### motion:

Linear motion
* is combined with circular motion
  - motion in a straight line
* represents constant velocity.

Motion blur
* is caused when either the camera or the subject moves during the exposure
  - specified through moving transformations and moving geometric primitives
* makes everything that moves, blurry.
* operates only within a character's outline.

Periodic motion
* is important in the study of sound, light, and other waves
  - motion that repeats itself
  - movement that is regular and repeating eg
* means motion with a certain period and frequency.

Perpetual motion
* exists in one sense.
* is motion

Planetary motion
* reflect the history of their formation.
* sweeps out equal areas in equal time.

Projectile motion
* case of two-dimensional motion.
* is always a parabola, because there is only a vertical force
  - an actual transfer of matter
  - applied today in jobs and other things too
  - simply free-fall with an initial horizontal velocity
  - the motion of an object that is projected into the air at an angle
  - translations

Proper motion
* causes the shape of constellations to distort over time.
* is an object 's change in position over time when seen from the Earth
  - measured in arcseconds per year
  - the measure of how far an object moves across the sky
* varies as the angle to the space-velocity vector changes.

Range of motion
* becomes limited as muscles shorten, tendons and ligaments become less elastic.
* can have a huge impact on a movement.
* is critical in athletic performance to avoid fatjgue and overuse injuries
  - the natural distance and direction of movement of a joint
* way of measuring the flexibility of the joint.

Repetitive motion
* can cause carpal ligaments to swell
  - injure the tendons, causing pain and warmth in the elbow
  - produce a tenosynovitis in the tendon sheaths of the long flexor muscles
* causes a wide-spread macrophages infiltration and cytokine production
  - systemic inflammation and reach pattern decrements in rats
* is also a frequent cause of soft tissue injuries.
* term frequently heard when discussing industrial injuries.

### motion:

Retraction
* are a warning sign that accessory muscles are necessary to maximize airflow.
* requires the contraction of two internal longitudinal muscles, known as the sternoglossi
+ Short-beaked Echidna, Description, Tongue: Mammals of Australia :: Mammals of New Guinea :: Monotremes
  * The tongue of the Short-beaked Echidna is the animal's only way of catching prey. The tongue is sticky because of the presence of glycoprotein-rich mucous. This mucus both lubricates movement in and out of the snout and helps to catch ants and termites, which stick to it. Sticking out the tongue is achieved by contracting the circular muscles that change the shape of the tongue and force it forward, and contraction of two muscles attached to the caudal end of the tongue and to the mandible. The protruded tongue is stiffened by the rapid flow of blood, allowing it to penetrate wood and soil. Retraction requires the contraction of two internal muscles. This allows the animal to both capture and grind food. The tongue moves with great speed, and has been measured to move in and out of the snout 100 times a minute. Doran G.A. and Baggett H. 1970.

Retrograde motion
* affects both individuals and worldwide events.
* arise from the combined motions of the planets and the Earth.
* is A. the changing of the Earth's speed as the Earth moves around the Sun
  - an optical illusion created by the orbits of the planets
  - caused by the motion of the Earth around the sun
  - the apparent motion backwards in the sky as viewed from the Earth
* occurs when a. the planets move on epicycles.