image on the right. This mirror image is reversed for a direct view that other people gain of me who look me in the face. That makes communication misleading if you want to discreetly point out to the other person with a finger pointing or words: "You have a goulash splash on your right cheek."

Only 2 mirrors, which open 90 ° from a vertical axis, depict your own face (and also other people next to you) through double reflections. The parting line between the mirror edges runs right through the face, unless the angle of the mirrors to one another is slightly reduced in a more acute direction, which means that the wider the mirror, the more parts of your face can be seen twice. A multi-surface pentaprism on the head of an SLR camera does nothing else, since the image on the horizontal screen by the deflecting mirror already appears to be reversed above and below compared to the image seen from behind in the film plane.

If you look at your own image on the screen during video chat or telephony via a camera - usually placed at the top of the screen - you expect your own mirror image, which is why hardware or software transmit the recorded image to the recipient, but display it as a mirror image for the sender. So if I move to the right in front of the screen, my picture also moves to the right side of the screen. This is also how (and only) the front cameras on the screen of smartphones and tablets behave, as do the additional front screens that some digital cameras have on their lens side for self-portraits.

### heraldry

In contrast to pictures, in heraldry, the position of the person wearing the shield defines the left and right side of a coat of arms . In the case of coats of arms depicted in books, for example, it is the coat of arms side that is on the left that is to the right of the center of the coat of arms as seen from the viewer of the book page.

The expression belongs to the technical language of blazon (description of coat of arms).

### Doors

In the case of cupboard and passage doors , as well as windows, the hinge side defines its side as agreed in Germany, seen from the room to which the door opens. The hinge or hinge side of a door is the one on which its hinges (also called hinges or hinges) are located, i.e. the one opposite the opening edge with the handle and lock. Based on this consideration, the respective asymmetrical door fittings (hinges, locks, handles [door handles, olives , closers] etc.) are also referred to as right or left. The Swiss VSSM standard and the European DIN standard differ in the case of passage doors : According to the European DIN standard, a lock that fits a door with a left-hand hinge is called a left-hand lock. In the Swiss VSSM standard, however, the same lock is referred to as the right lock. This results in the following situation: DIN: left hinge, left lock, left door; however VSSM: left band, right lock, left door. The screw-in hinges often used on room doors are, however, symmetrical anyway, mortise locks can be adjusted to the right or left before installation by turning the latch (the obliquely resilient protruding part) around their horizontal axis despite the chiral interior.

### Clothing, textiles, perforations

In the case of items of clothing, the surface that is visible on the right is the surface, while the left is the inside, also called the back. Right and left are also important in knitting , with many - for example, one-sided printed or treated, pattern-woven, velvet fabrics, knotted carpets, also embossed and not burr-free punched perforated sheet or wood fiber board, calendered plastic film, paper, as a twin rolled aluminum foil.

### theatre

In the theater, left and right are always defined as seen from the audience and referred to as stage left and stage right. For the actor, this means a reversal of the directions: the audience sees the left of the stage as being on the left and therefore also denotes the left for the actor. This reversal of directions concerning the actor using the terms left and right does not apply, however, since misunderstandings have repeatedly occurred when playing instructions were given from the control desk in the auditorium during rehearsals and when performances had to be ensured, errors of the actors regarding the to exclude scenically “correct” appearance. For this reason, the terms left and right no longer exist in opera houses with regard to the sides of the stage. At the Staatsoper Unter den Linden Berlin they are called “Berlin” and “Charlottenburg”, at the Richard Wagner Festspielhaus Bayreuth “West” and “East”, at the State Theater on Gärtnerplatz Munich “Klenzestraße” and “Reichenbachstraße” and at the Teatro Real Madrid “ Calle Felipe V ”and“ Calle Carlos III ”to name a few.

In the English-speaking area and at pop concerts also in the German-speaking area, the terms “stage left” and “stage right” are used, but here from the artist's perspective. The literal translation of stage links or stage law would therefore be wrong, so a translation is often avoided and the English terms are used as standing technical terms.

### Railway lines

For railway lines, the left and right are defined in the direction of the ascending kilometer . The terms "left of the track" and "right of the track" are also common. In Austria, for operational purposes, the direction from the starting point to the end point of a route is decisive for "left of the railway" and "right of the railway". This definition does not have to agree with the ascending kilometrage. For technical descriptions (left rail / right rail etc.), the increasing number of kilometers is generally used as a reference.

## etymology

### Right

The Indo-European reg as the root of linguistic history actually stood for straight ahead, straightening up, stretching, straightening and was also used for the good, the true and the perfect. The use of the same root word for the direction “right”, right and right ( Latin jus vs. dexter ) also exists in English ( right ), French ( droit ), Spanish ( derecha ), and the Slavic languages ( Polish prawo , Czech pravo , Russian право ) and in Persian ( rast ).

### Left

The New High German link (s) goes back to Middle High German  linc, lenc ; the original meaning was "awkward" (see "awkward"). Someone left, turn left one is coll. Cheat . Other expressions have become unusable over the centuries or have only survived in dialect (Middle High German lerc / lerz, tenc, winster ).

## Right-left weakness

Some people find it difficult to orientate themselves self-centeredly (i.e. following the right-left strategy) . The egocentric orientation is a cultural convention . Behavioral experiments on great apes , children and adults from indigenous peoples and from western cultures have shown that humans originally had an allocentric character, that is, they were oriented towards the environment and the cardinal points . This evolutionarily ancient environmental strategy is only of a stamping overlaid by language and culture. The natural behavior of grasping the location of an object in relation to the environment is thus masked in the course of childhood by the learned ability to describe the position of an object in relation to one's own body. This causes difficulties for around 20 to 30% of people, with no major differences found between the sexes . Around 120 times a year, patients in German hospitals are operated on the wrong side (2010).

## literature

• Wilhelm Ludwig : The right-left problem in the animal kingdom and in humans: With an appendix right-left characteristics of plants (= monographs from the entire area of ​​plants and animals. Vol. 27). Springer, Berlin 1970, ISBN 3-540-04963-0 (reprint of the first edition 1932).