physical law

7/28/2019 Physical Law

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Physical Law



What is physical law?

• A physical law or scientific law is, according tothe Oxford English dictionary, "a theoreticalprinciple deduced from particular facts,applicable to a defined group or class of phenomena, and expressible by the statementthat a particular phenomenon always occurs if certain conditions be present."

http://en.wikipedia.org/wiki/Principle

http://en.wikipedia.org/wiki/Phenomena

http://en.wikipedia.org/wiki/Phenomena

http://en.wikipedia.org/wiki/Principle



• They are typically conclusions based onrepeated scientific experiments andobservations over many years and which havebecome accepted universally within thescientific community

http://en.wikipedia.org/wiki/Experiment

http://en.wikipedia.org/wiki/Observations

http://en.wikipedia.org/wiki/Scientific_community

http://en.wikipedia.org/wiki/Scientific_community

http://en.wikipedia.org/wiki/Observations

http://en.wikipedia.org/wiki/Experiment



• Physical science purports to give explanationsof physical phenomena because it claims toexplain why physical events occur and how physical objects work. On one level, suchknowledge can have purely practical value. If we know how the natural world works, we canpredict events and prepare accordingly, we canmake use of natural principles to create devices

and processes that will make our lives easier ormore convenient, or fulfill various tasks we mayconceive.



But, they do not properly answerWHY things are the way they

are.



What are some of the general properties of physical law?

• True, at least within their regime of validity. Bydefinition, there have never been repeatablecontradicting observations.

•

Universal. They appear to apply everywhere in theuniverse.

• Simple. They are typically expressed in terms of asingle mathematical equation.

•

Absolute. Nothing in the universe appears to affectthem.

• Stable. Unchanged since first discovered

• Omnipotent. Everything in the universe apparently

must comply with them (according to observations)



What are examples of this so called physical law?

1. Newton's Three Laws of Motion:

• Sir Isaac Newton developed the Three Laws of Motion (law of gravity, conservation of mass-

energy, and conservation of momentum) whichdescribe basic rules about how the motion of physical objects change. Newton was able todefine the fundamental relationship betweenthe acceleration of an object and the total forces

acting upon it.

http://physics.about.com/od/classicalmechanics/a/lawsofmotion.htm


http://physics.about.com/od/glossary/g/acceleration.htm

http://physics.about.com/od/glossary/g/force.htm

http://physics.about.com/od/glossary/g/force.htm

http://physics.about.com/od/glossary/g/acceleration.htm





2. Laws of Thermodynamics

• The laws of thermodynamics are actuallyspecific manifestations of the law of

conservation of mass-energy as it relates tothermodynamic processes.

http://physics.about.com/od/thermodynamics/a/lawthermo.htm

http://physics.about.com/od/thermodynamics/a/lawthermo.htm



3. Electrostatic Laws • Coulomb's law and Gauss's law are

formulations of the relationship between

electrically charged particles to createelectrostatic force and electrostatic fields. Theformulas, it turns out, parallel the laws of universal gravitation in structure. There alsoexist similar laws relating to magnetism and

electromagnetism as a whole.

•



Physical Law andPhilosophy……



• Only a madman wouldinsist that ourformulation of quantitative law DOESNOT aid ourunderstanding of theworld. Physical Lawenables us to predictthings more or less. A world withoutpredictability would bea world without order;it would render ourexistence meaninglessand intolerable.



• Contrary to all currentthinking withinscience, the more weformulate the preciseand determining action

of a physical law, theless it tells us about theevents it governs. Wegain more and moreexactness about lessand less of the world'sconcrete expression.

• This can be illustratedby describing whathappens when werelease a leaf in avacuum chamber. The

leaf now "drops like arock". That is, we get atrajectory that seems tobe little more than thegraphic display of amathematicalexpression we call the

"law of gravity". To seean event in this way asa mathematicalnecessity made visiblegives us a powerfulsense of explanation.



• BUT, in doing this, we restrict ourselves to thesphere of our mathematical explanation and donot smuggle in qualitative aspects of thephenomenon lying outside the explanation



• Thus, instead of beingilluminating,philosophers believethat physical lawactually leads us tomore questions, like:

-How these laws relate tothe world they help usunderstand?

-Why are physical lawsthe way they are?

-Do physical laws makethings happen?

physical law

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