A new causal paradox in superluminal signaling is presented. In contrast to the Tolman paradox with tachyon exchange between two parties, the new paradox appears already in a one-way superluminal signaling, even without creating the time loop. This produces a universal ban on superluminal signals, which is stronger than the ban imposed by the Tolman paradox. The analysis also shows that records of evolution of a superluminal object observed from two different reference frames may be time-reversed with respect to each other. Interactions with such objects could add some new features to spectroscopy. Even though relativity embraces superluminal motions, thus making the world symmetric with respect to the invariant speed barrier, their ineptness for signaling makes the symmetry incomplete. Key words: superluminal signaling, tachyons, the Tolman paradox
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