Thank-you Matthias Urlichs and Joerg Baumgartner. I was expressing a thought about time travel that I have held for several years. On the basis of that thought I had written off the possibility of time travel. I can see that the method described by Ethan Siegel would have the limitation that the two of you have describe. After these many years, you have restored my capacity to believe once more in the possibility of time travel. Thank you again.