Content deleted Content added
Squeakachu (talk | contribs) m Reverted edit by 2603:6081:7E00:EDE7:30C7:2DA4:ACB0:2D4F (talk) to last version by Sluzzelin Tag: Rollback |
m rem double spaces throughout Tag: Visual edit |
||
(5 intermediate revisions by 5 users not shown) | |||
Line 1: | Line 1: | ||
{{AFI}} |
|||
{{Short description|Change in |
{{Short description|Change in |
||
position of an object}} |
position of an object}} |
||
Line 48: | Line 49: | ||
== Orders of magnitude == |
== 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]]. |
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. |
||
=== Universe === |
=== Universe === |
||
Line 132: | Line 133: | ||
=== Subatomic particles === |
=== Subatomic particles === |
||
Within the standard [[atomic orbital model]], [[electron]]s exist in a region around the nucleus of each atom. |
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> |
||
== Light == |
== Light == |
||
Line 140: | Line 141: | ||
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 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> |
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: |
||
* {{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 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}} |
* {{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 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> |
* {{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> |
||
=== Superluminal motion === |
=== 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 == |
== Types of motion == |
||
Line 161: | Line 162: | ||
* [[Vibration|Vibratory motion]] |
* [[Vibration|Vibratory motion]] |
||
* Combination (or simultaneous) motions – Combination of two or more above listed motions |
* Combination (or simultaneous) motions – Combination of two or more above listed motions |
||
* [[Projectile motion]] – |
* [[Projectile motion]] – uniform horizontal motion + vertical accelerated motion |
||
== Fundamental motions == |
== Fundamental motions == |