In this thread https://www.physicsforums.com/showthread.php?t=361915" I showed my viewpoint on a real length contraction https://www.physicsforums.com/showpost.php?p=2486767&postcount=21": and I've see no criticism on my view, neither acceptance nor denial, that a real length contraction must exist. Then I searched the words of Lorentz, Einstein and also what others are saying. Nowadays textbooks may reflect, AFAIK, the position that Lorentz viewpoint is out of order, but I find this point ‘out of consensus’. To ease the discussion first I post here the words of Lorentz, Einstein and others. In the next post is my own 'visualization' and some questions. --------------------- Einstein words on aether: A. Einstein, “Zur Elektrodynamik bewegter K¨orper,” Annalen der Physik 17, 891 (1905). Reprinted as “On the electrodynamics of moving bodies” The reason that special relativity was considered a better explanation than the Lorentz-FitzGerald hypothesis can best be illustrated by Einstein’s own words: “The introduction of a ‘luminiferous ether’ will prove to be superfluous inasmuch as the view here to be developed will not require an ‘absolutely stationary space’ provided with special properties.” A. Einstein, “¨Ather und Relativit¨atstheorie,” address delivered on May 5th, 1920, in the University of Leyden. Reprinted as “Ether and the Theory of Relativity” in: A. Einstein, Sidelights on Relativity, Methuen and Co., London (1922). “The next position which it was possible to take up in face of this state of things [the acceptance of the special theory of relativity] appeared to be the following. The ether does not exist at all. (...) More careful reflection teaches us, however, that the special theory of relativity does not compel us to deny ether. We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it.” ... “Think of waves on the surface of water. Here, we can describe two entirely different things. Either we may observe how the undulatory surface forming the boundary between water and air alters in the course of time; or else – with the help of small floats, for instance – we can observe how the position of the separate particles of water alters in the course of time. If the existence of such floats for tracking the motion of the particles of a fluid were a fundamental impossibility in physics – if, in fact, nothing else whatever were observable than the shape of the space occupied by the water as it varies in time, we should have no ground for the assumption that water consists of movable particles. But all the same we could characterise it as a medium.” ...“tracking the motion of the particles on a fluid [is] a fundamental impossibility in physics.” ... “according to the general theory of relativity space without ether is unthinkable. (...) But this ether should not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it,” --------------------------------------------------- Lorentz words on length contraction: H. A. Lorentz, Versuch einer Theorie der elektrischen und optischen Erscheinungen in bewegten K¨orpern, Brill, Leiden (1895). §§89-92 reprinted as “Michelson’s Interference Experiment” “one would have to imagine that the motion of a solid body (...) through the resting ether exerts upon the dimensions of that body an influence which varies according to the orientation of the body with respect to the direction of motion.” ... “Surprising though this hypothesis may appear at first sight, yet we shall have to admit that it is by no means far-fetched, as soon as we assume that molecular forces are also transmitted through the ether, like the electrical and magnetic forces. [Then] the translation will very probably affect the action between two molecules or atoms in a manner resembling the attraction or repulsion between charged particles.” --------------------------------------------------- http://digital.csic.es/bitstream/10261/3425/3/0705.4652v2.pdf" [Broken] http://www.springerlink.com/content/h9515q267275t760/ Carlos Barceló1 and Gil Jannes1 (2007) Abstract Many condensed matter systems are such that their collective excitations at low energies can be described by fields satisfying equations of motion formally indistinguishable from those of relativistic field theory. The finite speed of propagation of the disturbances in the effective fields (in the simplest models, the speed of sound) plays here the role of the speed of light in fundamental physics. However, these apparently relativistic fields are immersed in an external Newtonian world (the condensed matter system itself and the laboratory can be considered Newtonian, since all the velocities involved are much smaller than the velocity of light) which provides a privileged coordinate system and therefore seems to destroy the possibility of having a perfectly defined relativistic emergent world. In this essay we ask ourselves the following question: In a homogeneous condensed matter medium, is there a way for internal observers, dealing exclusively with the low-energy collective phenomena, to detect their state of uniform motion with respect to the medium? By proposing a thought experiment based on the construction of a Michelson-Morley interferometer made of quasi-particles, we show that a real Lorentz-FitzGerald contraction takes place, so that internal observers are unable to find out anything about their ‘absolute’ state of motion. Therefore, we also show that an effective but perfectly defined relativistic world can emerge in a fishbowl world situated inside a Newtonian (laboratory) system. This leads us to reflect on the various levels of description in physics, in particular regarding the quest towards a theory of quantum gravity.