A direct consequence of the expansion of space?

Abstract

Consider radar ranging of a distant galaxy in a Friedman-Lemaitre cosmological model. In this model the comoving coordinate of the galaxy is constant, hence the equations of null geodesics for photons travelling to the distant galaxy and back imply the following equation: \int_{t_e}^{t_r} dt/a(t) = \int_{t_r}^{t_o} dt/a(t). Here, t_e, t_r and t_o are respectively the times of emission, reflection and observation of the reflected photons, and a(t) is the scale factor. Since the universe is expanding, a(t) is a monotonically increasing function, so the return travel time, t_o - t_r, must be greater than the forward travel time, t_r - t_e. Clearly, space expands, and on their way back, the photons must travel a longer distance! The present paper explains why this argument for the expansion of space is wrong. We argue that, unlike the expansion of the cosmic substratum, the expansion of space is unobservable. We therefore propose to apply to it -- just like to the ether -- Ockham's razor.

arXiv comment6 MN-style pages, no figures; matches the version accepted for publication in MNRAS

References in corpus (5)

• Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe
• Joining the Hubble Flow: Implications for Expanding Space
• Is space really expanding? A counterexample
• Fundamental Aspects of the Expansion of the Universe and Cosmic Horizons
• The outermost gravitationally bound orbit around a mass clump in an expanding Universe: implication on rotation curves and dark matter halo sizes

Cited by in corpus (20)

• Hubble flow variance and the cosmic rest frame
• Cosmological equivalence principle and the weak-field limit
• The kinematic origin of the cosmological redshift
• The Apparent (Gravitational) Horizon in Cosmology
• Cosmological Redshift in FRW Metrics with Constant Spacetime Curvature
• Expanding Space: the Root of all Evil?
• Evidence for the Fifth Element Astrophysical status of Dark Energy
• The kinematic component of the cosmological redshift
• FRW Universe Models in Conformally Flat Spacetime Coordinates. II: Universe models with negative and vanishing spatial curvature
• Expanding space, quasars and St. Augustine's fireworks
• Coordinate Confusion in Conformal Cosmology
• Cosmological Radar Ranging in an Expanding Universe
• Harrison's interpretation of the cosmological redshift revisited
• A physical interpretation of Hubble's law and the cosmological redshift from the perspective of a static observer
• Uniformly accelerated traveler in an FLRW universe
• The One-Way Speed of Light and the Milne Universe
• Tantalizing New Physics from the Cosmic Purview
• There was movement that was stationary, for the four-velocity had passed around
• On the absence of shear from perfect Einstein rings and the stability of geometry
• Can an Infinitely Long Object Fit in an Expanding Universe?