Joe,
Not a dumb question, but let’s split it into 3 parts.
Part 1 - ignoring expansion of universe, time dilation and quantum mechanics:
Is time a dimension in the sense that we can travel through it, just as we can travel through space?
1. Yes (but see 6. below).
2. We are all time travellers. Because you, your chair, computer, room, planet etc. are traveling at the same rate (at 1 year per year *) you don’t notice it.
3. The scary thing is that although the EVIDENCE of what you did a year ago may still be accessible (though in a ‘fossilised’ form), you can't go back to the REALITY of there because it was used to create what you are now. You may replace the word ‘year’ with atto-femto-second or Plank-time if you like. So in a sense, the dimension of time is being created continually.
4. When you think of a classical object moving in 1d space you can still think of it as being described by a Gaussian(x - vt)/a probability density whose centre moves classically - where a is the x-spatial extent of the object. (This is an intermediate step to thinking quantum mechanically.) You easily make this more general by multiplying by corresponding y & z Gaussians.
5. Likewise when you generalise to 4d you need to replace (vt) with (u \tau) and multiply by a Gaussian(t - u^0\tau)/b where \tau is proper-time at the centre of the classical object, b is the temporal extent of the object, u is the ‘spatial component of 4d proper-velocity’ and u^0 is the ‘temporal component of the 4d proper-velocity’ *. Don’t worry! you can skip 4 & 5 above.
6. Just as you have a spatial extent (a) you also have a temporal extent (b). The main difference between them is that in 3d the spatial extent can be revisited, but not the temporal one (as explained in 2,3 &5). But in 4d space & time are considered as one entity, so the 4d-spatio-temporal extent can not be revisited either.
* When you just sit there (rather than running around) u^0 = 1year/year = 1sec/sec.
I am afraid I have dropped into the convention of writing c = 1.
Part 2 - concentrating on spatial expansion of universe
1. Just as time is being created at 1 billion-years per billion years, so is space at about 0.6 billion-light-years per billion years. I pulled 0.6 out of a hat to make the following point. If you think the universe is hurtling through space now, then it is hurtling even more through time.
2. The 2d analogy (or parable) is that of an expanding balloon with small paper discs stuck on the surface. The discs are the galaxies (held together by their own gravity) that do not expand, while the space between them expands. So the recession of further galaxies is faster than that of nearer galaxies (Hubble effect or cosmological red-shift).
3. The time (of 1.) & space (of 2) are not expanding into anything (like the hot air & debris of an explosion into already existing space). This time & space are being created.
Part 3 - time dilation due to observing receding objects.
1. This is the stuff of standard Special Relativity course. There is an analogy with the Doppler effect with sound in air - but be careful as there is no corresponding medium for light (other than space-time itself). You may find the following helpful http://www.csupomona.edu/~ajm/materials/twinparadox.html
2. The above red-shift is nothing to do with the cosmological red-shift of part 2 which is a GR effect.
3. Neither is it anything to do with gravitational red-shift due to light ‘climbing out’ of the sun or massive body - which is yet another GR effect.
Cautionary note: I have had these ideas so long now that they have become ‘common sense’ to me - and you know that Einstein did not think too highly of that.
Good luck with your quest, Mike.
m = m = m = m = m = m = m = m = m = m = m = m = m = m = m = m = m
