Wednesday, 6 May 2015

"Bid Time Return"

Years ago, a British astronomer told me that any time gained from time dilation on an outward journey would be repaid on the return journey so that there would be no difference at the end of a round trip. However:

How does the universe know the difference between an outward and a return journey?

If the equations entail his conclusion, then why does anyone think otherwise?

This is where Poul Anderson fans would benefit from a scientific education. But there must be blog readers out there with informed opinions on this matter? The astronomer's view would not affect works, like Tau Zero or The Boat Of A Million Years, in which there is no return journey but would invalidate the Rustum and Kith Histories and "Time Lag" - although, on the other hand, all hard sf reflects the scientific understanding of the time when it was written.

Regular readers might have noticed that this blog averaged eight posts per day for the first five days of May. This rate of productivity cannot possibly be sustained. I happened to be rereading The Boat Of A Million Years which is long and full of condensed information so that post followed post very easily. We have now returned to a more sedate pace.


  1. Dear Paul,

    I have something of a scientific education, and what that British astronomer told you, if you understood and are reporting it accurately, was probably in error, and certainly contrary to what most physicists believe. Special Relativity is based on the premises that space is homogenous and isotopic (and also that the speed of light is the same in whatever reference frame it is measured), so dilation of space and time should be the same whichever direction you're going. There are complications, but I'm pretty sure of that much.

    Best Regards,
    Nicholas D. Rosen

  2. Nicholas,
    Thank you. I thought it sounded suspicious.
    I have just returned from a few days in Belgium, by the way.