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In physics, motion is when an object changes its position with respect to a reference point in a given time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and frame of reference to an observer, measuring the change in position of the body relative to that frame with a change in time. The branch of physics describing the motion of objects without reference to their cause is called kinematics, while the branch studying forces and their effect on motion is called dynamics.

If an object is not in motion relative to a given frame of reference, it is said to be at rest, motionless, immobile, stationary, or to have a constant or time-invariant position with reference to its surroundings. Modern physics holds that, as there is no absolute frame of reference, Newton's concept of absolute motion cannot be determined.^[1] Everything in the universe can be considered to be in motion.^[2]^: 20–21

Motion applies to various physical systems: objects, bodies, matter particles, matter fields, radiation, radiation fields, radiation particles, curvature, and space-time. One can also speak of the motion of images, shapes, and boundaries. In general, the term motion signifies a continuous change in the position or configuration of a physical system in space. For example, one can talk about the motion of a wave or the motion of a quantum particle, where the configuration consists of the probabilities of the wave or particle occupying specific positions.

Equations of motion

In physics, equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time.^[3] More specifically, the equations of motion describe the behavior of a physical system as a set of mathematical functions in terms of dynamic variables. These variables are usually spatial coordinates and time, but may include momentum components. The most general choice are generalized coordinates which can be any convenient variables characteristic of the physical system.^[4] The functions are defined in a Euclidean space in classical mechanics, but are replaced by curved spaces in relativity. If the dynamics of a system is known, the equations are the solutions for the differential equations describing the motion of the dynamics.

Laws of motion

In physics, the motion of massive bodies is described through two related sets of laws of mechanics. Classical mechanics for super atomic (larger than an atom) objects (such as cars, projectiles, planets, cells, and humans) and quantum mechanics for atomic and sub-atomic objects (such as helium, protons, and electrons). Historically, Newton and Euler formulated three laws of classical mechanics:

First law:	In an inertial reference frame, an object either remains at rest or continues to move in a straight line at a constant velocity, unless acted upon by a net force.
Second law:	In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object: ${\vec {F}}=m{\vec {a}}$ . If the resultant force ${\vec {F}}$ acting on a body or an object is not equal to zero, the body will have an acceleration $a$ that is in the same direction as the resultant force.
Third law:	When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction onto the first body.

Classical mechanics

Classical mechanics is used for describing the motion of macroscopic objects moving at speeds significantly slower than the speed of light, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. It produces very accurate results within these domains and is one of the oldest and largest scientific descriptions in science, engineering, and technology.

Classical mechanics is fundamentally based on Newton's laws of motion. These laws describe the relationship between the forces acting on a body and the motion of that body. They were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, which was first published on July 5, 1687. Newton's three laws are:

A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force. (This is known as the law of inertia.)
Force ( ${\vec {F}}$ ) is equal to the change in momentum per change in time ( ${\frac {\Delta m{\vec {v}}}{\Delta t}}$ ). For a constant mass, force equals mass times acceleration ( ${\vec {F}}=m{\vec {a}}$ ).
For every action, there is an equal and opposite reaction. (In other words, whenever one body exerts a force ${\vec {F}}$ onto a second body, (in some cases, which is standing still) the second body exerts the force $-{\vec {F}}$ back onto the first body. ${\vec {F}}$ and $-{\vec {F}}$ are equal in magnitude and opposite in direction. So, the body that exerts ${\vec {F}}$ will be pushed backward.)^[5]

Newton's three laws of motion were the first to accurately provide a mathematical model for understanding orbiting bodies in outer space. This explanation unified the motion of celestial bodies and the motion of objects on Earth.

Relativistic mechanics

Modern kinematics developed with study of electromagnetism and refers all velocities $v$ to their ratio to speed of light $c$ . Velocity is then interpreted as rapidity, the hyperbolic angle $\varphi$ for which the hyperbolic tangent function $\tanh \varphi =v\div c$ . Acceleration, the change of velocity over time, then changes rapidity according to Lorentz transformations. This part of mechanics is special relativity. Efforts to incorporate gravity into relativistic mechanics were made by W. K. Clifford and Albert Einstein. The development used differential geometry to describe a curved universe with gravity; the study is called general relativity.

Quantum mechanics

Quantum mechanics is a set of principles describing physical reality at the atomic level of matter (molecules and atoms) and the subatomic particles (electrons, protons, neutrons, and even smaller elementary particles such as quarks). These descriptions include the simultaneous wave-like and particle-like behavior of both matter and radiation energy as described in the wave–particle duality.^[6]

In classical mechanics, accurate measurements and predictions of the state of objects can be calculated, such as location and velocity. In quantum mechanics, due to the Heisenberg uncertainty principle, the complete state of a subatomic particle, such as its location and velocity, cannot be simultaneously determined.^[7]

In addition to describing the motion of atomic level phenomena, quantum mechanics is useful in understanding some large-scale phenomena such as superfluidity, superconductivity, and biological systems, including the function of smell receptors and the structures of protein.^[8]

Orders of magnitude

Humans, like all known things in the universe, are in constant motion;^[2]^: 8–9 however, aside from obvious movements of the various external body parts and locomotion, humans are in motion in a variety of ways that are more difficult to perceive. Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation. The larger scales of imperceptible motions are difficult for humans to perceive for two reasons: Newton's laws of motion (particularly the third), which prevents the feeling of motion on a mass to which the observer is connected, and the lack of an obvious frame of reference that would allow individuals to easily see that they are moving.^[9] The smaller scales of these motions are too small to be detected conventionally with human senses.

Universe

Spacetime (the fabric of the universe) is expanding, meaning everything in the universe is stretching, like a rubber band. This motion is the most obscure as it is not physical motion, but rather a change in the very nature of the universe. The primary source of verification of this expansion was provided by Edwin Hubble who demonstrated that all galaxies and distant astronomical objects were moving away from Earth, known as Hubble's law, predicted by a universal expansion.^[10]

Galaxy

The Milky Way Galaxy is moving through space and many astronomers believe the velocity of this motion to be approximately 600 kilometres per second (1,340,000 mph) 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 582 kilometres per second (1,300,000 mph).^[11]^{[failed verification]}

Sun and Solar System

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 210 and 240 kilometres per second (470,000 and 540,000 mph).^[12] All planets and their moons move with the Sun. Thus, the Solar System is in motion.

Earth

The Earth is rotating or spinning around its axis. This is evidenced by day and night, at the equator the earth has an eastward velocity of 0.4651 kilometres per second (1,040 mph).^[13] The Earth is also orbiting around the Sun in an orbital revolution. A complete orbit around the Sun takes one year, or about 365 days; it averages a speed of about 30 kilometres per second (67,000 mph).^[14]

Continents

The Theory of Plate tectonics tells us that the continents are drifting on convection currents within the mantle, causing them to move across the surface of the planet at the slow speed of approximately 2.54 centimetres (1 in) per year.^[15]^[16] However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the Cocos Plate advancing at a rate of 75 millimetres (3.0 in) per year^[17] and the Pacific Plate moving 52–69 millimetres (2.0–2.7 in) per year. At the other extreme, the slowest-moving plate is the Eurasian Plate, progressing at a typical rate of about 21 millimetres (0.83 in) per year.

Internal body

The human heart is regularly contracting to move blood throughout the body. Through larger veins and arteries in the body, blood has been found to travel at approximately 0.33 m/s. Though considerable variation exists, and peak flows in the venae cavae have been found between 0.1 and 0.45 metres per second (0.33 and 1.48 ft/s).^[18] additionally, the smooth muscles of hollow internal organs are moving. The most familiar would be the occurrence of peristalsis, which is where digested food is forced throughout the digestive tract. Though different foods travel through the body at different rates, an average speed through the human small intestine is 3.48 kilometres per hour (2.16 mph).^[19] The human lymphatic system is also constantly causing movements of excess fluids, lipids, and immune system related products around the body. The lymph fluid has been found to move through a lymph capillary of the skin at approximately 0.0000097 m/s.^[20]

Cells

The cells of the human body have many structures and organelles that move throughout them. Cytoplasmic streaming is a way in which cells move molecular substances throughout the cytoplasm,^[21] various motor proteins work as molecular motors within a cell and move along the surface of various cellular substrates such as microtubules, and motor proteins are typically powered by the hydrolysis of adenosine triphosphate (ATP), and convert chemical energy into mechanical work.^[22] Vesicles propelled by motor proteins have been found to have a velocity of approximately 0.00000152 m/s.^[23]

Particles

According to the laws of thermodynamics, all particles of matter are in constant random motion as long as the temperature is above absolute zero. Thus the molecules and atoms that make up the human body are vibrating, colliding, and moving. This motion can be detected as temperature; higher temperatures, which represent greater kinetic energy in the particles, feel warm to humans who sense the thermal energy transferring from the object being touched to their nerves. Similarly, when lower temperature objects are touched, the senses perceive the transfer of heat away from the body as a feeling of cold.^[24]

Subatomic particles

Within the standard atomic orbital model, electrons exist in a region around the nucleus of each atom. This region is called the electron cloud. According to Bohr's model of the atom, electrons have a high velocity, and the larger the nucleus they are orbiting the faster they would need to move. If electrons were to move about the electron cloud in strict paths the same way planets orbit the Sun, then electrons would be required to do so at speeds that would far exceed the speed of light. However, there is no reason that one must confine oneself to this strict conceptualization (that electrons move in paths the same way macroscopic objects do), rather one can conceptualize electrons to be 'particles' that capriciously exist within the bounds of the electron cloud.^[25] Inside the atomic nucleus, the protons and neutrons are also probably moving around due to the electrical repulsion of the protons and the presence of angular momentum of both particles.^[26]

Light

Light moves at a speed of 299,792,458 m/s, or 299,792.458 kilometres per second (186,282.397 mi/s), in a vacuum. The speed of light in vacuum (or $c$ ) is also the speed of all massless particles and associated fields in a vacuum, and it is the upper limit on the speed at which energy, matter, information or causation can travel. The speed of light in vacuum is thus the upper limit for speed for all physical systems.

In addition, the speed of light is an invariant quantity: it has the same value, irrespective of the position or speed of the observer. This property makes the speed of light c a natural measurement unit for speed and a fundamental constant of nature.

In 2019, the speed of light was redefined alongside all seven SI base units using what it calls "the explicit-constant formulation", where each "unit is defined indirectly by specifying explicitly an exact value for a well-recognized fundamental constant", as was done for the speed of light. A new, but completely equivalent, wording of the metre's definition was proposed: "The metre, symbol m, is the unit of length; its magnitude is set by fixing the numerical value of the speed of light in vacuum to be equal to exactly 299792458 when it is expressed in the SI unit m s⁻¹."^[27] This implicit change to the speed of light was one of the changes that was incorporated in the 2019 revision of the SI, also termed the New SI.^[28]

Superluminal motion

Some motion appears to an observer to exceed the speed of light. Bursts of energy moving out along the relativistic jets emitted from these objects can have a proper motion that appears greater than the speed of light. All of these sources are thought to contain a black hole, responsible for the ejection of mass at high velocities. Light echoes can also produce apparent superluminal motion.^[29] This occurs owing to how motion is often calculated at long distances; oftentimes calculations fail to account for the fact that the speed of light is finite. When measuring the movement of distant objects across the sky, there is a large time delay between what has been observed and what has occurred, due to the large distance the light from the distant object has to travel to reach us. The error in the above naive calculation comes from the fact that when an object has a component of velocity directed towards the Earth, as the object moves closer to the Earth that time delay becomes smaller. This means that the apparent speed as calculated above is greater than the actual speed. Correspondingly, if the object is moving away from the Earth, the above calculation underestimates the actual speed.^[30]

Types of motion

Simple harmonic motion – motion in which the body oscillates in such a way that the restoring force acting on it is directly proportional to the body's displacement. Mathematically Force is directly proportional to the negative of displacement. Negative sign signifies the restoring nature of the force. (e.g., that of a pendulum).
Linear motion – motion that follows a straight linear path, and whose displacement is exactly the same as its trajectory. [Also known as rectilinear motion]
Reciprocal motion
Brownian motion – the random movement of very small particles
Circular motion
Rotatory motion – a motion about a fixed point. (e.g. Ferris wheel).
Curvilinear motion – It is defined as the motion along a curved path that may be planar or in three dimensions.
Rolling motion – (as of the wheel of a bicycle)
Oscillatory – (swinging from side to side)
Vibratory motion
Combination (or simultaneous) motions – Combination of two or more above listed motions
Projectile motion – uniform horizontal motion + vertical accelerated motion

Fundamental motions

References

^ Wahlin, Lars (1997). "9.1 Relative and absolute motion" (PDF). The Deadbeat Universe. Boulder, CO: Coultron Research. pp. 121–129. ISBN 978-0-933407-03-9. Archived (PDF) from the original on 2016-03-04. Retrieved 25 January 2013.
^ ^a ^b Tyson, Neil de Grasse; Charles Tsun-Chu Liu; Robert Irion (2000). One Universe : at home in the cosmos. Washington, DC: National Academy Press. ISBN 978-0-309-06488-0.
^ R.G. Lerner; George L. Trigg (1991). Encyclopedia of Physics (second ed.). New York: VCH Publishers. ISBN 0-89573-752-3. OCLC 20853637.
^ Hand, Louis N.; Janet D. Finch (1998). Analytical Mechanics. Cambridge: Cambridge University Press. ISBN 978-0-521-57572-0. OCLC 37903527.
^ Newton's "Axioms or Laws of Motion" can be found in the "Principia" on p. 19 of volume 1 of the 1729 translation Archived 2015-09-28 at the Wayback Machine.
^ "The Feynman Lectures on Physics Vol. I Ch. 38: The Relation of Wave and Particle Viewpoints". Archived from the original on 2022-08-14. Retrieved 2022-05-03.
^ "Understanding the Heisenberg Uncertainty Principle". ThoughtCo. Archived from the original on 2022-05-10. Retrieved 2022-05-10.
^ Folger, Tim (October 23, 2018). "How Quantum Mechanics Lets Us See, Smell and Touch: How the science of the super small affects our everyday lives". Discovery Magazine. Archived from the original on January 26, 2021. Retrieved October 24, 2021.
^ Safkan, Yasar. "Question: If the term 'absolute motion' has no meaning, then why do we say that the earth moves around the sun and not vice versa?". Ask the Experts. PhysLink.com. Archived from the original on 3 November 2013. Retrieved 25 January 2014.
^ Hubble, Edwin (1929-03-15). "A relation between distance and radial velocity among extra-galactic nebulae". Proceedings of the National Academy of Sciences. 15 (3): 168–173. Bibcode:1929PNAS...15..168H. doi:10.1073/pnas.15.3.168. PMC 522427. PMID 16577160.
^ Kogut, A.; Lineweaver, C.; Smoot, G.F.; Bennett, C.L.; Banday, A.; Boggess, N.W.; Cheng, E.S.; de Amici, G.; Fixsen, D.J.; Hinshaw, G.; Jackson, P.D.; Janssen, M.; Keegstra, P.; Loewenstein, K.; Lubin, P.; Mather, J.C.; Tenorio, L.; Weiss, R.; Wilkinson, D.T.; Wright, E.L. (1993). "Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps". Astrophysical Journal. 419: 1. arXiv:astro-ph/9312056. Bibcode:1993ApJ...419....1K. doi:10.1086/173453. S2CID 209835274.
^ Imamura, Jim (August 10, 2006). "Mass of the Milky Way Galaxy". University of Oregon. Archived from the original on 2007-03-01. Retrieved 2007-05-10.
^ Ask an Astrophysicist Archived 2009-03-11 at the Wayback Machine. NASA Goodard Space Flight Center.
^ Williams, David R. (September 1, 2004). "Earth Fact Sheet". NASA. Archived from the original on 2013-05-08. Retrieved 2007-03-17.
^ Staff. "GPS Time Series". NASA JPL. Archived from the original on 2011-07-21. Retrieved 2007-04-02.
^ Huang, Zhen Shao (2001). Elert, Glenn (ed.). "Speed of the Continental Plates". The Physics Factbook. Archived from the original on 2020-06-19. Retrieved 2020-06-20.
^ Meschede, M.; Udo Barckhausen, U. (November 20, 2000). "Plate Tectonic Evolution of the Cocos-Nazca Spreading Center". Proceedings of the Ocean Drilling Program. Texas A&M University. Archived from the original on 2011-08-08. Retrieved 2007-04-02.
^ Wexler, L.; D H Bergel; I T Gabe; G S Makin; C J Mills (1 September 1968). "Velocity of Blood Flow in Normal Human Venae Cavae". Circulation Research. 23 (3): 349–359. doi:10.1161/01.RES.23.3.349. PMID 5676450.
^ Bowen, R (27 May 2006). "Gastrointestinal Transit: How Long Does It Take?". Pathophysiology of the digestive system. Colorado State University. Archived from the original on 3 April 2015. Retrieved 25 January 2014.
^ M. Fischer; U.K. Franzeck; I. Herrig; U. Costanzo; S. Wen; M. Schiesser; U. Hoffmann; A. Bollinger (1 January 1996). "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiol. 270 (1): H358–H363. doi:10.1152/ajpheart.1996.270.1.H358. PMID 8769772.
^ "cytoplasmic streaming – biology". Encyclopædia Britannica. Archived from the original on 2008-06-11. Retrieved 2022-06-23.
^ "Microtubule Motors". rpi.edu. Archived from the original on 2007-11-30.
^ Hill, David; Holzwarth, George; Bonin, Keith (2002). "Velocity and Drag Forces on motor-protein-driven Vesicles in Cells". APS Southeastern Section Meeting Abstracts. 69: EA.002. Bibcode:2002APS..SES.EA002H.
^ Temperature and BEC. Archived 2007-11-10 at the Wayback Machine Physics 2000: Colorado State University Physics Department
^ "Classroom Resources". anl.gov. Argonne National Laboratory. Archived from the original on 2010-06-08. Retrieved 2009-03-09.
^ "Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory" (PDF). Archived (PDF) from the original on 2009-03-04. Retrieved 2009-03-09.
^ "The "explicit-constant" formulation". BIPM. 2011. Archived from the original on 11 August 2014.
^
See, for example:
- Conover, Emily (2 November 2016). "Units of measure are getting a fundamental upgrade". Science News. Archived from the original on 6 February 2022. Retrieved 6 February 2022.
- Knotts, Sandra; Mohr, Peter J.; Phillips, William D. (January 2017). "An Introduction to the New SI". The Physics Teacher. 55 (1): 16–21. Bibcode:2017PhTea..55...16K. doi:10.1119/1.4972491. ISSN 0031-921X. S2CID 117581000. Archived from the original on 2023-09-25. Retrieved 2022-08-20.
- "SI Redefinition". National Institute of Standards and Technology. 11 May 2018. Archived from the original on 6 February 2022. Retrieved 6 February 2022.
^ Bond, H. E.; et al. (2003). "An energetic stellar outburst accompanied by circumstellar light echoes". Nature. 422 (6930): 405–408. arXiv:astro-ph/0303513. Bibcode:2003Natur.422..405B. doi:10.1038/nature01508. PMID 12660776. S2CID 90973.
^ Meyer, Eileen (June 2018). "Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84". The Astrophysical Journal. 680 (1): 9. arXiv:1804.05122. Bibcode:2018ApJ...860....9M. doi:10.3847/1538-4357/aabf39. S2CID 67822924.

External links

Feynman's lecture on motion
Media related to Motion at Wikimedia Commons

[1] Wahlin, Lars (1997). "9.1 Relative and absolute motion" (PDF). The Deadbeat Universe. Boulder, CO: Coultron Research. pp. 121–129. ISBN 978-0-933407-03-9. Archived (PDF) from the original on 2016-03-04. Retrieved 25 January 2013.

[Tyson-2] Tyson, Neil de Grasse; Charles Tsun-Chu Liu; Robert Irion (2000). One Universe : at home in the cosmos. Washington, DC: National Academy Press. ISBN 978-0-309-06488-0.

[Equations_of_motion_Physics_1991-3] R.G. Lerner; George L. Trigg (1991). Encyclopedia of Physics (second ed.). New York: VCH Publishers. ISBN 0-89573-752-3. OCLC 20853637.

[Equations_of_motion_Analytical_Mechanics_2008-4] Hand, Louis N.; Janet D. Finch (1998). Analytical Mechanics. Cambridge: Cambridge University Press. ISBN 978-0-521-57572-0. OCLC 37903527.

[5] Newton's "Axioms or Laws of Motion" can be found in the "Principia" on p. 19 of volume 1 of the 1729 translation Archived 2015-09-28 at the Wayback Machine.

[6] "The Feynman Lectures on Physics Vol. I Ch. 38: The Relation of Wave and Particle Viewpoints". Archived from the original on 2022-08-14. Retrieved 2022-05-03.

[7] "Understanding the Heisenberg Uncertainty Principle". ThoughtCo. Archived from the original on 2022-05-10. Retrieved 2022-05-10.

[8] Folger, Tim (October 23, 2018). "How Quantum Mechanics Lets Us See, Smell and Touch: How the science of the super small affects our everyday lives". Discovery Magazine. Archived from the original on January 26, 2021. Retrieved October 24, 2021.

[9] Safkan, Yasar. "Question: If the term 'absolute motion' has no meaning, then why do we say that the earth moves around the sun and not vice versa?". Ask the Experts. PhysLink.com. Archived from the original on 3 November 2013. Retrieved 25 January 2014.

[10] Hubble, Edwin (1929-03-15). "A relation between distance and radial velocity among extra-galactic nebulae". Proceedings of the National Academy of Sciences. 15 (3): 168–173. Bibcode:1929PNAS...15..168H. doi:10.1073/pnas.15.3.168. PMC 522427. PMID 16577160.

[dipole-11] Kogut, A.; Lineweaver, C.; Smoot, G.F.; Bennett, C.L.; Banday, A.; Boggess, N.W.; Cheng, E.S.; de Amici, G.; Fixsen, D.J.; Hinshaw, G.; Jackson, P.D.; Janssen, M.; Keegstra, P.; Loewenstein, K.; Lubin, P.; Mather, J.C.; Tenorio, L.; Weiss, R.; Wilkinson, D.T.; Wright, E.L. (1993). "Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps". Astrophysical Journal. 419: 1. arXiv:astro-ph/9312056. Bibcode:1993ApJ...419....1K. doi:10.1086/173453. S2CID 209835274.

[fn4-12] Imamura, Jim (August 10, 2006). "Mass of the Milky Way Galaxy". University of Oregon. Archived from the original on 2007-03-01. Retrieved 2007-05-10.

[nasa_goodard-13] Ask an Astrophysicist Archived 2009-03-11 at the Wayback Machine. NASA Goodard Space Flight Center.

[earth_fact_sheet-14] Williams, David R. (September 1, 2004). "Earth Fact Sheet". NASA. Archived from the original on 2013-05-08. Retrieved 2007-03-17.

[15] Staff. "GPS Time Series". NASA JPL. Archived from the original on 2011-07-21. Retrieved 2007-04-02.

[16] Huang, Zhen Shao (2001). Elert, Glenn (ed.). "Speed of the Continental Plates". The Physics Factbook. Archived from the original on 2020-06-19. Retrieved 2020-06-20.

[17] Meschede, M.; Udo Barckhausen, U. (November 20, 2000). "Plate Tectonic Evolution of the Cocos-Nazca Spreading Center". Proceedings of the Ocean Drilling Program. Texas A&M University. Archived from the original on 2011-08-08. Retrieved 2007-04-02.

[18] Wexler, L.; D H Bergel; I T Gabe; G S Makin; C J Mills (1 September 1968). "Velocity of Blood Flow in Normal Human Venae Cavae". Circulation Research. 23 (3): 349–359. doi:10.1161/01.RES.23.3.349. PMID 5676450.

[19] Bowen, R (27 May 2006). "Gastrointestinal Transit: How Long Does It Take?". Pathophysiology of the digestive system. Colorado State University. Archived from the original on 3 April 2015. Retrieved 25 January 2014.

[20] M. Fischer; U.K. Franzeck; I. Herrig; U. Costanzo; S. Wen; M. Schiesser; U. Hoffmann; A. Bollinger (1 January 1996). "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiol. 270 (1): H358–H363. doi:10.1152/ajpheart.1996.270.1.H358. PMID 8769772.

[21] "cytoplasmic streaming – biology". Encyclopædia Britannica. Archived from the original on 2008-06-11. Retrieved 2022-06-23.

[22] "Microtubule Motors". rpi.edu. Archived from the original on 2007-11-30.

[23] Hill, David; Holzwarth, George; Bonin, Keith (2002). "Velocity and Drag Forces on motor-protein-driven Vesicles in Cells". APS Southeastern Section Meeting Abstracts. 69: EA.002. Bibcode:2002APS..SES.EA002H.

[24] Temperature and BEC. Archived 2007-11-10 at the Wayback Machine Physics 2000: Colorado State University Physics Department

[25] "Classroom Resources". anl.gov. Argonne National Laboratory. Archived from the original on 2010-06-08. Retrieved 2009-03-09.

[26] "Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory" (PDF). Archived (PDF) from the original on 2009-03-04. Retrieved 2009-03-09.

[27] "The "explicit-constant" formulation". BIPM. 2011. Archived from the original on 11 August 2014.

[28] See, for example:
Conover, Emily (2 November 2016). "Units of measure are getting a fundamental upgrade". Science News. Archived from the original on 6 February 2022. Retrieved 6 February 2022.

Knotts, Sandra; Mohr, Peter J.; Phillips, William D. (January 2017). "An Introduction to the New SI". The Physics Teacher. 55 (1): 16–21. Bibcode:2017PhTea..55...16K. doi:10.1119/1.4972491. ISSN 0031-921X. S2CID 117581000. Archived from the original on 2023-09-25. Retrieved 2022-08-20.

"SI Redefinition". National Institute of Standards and Technology. 11 May 2018. Archived from the original on 6 February 2022. Retrieved 6 February 2022.

[29] Conover, Emily (2 November 2016). "Units of measure are getting a fundamental upgrade". Science News. Archived from the original on 6 February 2022. Retrieved 6 February 2022.

[30] Knotts, Sandra; Mohr, Peter J.; Phillips, William D. (January 2017). "An Introduction to the New SI". The Physics Teacher. 55 (1): 16–21. Bibcode:2017PhTea..55...16K. doi:10.1119/1.4972491. ISSN 0031-921X. S2CID 117581000. Archived from the original on 2023-09-25. Retrieved 2022-08-20.

[31] "SI Redefinition". National Institute of Standards and Technology. 11 May 2018. Archived from the original on 6 February 2022. Retrieved 6 February 2022.

[29] Bond, H. E.; et al. (2003). "An energetic stellar outburst accompanied by circumstellar light echoes". Nature. 422 (6930): 405–408. arXiv:astro-ph/0303513. Bibcode:2003Natur.422..405B. doi:10.1038/nature01508. PMID 12660776. S2CID 90973.

[30] Meyer, Eileen (June 2018). "Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84". The Astrophysical Journal. 680 (1): 9. arXiv:1804.05122. Bibcode:2018ApJ...860....9M. doi:10.3847/1538-4357/aabf39. S2CID 67822924.

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@@ Line 1: / Line 1: @@
-{{Short description|Change in position of an object}}
+{{Short description|Change in the position of an object}}
 {{Other uses|Motion (disambiguation)}}
+[[File:Porsche race car Verschuur amk.jpg|thumb|300x300px|A [[car]] is moving in high [[speed]] during a [[championship]], with respect to the ground the [[Position (geometry)|position]] is changing according to [[time]] hence the car is in relative motion ]]
-[[File:Motor cycle stunt2 amk.jpg|thumb|A motorcyclist doing a [[wheelie]], representing motion|300x300px]]
-In [[physics]], '''motion''' is the [[phenomenon]] in which an object changes its [[Position (geometry)|position]] with respect to [[time]]. Motion is mathematically described in terms of [[Displacement (geometry)|displacement]], [[distance]], [[velocity]], [[acceleration]], [[speed]] and [[frame of reference]] to an observer and measuring the change in position of the body relative to that frame with change in time. The branch of physics describing the motion of objects without reference to its cause is called [[kinematics]], while the branch studying [[force]]<nowiki/>s and their effect on motion is called [[dynamics (mechanics)|dynamics]].
+In [[physics]], '''motion''' is when an object changes its [[Position (geometry)|position]] with respect to a reference point in a given [[time]]. Motion is mathematically described in terms of [[Displacement (geometry)|displacement]], [[distance]], [[velocity]], [[acceleration]], [[speed]], and [[frame of reference]] to an observer, measuring the change in position of the body relative to that frame with a change in time. The branch of physics describing the motion of objects without reference to their cause is called [[kinematics]], while the branch studying [[force]]s and their effect on motion is called [[dynamics (mechanics)|dynamics]].
-If an object is not changing relative to a given frame of reference, the object is said to be ''at rest'', ''motionless'', ''immobile'', ''[[wikt:stationary|stationary]]'', or to have a constant or [[time-invariant]] position with reference to its surroundings. Modern physics holds that, as there is no absolute frame of reference, [[Isaac Newton|Newton's]] concept of ''[[Absolute space and time|absolute motion]]'' cannot be determined.<ref>{{cite book|last=Wahlin|first=Lars|chapter=9.1 Relative and absolute motion|title=The Deadbeat Universe|year=1997|publisher=Coultron Research|location=Boulder, CO|isbn=978-0-933407-03-9|pages=121–129|chapter-url=http://www.colutron.com/download_files/chapt9.pdf|access-date=25 January 2013|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304090354/http://www.colutron.com/download_files/chapt9.pdf|url-status=live}}</ref> As such, everything in the universe can be considered to be in motion.<ref name="Tyson">{{cite book|last=Tyson|first=Neil de Grasse|url=https://archive.org/details/oneuniverse00neil|title=One Universe : at home in the cosmos|author2=Charles Tsun-Chu Liu|author2-link=Charles Tsun-Chu Liu|author3=Robert Irion|publisher=[[National Academy Press]]|year=2000|isbn=978-0-309-06488-0|location=Washington, DC|url-access=registration}}</ref>{{rp|20–21}}
+If an object is not in motion relative to a given frame of reference, it is said to be ''at rest'', ''motionless'', ''immobile'', ''[[wikt:stationary|stationary]]'', or to have a constant or [[time-invariant]] position with reference to its surroundings. Modern physics holds that, as there is no absolute frame of reference, [[Isaac Newton|Newton]]'s concept of ''[[Absolute space and time|absolute motion]]'' cannot be determined.<ref>{{cite book|last=Wahlin|first=Lars|chapter=9.1 Relative and absolute motion|title=The Deadbeat Universe|year=1997|publisher=Coultron Research|location=Boulder, CO|isbn=978-0-933407-03-9|pages=121–129|chapter-url=http://www.colutron.com/download_files/chapt9.pdf|access-date=25 January 2013|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304090354/http://www.colutron.com/download_files/chapt9.pdf|url-status=live}}</ref> Everything in the universe can be considered to be in motion.<ref name="Tyson">{{cite book|last=Tyson|first=Neil de Grasse|url=https://archive.org/details/oneuniverse00neil|title=One Universe : at home in the cosmos|author2=Charles Tsun-Chu Liu|author2-link=Charles Tsun-Chu Liu|author3=Robert Irion|publisher=[[National Academy Press]]|year=2000|isbn=978-0-309-06488-0|location=Washington, DC|url-access=registration}}</ref>{{rp|20–21}}
-Motion applies to various physical systems: objects, bodies, matter particles, matter fields, [[radiation]], radiation fields, radiation particles, [[curvature]], and [[Spacetime|space-time]]. One can also speak on the motion of images, shapes, and boundaries. In general, the term motion signifies a continuous change in the positions or configuration of a physical system in space. For example, one can talk about the motion of a wave or the motion of a [[quantum]] particle, where the configuration consists of probabilities of the wave or particle occupying specific positions.
+Motion applies to various physical systems: objects, bodies, [[matter]] [[Particle|particles]], matter fields, [[radiation]], radiation fields, radiation particles, [[curvature]], and [[Spacetime|space-time]]. One can also speak of the motion of images, shapes, and boundaries. In general, the term motion signifies a continuous change in the position or configuration of a physical system in space. For example, one can talk about the motion of a wave or the motion of a [[quantum]] particle, where the configuration consists of the probabilities of the wave or particle occupying specific positions.
 == Equations of motion ==
@@ Line 19: / Line 19: @@
 |Second law:
 |In an [[inertial reference frame]], the vector [[Vector sum|sum]] of the [[forces]] F on an object is equal to the [[mass]] ''m'' of that object multiplied by the [[acceleration]] a of the object: <math>\vec{F} = m\vec{a} </math>.
-If the resultant force <math>\vec{F}</math> acting on a body or an object is not equal to zero, the body will have an acceleration <math>a</math> which is in the same direction as the resultant force.
+If the resultant force <math>\vec{F}</math> acting on a body or an object is not equal to zero, the body will have an acceleration <math>a</math> that is in the same direction as the resultant force.
 |-
 |Third law:
-|When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
+|When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction onto the first body.
 |}
@@ Line 32: / Line 32: @@
 # A [[Physical body|body]] at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force. (This is known as the law of [[inertia]].)
 # Force (<math>\vec{F}</math>) is equal to the change in momentum per change in time (<math> \frac{\Delta m\vec{v}}{\Delta t}</math>). For a constant mass, force equals mass times acceleration (<math>\vec{F} = m\vec{a} </math> ).
-# For every action, there is an equal and opposite reaction. (In other words, whenever one body exerts a force <math>\vec{F}</math> onto a second body, (in some cases, which is standing still) the second body exerts the force <math>-\vec{F}</math> back onto the first body. <math>\vec{F}</math> and <math>-\vec{F}</math> are equal in magnitude and opposite in direction. So, the body which exerts <math>\vec{F}</math> will be pushed backward.)<ref>Newton's "Axioms or Laws of Motion" can be found in the "[[Mathematical Principles of Natural Philosophy|Principia]]" on [https://books.google.com/books?id=Tm0FAAAAQAAJ&pg=PA19#v=onepage&q=&f=false p. 19 of volume 1 of the 1729 translation] {{Webarchive|url=https://web.archive.org/web/20150928021402/https://books.google.com/books?id=Tm0FAAAAQAAJ&pg=PA19#v=onepage&q=&f=false |date=2015-09-28 }}.</ref>
+# For every action, there is an equal and opposite reaction. (In other words, whenever one body exerts a force <math>\vec{F}</math> onto a second body, (in some cases, which is standing still) the second body exerts the force <math>-\vec{F}</math> back onto the first body. <math>\vec{F}</math> and <math>-\vec{F}</math> are equal in magnitude and opposite in direction. So, the body that exerts <math>\vec{F}</math> will be pushed backward.)<ref>Newton's "Axioms or Laws of Motion" can be found in the "[[Mathematical Principles of Natural Philosophy|Principia]]" on [https://books.google.com/books?id=Tm0FAAAAQAAJ&pg=PA19 p. 19 of volume 1 of the 1729 translation] {{Webarchive|url=https://web.archive.org/web/20150928021402/https://books.google.com/books?id=Tm0FAAAAQAAJ&pg=PA19 |date=2015-09-28 }}.</ref>
 Newton's three laws of motion were the first to accurately provide a mathematical model for understanding [[orbit]]ing bodies in [[outer space]]. This explanation unified the motion of celestial bodies and the motion of objects on Earth.
@@ Line 47: / Line 47: @@
 == Orders of magnitude ==
-Humans, like all known things in the universe, are in constant motion;<ref name=Tyson />{{rp|8–9}} however, aside from obvious movements of the various external [[anatomy|body]] parts and [[animal locomotion|locomotion]], humans are in motion in a variety of ways which are more difficult to [[Motion perception|perceive]].  Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation. The larger scales of imperceptible motions are difficult for humans to perceive for two reasons: [[Newton's laws of motion]] (particularly the third) which prevents the feeling of motion on a mass to which the observer is connected, and the lack of an obvious [[frame of reference]] which would allow individuals to easily see that they are moving.<ref>{{cite web|last=Safkan|first=Yasar|title=Question: If the term 'absolute motion' has no meaning, then why do we say that the earth moves around the sun and not vice versa?|url=http://www.physlink.com/education/askexperts/ae118.cfm|work=Ask the Experts|publisher=PhysLink.com|access-date=25 January 2014|archive-date=3 November 2013|archive-url=https://web.archive.org/web/20131103182340/http://physlink.com/Education/AskExperts/ae118.cfm|url-status=live}}</ref> The smaller scales of these motions are too small to be detected conventionally with human [[sense]]s.
+Humans, like all known things in the universe, are in constant motion;<ref name=Tyson />{{rp|8–9}} however, aside from obvious movements of the various external [[anatomy|body]] parts and [[animal locomotion|locomotion]], humans are in motion in a variety of ways that are more difficult to [[Motion perception|perceive]]. Many of these "imperceptible motions" are only perceivable with the help of special tools and careful observation. The larger scales of imperceptible motions are difficult for humans to perceive for two reasons: [[Newton's laws of motion]] (particularly the third), which prevents the feeling of motion on a mass to which the observer is connected, and the lack of an obvious [[frame of reference]] that would allow individuals to easily see that they are moving.<ref>{{cite web|last=Safkan|first=Yasar|title=Question: If the term 'absolute motion' has no meaning, then why do we say that the earth moves around the sun and not vice versa?|url=http://www.physlink.com/education/askexperts/ae118.cfm|work=Ask the Experts|publisher=PhysLink.com|access-date=25 January 2014|archive-date=3 November 2013|archive-url=https://web.archive.org/web/20131103182340/http://physlink.com/Education/AskExperts/ae118.cfm|url-status=live}}</ref> The smaller scales of these motions are too small to be detected conventionally with human [[sense]]s.
 === Universe ===
@@ Line 53: / Line 53: @@
 === Galaxy ===
-The [[Milky Way Galaxy]] is moving through [[space]] and many astronomers believe the velocity of this motion to be approximately {{convert|600|km/s|mph|sigfig=3}} 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 {{convert|582|km/s|mph|sigfig=3}}.<ref name="dipole">{{cite journal
+The [[Milky Way Galaxy]] is moving through [[space]] and many astronomers believe the velocity of this motion to be approximately {{convert|600|km/s|mph|sigfig=3}} 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 {{convert|582|km/s|mph|sigfig=3}}.<ref name="dipole">
+{{cite journal
- |author1=Kogut, A. |author2=Lineweaver, C. |author3=Smoot, G.F. |author4=Bennett, C.L. |author5=Banday, A. |author6=Boggess, N.W. |author7=Cheng, E.S. |author8=de Amici, G. |author9=Fixsen, D.J. |author10=Hinshaw, G. |author11=Jackson, P.D. |author12=Janssen, M. |author13=Keegstra, P. |author14=Loewenstein, K. |author15=Lubin, P. |author16=Mather, J.C. |author17=Tenorio, L. |author18=Weiss, R. |author19=Wilkinson, D.T. |author20=Wright, E.L. | title=Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps
+ |author1=Kogut, A. |author2=Lineweaver, C. |author3=Smoot, G.F. |author4=Bennett, C.L. |author5=Banday, A. |author6=Boggess, N.W. |author-link6=Nancy Boggess|author7=Cheng, E.S. |author8=de Amici, G. |author9=Fixsen, D.J. |author10=Hinshaw, G. |author11=Jackson, P.D. |author12=Janssen, M. |author13=Keegstra, P. |author14=Loewenstein, K. |author15=Lubin, P. |author16=Mather, J.C. |author17=Tenorio, L. |author18=Weiss, R. |author19=Wilkinson, D.T. |author20=Wright, E.L.
+ | title=Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps
  | journal=Astrophysical Journal
  | year=1993
@@ Line 60: / Line 62: @@
  | page=1
  | bibcode=1993ApJ...419....1K  | doi = 10.1086/173453
-|arxiv = astro-ph/9312056 |s2cid=209835274 }}</ref>{{Failed verification|date=August 2016}}
+ |arxiv = astro-ph/9312056 |s2cid=209835274 }}</ref>{{Failed verification|date=August 2016
+}}
 === Sun and Solar System ===
 {{See also|Planetary motion}}
-The Milky Way is [[rotation|rotating]] around its [[density|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 {{convert|210|and|240|km/s|mph}}.<ref name="fn4">{{cite web
+The Milky Way is [[rotation|rotating]] around its [[density|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 {{convert|210|and|240|km/s|mph}}.<ref name="fn4">
+{{cite web
  | last=Imamura
  | first=Jim
@@ Line 71: / Line 75: @@
  | title=Mass of the Milky Way Galaxy
  | publisher=[[University of Oregon]]
- | access-date=2007-05-10 |archive-url = https://web.archive.org/web/20070301055338/http://zebu.uoregon.edu/~imamura/123/lecture-2/mass.html <!-- Bot retrieved archive --> |archive-date = 2007-03-01}}</ref> All planets and their moons move with the Sun. Thus, the [[Solar System]] is in motion.
+ | access-date=2007-05-10 |archive-url = https://web.archive.org/web/20070301055338/http://zebu.uoregon.edu/~imamura/123/lecture-2/mass.html <!-- Bot retrieved archive --> |archive-date = 2007-03-01
+}}</ref> All planets and their moons move with the Sun. Thus, the [[Solar System]] is in motion.
 === Earth ===
-The Earth is [[rotation|rotating]] or spinning around its [[Axis of rotation|axis]]. This is evidenced by [[day]] and [[night]], at the equator the earth has an eastward velocity of {{convert|0.4651|km/s|mph}}.<ref name="nasa goodard">[http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html Ask an Astrophysicist] {{Webarchive|url=https://web.archive.org/web/20090311000016/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html |date=2009-03-11 }}. NASA Goodard Space Flight Center.</ref> The Earth is also [[orbit]]ing around the [[Sun]] in an [[orbital revolution]]. A complete orbit around the sun takes one [[year]], or about 365&nbsp;days; it averages a speed of about {{convert|30|km/s|mph}}.<ref name="earth_fact_sheet">{{cite web | last = Williams | first = David R. | date = September 1, 2004 | url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html | title = Earth Fact Sheet | publisher = [[NASA]] | access-date = 2007-03-17 | archive-date = 2013-05-08 | archive-url = https://web.archive.org/web/20130508021904/http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html | url-status = live }}</ref>
+The Earth is [[rotation|rotating]] or spinning around its [[Axis of rotation|axis]]. This is evidenced by [[day]] and [[night]], at the equator the earth has an eastward velocity of {{convert|0.4651|km/s|mph}}.<ref name="nasa goodard">[http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html Ask an Astrophysicist] {{Webarchive|url=https://web.archive.org/web/20090311000016/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html |date=2009-03-11 }}. NASA Goodard Space Flight Center.</ref> The Earth is also [[orbit]]ing around the [[Sun]] in an [[orbital revolution]]. A complete orbit around the Sun takes one [[year]], or about 365&nbsp;days; it averages a speed of about {{convert|30|km/s|mph}}.<ref name="earth_fact_sheet">{{cite web | last = Williams | first = David R. | date = September 1, 2004 | url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html | title = Earth Fact Sheet | publisher = [[NASA]] | access-date = 2007-03-17 | archive-date = 2013-05-08 | archive-url = https://web.archive.org/web/20130508021904/http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html | url-status = live }}</ref>
 === Continents ===
-The Theory of [[Plate tectonic]]s tells us that the [[continent]]s are drifting on [[convection current]]s within the [[Mantle (geology)|mantle]], causing them to move across the surface of the [[planet]] at the slow speed of approximately {{convert|2.54|cm|in|sigfig=1}} per year.<ref>{{cite web
+The Theory of [[Plate tectonic]]s tells us that the [[continent]]s are drifting on [[convection current]]s within the [[Mantle (geology)|mantle]], causing them to move across the surface of the [[planet]] at the slow speed of approximately {{convert|2.54|cm|in|sigfig=1}} per year.<ref>
+{{cite web
  | author =Staff
  | url =http://sideshow.jpl.nasa.gov/mbh/series.html
@@ Line 86: / Line 92: @@
  | archive-url =https://web.archive.org/web/20110721050552/http://sideshow.jpl.nasa.gov/mbh/series.html
  | url-status =live
- }}</ref><ref>{{cite web
+}}</ref><ref>
+{{cite web
-| last =Huang
+ | last =Huang
-| first =Zhen Shao
+ | first =Zhen Shao
-| year =2001
+ | year =2001
-| url =http://hypertextbook.com/facts/1997/ZhenHuang.shtml
+ | url =http://hypertextbook.com/facts/1997/ZhenHuang.shtml
-| title =Speed of the Continental Plates
+ | title =Speed of the Continental Plates
-| work =The Physics Factbook
+ | work =The Physics Factbook
-| editor-first =Glenn
+ | editor-first =Glenn
-| editor-last =Elert
+ | editor-last =Elert
-| access-date =2020-06-20
+ | access-date =2020-06-20
-| archive-date =2020-06-19
+ | archive-date =2020-06-19
-| archive-url =https://web.archive.org/web/20200619200724/https://hypertextbook.com/facts/1997/ZhenHuang.shtml
+ | archive-url =https://web.archive.org/web/20200619200724/https://hypertextbook.com/facts/1997/ZhenHuang.shtml
-| url-status =live
+ | url-status =live
-}}</ref> However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the [[Cocos Plate]] advancing at a rate of {{convert|75|mm|in}} per year<ref>{{cite web
+}}</ref> However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the [[Cocos Plate]] advancing at a rate of {{convert|75|mm|in}} per year<ref>
+{{cite web
  | author1 = Meschede, M.
  | author2 = Udo Barckhausen, U.
@@ Line 111: / Line 119: @@
  | archive-url = https://web.archive.org/web/20110808174226/http://www-odp.tamu.edu/publications/170_SR/chap_07/chap_07.htm
  | url-status = live
- }}</ref> and the [[Pacific Plate]] moving {{convert|52|-|69|mm|in}} per year. At the other extreme, the slowest-moving plate is the [[Eurasian Plate]], progressing at a typical rate of about {{convert|21|mm|in}} per year.
+}}</ref> and the [[Pacific Plate]] moving {{convert|52|-|69|mm|in}} per year. At the other extreme, the slowest-moving plate is the [[Eurasian Plate]], progressing at a typical rate of about {{convert|21|mm|in}} per year.
 === Internal body ===
-The human [[heart]] is constantly contracting to move [[blood]] throughout the body. Through larger veins and arteries in the body, blood has been found to travel at approximately 0.33&nbsp;m/s. Though considerable variation exists, and peak flows in the [[venae cavae]] have been found between {{convert|0.1|and|0.45|m/s|ft/s}}.<ref>{{cite journal|last=Wexler|first=L.|author2=D H Bergel |author3=I T Gabe |author4=G S Makin |author5=C J Mills |title=Velocity of Blood Flow in Normal Human Venae Cavae|journal=Circulation Research|date=1 September 1968|volume=23|issue=3|pages=349–359|doi=10.1161/01.RES.23.3.349|pmid=5676450|doi-access=free}}</ref> additionally, the [[smooth muscle]]s of hollow internal [[viscera|organs]] are moving. The most familiar would be the occurrence of [[peristalsis]] which is where digested [[food]] is forced throughout the [[digestive tract]]. Though different foods travel through the body at different rates, an average speed through the human [[small intestine]] is {{convert|3.48|km/h|mph}}.<ref>{{cite web|last=Bowen|first=R|title=Gastrointestinal Transit: How Long Does It Take?|url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html|work=Pathophysiology of the digestive system|publisher=[[Colorado State University]]|date=27 May 2006|access-date=25 January 2014|archive-date=3 April 2015|archive-url=https://web.archive.org/web/20150403015943/http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html|url-status=live}}</ref> The human [[lymphatic system]] is also constantly causing movements of excess [[fluids]], [[lipids]], and immune system related products around the body. The lymph fluid has been found to move through a lymph capillary of the [[human skin|skin]] at approximately 0.0000097&nbsp;m/s.<ref>{{cite journal
+The human [[heart]] is regularly contracting to move [[blood]] throughout the body. Through larger veins and arteries in the body, blood has been found to travel at approximately 0.33&nbsp;m/s. Though considerable variation exists, and peak flows in the [[venae cavae]] have been found between {{convert|0.1|and|0.45|m/s|ft/s}}.<ref>{{cite journal|last=Wexler|first=L.|author2=D H Bergel |author3=I T Gabe |author4=G S Makin |author5=C J Mills |title=Velocity of Blood Flow in Normal Human Venae Cavae|journal=Circulation Research|date=1 September 1968|volume=23|issue=3|pages=349–359|doi=10.1161/01.RES.23.3.349|pmid=5676450|doi-access=free}}</ref> additionally, the [[smooth muscle]]s of hollow internal [[viscera|organs]] are moving. The most familiar would be the occurrence of [[peristalsis]], which is where digested [[food]] is forced throughout the [[digestive tract]]. Though different foods travel through the body at different rates, an average speed through the human [[small intestine]] is {{convert|3.48|km/h|mph}}.<ref>{{cite web|last=Bowen|first=R|title=Gastrointestinal Transit: How Long Does It Take?|url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html|work=Pathophysiology of the digestive system|publisher=[[Colorado State University]]|date=27 May 2006|access-date=25 January 2014|archive-date=3 April 2015|archive-url=https://web.archive.org/web/20150403015943/http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/transit.html|url-status=live}}</ref> The human [[lymphatic system]] is also constantly causing movements of excess [[fluids]], [[lipids]], and immune system related products around the body. The lymph fluid has been found to move through a lymph capillary of the [[human skin|skin]] at approximately 0.0000097&nbsp;m/s.<ref>
+{{cite journal
- |author1=M. Fischer |author2=U.K. Franzeck |author3=I. Herrig |author4=U. Costanzo |author5=S. Wen |author6=M. Schiesser |author7=U. Hoffmann |author8=A. Bollinger | title=Flow velocity of single lymphatic capillaries in human skin
+ | author1=M. Fischer |author2=U.K. Franzeck |author3=I. Herrig |author4=U. Costanzo |author5=S. Wen |author6=M. Schiesser |author7=U. Hoffmann |author8=A. Bollinger
+ | title=Flow velocity of single lymphatic capillaries in human skin
  | journal=Am J Physiol Heart Circ Physiol
- |date=1 January 1996
+ | date=1 January 1996
  | volume=270
  | pages=H358–H363
  | pmid=8769772
  | issue=1
- |doi=10.1152/ajpheart.1996.270.1.H358 }}</ref>
+ | doi=10.1152/ajpheart.1996.270.1.H358
+}}</ref>
 === Cells ===
-The [[cell (biology)|cells]] of the [[human body]] have many structures and organelles which move throughout them. [[Cytoplasmic streaming]] is a way in which cells move molecular substances throughout the [[cytoplasm]],<ref>{{cite encyclopedia|url=https://www.britannica.com/eb/article-9028448/cytoplasmic-streaming|title=cytoplasmic streaming – biology|encyclopedia=Encyclopædia Britannica|access-date=2022-06-23|archive-date=2008-06-11|archive-url=https://web.archive.org/web/20080611094209/http://www.britannica.com/eb/article-9028448/cytoplasmic-streaming|url-status=live}}</ref> various [[motor proteins]] work as [[molecular motors]] within a cell and move along the surface of various cellular substrates such as [[microtubules]], and motor proteins are typically powered by the [[hydrolysis]] of [[adenosine triphosphate]] (ATP), and convert chemical energy into mechanical work.<ref>{{cite web|url=http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/kinesin.htm|title=Microtubule Motors|work=rpi.edu|url-status=dead|archive-url=https://web.archive.org/web/20071130175151/http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/kinesin.htm|archive-date=2007-11-30}}</ref> [[Vesicle (biology)|Vesicles]] propelled by motor proteins have been found to have a velocity of approximately 0.00000152&nbsp;m/s.<ref>{{cite journal| bibcode=2002APS..SES.EA002H | title=Velocity and Drag Forces on motor-protein-driven Vesicles in Cells | journal=APS Southeastern Section Meeting Abstracts | volume=69 | pages=EA.002 | last1=Hill | first1=David | last2=Holzwarth | first2=George | last3=Bonin | first3=Keith | year=2002 }}</ref>
+The [[cell (biology)|cells]] of the [[human body]] have many structures and organelles that move throughout them. [[Cytoplasmic streaming]] is a way in which cells move molecular substances throughout the [[cytoplasm]],<ref>{{cite encyclopedia|url=https://www.britannica.com/eb/article-9028448/cytoplasmic-streaming|title=cytoplasmic streaming – biology|encyclopedia=Encyclopædia Britannica|access-date=2022-06-23|archive-date=2008-06-11|archive-url=https://web.archive.org/web/20080611094209/http://www.britannica.com/eb/article-9028448/cytoplasmic-streaming|url-status=live}}</ref> various [[motor proteins]] work as [[molecular motors]] within a cell and move along the surface of various cellular substrates such as [[microtubules]], and motor proteins are typically powered by the [[hydrolysis]] of [[adenosine triphosphate]] (ATP), and convert chemical energy into mechanical work.<ref>{{cite web|url=http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/kinesin.htm|title=Microtubule Motors|work=rpi.edu|url-status=dead|archive-url=https://web.archive.org/web/20071130175151/http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb2/part1/kinesin.htm|archive-date=2007-11-30}}</ref> [[Vesicle (biology)|Vesicles]] propelled by motor proteins have been found to have a velocity of approximately 0.00000152&nbsp;m/s.<ref>{{cite journal| bibcode=2002APS..SES.EA002H | title=Velocity and Drag Forces on motor-protein-driven Vesicles in Cells | journal=APS Southeastern Section Meeting Abstracts | volume=69 | pages=EA.002 | last1=Hill | first1=David | last2=Holzwarth | first2=George | last3=Bonin | first3=Keith | year=2002 }}</ref>
 === Particles ===
-According to the [[laws of thermodynamics]], all [[Subatomic particle|particles]] of [[matter]] are in constant random motion as long as the [[temperature]] is above [[absolute zero]]. Thus the [[molecule]]s and [[atom]]s which make up the human body are vibrating, colliding, and moving. This motion can be detected as temperature; higher temperatures, which represent greater [[kinetic energy]] in the particles, feel warm to humans who sense the thermal energy transferring from the object being touched to their nerves. Similarly, when lower temperature objects are touched, the senses perceive the transfer of heat away from the body as a feeling of cold.<ref>[http://www.colorado.edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/bec/temperature.html Temperature and BEC.] {{webarchive|url=https://web.archive.org/web/20071110174808/http://www.colorado.edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/bec/temperature.html |date=2007-11-10 }} Physics 2000: Colorado State University Physics Department</ref>
+According to the [[laws of thermodynamics]], all [[Subatomic particle|particles]] of [[matter]] are in constant random motion as long as the [[temperature]] is above [[absolute zero]]. Thus the [[molecule]]s and [[atom]]s that make up the human body are vibrating, colliding, and moving. This motion can be detected as temperature; higher temperatures, which represent greater [[kinetic energy]] in the particles, feel warm to humans who sense the thermal energy transferring from the object being touched to their nerves. Similarly, when lower temperature objects are touched, the senses perceive the transfer of heat away from the body as a feeling of cold.<ref>[http://www.colorado.edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/bec/temperature.html Temperature and BEC.] {{webarchive|url=https://web.archive.org/web/20071110174808/http://www.colorado.edu/UCB/AcademicAffairs/ArtsSciences/physics/PhysicsInitiative/Physics2000/bec/temperature.html |date=2007-11-10 }} Physics 2000: Colorado State University Physics Department</ref>
 === Subatomic particles ===
-Within the standard [[atomic orbital model]], [[electron]]s exist in a region around the nucleus of each atom.  This region is called the [[electron cloud]].  According to [[Bohr model|Bohr's model]] of the atom, electrons have a high [[Electron velocity|velocity]], and the larger the nucleus they are orbiting the faster they would need to move.  If electrons were to move about the electron cloud in strict paths the same way planets orbit the sun, then electrons would be required to do so at speeds which would far exceed the speed of light.  However, there is no reason that one must confine oneself to this strict conceptualization (that electrons move in paths the same way macroscopic objects do), rather one can conceptualize electrons to be 'particles' that capriciously exist within the bounds of the electron cloud.<ref>{{cite web|url=http://www.newton.dep.anl.gov/newton/askasci/1993/physics/PHY112.HTM|title=Classroom Resources|publisher=Argonne National Laboratory|work=anl.gov|access-date=2009-03-09|archive-date=2010-06-08|archive-url=https://web.archive.org/web/20100608223005/http://www.newton.dep.anl.gov/newton/askasci/1993/physics/PHY112.HTM|url-status=live}}</ref> Inside the [[atomic nucleus]], the [[proton]]s and [[neutron]]s are also probably moving around due to the electrical repulsion of the protons and the presence of [[angular momentum]] of both particles.<ref>{{Cite web |url=http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap02.pdf |title=Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory. |access-date=2009-03-09 |archive-date=2009-03-04 |archive-url=https://web.archive.org/web/20090304064927/http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap02.pdf |url-status=live }}</ref>
+Within the standard [[atomic orbital model]], [[electron]]s exist in a region around the nucleus of each atom. This region is called the [[electron cloud]]. According to [[Bohr model|Bohr's model]] of the atom, electrons have a high [[Electron velocity|velocity]], and the larger the nucleus they are orbiting the faster they would need to move. If electrons were to move about the electron cloud in strict paths the same way planets orbit the Sun, then electrons would be required to do so at speeds that would far exceed the speed of light. However, there is no reason that one must confine oneself to this strict conceptualization (that electrons move in paths the same way macroscopic objects do), rather one can conceptualize electrons to be 'particles' that capriciously exist within the bounds of the electron cloud.<ref>{{cite web|url=http://www.newton.dep.anl.gov/newton/askasci/1993/physics/PHY112.HTM|title=Classroom Resources|publisher=Argonne National Laboratory|work=anl.gov|access-date=2009-03-09|archive-date=2010-06-08|archive-url=https://web.archive.org/web/20100608223005/http://www.newton.dep.anl.gov/newton/askasci/1993/physics/PHY112.HTM|url-status=live}}</ref> Inside the [[atomic nucleus]], the [[proton]]s and [[neutron]]s are also probably moving around due to the electrical repulsion of the protons and the presence of [[angular momentum]] of both particles.<ref>{{Cite web |url=http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap02.pdf |title=Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory. |access-date=2009-03-09 |archive-date=2009-03-04 |archive-url=https://web.archive.org/web/20090304064927/http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap02.pdf |url-status=live }}</ref>
 == Light ==
@@ Line 139: / Line 150: @@
 In addition, the speed of light is an [[invariant (physics)|invariant]] quantity: it has the same value, irrespective of the position or speed of the observer. This property makes the speed of light ''c'' a natural measurement unit for speed and a [[physical constant|fundamental constant]] of nature.
-In 2011, the speed of light was redefined alongside all seven SI base units using what it calls "the explicit-constant formulation", where each "unit is defined indirectly by specifying explicitly an exact value for a well-recognized fundamental constant", as was done for the speed of light. A new, but completely equivalent, wording of the metre's definition was proposed: "The metre, symbol m, is the unit of length; its magnitude is set by fixing the numerical value of the speed of light in vacuum to be equal to exactly {{Val|299792458}} when it is expressed in the SI unit {{Nowrap|m s<sup>−1</sup>}}."<ref>{{Cite web |date=2011 |title=The "explicit-constant" formulation |url=http://www.bipm.org/en/si/new_si/explicit_constant.html |archive-url=https://web.archive.org/web/20140811195806/http://www.bipm.org/en/si/new_si/explicit_constant.html |archive-date=11 August 2014 |website=BIPM}}</ref>  This implicit change to the speed of light was one of the changes that was incorporated in the [[2019 redefinition of the SI base units]], also termed the ''New SI''.<ref>See, for example:
+In 2019, the speed of light was redefined alongside all seven SI base units using what it calls "the explicit-constant formulation", where each "unit is defined indirectly by specifying explicitly an exact value for a well-recognized fundamental constant", as was done for the speed of light. A new, but completely equivalent, wording of the metre's definition was proposed: "The metre, symbol m, is the unit of length; its magnitude is set by fixing the numerical value of the speed of light in vacuum to be equal to exactly {{Val|299792458}} when it is expressed in the SI unit {{Nowrap|m s<sup>−1</sup>}}."<ref>{{Cite web |date=2011 |title=The "explicit-constant" formulation |url=http://www.bipm.org/en/si/new_si/explicit_constant.html |archive-url=https://web.archive.org/web/20140811195806/http://www.bipm.org/en/si/new_si/explicit_constant.html |archive-date=11 August 2014 |website=BIPM}}</ref> This implicit change to the speed of light was one of the changes that was incorporated in the [[2019 revision of the SI]], also termed the ''New SI''.<ref>See, for example:
+* {{cite web |last=Conover |first=Emily |author-link=Emily Conover |date=2 November 2016 |title=Units of measure are getting a fundamental upgrade |url=https://www.sciencenews.org/article/units-measure-are-getting-fundamental-upgrade |access-date=6 February 2022 |website=[[Science News]] |language=en-US |archive-date=6 February 2022 |archive-url=https://web.archive.org/web/20220206103439/https://www.sciencenews.org/article/units-measure-are-getting-fundamental-upgrade |url-status=live }}
+* {{cite journal |last1=Knotts |first1=Sandra |last2=Mohr |first2=Peter J. |last3=Phillips |first3=William D. |date=January 2017 |title=An Introduction to the New SI |url=http://scitation.aip.org/content/aapt/journal/tpt/55/1/10.1119/1.4972491 |journal=[[The Physics Teacher]] |language=en |volume=55 |issue=1 |pages=16–21 |bibcode=2017PhTea..55...16K |doi=10.1119/1.4972491 |issn=0031-921X |s2cid=117581000 |access-date=2022-08-20 |archive-date=2023-09-25 |archive-url=https://web.archive.org/web/20230925015417/https://pubs.aip.org/aapt/pte/article-abstract/55/1/16/618986/An-Introduction-to-the-New-SI?redirectedFrom=fulltext |url-status=live }}
-* {{Cite web |last=Conover |first=Emily |author-link=Emily Conover |date=2 November 2016 |title=Units of measure are getting a fundamental upgrade |url=https://www.sciencenews.org/article/units-measure-are-getting-fundamental-upgrade |access-date=6 February 2022 |website=[[Science News]] |language=en-US}}
+* {{cite journal |date=11 May 2018 |title=SI Redefinition |url=https://www.nist.gov/si-redefinition |journal=[[National Institute of Standards and Technology]] |language=en |access-date=6 February 2022 |archive-date=6 February 2022 |archive-url=https://web.archive.org/web/20220206103441/https://www.nist.gov/si-redefinition |url-status=live }}</ref>
-* {{Cite journal |last1=Knotts |first1=Sandra |last2=Mohr |first2=Peter J. |last3=Phillips |first3=William D. |date=January 2017 |title=An Introduction to the New SI |url=http://scitation.aip.org/content/aapt/journal/tpt/55/1/10.1119/1.4972491 |journal=[[The Physics Teacher]] |language=en |volume=55 |issue=1 |pages=16–21 |bibcode=2017PhTea..55...16K |doi=10.1119/1.4972491 |issn=0031-921X |s2cid=117581000}}
-* {{Cite journal |date=11 May 2018 |title=SI Redefinition |url=https://www.nist.gov/si-redefinition |journal=[[National Institute of Standards and Technology]] |language=en |access-date=6 February 2022}}</ref>
 === Superluminal motion ===
+{{See also|Superluminal motion}}
-Some motion appears to an observer to exceed the speed of light. Bursts of energy moving out along the [[relativistic jet]]s emitted from these objects can have a [[proper motion]] that appears greater than the speed of light. All of these sources are thought to contain a [[black hole]], responsible for the ejection of mass at high velocities. [[Light echo]]es can also produce apparent superluminal motion.<ref>{{cite journal |last=Bond |first=H. E. |display-authors=etal |year=2003 |title=An energetic stellar outburst accompanied by circumstellar light echoes |journal=[[Nature (journal)|Nature]] |volume=422 |issue=6930 |pages=405–408 |arxiv=astro-ph/0303513 |bibcode=2003Natur.422..405B |doi=10.1038/nature01508 |pmid=12660776 |s2cid=90973}}</ref> This occurs owing to how motion is often calculated at long distances; oftentimes calculations fail to account for the fact that the speed of light is finite. When measuring the movement of distant objects across the sky, there is a large time delay between what has been observed and what has occurred, due to the large distance the light from the distant object has to travel to reach us. The error in the above naive calculation comes from the fact that when an object has a component of velocity directed towards the Earth, as the object moves closer to the Earth that time delay becomes smaller. This means that the apparent speed as calculated above is ''greater'' than the actual speed. Correspondingly, if the object is moving away from the Earth, the above calculation underestimates the actual speed.<ref>{{cite journal |last1=Meyer |first1=Eileen |date=June 2018 |title=Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84 |journal=The Astrophysical Journal |volume=680 |issue=1 |page=9 |arxiv=1804.05122 |bibcode=2018ApJ...860....9M |doi=10.3847/1538-4357/aabf39 |s2cid=67822924}}</ref>
+Some motion appears to an observer to exceed the speed of light. Bursts of energy moving out along the [[relativistic jet]]s emitted from these objects can have a [[proper motion]] that appears greater than the speed of light. All of these sources are thought to contain a [[black hole]], responsible for the ejection of mass at high velocities. [[Light echo]]es can also produce apparent superluminal motion.<ref>{{cite journal |last=Bond |first=H. E. |display-authors=etal |year=2003 |title=An energetic stellar outburst accompanied by circumstellar light echoes |journal=[[Nature (journal)|Nature]] |volume=422 |issue=6930 |pages=405–408 |arxiv=astro-ph/0303513 |bibcode=2003Natur.422..405B |doi=10.1038/nature01508 |pmid=12660776 |s2cid=90973}}</ref> This occurs owing to how motion is often calculated at long distances; oftentimes calculations fail to account for the fact that the speed of light is finite. When measuring the movement of distant objects across the sky, there is a large time delay between what has been observed and what has occurred, due to the large distance the light from the distant object has to travel to reach us. The error in the above naive calculation comes from the fact that when an object has a component of velocity directed towards the Earth, as the object moves closer to the Earth that time delay becomes smaller. This means that the apparent speed as calculated above is ''greater'' than the actual speed. Correspondingly, if the object is moving away from the Earth, the above calculation underestimates the actual speed.<ref>{{cite journal |last1=Meyer |first1=Eileen |date=June 2018 |title=Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84 |journal=The Astrophysical Journal |volume=680 |issue=1 |page=9 |arxiv=1804.05122 |bibcode=2018ApJ...860....9M |doi=10.3847/1538-4357/aabf39 |s2cid=67822924 |doi-access=free }}</ref>
 == Types of motion ==
 * [[Simple harmonic motion]] – motion in which the body oscillates in such a way that the restoring force acting on it is directly proportional to the body's displacement. Mathematically Force is directly proportional to the negative of displacement. Negative sign signifies the restoring nature of the force. (e.g., that of a [[pendulum]]).
-* [[Linear motion]] – motion which follows a straight [[Line (geometry)|linear]] path, and whose [[displacement (vector)|displacement]] is exactly the same as its [[trajectory]]. [Also known as [[rectilinear motion]]]
+* [[Linear motion]] – motion that follows a straight [[Line (geometry)|linear]] path, and whose [[displacement (vector)|displacement]] is exactly the same as its [[trajectory]]. [Also known as [[rectilinear motion]]]
 * [[Reciprocating motion|Reciprocal motion]]
-* [[Brownian motion]] (i.e. the random movement of particles)
+* [[Brownian motion]] – the random movement of very small particles
 * [[Circular motion]]
 * [[Rotational motion|Rotatory motion]] – a motion about a fixed point. (e.g. [[Ferris wheel]]).
@@ Line 160: / Line 171: @@
 * [[Vibration|Vibratory motion]]
 * Combination (or simultaneous) motions – Combination of two or more above listed motions
-* [[Projectile motion]] –  uniform horizontal motion + vertical accelerated motion
+* [[Projectile motion]] – uniform horizontal motion + vertical accelerated motion
 == Fundamental motions ==
@@ Line 168: / Line 179: @@
 * [[Wave]]
 * [[Relative motion]]
-* [[Fundamental motions]]
+* [[Rotary motion]]
 == See also ==
 {{Portal|Physics}}
 * {{Annotated link|Deflection (physics)}}
+* {{Annotated link|Flow (physics)}}
 * {{Annotated link|Kinematics}}
 * {{Annotated link|Simple machines}}
@@ Line 185: / Line 197: @@
 == References ==
-{{Reflist}}
+{{reflist}}
 == External links ==