Apparent motion

Apparent motion may refer to:

In astronomy:

• Apparent retrograde motion, the appearance that objects in the night sky move against the typical direction of motion
• Improper motion, any effect which appears to cause the position of a celestial object to move
  • Aberration of light, improper motion due to the finite speed of light and the motion of Earth in its orbit around the Sun
  • Diurnal motion, improper motion due to the Earth's rotation on its axis
  • Parallax, improper motion caused by the Earth's orbit around the sun

In perceptual illusions:

• Beta movement, an illusion of movement where two or more still images are combined by the brain into surmised motion
• Illusory motion, the appearance of movement in a static image
• Phi phenomenon, an illusion of movement created when two or more adjacent lights blink on and off in succession
• Stroboscopic effect, a phenomenon that occurs when continuous motion is represented by a series of short or instantaneous samples
  • Wagon-wheel effect, temporal aliasing effect in which a spoked wheel appears to rotate differently from its true rotation
• The illusion of movement deliberately sought by certain forms of op art (optical art)

Other uses:

• Optical flow, a term used in computer science for the apparent motion of objects in a scene caused by the relative motion between an observer and the scene
• The motion of objects observed from a non-inertial reference frame