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Topic: Twin paradox

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Minkowski diagram

Time dilation

Physical paradox

Special theory of relativity

Special relativity

Proper time

Twin

Speed of light

Interstellar travel

Paradox

Theory of relativity

General relativity

Acceleration

Bucket argument

Relativistic rocket

	Paradox - Wikipedia, the free encyclopedia
		Paradoxes that arise from apparently intelligible uses of language are often of interest to logicians and philosophers.
		Russell's paradox, which shows that the notion of the set of all those sets that do not contain themselves leads to a contradiction, was instrumental in the development of modern logic and set theory.
		Paradoxes which are not based on a hidden error generally happen at the fringes of context or language, and require extending the context or language to lose their paradox quality.
	en.wikipedia.org /wiki/Paradox (969 words)

	Twin paradox - Wikipedia, the free encyclopedia
		The twin paradox, sometimes called the "clock paradox", stems from Paul Langevin's 1911 thought experiment in special relativity: one of two twin brothers undertakes a long space journey with a high-speed rocket at almost the speed of light, while the other twin remains on Earth.
		The perception of paradox is rooted in a misunderstanding of the meaning of equivalent frames in relativity and therefore arises in both SR and GR.
		The twin on Earth rests in the same inertial frame for the whole duration of the flight (no accelerating or decelerating forces apply to him) and he is therefore able to distinguish himself as "privileged" compared with the space ship twin.
	en.wikipedia.org /wiki/Twin_paradox (3903 words)

	Omnipotence paradox: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-11-07)
		A paradox is an apparently true statement or group of statements that seems to lead to a contradiction or to a situation that defies intuition, such as "this...
		The twin paradox is a thought experiment in special relativity of two twin brothers one undertakes a long space journey with a very high-speed rocket at almost...
		The raven paradox is a paradox proposed by the german logician carl gustav hempel in the 1940s to illustrate a problem where inductive logic violates...
	www.absoluteastronomy.com /encyclopedia/o/om/omnipotence_paradox.htm (3070 words)

	:::. Twin Paradox .:::. Time Travel .:::. Paradox Theories .:::. CODE 10 .:::. Myth and Mystery .::: (Site not responding. Last check: 2007-11-07)
		This is not really a paradox, but it has been given that name because it is usually oversimplified, it is mistakenly thought to be a justification of the theory and it really is contrary to common experience.
		This means that the space ship twin can validly say that it is the Earth that has travelled away from her and then back again and that therefore the twin on the speeding planet should be the younger when they meet again.
		These hypothetical gymnastics should help explain, not the paradox, but how there is no paradox when sufficient information is taken into account, the experience of a twin on the probe and another on a buoy are qualitatively different and so it should not be so surprising that they are quantitatively different too.
	www11.brinkster.com /code10v2/paradox/main/time_travel/twin_paradox.html (1289 words)

	Paradoxes Resolved, Origins Illuminated - Twin paradox "resolution" article
		But the paradox is all about why this is happening in SR and not about how it is happenning, which is the subject dealt in the article.
		This is exactly why it is called a paradox within the framework of SR because one of the postulates, axiom, laws or whatever you want to call them, of that theory is the non-preferred reference frame notion.
		In your twin paradox interpretation that involves a constant travelling velocity, the reciprocity may break down if the moving twin experiences an accelaration for an interval dt, sufficient enough to excert a force on her.
	www.metaresearch.org /msgboard/topic.asp?TOPIC_ID=283 (4416 words)

	YE OLDE TWIN PARADOX
		The Lorentz transform of this "journey's end" event to the T frame, in which the travelling twin is at rest is (0,0.57)T. Between the start and the end of the journey, 4.04 years have elapsed in the S frame, and 0.57 years (around 7 months) have elapsed in the T frame.
		The twin who has travelled from Earth to Proxima is 0.57 years old at the journey's end, because only 0.57 years have elapsed between the start and the end of the journey in his frame.
		In terms of the twins' original adventure, where the twin in the T frame (call him the T twin, or twin T for short) was going to Proxima, the physics of the journey required that he age continuously from t'=0 to t'=0.57 during the journey.
	chabin.laurent.free.fr /twinzz.htm (7206 words)

	Twin Paradox
		If the earthbound twin were to subtract the light travel time from these readings, he would obtain the values shown in the second clock.
		The leftmost bar shows the age of the Earthbound twin, the middle bar gives the simultaneous (according to Earth) age of the traveling twin, and the rightmost bar gives the age of the traveling twin as viewed by the Earthbound twin through his telescope.
		If the earthbound twin were to subtract the light travel time from these readings, she would obtain the values shown in the second clock.
	webphysics.davidson.edu /physletprob/ch10_modern/twin.html (453 words)

	The twin paradox (Site not responding. Last check: 2007-11-07)
		A paradox is a seemingly self-contradictory result that presents a puzzle as to its interpretation.
		One twin is sent traveling at 95% the speed of light around the galaxy.
		The reason this provides a paradox is that to the twin in the rocket, the first Earth-bound twin's clocks should be slow, and should therefore be slower.
	www.pa.msu.edu /courses/1997spring/phy232/lectures/relativity/paradox.html (154 words)

	Twin Paradox
		The ``paradox'' part of the twin paradox arises from making the symmetric argument in which one assumes the reference frame of the traveling twin to be stationary.
		The frame of the earth-bound twin must then travel in the sense opposite that of the erstwhile traveling twin, which means that the earth-bound twin must age less rather than more.
		During this interval, the line of simulaneity of the traveling twin rotates, as illustrated in figure 4.9, such that the twin staying at home rapidly ages in the reference frame of the traveler.
	www.physics.nmt.edu /~raymond/classes/ph13xbook/node46.html (422 words)

	Time Supplement [Internet Encyclopedia of Philosophy]
		This paradox, also called the clock paradox and the twin paradox, is an argument about time dilation that uses the theory of relativity to produce a contradiction.
		If the first half of the analysis is correct in assuming that the Earth-based twin remains in an inertial frame during the entire flight of the spaceship, then the second half is incorrect in assuming that the spaceship could remain stationary in some inertial frame during the entire flight.
		The argument of the twins paradox applies the heuristic principle anyway, and draws an incorrect conclusion that there is a contradiction.
	www.iep.utm.edu /ancillaries/time-sup.htm (13049 words)

	Scientific American: How does relativity theory resolve the Twin Paradox? (Site not responding. Last check: 2007-11-07)
		In this supposed paradox, one of two twins travels at near the speed of light to a distant star and returns to the earth.
		The paradox lies in the question "Why is the traveling brother younger?" Special relativity tells us that an observed clock, traveling at a high speed past an observer, appears to run more slowly.
		When the paradox is addressed, it is usually done so only briefly, by saying that the one who feels the acceleration is the one who is younger at the end of the trip.
	sciam.com /print_version.cfm?articleID=000BA7D8-2FB2-1E6D-A98A809EC5880105 (1131 words)

	The Twin Paradox: (Site not responding. Last check: 2007-11-07)
		The path (world line) of the rocket twin is shown by the solid line that slants to the right, and then to the left, meeting up with the earth twin after 8 ticks of the earth clock.
		As discussed above, in the earth twin's frame, the rocket ticks occur less frequently (since the rocket clock is moving), and therefore the rocket twin will age less then the earth twin when they again meet.
		One would naively believe that the situation is symmetric and that from the rocket twin's point of view, the earth twin should have aged less then the rocket twin.
	www.physics.nyu.edu /courses/V85.0020/node44.html (355 words)

	Twin Paradox (Site not responding. Last check: 2007-11-07)
		The players in the Twin Paradox are two twins called A and B. Each has a clock.
		The common explanation for the Twin Paradox is that A is at rest in an inertial frame and B is in an accelerated frame (which requires General Relativity).
		The speed of B in the Twin Paradox is not constant.
	users.telenet.be /nicvroom/twinpar.htm (462 words)

	Alternate View Column AV-38
		The relativistic twin paradox, the slowing of biological clocks by relativistic time dilation and the differences in aging thereby produced are not new in science fiction.
		Therefore, the twin paradox cannot be analyzed with special relativity alone, and we can't simply use the Lorentz transformations to say what the two clock readings will be after the trip.
		The Lorentz transformations of special relativity on which the twin paradox is based assume that the set of observations of mass, length, and time is made from one inertial reference frame, one coordinate system that is either at rest or is moving with an unchanging speed in a particular direction.
	www.npl.washington.edu /AV/altvw38.html (2172 words)

	Twin paradox and other special relativity topics
		The story is that one of a pair of twins leaves on a high speed space journey during which he travels at a large fraction of the speed of light while the other remains on the Earth.
		Because of time dilation, time is running more slowly in the spacecraft as seen by the earthbound twin and the traveling twin will find that the earthbound twin will be older upon return from the journey.
		The clear implication is that the traveling twin would indeed be younger, but the scenario is complicated by the fact that the traveling twin must be accelerated up to traveling speed, turned around, and decelerated again upon return to Earth.
	hyperphysics.phy-astr.gsu.edu /hbase/relativ/twin.html (415 words)

	twin paradox
		The twin on Earth is justified in saying that the twin in the spaceship's clock is moving slower, and, at the same time, the twin in the spaceship is justified in saying the twin on the Earth's clock is moving slower.
		The twin on the spaceship will claim the clock on Earth actually started a long time before his clock, while the twin on the Earth will claim the clocks were synchronized.
		The important difference is that while distance is shorter, for the twin paradox the elapsed time is _longest_ for the observer who follows the straight path.
	www.physicsforums.com /showthread.php?threadid=77441 (1496 words)

	Twin Paradox
		What is a paradox is that as each observer is in an inertial frame of reference each twin thinks the other is 'younger'.
		The SR twin paradox is resolved by considering the two observers different surfaces of simultaneity.
		However in the cosmological twin paradox in a closed universe two observers could meet and one circumnavigate the universe and they meet again much later.
	www.physicsforums.com /showthread.php?t=55888 (1943 words)

	Twin Paradox (Site not responding. Last check: 2007-11-07)
		Special Relativity predicts that two twins, one on Earth, call her Elizabeth, and another traveling at close to the speed of light, call her Alice, will age at different rates.
		The paradox arises because you might be thinking that Alice and Elizabeth's situations are symmteric.
		Contrast this version of the twin paradox with the adventures of Alice and Elizabeth in "The Twin Paradox?" by Gordon E. Sarty 2004, Education Notes, Journal of the Royal Astronomical Society of Canada.
	geology.wcupa.edu /mgagne/ess355/activities/twin-paradox-7.html (982 words)

	Ray on the Twin Paradox
		Beginning on Earth, two biologically identical twins are separated by one twin's departure on a space journey during which the travelling twin achieves near-lightspeed velocity (relative to the stay-at-home twin).
		A very ingenious revision of the standard twin scenario was concocted by defenders of the sufficiency of SR to make their case ([3], p.
		So I have no doubt that SR is logically sufficient to explain both the twins and triplets paradoxes in terms of the geometry of SR spacetime _given_ that the participants of the scenarios are already in their respective relative motions.
	www.vivboard.net /doc/n005f.htm (2280 words)

	Hypography Science Forums - Twin paradox (Site not responding. Last check: 2007-11-07)
		Twin leaves earth on rocket at near speed of light.
		Twin A (in rocket) sees time slow down on earth, twin B (on earth) sees time slow down in rocket.
		He sees Twin B who is younger than he is, but he slows down, lands gets out, and sees that Twin B is in fact older.
	forums.hypography.com /.../5802-twin-paradox.html#post90766 (749 words)

	Einstein, Sommerfeld and the twin paradox
		Many have written on this inconsistency, known as the "twin paradox" or the "clock paradox" and more than a few have not understood that the "paradox" does not refer to the strangeness of time dilation but to a logical inconsistency in what is now known as the special (for "special case") theory of relativity.
		GR resolves the paradox non-globally, in that Einstein now holds that some accelerations are not strictly relative, but functions of a set of curvatures.
		So yes, GR partly resolves the clock paradox and, by viewing the 1905 equations for uniform motion as a special case of the 1915 equations, retroactively removes the paradox from SR, although it appears that Einstein avoided pointing this out in 1915 or thereafter.
	www.angelfire.com /az3/nfold/relativity.html (2427 words)

	sciforums.com - The Twin Paradox
		This paradox arises becuase, according to relativity, if one of two identical twins spent his life in a rocketship traveling near the speed of light, when he comes back to earth, he will be younger than his sibling.
		The twin paradox says that one twin, Bob, stays on Earth and another twin, Ann, goes off into space in a spaceship traveling near the speed of light.
		So the two twins would disagree on their ages, but it's got to be one or the other.
	www.sciforums.com /showthread.php?t=89 (1725 words)

	twin paradox (Site not responding. Last check: 2007-11-07)
		Both twins have the same relative velocity with repect to one another at all times during the trip.
		The traveling twin does not stay put in a single nonaccelerating frame of reference during his journey, however, so life is more complicated for him.
		On out outgoing part, the traveling twin thinks his stay-at-home twin's watch is running slow, just like his stay-at-home twin thinks the traveling twin's watch is runnning slow.
	van.hep.uiuc.edu /van/qa/section/New_and_Exciting_Physics/Relativity/20030515013450.htm (717 words)

	Feenburg’s Twin Paradox Still Unsolved? - Science Articles
		Twin A and B both observe the star’s frequency as f0 when at rest on the Earth.
		After a set length of proper time, ½tb, twin* B stops and begins the return to Earth maintaining the same speed (for simplicity) as during the departure.
		So the transverse Doppler effect must warrant that the frequency of the variable with respect to B’s clocks and rulers to be fb=f0/√(1-v2/c2) where c is the speed of light in the vacuum of space.
	www.physicspost.com /articles.php?articleId=160 (1023 words)

	The Twin Paradox (from Einstein Light)
		The twin paradox uses the symmetry of time dilation to produce a situation that seems paradoxical.
		In these diagrams, we have resolved the paradox by pointing out that the problem is not symmetrical: Jane actually has two different inertial frames of reference, the outgoing voyage and the return.
		This is quite important, because proponents of the twin paradox sometimes argue that, whatever the effect of the turn around, it can be made negligible by making the journey far enough.
	www.phys.unsw.edu.au /einsteinlight/jw/module4_twin_paradox.htm (1959 words)

	COSMOLOGY MODELS - The Twin Paradox (Site not responding. Last check: 2007-11-07)
		The paradox comes about because it would seem that if we took as our reference frame the frame in which twin B is at rest on the outbound leg and twin A is thus moving throughout the adventure, then twin A's clock should be slower hence the seeming contradiction.
		We should realize however that in the reference frame of twin B at the start he is not moving but after the distant point passes him he has to go at much greater speed than the other twin's speed in order to catch up and hence his clock is more greatly slowed.
		The equations go as follows: on the outbound leg twin B is at rest and twin A is moving at velocity v (for the whole adventure).
	www.cosmologymodels.com /twin-paradox.html (518 words)

	Twin Paradox (Site not responding. Last check: 2007-11-07)
		The Twin Paradox of Einstein is an interesting thought experiment involving two twins (who are nearly exactly the same age), one of whom sets out on a journey into space and back.
		A lot of explanations of the twin paradox have claimed that it is necessary to include a treatment of accelerations, or involve General Relativity.
		The three inertial frames are 1) at-home twin 2) the going-away twin and 3) the coming-back twin.
	mentock.home.mindspring.com /twins.htm (460 words)

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