What Time Is It?

I've been thinking about time again.  Yeah, I know there are theoretical physicists getting paid to ponder the same thing - what is time? - but that shouldn't keep me from thinking about it any more than the existence of NASCAR drivers should keep me from getting behind the wheel of my truck.  They're professionals, and they run their race very well, but they can't get me where I need to go, that's my job.

As Einstein demonstrated, space and time are connected, the same fabric.  It's where we get the concept of spacetime.  And we are embedded in spacetime, all four dimensions of it.  Which is why, I think, we experience time as a one-way arrow.  In order to step outside of time, we'd have to be able to experience a fifth dimension which would allow us a separate perspective on our original four.
    Think of it in terms of Flatland, a hypothetical two-dimensional world.  The Flatlanders have forward and back, and left and right, but they do not have up and down.  They can't even conceive of up and down, since that's a third dimension and they have only two.  Everything they do is constrained to those two dimensions, and even if they were somehow transported through a third dimension they'd never know it, since they can't perceive it.

Same thing with us and time.  It's a fourth dimension, but we're stuck in it like it's 4-D flypaper, nothing we can do to get out of it.  It's not only all we know, it's all we can know.

There's a very good question about time travel:  If time travel is possible, where are all the time travelers?  Once time travel is invented, no matter how far in the future, every era would be lousy with time tourists, because every moment in time would essentially be 'now.'  Since we don't see any time travelers, ipso facto, time travel must not be possible.
   But I put this to you:  if time travel is possible, it's only possible through a fifth dimension.  And since we can't perceive that fifth dimension, we can't perceive any time travelers, who must, of necessity, be five-dimensional beings.  So maybe there are time travelers all around us right now.  We'd never know it, just like Flatlanders could never know us higher-dimensional beings.

Which brings us to another notion about time.  We experience time as a linear flow, but if there is a fifth dimension outside of our four familiar dimensions of spacetime, wouldn't someone in that fifth dimension be able to see all of time?  To them, wouldn't time be just another dimension they could move along, forward or backward or sideways or what have you?  Furthermore, wouldn't that mean that time - though we experience it linearly - is actually all happening at once?  Is every moment in time really lined up in order like a huge card catalog* we leaf through from front to back because we have to by virtue of our four-dimensionality?

I think the notion of there being no real 'now,' just a card-catalog moment we experience as now is both disturbing and poetic.  It's like we live each moment like it's a frame of movie film, one at a time, one after the other. 
    Which has all sorts of implications for the notion of free will.  But that's another sleepless night lying in bed.


* kids, a card catalog is what libraries used to keep track of their books in the days before computers did everything for us.