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Path: ...!fu-berlin.de!uni-berlin.de!not-for-mail From: ram@zedat.fu-berlin.de (Stefan Ram) Newsgroups: sci.physics.relativity Subject: Re: Langevin's paradox again Date: 11 Jul 2024 14:09:32 GMT Organization: Stefan Ram Lines: 59 Expires: 1 Feb 2025 11:59:58 GMT Message-ID: <acceleration-20240711150210@ram.dialup.fu-berlin.de> References: <FER4K03RCuXsBiIlfVNSgR0vilQ@jntp> <FlDiO.56506$GVTf.837@fx01.ams4> <lf40ddFdu9kU3@mid.individual.net> <Qjq15Muw8aIiGRVOKV0Bu2oT9_k@jntp> <v6mlhe$21277$2@dont-email.me> <9oTvw4-YSIPb1dubtdBwcc_MeX8@jntp> <v6ojjl$2fb4i$1@dont-email.me> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Trace: news.uni-berlin.de ligpzqd+TyDgTgdDKImIWAGeh3tsKiKHtj5VzK1Ep68+0I Cancel-Lock: sha1:ZCItv99LRuLy+XIjbmzM/VkMILc= sha256:JRJQi4HSuGWF+vC79QygVBVW5A40W/bh7xVwlL19t64= X-Copyright: (C) Copyright 2024 Stefan Ram. All rights reserved. Distribution through any means other than regular usenet channels is forbidden. It is forbidden to publish this article in the Web, to change URIs of this article into links, and to transfer the body without this notice, but quotations of parts in other Usenet posts are allowed. X-No-Archive: Yes Archive: no X-No-Archive-Readme: "X-No-Archive" is set, because this prevents some services to mirror the article in the web. But the article may be kept on a Usenet archive server with only NNTP access. X-No-Html: yes Content-Language: en-US Bytes: 4355 "Paul.B.Andersen" <relativity@paulba.no> wrote or quoted: >But what happens when twin B is accelerating makes all the difference. From the perspective of the twin chilling back on Earth, the traveling twin is getting the time dilation treatment the whole time, so he ages way less. That part's a no-brainer. But now let's flip the script and look at it /from the traveling twin's point of view/: When the traveling twin bounces from Earth (I'm assuming constant velocity for simplicity), time on Earth starts slowing down for them. Not like, looking through a telescope slow, but like, the time between two moments on Earth that line up with a single second on the spaceship is actually less than a second. Trippy, right? Then when the traveling twin boomerangs back to Earth, time is still dragging for them. That's the time dilation working its magic - independent of the direction of the movement. So the traveling twin should be thinking his Earth-bound bro is aging slower. But somehow, it's the opposite - the Earth twin is looking way more mature. What gives? Could it have something to do with that quick boost in the middle to flip the script and head back? This is the question that's been stumping everyone, but get this - I found the answer last year in some old Einstein text. Here's how it breaks down: The traveler thinks of himself as stationary and unaccelerated. But how does he keep that mindset when the engines are blasting during the turnaround? It's like there's a uniform gravitational field filling the whole space - the engines are just keeping the ship from falling in it, so it stays at rest! So if the traveler sees himself as at rest during that acceleration, a uniform gravitational field is filling the whole space for him. In this field, the traveler and Earth twin are at totally different potentials (and the farther apart, the bigger the difference). This potential gap makes time on Earth zoom by so fast, it more than makes up for the slowdown on the outbound and return legs! And that's why, /also from the traveler's point of view/, more time has passed on Earth than on their ship by the end of the trip! ~~ BTW: I just read the name "Langevin" in some book: |In 1924, Prince Louis de Broglie of France proposed in his |doctoral dissertation that the electron, evidently a discrete |point particle, might actually be a wave. De Broglie's thesis |advisor, Paul Langevin, did what befuddled senior professors |are wont to do: defer to a higher authority. He sent the |dissertation to Einstein, who recognized its importance |immediately. On Einstein's say-so, Langevin gave de Broglie |his degree. .