Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Thomas Heger Newsgroups: sci.physics.relativity,sci.math Subject: Re: What amount of acceleration involved is too high for SR to apply? Date: Sat, 8 Aug 2026 07:59:56 +0200 Lines: 32 Message-ID: References: <10qhdbr$3mfl8$1@dont-email.me> <114ku54$3pu7t$1@news.nntp4.net> <114pvvg$2e49$1@news.nntp4.net> <1154bfr$jtrc$2@news.nntp4.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net n8k4qFeQpSzVEV62UTHL6QTFhD78BjOn+vIfCf3Ddio70UVB9e Cancel-Lock: sha1:n63RkNZ672mbTZcQxAZIP/c9bi4= sha256:OK3GkLQ8kGKWlpY3IM3W9o10F+30X0nGwb4/eYYQ4cU= User-Agent: Mozilla Thunderbird Content-Language: de-DE, en-US In-Reply-To: <1154bfr$jtrc$2@news.nntp4.net> Xref: csiph.com sci.physics.relativity:671891 sci.math:647186 Am Freitag000007, 07.08.2026 um 12:19 schrieb Leslie Ruzimatov: > Thomas Heger wrote: > >> you don't need to have a reference point to measure acceleration, but >> you need a reference point, if you want to measure your own velocity (in >> a space like that of SRT). > > yet another student not knowing what acceleration is Actually I know how 'acceleration' is defined: https://en.wikipedia.org/wiki/Acceleration Quote: "It is defined as the rate of change of the velocity. Like velocity, acceleration has a magnitude and a direction, making it a vector quantity" The direction could be taken from the direction of motion (which is the observers own direction 'forward') and some arbitrary point for rotation (say: left). This requires no external reference points, hence acceleration could be measured without knowing, where you are. Velocity, on the other hand, cannot be measured without an external reference point, because velocity is a change, too, but not of velocity but of distance. And distance always needs two points at the ends of a straight line. TH