If you went back in time and killed your grandfather, what would happen?
 

:shrug:

Well you would cease to exist if your Grandfather and Grandmother haven't had your parent yet.

You obviously would'nt exist.Have you never seen Back To The Future?

Didn't Futurama solve this one a few years ago, you just have to sleep with your Grandmother to ensure that you still exist

If you went back in time it would be a different universe. so it's true that you would never be born in that timeline, but it wouldn't affect the timeline you came from at all. There are tons of different parallel universes and timelines.

I think it may one day be possible to travel in time into the future when we have the tech to travel fast enough.Traveling back in time though i highly highly highly doubt could be done ever.

Ahh the grandfather paradox. "But if you never existed then you didn't kill him, so he lived, so you do exist, so you could kill him."

There are really only three options here:

#1 Multiverse theory. This is essentially how "Terminator time travel" works according to the most recent, most crappy film and many other Sci fi stories. Basically, each decision creates a new timeline but doesn't erase the old one. So, you in timeline A go back and kill your grandfather in timeline A, creating timeline B where everything is different. However, timeline A still exists in parallel and so you (being from timeline A) still exist. This is the least problematic time travel variation.

Option #2 The future is erased as soon as you travel back. Nothing past the point of arrival ever happened and you and anything you brought back are now an "anomaly". Your actions now create the new future. Killing your grandfather doesn't do anything, because that future is gone but you are still "from there". Sort of like a copy and paste, I suppose.

Option #3 Time travel is impossible because, if it were possible, it would be happening constantly (because infinity) meaning that there is no such thing as reality at all. Reality would be in a blender.

Option #4 the grandfather paradox is alive and well but no one has discovered time travel YET. As soon as someone does, they go back in time, any tiny change they make disrupts the future (doesn't need to be as severe as killing an ancestor - the butterfly effect suggests that a no number of tiny alterations might stop you from existing, stop time travel being invented, change future motivations etc.) and then the paradox activates and the universe implodes from that point onwards. Luckily, the first person to discover it didn't travel back as far as 2015 in human years.

Even if time travel to the past was possible, it would only be possible to travel back into the past once the machine was invented. The machine would have to be invented and then stay on constantly, then people from the future where the machine continues to exist would bring you back.

But there's no way to ever go back to the past before humans, or to any time in the past before that machine existed.

Well, since he is my father´s father, if he is killed, my father wouldn´t exist, meaning i probably wouldn´t exist either.

not necessarily, maybe your father has already been born and continues to exist, so killing your grandfather wouldn't change anything.

Is your grandfather still alive? if you killed him tomorrow would you cease to exist?

But what if it was a machine like the Back To The Future car that comes with you on your journey?Your theory is more like the Terminator/Twelve Monkeys time machine where you travel to the same machine at different points in time.

Surely that's hypothetically possible through cryo though? If it's "perfect". You freeze yourself, the world goes on as normal around you for however long, then in 200 years someone wakes you up. You're the same age as you were, you were unaware of the passage of time so you feel like you were only asleep for minutes. Isn't that effectively "time travelling to the future"? And as above, you obviously can't go back.

OMG sleeping is mini time travel :omgno:

Maybe as TS said.Your grandfather still does exist because by traveling through time you have just created an alternate reality?

But really you were still there travelling through time at the same rate as everybody else.You were just frozen.Even if you don't physically age.You were still there with everybody else.

What if the time machine has a glitch and you end up just constantly being taken back in time just a split second like when a CD get's stuck and starts making that annoying sound... does that mean you can live forever?... the same split second for all eternity.

Yes but there's no obvious difference between the two for the "traveller", so would that matter? Let's say "jumping forward" in a time machine costs ten times as much as freezing yourself for the same amount of time... Would there be any reason to do it the more expensive way?

Well no.It's a cool idea.But you would'nt actually be travelling through time faster than anyone else would you?

Did you watch Interstellar?

The "time travel" in interstellar is (effectively) the same principle... The characters don't travel through time more quickly than anyone else, everyone else just keeps aging and time moves on around them while they are "frozen" (moving very, very slowly in relativity to those outside the time distortion)

:clap1::clap1::clap1: This excellent post actually says all that I was going to post, and a hell of a lot more. So no more to be said really.

Yes!That was a very clever film.Really enjoyed it.

There really is no 'right' time in the universe is there?Everything in the universe travels at its own time frame depending on the speed it's traveling.If an object is in close proximity to another object(like us to the sun and the sun to the galaxy) etc then it travels faster due to its orbit and the faster an object travels then the slower time around it goes.Is that right?That's my basic understanding.

Also add on top of that the fact that everything is traveling through space.The galaxy's etc which also has an effect on time.

Time really is relative.

Is'nt there a part in Interstellar where one of them stays on the ship and a team go down to the surface of a planet but because the planet is so close to a black hole time travels much faster for them.When they get back up to the ship the guy who stayed behind has aged like 20 years or something?

But if you didn't exist then who killed your grandfather? :shrug: