What Could I Do in the Past?

Another philosophy night at Zeno's: As Maggie and Charles were talking about paradoxes, a faithful patron, Julie S., raised the issue of time travel. "Suppose that physicists' talk about worm holes, parallel universes and the like are correct, in that---theoretically---one could travel back in time," she postulated. "If this were true, then let's discuss a line of questions that have been posed by philosophers and others, namely: Could I travel to a past time where I meet my grandfather? Could we shake hands? If, for some bizarre reason, could I kill him before he even met my grandmother?" 

"Bizarre, indeed! And rather perverse," exclaimed Charles, who imagined such a vile scene. "Why would you want to do such a horrible thing? Shaking his hand is one thing, but killing him is sick!"

Julie S. quickly replied "Hold on, Charles, my point was simply that if I could travel back in time to meet, and shake hands with my grandfather, why couldn't I take his life, as horrible as that sounds? Could I?" 

Charles looked amazingly puzzled, as he explored the implications.

Wow! Julie S. does raise an interesting question theoretically about time travel. If she could meet her grandfather and shake his hand, then could she not put an end to his life before he met Julie's grandmother? If she could extend her hand for a shake, then why not extend her hand with a pistol and squeeze the trigger? But wait, if that were so, then Julie's actual mother would not have been born, and hence neither Julie! Right? That's weird, and seems to yield a contradictory assumption. Yet what's the theoretical difference between shaking hands and killing him? A physical force? Not likely. Is her killing grandpa possible? Or is even her meeting grandpa possible? What does this tell you about time travel? Patrons, please help!

------------------------------------------------------------------------------------------------------------------------------------------------

For your ongoing enjoyment, I have retained these so-called Impossible Objects on here, as you contemplate the new challenge. I continually receive positive comments from many loyal Coffeehouse patrons. If you locate other good ones, please let me know. Please do this for our many visitors. Enjoy!...Ron Barnette

Some Impossible Objects

I credit Jim Loy for these marvelous example of so-called impossible objects, which should amuse you faithful Zeno's patrons, who appreciate thought-provoking stimulation.

		1. Asymmetric crate. An M. C. Escher creation, I surmise
		2. The Penrose staircase: Often drawn by M. C. Escher. Clockwise is downstairs forever.
		3. The tribar: Another impossible object by R. Penrose. It's hard to know how to color it, as the interior becomes the exterior.
		4. The Penrose triangle: Another famous impossible object by R. Penrose. This is sometimes called a tribar (see #3, above).
		5. An ambiguous ring...What is the outside? The inside?