70:, which contains a unique set of events that constitutes the observer's present moment. Observers moving at different relative velocities have different planes of simultaneity, and hence different sets of events that are present. Each observer considers their set of present events to be a three-dimensional universe, but even the slightest movement of the head or offset in distance between observers can cause the three-dimensional universes to have differing content. If each three-dimensional universe exists, then the existence of multiple three-dimensional universes suggests that the universe is four-dimensional. The
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101:, then events in this galaxy might be hours or even days advanced of the events on Andromeda for the person walking in the other direction. If this occurs, it would have dramatic effects on our understanding of time. Penrose highlighted the consequences by discussing a potential invasion of Earth by aliens living in the Andromeda Galaxy. As Penrose put it:
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The "paradox" consists of two observers who are, from their conscious perspective, in the same place and at the same instant having different sets of events in their "present moment". Notice that neither observer can actually "see" what is happening in
Andromeda, because light from Andromeda (and the
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Two people pass each other on the street; and according to one of the two people, an
Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will actually take place has not yet been made. How can there still be some uncertainty as
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of the launching of the space fleet. They can know only later, when telescopic observations from Earth reveal that the fleet is indeed on its way. Then they can hark back to that chance encounter, and come to the conclusion that at
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hypothetical alien fleet) will take 2.5 million years to reach Earth. The argument is not about what can be "seen"; it is purely about what events different observers consider to occur in the present moment.
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in which he points out that two people walking past each other on the street could have very different present moments. If one of the people were walking towards the
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That no inherent meaning can be assigned to the simultaneity of distant events is the single most important lesson to be learned from relativity.
299:, The Western Ontario Series in Philosophy of Science, volume 73, Springer Science+Business Media B.V., 2009, p. 349, ISBN 978-1-4020-9106-3
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time, according to one of them, the decision lay in the uncertain future, while to the other, it lay in the certain past. Was there
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is named after the discussions by
Rietdijk (1966) and Putnam (1967). It is sometimes called the Rietdijk–Putnam–Penrose argument.
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The interpretations of relativity used in the
Rietdijk–Putnam argument and the Andromeda paradox are not universally accepted.
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be any uncertainty. The launching of the space fleet is an inevitability. In fact neither of the people can yet
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Rietdijk, C. Wim (1966) "A Rigorous Proof of
Determinism Derived from the Special Theory of Relativity",
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Quantum
Reality, Relativistic Causality, and Closing the Epistemic Circle: Essays in Honour of Abner Shimony
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337:, Elsevier, Amsterdam, 2006; "Philosophy and Foundations of Physics" Series, pp. 207–228
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So stressing that the "present moment" cannot be applied to very distant events with any accuracy.
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is a local concept that cannot be extended to global hyperplanes. Furthermore,
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Vesselin Petkov (2005) "Is There an
Alternative to the Block Universe View?"
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The
Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics
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The
Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics
314:, Princeton University Press, Princeton (NJ), 2021, ISBN 978-0-6912-1877-9
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53:, uses 20th-century findings in physics – specifically in
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If special relativity is true, then each observer will have their own
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Wikibook:The relativity of simultaneity and the
Andromeda paradox
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Fashion, Faith, and Fantasy in the New Physics of the Universe
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person the decision has already been made, then surely there
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advanced a form of this argument that has been called the
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any uncertainty about that future? Or was the future of
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Philosophical argument based on the theory of relativity
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Putnam, Hilary (1967) "Time and Physical Geometry",
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466:The Large, the Small and the Human Mind
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565:Penrose–Hawking singularity theorems
250:. Oxford University Press. pp.
348:Stanford Encyclopedia of Philosophy
227:Stanford Encyclopedia of Philosophy
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610:Orchestrated objective reduction
483:White Mars or, The Mind Set Free
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570:Riemannian Penrose inequality
477:and Stephen Hawking) (1997)
452:The Nature of Space and Time
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634:Conformal cyclic cosmology
595:Penrose graphical notation
535:Weyl curvature hypothesis
335:The Ontology of Spacetime
291:Savitt, Steven F. (2009)
282:, 58:2 (1991) pp. 147–167
555:Newman–Penrose formalism
308:Mermin, N. David (2005)
216:, 64, (1967) pp. 240–247
131:people already "fixed"?
36:Rietdijk–Putnam argument
515:Abstract index notation
242:Penrose, Roger (1989).
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67:plane of simultaneity
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