Hi Karsten, The *definition* of a lightyear is *fixed*, i.e., the 'distance light travels in a year', and not directly measurable, e.g., tag a photon and measure its progress thoughout one year.
The problem is that the *distance* each photon travels in a year may not be the same. You are correct re 'speed of light'. The *definition* of a lightyear was created and agreed upon to facilitate measurement. The 'trap' is trying to turn this 'convenience' into a physical constant.. Regards! -Thomas Clark Karsten Hilbert wrote: >>>And not constant either, at that. >>> >>> >>Bugger. >>http://www.everything2.com/index.pl?node_id=29831&lastnode_id=11221 >> >> >I stand corrected as I was being imprecise. I was referring to >a) the speed of light is depending an material, and b) the >speed of light seems to not be constant over time even in a >given material. > >However, the *definition* of a lightyear certainly *is* >constant so you are correct. > >Karsten > > - If you have any questions about using this list, please send a message to d.lloyd at openehr.org
