Sabine Hossenfelder: "Before Einstein, time was this universal parameter. We all shared the same moment of time; the same moment of now that we could all agree on. But then Einstein came and he said, "Well, it's not that simple." And the major reason for
this is that the speed of light is finite, and nothing can go faster than the speed of light - IT'S THE SAME FOR ALL OBSERVERS. And this sounds like a really innocent assumption, but it has a truly fundamental consequence..." https://youtu.be/8ePu81ssU4M?
t=85

So Hossenfelder now knows that the invariance of the speed of light is a crucial assumption in special relativity. Earlier she used to teach that "it is unnecessary to postulate that the speed of light is invariant":

Sabine Hossenfelder: "If photons had a restmass, special relativity would still be as valid as it's always been. The longer answer is that the invariance of the speed of light features prominently in the popular explanations of special relativity for
historic reasons, not for technical reasons. Einstein was lead to special relativity contemplating what it would be like to travel with light, and then tried to find a way to accommodate an observer's motion with the invariance of the speed of light. But
the derivation of special relativity is much more general than that, and it is unnecessary to postulate that the speed of light is invariant." http://backreaction.blogspot.bg/2016/05/dear-dr-b-if-photons-have-mass-would.html

Pentcho Valev https://twitter.com/pentcho_valev

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Sabine Hossenfelder couldn't care less about criticism coming from cranks, crackpots, trolls etc., but now a brother Einsteinian informs the world that she doesn't understand relativity:

The REAL Reason You Don't Understand Relativity https://www.youtube.com/watch?v=an6JiBLQqXY&t=519s

True, the brother Einsteinian claims that nobody, not even the greatest minds in physics, understands Einstein's relativity, but I don't think Sabine will find this reassuring.

Pentcho Valev https://twitter.com/pentcho_valev

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That "it is unnecessary to postulate that the speed of light is invariant" was not Sabine Hossenfelder's idea of course - she borrowed it from higher priests in the Einstein Cult:

Mitchell J. Feigenbaum: "In this paper, not only do I show that the constant speed of light is unnecessary for the construction of the theories of relativity, but overwhelmingly more, there is no room for it in the theory." http://arxiv.org/PS_cache/
arxiv/pdf/0806/0806.1234v1.pdf

Mark Buchanan: "...a photon with mass would not necessarily always travel at the same speed. Feigenbaum's work shows how, contrary to many physicists' beliefs, this need not be a problem for relativity." http://www.newscientist.com/article/mg20026801.500-
why-einstein-was-wrong-about-relativity.html

Jean-Marc Levy-Leblond: "The evidence of the nonzero mass of the photon would not, as such, shake in any way the validity of the special relativity. It would, however, nullify all its derivations which are based on the invariance of the photon velocity."
http://o.castera.free.fr/pdf/One_more_derivation.pdf

Jean-Marc Lévy-Leblond: "It could even be that future measurements highlight a tiny, but not zero, mass of the photon; the light then would no longer go at the "speed of light", or, more precisely, the speed of light, henceforth variable, would no
longer be identified with the invariant speed limit. The operational procedures brought into play by the "second postulate" would become null and void ipso facto. Would the theory itself be invalidated? Fortunately, not at all." http://o.castera.free.fr/
pdf/Chronogeometrie.pdf

Pentcho Valev https://twitter.com/pentcho_valev

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