Time travel and saying hello and changing the future.

[flobadob]

If you were to travel to the past and walk up to your grandfather and just say hello, would you then never be born? I was just thinking that say for example, there are 100,000 sperm in every ejaculation and only one gets to make a baby. Obviously these sperm are constantly moving so even a delay of a second would mean a different sperm would fertilise the egg in question. Does it therefore stand that the delay in his life cycle responding to your greeting would have repurcussions resulting in different children being born to him and thus you never being conceived?

[flobadob]

I'd believe in The Matrix before parallel universes. They are akin to believing in a God I think.

[jake-the-peg]

Do you believe that things can be in two different places at the same time?

Because when you look at quantum mechanics you may as well leave your common sense at home!

I keep an open mind - there are of course many different types of proposed parallel universe depending on what you're talking about

[flobadob]

jake, just when you mention quantum mechanic, I watched a show on BBC a few weeks back and the opening line of the programme went along the lines of a guy standing at a wall and saying "I cannot walk through this wall, but according to quantum mechanics if I stand here long enough I will". That must sum up quantum mechanics.

[jake-the-peg]

Yup - of course at his size long enough is billions of times longer than the history of the Universe.

But at the micro level it happens all the time - you may not like it, it runs counter to all our large scale intuition but it happens.

Indeed some of the electronics in your computer rely on the fact

[modeller]

I'm only playing with ideas but assuming multiple universes exist they can't be altered if you go back as a physical being as you would have no past or future in that universe. However if you went there in spirit form such as your grandfather hearing a voice in his head that could create another universe., both universes would have the same past but different futures and also they would not be chronologically the same . The new one would lag behind yours by how far you went back ..
Which is no problem as parallel universes do not have to be in synchronism.
Who knows those people who hear voices may in fact be hearing voices from the future or from another universe. There may be an infinite number of universes being created every moment of every moment. Sounds daft to us in our universe it is as factor says
//These discussions usually go round in circles //

[ljdksa]

Surely, if Time Travel ever becomes possible, we would have been visited by people from the future already?

[modeller]

ijdksa // Surely, if Time Travel ever becomes possible, we would have been visited by people from the future already? //
Maybe we have many times. How would we know ?
I had two knocking on my door last week . They must have been because they were able to tell me exactly what was going to happen in the future. I think they were hiding their identity by calling themselves Jehovah Witnesses .