First half was o.k best bits were Matt Smith and Charles Dance.

Just caught this on I-player and, even as a complete Science dunce (and I have my GCSE results to back that up ) I thoroughly enjoyed it. Very well done Mr Cox (who made a rather good straight man to Matt) . Nice to see an intelligent, informative piece of television with guest appearances by the Doctor. What's not to like?

And I echo saladfingers81's comments re: Mr Smith. Ahhh, Matt.

Wig!!!! (slurp)

Sorry, that's my drinking game. (There's an idea for a thread! Hmmm...)

I enjoyed it. The only poor part was Cox's acting. He really should stick to presenting.

Bringing it back to Doctor Who, this was part of the premise of Remembrance of the Daleks. The Daleks already had wormhole-style time corridors, but were after the better TARDIS-style black hole-based technology.

I don't think the lecture's suggestion that the Eye of Harmony allows Time Travel due to the nature of light bending around a Black Hole is really how the TARDIS' travel through time is portrayed in the show.

The TARDIS travels through the Vortex, a place outside of Space and Time (probably a worm hole, based on the title graphics). The Eye of Harmony powers the TARDIS but it isn't using the mechanism described in the lecture.

Except that, if you can decide where in Space you want the wormhole to come out then why can't you decide where in Time it comes out? Time is just an additional dimension to the three Spatial dimensions. Together they form the continuum to which the wormhole connects. So if you can aim the wormhole's end at three of those dimensions, why not the fourth?

The limitation seems to be based on the assumption that wormholes are created between two points in Space but the same point in Time. That being the case then, yes, you can create Time Travel by accelerating one end differently to the other. But I don't understand why we're making that assumption. Why limit wormhole creation to two points in Space. Why can't your initial connection decide that the end appears in a different point along the continuum of Space/Time.

Whether Science believes it's possible or not, it seems pretty clear that that's how the world of Doctor Who works. I think it's the only practical way you could envisage directed Time Travel working.

How are you going to aim the end of the wormhole to that specific point in past time unless you can already time travel there? And if you can already time travel there, you don't need the wormhole.

Your only hope is to find a suitable, ready-made wormhole that already just happens to go to the part of the past that you want to visit. And the chances of that happening are pretty slim!

If you want to tunnel through a mountain instead of going over the top of it or around it, you don't need to be able to reach the other side before you start the tunnel. You just have to be able to tunnel through the mountain.

That's how I see time travel working. We can only perceive the three dimensions of space and the fourth dimension time but space/time can be curved. If we can fold space/time in on itself (or if, in fact, it is already a convoluted tangle like a ball of string from the point of view of the 5th dimension), then we can then bore a hole through from one point to another by tunnelling in a different direction, along a different dimension to any of the four we know about. If we can control our direction of travel in this dimension then we can come out wherever we want in space and time.

All of the lecture's ideas of time travel involved travel along the surface of space/time. Even when he curved space/time round to meet itself, it was still the assumption that we would travel along the surface of the paper. If, after we've folded space/time we can bore into it, through a void which is outside of space and time (i.e. the Vortex) then we can come out wherever we want along its surface. That's what I've always assumed a wormhole was, a tunnel through the dimension that is outside of space/time.