# Motion

In physics, motion means a constant change in the location of a body. Change in motion is the result of applied force. Motion is typically described in terms of velocity, acceleration, displacement, and time.[1] An object's velocity cannot change unless it is acted upon by a force, as described by Newton's first law. An object's momentum is directly related to the object's mass and velocity, and the total momentum of all objects in a closed system (one not affected by external forces) does not change with time, as described by the law of conservation of momentum.

A body which does not move is said to be at rest, motionless, immobile, stationary, or to have constant (time-invariant) position.

Motion is always observed and measured relative to a frame of reference. As there is no absolute reference frame, absolute motion cannot be determined; this is emphasised by the term relative motion.[2] A body which is motionless relative to a given reference frame, moves relative to infinitely many other frames. Thus, everything in the universe is moving.[3]

## List of "imperceptible" human motions

Humans, like all things in the universe are in constant motion,[4] however, aside from obvious movements of the various external body parts and locomotion, humans are in motion in a variety of ways which 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: 1) Newton's laws of motion (particularly Inertia) which prevent humans from feeling motions of a mass to which they are connected, and 2) the lack of an obvious frame of reference which would allow individuals to easily see that they are moving.[5]] The smaller scales of these motions are too small for humans to sense.

### Universe

• Spacetime (the fabric of the universe) is actually expanding. Essentially, everything in the universe is stretching like a rubber band. This motion is the most obscure as it is not physical motion as such, 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 us ("Hubble's law") as predicted by a universal expansion.[6] Full article, PDF]

### Solar System

• The Milky Way is rotating around its dense galactic center, thus the solar system 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 km/s.[7]

### 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 km/s (or 1040 mi/h).[8]
• The Earth is 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 km/s (or 67,000 mi/h).[9]

### 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 1 inch (2.54 cm) per year.[10]

[11] However, the velocities of plates range widely. The fastest-moving plates are the oceanic plates, with the Cocos Plate advancing at a rate of 75mm/yr[12] (3.0 in/yr) and the Pacific Plate moving 52–69 mm/yr (2.1-2.7 in/yr). At the other extreme, the slowest-moving plate is the Eurasian Plate, progressing at a typical rate of about 21mm/yr (0.8;in/yr).

### 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 m/s.[13] Though considerable variation exists, and peak flows in the venae cavae have been found to range between 0.1 m/s and 0.45 m/s.[14]
• The smooth muscles of hollow internal organs are moving. The most familiar would be peristalsis which is where digested food is forced throughout the digestive tract. Though different foods travel through the body at rates, an average speed through the human small intestine is 2.16 m/h or 0.036 m/s.[15]
• Typically some sound is audible at any given moment, when the vibration of these sound waves reaches the ear drum it moves in response and allows the sense of hearing.
• The human lymphatic system is constantly moving 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.[16]

### Cells

The cells of the human body have many structures which move throughout them.

### Subatomic particles

• Within each atom the electrons are speeding around the nucleus so fast that they are not actually in one location, but rather smeared across a region of the electron cloud. Electrons have a high velocity, and the larger the nucleus they are orbiting the faster they move. In a hydrogen atom, electrons have been calculated to be orbiting at a speed of approximately 2,420,000 m/s[20]
• Inside the atomic nucleus the protons and neutrons are also probably moving around due the electrical repulsion of the protons and the presence of angular momentum of both particles.[21]

## Light

Light is both a photon and a wave, and moves at 186,000 miles per second (299,792 km per second). It is the fastest moving thing known to man, and, according to Einstein, a limit which nothing can travel faster than. Lorentz's Equations predicted that time would "slow down" for whatever was traveling near light speed; so, if a person was moving near light speed, they would age slower than someone who was not. Since light is what humans depend on to see the universe, there are tiny, imperceptible changes in what one observer is seeing compared to another. This is because, of course, that light still has to travel to get to an observer; so, if Observer #2 was twice as far from an object than Observer #1, Observer #2 would see it two times later than Observer #1. This can especially be seen when you look at stars many light-years away: you are actually seeing the past of that star, not what is happening at moment, since the light from that star must travel years and years to reach earth (depending on exactly how far away it was).

## Quote

Motion is not inherent on Paradise; it is volitional.[22]

## References

1. Nave, R. 2005. Motion. HyperPhysics. Georgia State University
2. Wåhlin, L. 1997. "THE DEADBEAT UNIVERSE", Chapter 9. Colutron Research Corporation ISBN 0 933407 03 3
3. De Grasse Tyson, N., Liu, C., & Irion, R. 2000. One Universe: At home in the cosmos. p.20-21. Joseph Henry Press. ISBN-10: 0-309-06488-0
4. De Grasse Tyson, N., Liu, C., & Irion, R. 2000. One Universe: At home in the cosmos. p.8-9. Joseph Henry Press. ISBN-10: 0-309-06488-0
5. Safkan, Y. 2007 "f 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. PhysicsLink
6. Hubble, Edwin, "A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae" (1929) Proceedings of the National Academy of Sciences of the United States of America, Volume 15, Issue 3, pp. 168-173 (Full article, PDF)
7. 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. doi:10.1086/173453. https://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993ApJ...419....1K. Retrieved on 2007-05-10.
8. Imamura, Jim (August 10, 2006). "Mass of the Milky Way Galaxy". University of Oregon. https://zebu.uoregon.edu/~imamura/123/lecture-2/mass.html. Retrieved on 2007-05-10.
9. Ask and Astrophysicist. NASA Goodard Space Flight Center.
10. Williams, David R. (September 1, 2004). "Earth Fact Sheet". NASA. https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html. Retrieved on 2007-03-17.
11. Staff. "GPS Time Series". NASA JPL. https://sideshow.jpl.nasa.gov/mbh/series.html. Retrieved on 2007-04-02.
12. Huang, Zhen Shao. "Speed of the Continental Plates". The Physics Factbook. https://hypertextbook.com/facts/ZhenHuang.shtml. Retrieved on 2007-11-09.
13. 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. https://www-odp.tamu.edu/publications/170_SR/chap_07/chap_07.htm. Retrieved on 2007-04-02.
14. Penny, P. 2003. Hemodynamic: Blood Velocity
15. LEWIS WEXLER, DEREK H. BERGEL, IVOR T. GABE, GEOFFREY S. MAKIN, & CHRISTOPHER J. MILLS (1968). "Velocity of Blood Flow in Normal Human Venae Cavae". Circulation Research. 23: 349. PMID 5676450. https://circres.ahajournals.org/cgi/content/abstract/circresaha;23/3/349. Retrieved on 2007-11-14.
16. Bowen, R. 2006. Gastrointestinal Transit: How Long Does It Take? Colorado State University.
17. M. Fischer, U. K. Franzeck, I. Herrig, U. Costanzo, S. Wen, M. Schiesser, U. Hoffmann and A. Bollinger (1996). "Flow velocity of single lymphatic capillaries in human skin". Am J Physiol Heart Circ Physiology 270: H358–H363. PMID 8769772. https://ajpheart.physiology.org/cgi/content/abstract/270/1/H358. Retrieved on 2007-11-14.
18. Cytoplasmic Streaming: Encyclopedia Britannica
19. Microtubule Motors: Rensselaer Polytechnic Institute.
20. Hill, David; Holzwarth, George; Bonin, Keith (2002). "Velocity and Drag Forces on motor-protein-driven Vesicles in Cells". American Physical Society, The 69th Annual Meeting of the Southeastern abstract #EA.002. https://adsabs.harvard.edu/abs/2002APS..SES.EA002H. Retrieved on 2007-11-14.
21. Temperature and BEC. Physics 2000: Colorado State University Physics Department
22. Ask a scientist archive. Argonne National Laboratory, United States Department of Energy
23. Chapter 2, Nuclear Science- A guide to the nuclear science wall chart. Berkley National Laboratory.