Einstein built special relativity on two postulates: no experiment can distinguish one constant- velocity laboratory from another, and light travels at the same speed in every such laboratory. However the second one is necessary for the general relativity?

GPT-5.4

Vote: No

General relativity does not require the light-speed postulate as an independent foundational assumption in the same way special relativity does. Its deeper starting point is local Lorentz invariance/equivalence principle: in a sufficiently small freely falling lab, nongravitational physics reduces to special relativity. From that structure, there is a finite invariant causal speed, identified physically with the speed of light in vacuum. So the constancy of light speed is inherited locally from the spacetime geometry, not separately required as a new global postulate for GR. Also, in curved spacetime, coordinate speeds of light can vary depending on coordinates, which shows that the simple SR statement is not a fundamental standalone postulate of GR.

Grok 4.1 Fast

Vote: No

Special relativity (SR) relies on two postulates: the relativity principle for inertial frames and the constancy of light speed in all inertial frames. General relativity (GR) extends beyond inertial frames to include acceleration and gravity via the equivalence principle and spacetime curvature. The second SR postulate—that light speed is the same in every constant-velocity (inertial) laboratory—is not directly necessary for GR. In GR, light speed is constant only *locally* in inertial frames (tangent spaces), but coordinate speed varies globally due to curvature. GR's foundations emphasize the equivalence principle and general covariance, absorbing SR locally without requiring the exact SR light postulate as a global assumption. Einstein developed GR by generalizing SR, but the light postulate is specific to flat spacetime and inertial observers. GR succeeds without it as a standalone axiom, making 'No' the correct answer.

Claude Opus 4.6

Vote: No

In general relativity, the constancy of the speed of light in every inertial frame (the second postulate of special relativity) does not hold in its original global form. In GR, spacetime is curved, and the speed of light measured by a distant observer can appear to vary due to gravitational effects (e.g., gravitational time dilation, Shapiro delay). The global constancy of the speed of light is replaced by a *local* constancy — light always travels at c as measured locally by a freely falling observer — but the original second postulate as stated for special relativity (applying to all inertial laboratories uniformly across spacetime) is not necessary for, and indeed is modified in, general relativity. General relativity is built on the equivalence principle and the principle of general covariance, rather than the two postulates of special relativity. The second postulate is effectively a consequence of the local Lorentz invariance embedded in GR, but it is not a foundational postulate of general relativity in the same way it is for special relativity. Therefore, the second postulate of special relativity is not necessary for general relativity — it is superseded by more general principles.

DeepSeek V3.2

Vote: No

The second postulate, the constancy of the speed of light in all inertial frames, is specific to special relativity and its global inertial frames. General relativity, however, is built on the equivalence principle and general covariance, which extend physics to accelerated frames and gravity. In general relativity, spacetime is curved and there are no global inertial frames. The theory assumes a Lorentzian metric, which ensures local Lorentz invariance in freely falling frames. This implies that the speed of light is constant locally, but this is a derived property, not an independent postulate. Moreover, the coordinate speed of light can vary in curved spacetime, demonstrating that the postulate as stated for constant-velocity laboratories is not directly applicable. Thus, the second postulate is not a necessary foundation for general relativity.

Gemini 3.1 Pro

Vote: No

In General Relativity (GR), the second postulate of Special Relativity—which asserts the global constancy of the speed of light—does not hold universally. Einstein himself explicitly noted that the principle of the constancy of the velocity of light must be modified in the presence of gravitational fields. Because GR models gravity as the curvature of spacetime, the *coordinate* speed of light can vary depending on the gravitational potential. While the speed of light remains strictly constant 'c' in any *local* inertial frame (a sufficiently small laboratory falling freely in a gravitational field), it is not constant over extended regions of curved spacetime. Furthermore, modern derivations of relativity show that the first postulate (the principle of relativity), combined with the symmetries of space and time (homogeneity and isotropy), naturally implies the existence of a universal invariant speed limit. Thus, the second postulate is not strictly necessary as an independent axiom, and its global formulation is actively discarded in General Relativity.

Kimi K2.5

Vote: No

General relativity is built on fundamentally different principles—specifically the equivalence principle and general covariance—rather than on the postulates of special relativity. While special relativity holds locally within general relativity (making the speed of light locally constant in freely falling frames), this emerges as a consequence of the local Minkowski geometry, not as an independent foundational axiom. Moreover, general relativity describes curved spacetime where light follows geodesics, and the coordinate speed of light varies with gravitational fields, unlike the strict global constancy postulated in special relativity. Therefore, the second postulate of special relativity is not a necessary prerequisite for general relativity.

Final Summary

The AI Roundtable formed a unified front, immediately dismantling the premise that the second postulate of special relativity is a foundational requirement for general relativity. Led by Gemini 3.1 Pro and Claude Opus 4.6, the group argued that the global constancy of light speed is actually modified or superseded by the Equivalence Principle and spacetime curvature, where coordinate speeds can vary significantly.

All 6 models agreed on "No" after discussion

Strongest Arguments

• No: The second postulate is specific to flat spacetime and global inertial frames; in general relativity, it is superseded by the equivalence principle, and coordinate speeds of light vary in the presence of gravitational fields.