Time Travel
No, I cannot wrap my head around theoretical multi-dimensional travel. But in our dimension and/or universe it is surely an impossibility?
Go stand on your street. Look around. Look at the buildings and wonder what stood before them.
Now try to imagine standing on that street in 1994. I mean, really imagine it.
You're there. You're there right now.
Now try to imagine standing on that street in 1966. Really. 49 years ago.
You're there again. In 1966.
Now try to imagine standing on that street in 1739.
You're still there.
You can't 'go back' to where it was then because you are where it 'was'. The square mile where you're standing hasn't been recorded, saved or stored in some kind of meta-dimensional cloud, to be accessed at a future date. If you stay where you are now and wait 50 years, it'll be the exact same location in space-time as it will be in 2065 and someone else wondering "I wonder if I could go back to here in 2015?". You would have still been there. In the precise same place.
Where you are standing is the exact same place as the place where people were standing 10, 50, 100 or ever 1,000 years ago. It is immutable.
The hospital where I was born no longer exists. I can never go back and revisit it. That particular location is as true in 1991 as it is now; the buildings and surroundings might have changed drastically since man is first recorded in North East Wales 29,000 years ago but the area itself hasn't 'moved' anywhere.
Time is something we measure like mass, volume, temperature and height. It is something tangible, not something we can 'access'. The numeric figure for time can be manipulated depending on the scale used just like weight, velocity and density. It is a measurement, a concept, not a 'thing'.
Or is this just me? As I initially outlined, I do not understand quantum physics or dimension theory very well at all. The idea of being able to go back in time seems completely impossible to me. Certainly in our universe. Forwards is different with time dilation, date lines and space travel, but not backwards.