2 research outputs found
Comments on the tethered galaxy problem
In a recent paper Davis et al. make the counter intuitive assertion that a
galaxy held `tethered' at a fixed distance from our own could emit blueshifted
light. Moreover, this effect may be derived from the simplest
Friedmann-Robertson-Walker spacetimes and the (0.3,0.7) case which is believed
to be a good late time model of our own universe.
In this paper we recover the previous authors' results in a more transparent
form. We show how their results rely on a choice of cosmological distance scale
and revise the calculations in terms of observable quantities which are
coordinate independent. By this method we see that, although such a tethering
would reduce the redshift of a receding object, it would not do so sufficiently
to cause the proposed blueshift. The effect is also demonstrated to be much
smaller than conjectured below the largest intergalactic scales. We also
discuss some important issues, raised by this scenario, relating to the
interpretation of redshift and distance in relativistic cosmology.Comment: 6 pages, 3 figures, submitted to Am.J.Phy