question: Why does sky seem to "move with us" when we move our head around (especially when looking at stars)?
comment: Our perspective changes and our brains trick us into thinking it's moving with us. Kind of like how some paintings if you move seem like the eyes are following you
passages: BULLET::::- To the cerebellum. Signals sent to the cerebellum are relayed back as muscle movements of the head, eyes, and posture.
  
  BULLET::::- To nuclei of cranial nerves III, IV, and VI. Signals sent to these nerves cause the vestibulo-ocular reflex. They allow for the eyes to fix on a moving object while staying in focus.
  
  BULLET::::- To the reticular formation. Signals sent to the reticular formation signal the new posture the body has taken on, and how to adjust circulation and breathing due to body position.
   BULLET::::- Visual input from the eye relays information to the brain about the craft's position, velocity, and attitude relative to objects in the outside-world (OTW) visual scene. The rate of change of perspective of a moving visual scene is a strong cue in the real world, and the visual system in a simulator uses computer graphics to model the real scene.
  
  Section::::How human physiology processes and responds to motion.:Proprioceptors.
   The visual system in the brain is too slow to process that information if the images are slipping across the retina at more than a few degrees per second. Thus, to be able to see while we are moving, the brain must compensate for the motion of the head by turning the eyes. Another specialisation of visual system in many vertebrate animals is the development of a small area of the retina with a very high visual acuity. This area is called the fovea, and covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Eye movement is thus very important for visual perception, and any failure can lead to serious visual disabilities. To see a quick demonstration of this fact, try the following experiment: hold your hand up, about one foot (30 cm) in front of your nose. Keep your head still, and shake your hand from side to side, slowly at first, and then faster and faster. At first you will be able to see your fingers quite clearly. But as the frequency of shaking passes about 1 Hz, the fingers will become a blur. Now, keep your hand still, and shake your head (up and down or left and right). No matter how fast you shake your head, the image of your fingers remains clear. This demonstrates that the brain can move the eyes opposite to head motion much better than it can follow, or pursue, a hand movement. When your pursuit system fails to keep up with the moving hand, images slip on the retina and you see a blurred hand.
   Humans can sense head tilting and linear acceleration even in dark environments because of the orientation of two groups of hair cell bundles on either side of the striola. Hair cells on opposite sides move with mirror symmetry, so when one side is moved, the other is inhibited. The opposing effects caused by a tilt of the head cause differential sensory inputs from the hair cell bundles allow humans to tell which way the head is tilting, Sensory information is then sent to the brain, which can respond with appropriate corrective actions to the nervous and muscular systems to ensure that balance and awareness are maintained.
   Eccentricity, which is a mathematical constant conveyed in the form of a ratio and essentially describes to what degree a conic section deviates from being circular. Another variable that impacts motion silencing, eccentricity determines to what extent motion causes silencing. Choi, Bovik, and Cormack (2016) observed that when eccentricity in peripheral vision increases, motion silencing decreases.
  
  Section::::Theoretical explanations.
   The human eye is an important source of information in motion simulation where a high resolution picture is available such as by day in good visibility. The eye relays information to the brain about the craft's position, velocity, and attitude relative to the ground. As a result, it is essential for realistic simulation that cues from a motion platform (if fitted) works in synchronization to the external visual scene. As discussed above, in the real world motion cues are processed by the brain before visual changes, and this must be followed in a simulator or dizziness and even nausea can occur in some people, so called "simulator sickness".
   The Milky Way is rotating around its dense galactic center, thus the sun is moving in a circle within the galaxy's gravity. Away from the central bulge, or outer rim, the typical stellar velocity is between . All planets and their moons move with the sun. Thus, the solar system is moving.
  
  Section::::List of "imperceptible" human motions.:Earth.
   The Milky Way Galaxy is moving through space and many astronomers believe the velocity of this motion to be approximately relative to the observed locations of other nearby galaxies. Another reference frame is provided by the Cosmic microwave background. This frame of reference indicates that the Milky Way is moving at around .
  
  Section::::List of "imperceptible" human motions.:Sun and solar system.
   Dogs can detect a change in movement that exists in a single diopter of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movement.
   Optokinetic nystagmus (OKN) is nystagmus that occurs in response to a rotation movement. It is present normally. The optokinetic response allows the eye to follow objects in motion when the head remains stationary (e.g., observing individual telephone poles on the side of the road as one travels by them in a car, or observing stationary objects while walking past them).
  
  Section::::Eliciting optokinetic nystagmus.
   Vestibular display: These displays provide a sense of motion to the user (motion simulator). They often manifest as motion bases for virtual vehicle simulation such as driving simulators or flight simulators. Motion bases are fixed in place but use actuators to move the simulator in ways that can produce the sensations pitching, yawing or rolling. The simulators can also move in such a way as to produce a sense of acceleration on all axes (e.g., the motion base can produce the sensation of falling).
  
  Section::::Clinical healthcare simulators.
   Most of the utricular signals elicit eye movements, while the majority of the saccular signals projects to muscles that control our posture.
  
  While the interpretation of the rotation signals from the semicircular canals is straightforward, the interpretation of otolith signals is more difficult: since gravity is equivalent to a constant linear acceleration, one somehow has to distinguish otolith signals that are caused by linear movements from those caused by gravity. Humans can do that quite well, but the neural mechanisms underlying this separation are not yet fully understood. 
   Section::::Neurophysiology.:Neural mechanism: starburst amacrine cells.
   In many animals, including human beings, the inner ear functions as the biological analogue of an accelerometer in camera image stabilization systems, to stabilize the image by moving the eyes. When a rotation of the head is detected, an inhibitory signal is sent to the extraocular muscles on one side and an excitatory signal to the muscles on the other side. The result is a compensatory movement of the eyes. Typically eye movements lag the head movements by less than 10 ms.
  
  Section::::See also.
  
  BULLET::::- Adaptive optics
  
  BULLET::::- Deblurring
  
  BULLET::::- Heligimbal
  
  BULLET::::- Hyperlapse
  
  BULLET::::- Motion compensation
  
  BULLET::::- Shaky camera
   Section::::Vestibular influences.
   During the first days in orbit, the asymmetry of vertical eye movements in response to moving visual scenes is inverted. A return to symmetry of the vestibulo-ocular and optokinetic reflexes is then observed. Some studies have shown increased latencies and decreased peak velocities of saccades, while others have found just the opposite. It is possible that these conflicting results depend on when the measures were obtained during the mission. There is also a serious disruption of smooth pursuit eye movements, especially in the vertical plane.
   Section::::Anatomy.:Neuroanatomy.
  
  The brain exerts ultimate control over both voluntary and involuntary eye movements. Three cranial nerves carry signals from the brain to control the extraocular muscles. These are the oculomotor nerve, which controls the majority of the muscles, the trochlear nerve, which controls the superior oblique muscle, and the abducens nerve, which controls the lateral rectus muscle.
  
  In addition to the movement of muscles, numerous areas in the brain contribute to involuntary and voluntary eye movements. These include providing the conscious perception of vision, as well as areas that facilitate tracking.
  
  BULLET::::- Brain
  
  BULLET::::- Cerebral cortex
   Spatial disorientation can also affect instrument-rated pilots in certain conditions. A powerful tumbling sensation (vertigo) can be set up if the pilot moves his or her head too much during instrument flight. This is called the Coriolis illusion. Pilots are also susceptible to spatial disorientation during night flight over featureless terrain.
  
  Section::::Spatial orientation.
   Section::::Visual capacity of the horse.:Visual acuity and sensitivity to motion.
  
  The horse has a "visual streak", or an area within the retina, linear in shape, with a high concentration of ganglion cells (up to 6100 cells/mm in the visual streak compared to the 150 and 200 cells/mm in the peripheral area). Horses have better acuity when the objects they are looking at fall in this region. They therefore will tilt or raise their heads, to help place the objects within the area of the visual streak.
   "Vergence movement" or convergence is the movement of both eyes to make sure that the image of the object being looked at falls on the corresponding spot on both retinas. This type of movement helps in the depth perception of objects
  
  "Pursuit movement" or smooth pursuit is the movement the eyes make while tracking an object's movement, so that its moving image can remain maintained on fovea.
  
  Section::::Physiology.:Saccades.
   Using an fMRI, Roger B. H. Tootel "et al." were able to identify the area of the brain that is active when experiencing illusory motion. Tootel and his colleagues had participants view a set of concentric rings that appeared to move inward and outward. Participants would experience a motion aftereffect after viewing the moving stimuli for 40 seconds. Participants showed an increased activity in the MT area of the brain.
  
  Section::::Occurrences.
  
  Theoretical example with the Illusion of motion: "It appears that the sky is falling, while the reality is that the ocean is rising."
  
  Illusory motion can occur in different circumstances.
   Section::::Neurophysiology.
  
  Motion sensing using vision is crucial for detecting a potential mate, prey, or predator, and thus it is found both in vertebrates and invertebrates vision throughout a wide variety of species, although it is not universally found in all species. In vertebrates, the process takes place in retina and more specifically in retinal ganglion cells, which are neurons that receive input from bipolar cells and amacrine cells on visual information and process output to higher regions of the brain including, thalamus, hypothalamus, and mesencephalon.
   Section::::Types.:Motion seen but not felt.
  
  In these cases, motion is detected by the visual system and hence the motion is seen, but no motion or little motion is sensed by the vestibular system. Motion sickness arising from such situations has been referred to as "visually induced motion sickness" (VIMS).
  
  Section::::Types.:Motion seen but not felt.:Space motion sickness.
   Section::::Posture, movement, and locomotions.
   BULLET::::- A non-conscious reaction is seen in the human proprioceptive reflex, or righting reflex—in the event that the body tilts in any direction, the person will cock their head back to level the eyes against the horizon. This is seen even in infants as soon as they gain control of their neck muscles. This control comes from the cerebellum, the part of the brain affecting balance.
  
  Section::::Mechanisms.
  
presuppositions: When a person moves their head whilst looking at the sky, the sky moves along with the viewer. 
corrections: The sky is not moving with the viewer, but the brain perceives the sky as if it is moving with the viewer.
raw_presuppositions: When a person moves their head whilst looking at the sky, the sky moves along with the viewer.  The sky moves with us when we move our head around.
raw_corrections: The sky is not moving with the viewer, but the brain perceives the sky as if it is moving with the viewer. Our brain tricks us into thinking the sky moves with us when we move our head around.