[oldbrowser]

So, if you know the present, you cannot change it. If, for example, you know your father is alive today, the laws of the quantum universe state that there is no possibility of him being killed in the past.

So it is impossible to change anything. But then by simply going into the past you would be changing something, the air you breathe ?

You guys are kidding, right ?

[mysterio]

No. If at some time in the future you are going to go into the past, then at this moment, you have already been in the past. You can't change anything.

[RegulatorCountry]

" But then by simply going into the past you would be changing something, the air you breathe ?"

Oh... sort of like the old butterfly flapping it's wings in China thing, any change -no matter how minor- will affect a chaotic system in seemingly unpredictable and increasingly complex ways? You do have a point. Not sure that it would preclude time travel into the past, but this would make it seemingly much more difficult, close to impossible.