I just watched the above titled
"Seeing the invisible: observing the dark side of the universe"
by Dr Sarah Bridle, University College London. Presented 1st Oct this year to commemorate the International Year of Astronomy. It is introduced by Martin Rees, Astronomer Royal.
You might want to have more than a casual interest in topics such as gravitational lensing etc to watch this 60 min piece (circa 45 talk - 15 min questions).
I fully enjoyed it myself - its a public lecture so it barely touches maths and graphs - lots of illustrations and very well presented. Includes a challenge for anyone into Software /data-reduction / image processing to help improve the way they measure the shapes of very small, very fuzzy galaxies.
www.great08challenge.info/
I've had a quick look at it - very heavy - challenge runs for six months. I think only academics could make a stab at that.
Its voice and slide show (some of which are animated). If you miss a bit don't use the scroll bar - better go goto previous slide and then forward one to retrace steps.
Might interest.
royalsociety.tv/dpx_royalsociety/dpx.php...ser=dpx_v12&pres=377
Mark
  