Special Relativity:
The Laws of Physics are the Same for All Nonaccelerating Observers: No matter how fast an observer is moving, they will measure the same speed of light and observe the same laws of physics.
The Speed of Light is Constant: The speed of light in a vacuum is the same for all observers, regardless of their relative motion or the motion of the light source.
Conclusions:
Time dilation: the convention from 1905: Time passes slower for objects moving at high speeds compared to those at rest. This effect becomes significant only speeds close to the speed of light.
Length Contraction: Objects contract in length along the direction of motion as they approach the speed of light.
E = mc^2: This famous equation relates energy (E) to mass (m) with the speed of light (c) as the constant of proportionality. It implies that energy and mass are interchangeable....
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"No matter how fast an observer is moving...." (Speed is 'local', 'finite', and 'relative' and there exists such equals but opposite elements as 'nonlocal', 'nonfinite', and 'nonrelative').
The Speed of Light is Constant: Constant to an infinitely variable rest . . . an infinitely variable '0'. Light is emitted in spontaneous REALTIME, thus singularly photo-event frame histories.
Conclusions:
Time Dilation: The conventional deals in absolutism alone, explicitly stated and implied. There is no such thing as "close to the speed of light" except in a closed (enclosed) system. The open (opening) system is immeasurable.
Length Contraction: In the open (the opening) system, objects do not contract in length along the direction of motion since they do not ever approach the speed of light. Length contraction, and time dilation. are in the observed, the observable, light clock, not the unobserved, the unobservable, object (clock) always forward -- quantum disentangled and disentangling -- in time of the light "at a distance" (any distance at all going away or oncoming).
E = mc^2: Open or opening 2-d flatland universe surface (aka matter) versus enclosed 3-d spherical universe volume (aka mass-energy): c = +300,000kps |0| -300,000kps as the constant of proportionality (Rest ('|0|'), tensor flexibly, infinitely variable (infinite '0')).