Time

Seeing as tonight sees the broadcast of a whole new Doctor Who episode, this might be the right moment to write about one of my greatest problems with the show: Time. And time travel. Especially the Earth-centricness.

I don't have any problems with space travel, mainly because space travel is just covering distance and whether covering a certain distance in little to no time passing at all might well be possible when technology improves. Sure, if one travels by coordinates - as the Doctor seems to be doing - one needs to be extremely specific in order not to land halfway in the ground somewhere, or stuck in a ceiling - one would need to know the exact location of every atom in the general area of where one would want to land (which, so I've been told, is one of Physics's major practical problems in making teleportation possible). But I'm sure the TARDIS is perfectly equipped for this, and there appears to be a Galactic Zero Centre (http://tardis.wikia.com/wiki/Galactic_centre), like our global coordinates are at 0 where the equator crosses the Greenwich meridian, just off the coast of Africa. Such a zero point is an agreed-upon point and so not an absolute, but can still be used to measure against and so base travel upon. There need to be no extremes known - you don't need to know the "end", just keep on counting. It does not even need to be a Galaxy-widely held convention, even if only the TARDIS would use such a zero point, it can be used for travel, as long as elevation or at least a third dimension is taken into account.

But Time. Time does not truly exist, does it, other than as a purely abstract idea to mark the duration of a sequence of events. Time, as a concept, is a human invention - the basic notion is the rotation of the Earth and the orbiting of the Earth around the Sun, nothing more. A day is the duration for one point - or line, the Greenwich meridian - to move from a specific location relative to the Earth's axis to that same location relative to the Earth's axis, or from Midnight to Midnight. But that's a modern invention, as for instance in the Ancient world, if I remember correctly, a full day lasted from sun up to sun up and so the duration of a day varied. But an agreed duration for a day is good, so humans could divide it by 24, and then by 60, and then by 60 again, and so forth, to find out hours and minutes and seconds and miliseconds. There wasn't even a unified time per country until railways demanded it, and then it still took a while for everyone - it took especially the French very long - to agree that time is to be derived from the Greenwich meridian.
A year is just the same, the number of days it takes to orbit around the Sun - 365.24... something, so we need a leap year every four years except some. To us, that is, because to the Ancient Egyptians a year was 360 days (12 months, 30 days per months, 3 weeks per month, 10 days per week) plus a festival of five days for the Gods, which fell outside the year.
And what is our zero for years? Some Pope decided that the birth of Christ was supposed to be zero, so he calculated zero, and still got it wrong, so that our calendar begins at a completely random point in time. Fair enough though if we can all agreed that that random point is zero, but then the Jewish are currently in the year 5773. And we can't even agree on the point when the year should begin - Midnight at the start of the 1st of January? Or later, in late January/early February, like the Chinese New Year? Roman New Year did not start until March, while Ancient Egyptian New Year was some time over summer.
Fine, so let's say the TARDIS travels by Gallifreyan time - one could presume that at least the Gallifreyans would agree on one time, some of them being Time Lords, after all.
Travelling forward in time should perhaps not be too difficult, if one can teleport or travel really really fast - something with time running slower than elsewhere, something Einstein, something relativity.
But travelling back in time should only be possible if each event, or each sequence of events, is stored in some dimension, and that time passing is just - I'm going fairly metaphysical here - our consciousness passing through those dimensions. A bit like our consciousnesses are watching a stop-motion film, but then they are part of that stop-motion film. I guess this could be possible with parallel universes etc., quantum physics and what not. Schroedinger's Cat and that.
Besides, time travel should only be possible if one can map time against something - but against what?

But perhaps I'm taking time too much as a linear thing and instead it is "a big ball of wibbly-wobbly timey-wimey... stuff".

Anyway. What I did realise is possible was what I realised yesterday as I was trying to fall asleep. Basically, we only see parts of the Doctor's adventures (most notably the Eleventh Doctor suddenly ages from 900-something to 1100-something over a series, and we don't really see what happens in the 200 years in between), so at any point in time, if the Doctor were real, we humans could meet just about every incarnation - a TARDIS could appear right here in the grad lounge and the First Doctor could come stepping out "hmm"-ing (or, more interestingly to me, the Tenth could step out brandishing the sonic screwdriver). Of course that would also mean (I haven't watched any episode yet in which the Doctor meets himself, so bear with me) that a Doctor with little to no hang-ups about crossing his own timeline could easily meet himself in an earlier (or even the same - but hang on, he did that more or less when Rose wanted to save her Dad) regeneration. I'd love for the First Doctor to meet the Eleventh and go all "hmm" and "my boy" and patronising and all that until the Eleventh points out that he is him but - hilariously - older.

What if time passed faster in the TARDIS (or any other other dimension) than it does in the outside world? It would explain why suddenly the Eleventh Doctor is 200 years older, for I doubt he'd travel without the Ponds for 200 years while the Ponds were still free. If one is used to a human pace, and time moves faster in another dimension, what would seem like a month could indeed easily be a year, or even two centuries.
It would also explain why some Doctors (especially the Tenth and Eleventh - I've yet to observe Two to Seven) seem a bit hyperactive compared to a human pace.
Sort of reversed relativity.
Perhaps it WOULD, in case of reversed relativity of time, be possible to travel back in time. Perhaps the pace of time inside the TARDIS can be altered so that travelling in time both ways is made possible. I don't know.
Hang on. Time goes faster on the inside than on the outside.
The TARDIS is Narnia.
That, or the Eleventh Doctor spent 200 years in Narnia.
Either one is cool.

Fascinating stuff, time. I just have difficulty grasping it - I do wish I hadn't dropped my science courses in secondary school. The upside of all this is that if time was a stop-motion film observed by our consciousnesses, I'd be totally right in believing there is no Truth and all there is, is our observed reality.

Physicists, do feel free to step in and answer my questions...

PS I love this: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html. I'm quite terrible at the whole sine/cosine/tangent bit of mathemathics (only mathematics test I failed back when I was still good at maths), but let's ignore that bit. This bit: "The Earth is doing a lot more than rotating, although that is certainly the motion we notice most, because day follows night as a result. We also orbit the Sun once a year. The circumference of the Earth's orbit is about 940 million kilometers, so if you divide that by the hours in a year you will get our orbital speed in kilometers per hour. We are also moving with the Sun around the center of our galaxy and moving with our galaxy as it drifts through intergalactic space!". Pure Epic. Basically, it tells me that there should be four basic units of time on Earth: a day (rotation), an Earth year (orbit), a Galatic year (moving around the centre of the Galaxy) and an Intergalactic period (a distance in drifting through Intergalatic Space). Yes, I *am* ignoring time derived from atom clocks etc.. So basically, the TARDIS would not only have to have a sort of internal library of the positions of every atom - impressive enough to start with - but also of every atom's movement through time - and surely this must include 'paths not taken', i.e. unrealised futures and disregarded pasts.
Whoa. Time Lord technology must be truly awesome. No wonder the sonic screwdriver can do lots of things that seem like deus ex machina plot-tricks to us mere humans...