Thumb twiddling is an activity that is done with the hands of an individual whereby the fingers are interlocked and the thumbs circle around a common point, usually in the middle of the distance between the two thumbs.
While it is an expression of at least a moderate amount of manual dexterity, thumb twiddling is frequently used as an example of a useless, time-wasting activity. [1]
Thumb twiddling can be used as a simple test for manual dexterity. [2]
Contra-rotation involves moving the thumbs in opposing directions. While thumb twiddling comes naturally for almost everyone, it is extremely rare for people to be able to naturally contra-rotate their thumbs without spending a significant amount of time training the new technique. [3] Typically, a person will get through a half rotation before both of the thumbs will inexplicably synchronize directions. A similar phenomenon occurs using similar finger or arm movements. [4]
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror symmetry. Unlike other sources of birefringence which alter a beam's state of polarization, optical activity can be observed in fluids. This can include gases or solutions of chiral molecules such as sugars, molecules with helical secondary structure such as some proteins, and also chiral liquid crystals. It can also be observed in chiral solids such as certain crystals with a rotation between adjacent crystal planes or metamaterials.
A scrollbar is an interaction technique or widget in which continuous text, pictures, or any other content can be scrolled in a predetermined direction on a computer display, window, or viewport so that all of the content can be viewed, even if only a fraction of the content can be seen on a device's screen at one time. It offers a solution to the problem of navigation to a known or unknown location within a two-dimensional information space. It was also known as a handle in the very first GUIs. They are present in a wide range of electronic devices including computers, graphing calculators, mobile phones, and portable media players. The user interacts with the scrollbar elements using some method of direct action, the scrollbar translates that action into scrolling commands, and the user receives feedback through a visual updating of both the scrollbar elements and the scrolled content.
In mathematics and physics, the right-hand rule is a convention and a mnemonic, utilized to define the orientation of axes in three-dimensional space and to determine the direction of the cross product of two vectors, as well as to establish the direction of the force on a current-carrying conductor in a magnetic field.
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.
Pen spinning is a form of object manipulation that involves the deft manipulation of a writing instrument with hands. Although it is often considered a form of self-entertainment, multinational competitions and meetings are sometimes held. It is sometimes classified as a form of contact juggling; however, some tricks, e.g. "spreads" and "aerial tricks" do leave contact with the body. In addition to writing instruments, it is often also seen performed by drummers with their drumsticks. In fact, drumsticks are substantially easier to manipulate than pens, because of their extra mass and length. Pen spinning has quickly gained international popularity through online video sharing and forums. The hobby has been popular around the world since at least the 1970s.
Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation. Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply.
Aircraft equipped with contra-rotating propellers (CRP) coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single piston or turboprop engine to drive a pair of coaxial propellers in contra-rotation. Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission. Contra-rotating propellers are also known as counter-rotating propellers, although the term counter-rotating propellers is much more widely used when referring to airscrews on separate non-coaxial shafts turning in opposite directions.
Cardistry is the performance art of card flourishing. Unlike card magic, cardistry is meant to be visually impressive and appear very hard to execute.
The shaka sign, sometimes known as "hang loose" is a gesture with friendly intent often associated with Hawaii and surf culture. It consists of extending the thumb and smallest finger while holding the three middle fingers curled, and gesturing in salutation while presenting the front or back of the hand; the wrist may be rotated back and forth for emphasis. The shaka sign is similar to the letter Y in the American manual alphabet in American Sign Language. The shaka sign should not be confused with the sign of the horns, where the index and pinky finger are extended and the thumb holds down the middle two fingers.
Helicopter flight controls are used to achieve and maintain controlled aerodynamic helicopter flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a desired way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.
Wrist spin is a type of bowling in the sport of cricket. It refers to the cricket technique and specific hand movements associated with imparting a particular direction of spin to the cricket ball. The other spinning technique, usually used to spin the ball in the opposite direction, is finger spin. Wrist spin is bowled by releasing the ball from the back of the hand, so that it passes over the little finger. Done by a right-handed bowler, this imparts an anticlockwise rotation to the ball, as seen from the bowler's perspective; a left-handed wrist spinner rotates the ball clockwise.
Table tennis is unique among racket sports in that it supports a wide variety of playing styles and methods of gripping the racket, at even the highest levels of play. This article describes some of the most common table tennis grips and playing styles seen in competitive play. The playing styles listed in this article are broad categories with fuzzy boundaries, and most players will possess some combination of these styles while leaning towards a "favorite". Many advanced players will also add some "special" shots of their own.
A coaxial-rotor aircraft is an aircraft whose rotors are mounted one above the other on concentric shafts, with the same axis of rotation, but turning in opposite directions (contra-rotating).
Baoding balls are metal balls small enough to hold in one hand, used for physical exercise and therapy. They are also known as Chinese "balls for ball practice" exercise balls, Chinese health balls, Chinese meditation balls, and Chinese medicine balls. Baoding balls are used by rotating two or more balls repeatedly in the hand. Intended to improve finger dexterity, relax the hand, or aid in the recovery of muscle strength and motor skills after surgery, Baoding balls work similarly to Western stress balls.
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative to the anatomical position of the body parts involved. Anatomists and others use a unified set of terms to describe most of the movements, although other, more specialized terms are necessary for describing unique movements such as those of the hands, feet, and eyes.
Hook grip is a method of gripping a barbell used in many strength-related sports such as Olympic weightlifting, Crossfit, and powerlifting by overlapping the index and middle finger over the thumb. This method of gripping the bar provides a secure bar grip while performing pulling motion with the barbell such as the clean and jerk, snatch, and deadlift. To perform a hook grip one must first wrap their thumb around the bar placing it parallel to the barbell and then wrap their index, and middle finger around the outside of the thumb. The pinky and ring finger typically ends up resting on the barbell. It is important to actively hooking on to the thumb with the index and middle finger while performing Hook grip compared to providing direct pressure on to the thumb.
Fulcrum is a drumming term. Traditionally, the fulcrum is said to denote the part of a percussionist's grip that is the main lever for the drumstick/mallet to rotate. This is usually created by the thumb + index finger, the thumb + middle finger, or a combination of the index, middle, and thumb.
The front crawl or forward crawl, also known as the Australian crawl or American crawl, is a swimming stroke usually regarded as the fastest of the four front primary strokes. As such, the front crawl stroke is almost universally used during a freestyle swimming competition, and hence freestyle is used metonymically for the front crawl. It is one of two long axis strokes, the other one being the backstroke. Unlike the backstroke, the butterfly stroke, and the breaststroke, the front crawl is not regulated by the FINA. This style is sometimes referred to as the Australian crawl although this can sometimes refer to a more specific variant of front crawl.
Fine motor skill is the coordination of small muscles in movement with the eyes, hands and fingers. The complex levels of manual dexterity that humans exhibit can be related to the nervous system. Fine motor skills aid in the growth of intelligence and develop continuously throughout the stages of human development.
In percussion, grip refers to the manner in which the player holds the sticks or mallets, whether drum sticks or other mallets.