Considerations about the apparent «superluminal expansions» observed in astrophysics

Localized Waves: A Historical and Scientific Introduction

“…[88]. Here, let us mention only that simple geometrical considerations in Minkowski space show that a single Superluminal source of light would appear [88,1]: (i) initially, in the "optical boom" phase (analogous to the acoustic "boom" produced by an airplane traveling with constant supersonic speed), as an intense source which suddenly comes into view; and which, afterwards, (ii) seems to split into TWO objects receding one from the other with speed V > 2c [all of this being similar to what is actually observed, according to refs. [86]].…”

Superluminal waves and objects: An overview of the relevant experiments

“…Here, let us mention only that simple geometrical considerations in Minkowski space show that a single Superluminal light source would appear [11,3]: (i) initially, as a source in the "optical boom" phase (analogous to the acoustic "boom" produced by an airplane travelling with constant supersonic speed): namely, as an intense source which suddenly comes into view; and that (ii) afterwards seems to split into TWO objects receding one from the other with speed V > 2c [both phenomena being similar to those actually observed, according to refs. [9]].…”

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“…For a theoretical discussion, see ref. [11]. Here, let us mention only that simple geometrical considerations in Minkowski space show that a single Superluminal light source would look [11,3]: (i) initially, in the "optical boom" phase (analogous to the acoustic "boom" produced by a plane travelling with constant supersonic speed), as an intense source which appears suddenly; and that (ii) afterwards seem to split into TWO objects receding one from the other with speed V > 2c.…”