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Topic: Length contraction

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	Length contraction - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-11-06)
		Length contraction, according to Albert Einstein's special theory of relativity, is the decrease in length experienced by people or objects traveling at a substantial fraction of the speed of light.
		It is experienced only in the direction in which the body is travelling and not transverse to this direction, which in turn is dependent on the frame of reference relative to which that motion is being measured.
		From this simple maths which is part of the Lorentz transformations, we can see that an observer travelling at the speed of light (which, according to general relativity, is impossible for any object with a non-zero rest mass) would measure all distances in the direction of motion as 0.
	en.wikipedia.org /wiki/Length_contraction (233 words)

	Special Theory of Relativity -- Length Contraction (Site not responding. Last check: 2007-11-06)
		Length contraction occurs only in the dimension of an object that is in the direction of motion.
		Yet, the amount of contraction is noticeable only when the object is moving at an extremely high velocity that human beings are not able to achieve with current technology.
		Notice that according to the time dilation and length contraction formulae, the observer in the inertial (rest) reference frame sees that the object moving at a high velocity appear shorter and that the event in that object takes a longer time interval to complete.
	members.tripod.com /wmhxbigguy/Theory/length.html (697 words)

	Time dilation/length contraction
		The length of any object in a moving frame will appear foreshortened in the direction of motion, or contracted.
		The amount of contraction can be calculated from the Lorentz transformation.
		The length is maximum in the frame in which the object is at rest.
	hyperphysics.phy-astr.gsu.edu /hbase/relativ/tdil.html (431 words)

	Sharp Blue: Length contraction
		A closely related effect is the phenomenon of length contraction (sometimes known as "Lorentz contraction", "FitzGerald contraction" or even "Lorentz-FitzGerald contraction" after the physicists who predicted it on the basis of a crude forerunner of special relativity).
		Both time dilation and length contraction are immediate consequences of the Lorentz transformation (which I described in my article Relativity, FTL and Causality), and hence an essential part of any relativistic understanding of the world.
		Length contraction is an effect that applies to any moving object, but it's easiest to consider the case of a one-dimensional rod (this follows the grand tradition in physics of ignoring any details which are extraneous to the explanation!).
	www.theculture.org /rich/sharpblue/archives/000120.html (934 words)

	Special Relativity prescribes a New Definition of Measurement-I (Site not responding. Last check: 2007-11-06)
		A clue to the nature of this association is given by an analysis of length contraction which shows that light is necessarily involved in the operations of measuring length and that these operations are the same for all inertial observers.
		This, in turn, implies that the origin of the dependence of the length of a rod on its speed is located outside the rod, whereas its all other dependences concern the inside of the rod.
		This relation of c to the operations of measuring length implies that light is necessarily involved in the operations of measuring length and that these operations are the same for all inertial observers.
	wbabin.net /physics/minhas.htm (2736 words)

	The Physics Classroom
		One of the peculiar aspects of Einstein's theory of special relativity is that the length of objects moving at relativistic speeds undergo a contraction along the dimension of motion.
		The amount of contraction of the object is dependent upon the object's speed relative to the observer.
		Note that the length contraction is only significant when the object is moving at relativistic speeds - i.e., speeds which are a significant fraction of the speed of light.
	www.physicsclassroom.com /mmedia/specrel/lc.html (318 words)

	Relativity Train
		The demonstration is used to show how the preservation of the postulated constancy of physical laws and the speed of light in all inertial frames requires length contraction and time dilation in the train frame relative to the lab frame of reference.
		(i) First measure the length of a meter stick in the station frame (no clocks are required for this) by simply placing arrow markers at the ends of the stick (at arbitrary times) and stating that the length of the stationary meter stick is equal to the distance between the two arrow markers.
		Thus, having introduced time dilation (and length contraction) one can now demonstrate that (a) the velocity of light is the same in both frames, (b) each frame measures the other's clock as running slow and, (c) relative velocities are the same in both frames.
	www.fas.harvard.edu /~scdiroff/lds/QuantumRelativity/RelativityTrain/RelativityTrain.html (2538 words)

	Length Contraction
		The apparent length (L') is proportional to the actual length, L, as measured in the objects frame of reference.
		Length contraction tells us that the size of a muon moving at 0.99c will appear contracted to one seventh of its true size (or just over a millimeter) when viewed by an Earthbound observer.
		Thus, as expected, lengths of objects attached to the muon appear contracted as seen from Earth, whereas lengths of objects moving with the Earth appear contracted as measured in the muon's frame.
	theory.uwinnipeg.ca /mod_tech/node136.html (453 words)

	[No title]
		Both arms of the interferometer have the same length L. The arm of the interferometer, which is parallel to the x,x'-axis (the "parallel arm"), is limited by a mirror M2, whereas the arm parallel to the y-axis (the "perpendicular" arm) is limited by a mirror M1.
		The length measured by the moving observer is shorter.
		This implies that L' = L * sqrt(1-v^2/c^2), iow, that the length of the parallel arm is contracted by sqrt(1-v^2/c^2).
	perso.wanadoo.fr /mluttgens/mmx.htm (1322 words)

	Physics Help and Math Help - Physics Forums - Length contraction problem
		The SR length contraction is only down to 0.87 of original length at that speed.
		also the length contraction would not neutralize the centrifical force at all, the tension on the train would still remain the same even if the train did contract a considerable amount, and so the train would ripp appart either way.
		When an objects undergoes length contraction, its mass is not effected and so it has the same number of atoms.
	www.physicsforums.com /printthread.php?t=9063&pp=40 (1213 words)

	A Direct Test of the Lorentz Length Contraction (Site not responding. Last check: 2007-11-06)
		If we measure the length of the sides by the angle subtended, they will be shortened, but since the cube appears rotated, the amount of Lorentz shortening will exactly match the amount of expected foreshortening due to the apparent rotation, and the impression on our observations will be that the Lorentz contraction has not occurred.
		The only effect the galaxies own proper motion has with respect to length contraction is that the angle subtended from one end of the galaxy to the other in the direction of motion is foreshortened.
		The aberration of the contracted position virtual source occurs due to the velocity addition formula applied to the motion of light from the virtual source reaching the moving observer, as we saw in section 5.
	renshaw.teleinc.com /papers/simiee2/simiee2.stm (6131 words)

	Length Contraction (Site not responding. Last check: 2007-11-06)
		Length contraction is a phenomenon in which the length of an object measured by someone in a reference frame that is moving with respect to the object is always less than the proper length (L
		Example of Length Contraction: If you were standing still and Santa Clause rode by you on his sleigh at a velocity of 0.8c, the sleigh would be 60% shorter in your reference frame than it was when you saw it parked on your roof.
		Santa, on the other hand, would see no difference in the length of the sleigh because the sleigh was at rest with respect to his frame of reference while on the roof and in the air.
	www.upei.ca /~physics/p221/pro00/lengthcon (571 words)

	Changing Length - Introduction
		The same when the point b meets B. Length contraction is demonstrated when the observer O does not see the two lights simultaneous.
		Again Length contraction is demonstrated when the observer O does not see the two lights simultaneous.
		When you want to study length contraction and more specific the Lorentz Transformations the speed of the object in your rest frame is very important.
	users.telenet.be /nicvroom/length.htm (1392 words)

	MECHANISMSKELMUSCLECONTR
		The length of the sarcomeres, A and I bands were measured on densitometer tracings.
		Further experimentation revealed that during contraction the length of the actin containing thin filaments and the length of the myosin containing thick filaments remain constant.
		Thus, during contraction the length of the sarcomere and I band decrease, the overlap between thick and thin filaments increases, the length of the thick and thin filaments remains unchanged.
	www.uic.edu /classes/phyb/phyb516/mechanismskelmusclecontru3.htm (963 words)

	TIME WILL TELL
		What is not obvious is that although any length may be measured to great accuracy as parts of, or multiples of, this standard meter; we do not know, nor can we ever know, how long a meter is. We have created an unknown and random length, and defined it to be one meter.
		Since it is not possible to know the absolute length of the standard meter, it is not possible to know the absolute lengths or distances of objects and places in the Universe.
		Similar to length, we can measure relative mass to a great accuracy, but we cannot measure any mass in an absolute sense, because the mass of our standard kilogram is unknown, outside of our definition (one kilogram).
	www.beotel.yu /~mmalovic/newtime.htm (8571 words)

	Natural Length Contraction Mechanism Due to Kinetic Energy
		Einstein's theory of relativity predicts length contraction, but does not explain how matter can be physically contracted or why this phenomenon is not reversible when the mass in the moving frame is accelerated back to the original frame.
		However, the physical length of the rod is certainly different in the moving frame.
		who found that length contractions and dilations are not measurable to the observer in the moving frame.
	www.newtonphysics.on.ca /kinetic/length.html (5912 words)

	Physics and Astronomy Forums - Length Contraction - General Undergrad / College Discussion
		Or could it be taken that what we see as length contraction is more that 'just what we see'.
		But if you see object X as contracted, then all the laws of physics and any experiments you do will tell you X is well and truly contracted, in actual fact.
		He said that undergoing Lorentz contraction or time dialation was akin to a "rotation" in space-time.
	www.physlink.com /community/forums/viewmessages.cfm?Forum=11&Topic=874 (807 words)

	McGraw-Hill AccessScience: Sample Biography
		The Michelson-Morley experiment had demonstrated conclusively in 1881 and again in 1887 that the velocity of light is constant and does not vary with the motion of either the source or the observer.
		If a system were to move at the velocity of light, to an observer its length would be zero, time would be at a stop and its mass would be infinite.
		Length contraction follows from these observations, and no velocity greater than light has ever been detected.
	www.accessscience.com /Samples/Biography (2213 words)

	The Physical Reality of Length Contraction
		Since length contraction appears as a consequence of quantum mechanical calculations, the physical reality of those predictions can be verified experimentally.
		Length contraction or dilation is real and is demonstrated here as the result of actual experiments.
		It is important to notice that length dilation or contraction is predicted and explained here without using the relativistic Lorentz equations nor the constancy of the velocity of light.
	www.newtonphysics.on.ca /EINSTEIN/Chapter1.html (4321 words)

	Accel-OneD Length Contraction
		Even though the sound byte "length contraction" was familiar to me, and even though my intuition usually told me how to solve length contraction problems, I didn't really understand the concept until this was done.
		In special relativity terms, "length contraction" problems involve THREE events - which we might refer to as left measure event common to both frames, and the right measure at rest and right measure moving events which take place simultaneously on the other end of the ruler from the viewpoint of one observer or another.
		To pose a specific problem, imagine a large ruler, one light-year in length, and an inertial frame which measures at one of its "instants" the length of this ruler while traveling at a constant coordinate velocity of one third of a lightyear per inertial year (i.e.
	newton.umsl.edu /~run/contract.html (761 words)

	Comments on the Derivations of Time Dilation & Length Contraction (Site not responding. Last check: 2007-11-06)
		That is, the length of the ruler as measured by the astronaut is reduced ("contracted") by a factor of
		The greatest length that ever would be measured for the ruler would be that measured by an observer at rest relative to the ruler.
		Furthermore, all observers agree on who measures the proper length — it is an unambiguous definition of a particular length (or distance between two events).
	pages.slc.edu /~physics/Documents/SR_comments.html (1422 words)

	Physlet Quantum Mechanics: Illustration 2.4
		One of the best ways to visualize time dilation and length contraction of moving objects is with the construction of a light clock.
		The green clock moves at half the speed of light (ignore the length contraction of the horizontal size of the light clock as it is irrelevant for this discussion).
		In fact the clock must be contracted to L' = L / γ where L is the length of the clock as seen in the reference frame of the clock (whether moving or stationary) and L' is the length of the moving clock as seen from the stationary frame.
	webphysics.davidson.edu /physlet_resources/special_relativity/illustration4.html (633 words)

	The State of Experimental Evidence for Length Contraction
		Sherwin realized that if the Lorentz worldview was correct, that the spring would undergo a length contraction when it was aligned with its motion through the ether, while it would not experience the length contraction when it was aligned perpendicular to its motion through the ether.
		However, for the real length contractions of the Lorentz theory, the spring should truly contract along its long dimension when it is aligned with it's velocity through the ether.
		Again, if the atoms slide along their common point of contact they are able to smoothly transition from the case of a longitudinal length contraction of the spring to that of a transversely contracted spring.
	itis.volta.alessandria.it /episteme/ep6/ep6-lars1.htm (2872 words)

	Science Forums and Debate - Measure this!!!
		This is because length contraction only occurs if the observed length of the system you are measuring is moving as a whole respective to the stationary observer.
		In your scenario, the measured length of the two points are not moving together with respect to the stationary observer, and hence no length contraction results as oberved by the stionary observer.
		i was under the impression that the contraction was done by the object and not the space between two objects.
	www.scienceforums.net /forums/printthread.php?t=7394 (412 words)

	Hans Reichenbach [Internet Encyclopedia of Philosophy]
		For example, the unit of length, ie the metre, is defined by a co-ordinative definition; the physical object corresponding to the metre is the standard rod in Paris (Museum of weights and measures in Paris houses the units of measure for International System of Units).
		The special theory of relativity states that the length of a rod measured using a metre that is at rest with respect to the rod is different from the length measured using a metre which is moving with respect to the rod.
		It must be acknowledged that the length of a moving rod is a matter of definition, but the length contraction is a genuine physical hypothesis confirmed by experiments.
	www.iep.utm.edu /r/reichenb.htm (8071 words)

	[No title]
		The effective physical angular separation of the poles after length contraction is: EMBED Equation.3 (9) The local visual effect of aberration will be applied with respect to light arriving from the new positions of the poles obtained due to the real Lorentz length contraction.
		Aberration Vs. Lorentz Contraction We must look at the cause of aberration in special relativity closely to see that this observed effect is independent of, and in addition to, the Lorentz length contraction.
		The combined length contraction effect of the galaxies proper motion plus that of the Earth is, to first order in v2/c2 simply the sum of the two values, with the component due to proper motion representing a constant offset for all Earth velocities.
	renshaw.teleinc.com /papers/simiee2/simiee2.doc (5304 words)

	The physics of length contraction.
		The length of a rod at rest in its (rest) frame is called its proper length.
		That means the length L0' of train A'B' at rest is longer than the length L0 of train AB.
		For observer M' length contraction is not an issue.
	users.pandora.be /nicvroom/vabsolute.htm (2241 words)

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