Path: ...!fu-berlin.de!uni-berlin.de!not-for-mail From: ram@zedat.fu-berlin.de (Stefan Ram) Newsgroups: sci.physics.relativity Subject: Energy? Date: 28 Jul 2024 09:37:36 GMT Organization: Stefan Ram Lines: 28 Expires: 1 Jul 2025 11:59:58 GMT Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Trace: news.uni-berlin.de shI946F2pktmRQJvzUrK2QwA1sM5FFltLMEOrIbKaJQpcg Cancel-Lock: sha1:l2ueG/ajBgLEifq7CYmP8a1GLcU= sha256:Az1nwjuJApsnLHLNqdnMvk7YvBn0wiiPPWnDZtseKPs= 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: 2151 In a chapter of a book, the author gives this relation for a system with mass m = 0: E^2/c^2 = p^"3-vector" * p^"3-vector" . Then he writes, "This implies that either there is no particle at all, E = 0, or we have a particle, E <> 0, and therefore p^'3-vector' <> 0.". So, his intention is to kind of prove that a particle without mass must have momentum. But I wonder: Does "E = 0" really mean, "there is no particle."? 300 years ago, folks would have said, "m = 0" means that there is no particle! Today, we know that there are particles with no mass. Can we be confident that "E = 0" means "no particle", or could there be a particle with "E = 0"? Here's the Unicode: E²/c² = p⃗ · p⃗ and |This implies that either there is no particle at all, E = 0, or we |have a particle, E ≠ 0, and therefore p⃗ ≠ 0.