Both the General & Special Relativity discarded Newtonian mechanics of absoluteness. According to Einstein's view, Time, Mass, Length and Space are interdependent. So, Did Relativity discarded only absoluteness in space and mentioned that all motions are relative... What else suffocated in Physics due to Relativity..?

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## closed as too broad by centralcharge, Emilio Pisanty, akhmeteli, Manishearth♦Sep 29 '13 at 7:17

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"all are relative" is precisely the wrong way to think about relativity. One of the tenets of relativity theory is that "the laws of physics appear the same to all inertial observers"; one may argue from this that relativity postulates a more absolute law of physics compared to the Newtonian version. – Willie Wong Sep 6 '12 at 16:02

With SR, the absoluteness of simultaneity was discarded, i.e., two events may have the same time coordinate in one inertial frame but not in relatively moving others.

In GR, where the geometry of a general spacetime evolves, the very notion of simultaneous is arbitrary. From "Gravitation" by MTW:

In Newtonian theory or special relativity, one chooses hypersurfaces of constant time. But in dynamic regions of curved spacetime, no naturally preferred time coordinate exists. This situation forces one to make a totally arbitrary choice of hypersurfaces to use in visualizing the time-development of geometry, and to keep in mind how very arbitrary that choice was.

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In short Newtonian mechanics with Galilean relativity allowed that all observer could agree on both

• The spatial distance $\mathrm{d}r^2 = \mathrm{d}x^2 + \mathrm{d}y^2 + \mathrm{d}z^2$
• The time difference $\mathrm{d}t$ between two events

Special relativity holds that neither of these differences are invariant, but that all inertial observers can agree on the interval $\mathrm{d}s^2 = c^2\mathrm{d}t^2 -\mathrm{d}x^2 - \mathrm{d}y^2 - \mathrm{d}z^2$ between two events.

General relativity complicates the matter more by inserting a possibly non-flat metric intro the calculation of the interval.

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Basically, relativity simply replaces the absoluteness in Newtonian mechanics with a different kind of absoluteness. Relativity is a rather misleading name. – Siyuan Ren Sep 6 '12 at 17:04
Relativity is a very misleading name. – Argus Sep 6 '12 at 18:19

The assumption of absolute spacial references was easily disprovable even in Newton's time, from the fact that his laws of motion were preserved in inertial frames, making it impossible to state that something is objectively not moving. However, this pseudo-religious standpoint of Newton's fit in well with the then generally held belief of an absolute time reference, which was surely a more forgivable mistake due to the nearly imperceptible effect of time dilation in normal life. Another of Newton's prejudices was handed down to him through centuries of teachings in geometry, namely that the universe was entirely Euclidean. That this idea was inevitably to give way to general relativity echoes what relativity did to the idea of absolute space/time.

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