Frank Wappler (@MisterRelativity@mathstodon.xyz)

@LaEsperantaHominoid@mastodon.social wrote (22. Jan. 2026, 06:37): > _I keep hearing "relativity says nothing can travel faster than causality"_ This exact wording you didn't hear from me. ... Damn shame we can no longer search exactly what was to be heard (read) directly from Einstein; as per: https://en.wikipedia.org/wiki/Einstein_Papers_Project#(2014-2025)_The_Digital_Einstein_Papers FWIW, I'd sound more like "In #relativity , attention is given to the front of a signal, i.e. to the very first indication which an (sensitive) observer perceived of an event actually having happend in which he didn't take part himself. Whatever a particular observer noticed of a particular event, or causally due to this event, he must have noticed at, or after, having noticed the signal front of this event." > _Well what if just assume it can and do the mathematics anyways?_ Referring to notions + symbols https://en.wikipedia.org/wiki/Causal_structure#Causal_relations we can suitably formalize - (the timelike world line \(\mathcal W\) of) an observer, as a chronologically ordered set of events: \( \forall a, b \in \mathcal W : (((a \ll b) \land \) \( \qquad (not[ b \leq a ])) \lor ((b \ll a) \land (not[ a \leq b ])) \lor (a \equiv b)) \) \( \forall a, b, c \in \mathcal W : (((a \ll b) \land (b \ll c)) \implies (a \ll c)) \) - the event of \(\mathcal W\), which is unique provided it exists at all, which belongs to the signal front of a given event \(\varepsilon\): \( f \in \mathcal W : (f \neq \varepsilon) \land (\varepsilon < f) \land \) \( \qquad (\forall x \in \mathcal W : (\varepsilon < x) \implies ((x \equiv f) \lor (f \ll x))) \) So: "just assuming" \[ \exists y \in \mathcal W : (\exists f) \implies (\varepsilon < y) \land (y \ll f))) \] ... says: the very assumption of \(y\) existing as described is an absurdity.