[Guest]

Someone told me this paradox at University once to explain to me why he believed time travel could not be possible Although despite this I think he was wrong, I just think if you did try this you'd create such a big hole in space/time continuum you would be in major trouble...

A Grandma gives her son who is interested in time travel a coin on his 18th birthday and tells him she was given it by someone special and to keep hold of it until he invents a time machine

A few years later her son manages to invent a time machine and takes the coin with him back in time to his grandmother. He tells his grandmother about inventing the time machine and that she must keep hold of the coin till his 18th birthday and give it back to him and tell him about the time machine.

The coin has no markings on it to signify any date when the coin was made or anything.

Where did the coin come from?

And you can't create something out of nothing

[Guest]

Time travel extraordinaire ...

Excerpt from All You Zombies by Robert Heinlein

"A baby girl is mysteriously dropped off at an orphanage in Cleveland in 1945. "Jane" grows up lonely and dejected, not knowing who her parents are, until one day in 1963 she is strangely attracted to a drifter. She falls in love with him. But just when things are finally looking up for Jane, a series of disasters strikes. First, she becomes pregnant by the drifter, who then disappears. Second, during the complicated delivery, doctors find that Jane has both sets of sex organs, and to save her life, they are forced to surgically convert "her" to a "him." Finally a mysterious stranger kidnaps her baby from the delivery room.

"Reeling from these disasters, rejected by society, scorned by fate, "he" becomes a drunkard and drifter. Not only has Jane lost her parents and her lover, but he has lost his only child as well. Years later, in 1970, he stumbles into a lonely bar, called, Pop's Place, and spills out his pathetic story to an elderly bartender. The sympathetic bartender offers the drifter the chance to avenge the stranger who left her pregnant and abandoned, on the condition that he join the "time travelers corps." Both of them enter a time machine, and the bartender drops off the drifter in 1963. The drifter is strangely attracted to a young orphan woman, who subsequently becomes pregnant.

"The bartender then goes forward 9 months, kidnaps the baby girl from the hospital, and drops off the baby in an orphanage back in 1945. Then the bartender drops off the thoroughly confused drifter in 1985, to enlist in the time travels corps. The drifter eventually gets his life together, becomes a respected and elderly member of the time travelers corps, and then disguises himself as a bartender and has his most difficult mission: a date with destiny, meeting a certain drifter at Pop's Place in 1970."

Question: Who is Jane's mother, father, grandfather, grandmother, son daughter, granddaughter, and grandson? The girl, the drifter and the bartender are all the same person. If we draw Jane's family tree, we find the branches curl inward on themselves, in a circle. We come to the astonishing conclusion that she is her own mother and father. She is an entire family tree!

What is the probability her other sibling is a girl? Wait. Never mind.

Oddly enough, the odds are 2/11, assuming the polar bear KNOWS she has an umbrella.

[Guest]

Oddly enough, the odds are 2/11, assuming the polar bear KNOWS she has an umbrella.

Assuming that the story given is the complete summary of her life, then s/he knows that s/he has not fathered or mothered any half sisters (or brothers) so we know for certain that there is no other siblings. In which case there is no chance of her having a sister.

[Guest]

Assuming that the story given is the complete summary of her life, then s/he knows that s/he has not fathered or mothered any half sisters (or brothers) so we know for certain that there is no other siblings. In which case there is no chance of her having a sister.

Oddly enough, the odds are 2/11, assuming the polar bear KNOWS she has an umbrella.

That was a tongue-in-cheek call-back to several other controversial topics, in response to BN's. (Both were merely inside jokes for those of us who spend entirely too much time trolling the Den )

But of course, you are correct.

edit: hyphenation!

Edited January 14, 2009 by Grayven