We define \emph{engineered simultaneity}: the construction of a system that requires temporal comparison of events at spacelike-separated locations, implements this comparison via an implicit simultaneity convention, and represents the result as an objective measurement rather than a conventional choice. We show that the National Best Bid and Offer (NBBO) -- the regulatory cornerstone of U.S. equity markets -- is an instance of engineered simultaneity. The NBBO requires determining ``current'' prices across exchanges whose spatial separation places their price events outside each other's light cones. Special relativity proves that the temporal ordering of such events is frame-dependent: there exist inertial reference frames in which the NBBO differs from the value reported by the Securities Information Processor. The impossibility is not approximate; it is exact and unavoidable within the causal structure of Minkowski spacetime. General relativity compounds the impossibility: gravitational time dilation introduces frame-rate discrepancies between exchanges at different altitudes, and recent work on indefinite causal order in quantum information theory undermines the premise of a fixed causal structure altogether. We formalize the special-relativistic argument using the causal precedence relation, connect it to Lamport's theorem on distributed ordering, and note that approximately \$5~billion per year in latency arbitrage profits are extracted from the gap between the NBBO's implicit simultaneity convention and physical reality.

翻译：本文定义"工程化同时性"：构建一个系统，要求对类空间隔位置的事件进行时间比较，通过隐含的同时性约定实现这种比较，并将结果表示为客观测量而非约定选择。我们证明美国股票市场的监管基石——全国最优买卖报价（NBBO）——正是工程化同时性的实例。NBBO要求确定各交易所的"当前"价格，而这些交易所的空间间隔使其价格事件处于彼此的光锥之外。狭义相对论证明此类事件的时间顺序具有参考系依赖性：存在惯性参考系使NBBO与证券信息处理器报告的值不同。这种不可能性并非近似，而是在闵可夫斯基时空因果结构中精确且不可避免的。广义相对论加剧了这种不可能性：引力时间膨胀导致不同海拔交易所之间存在帧率差异，而量子信息理论中关于非定域因果顺序的最新研究则从根本上动摇了固定因果结构的前提。我们使用因果优先关系形式化狭义相对论论证，将其与Lamport分布式排序定理相联系，并指出每年约50亿美元的延迟套利利润正是从NBBO隐含的同时性约定与物理现实之间的裂隙中获取的。