BBC Light and Dark 1of2 PDTV x264 AAC

two-part series in which professor jim al-khalili shows how, by uncovering its secrets, scientists have
used light to reveal almost everything we know about the universe. but in the last 30 years we have
discovered that far from seeing everything, we have seen virtually nothing. our best estimate is that
more than 99 per cent of the universe is actually hidden in the dark.

thank you, rogue88, for the description.

http://docuwiki.net/index.php?title=light_and_dark

light -- the story begins in the 3rd century bc when, by trying to understand the tricks of
perspective, the greek mathematician euclid discovered that light travels in straight lines, which meant
that if we could change its path we could change how we see the world. in renaissance italy 2,000
years later, galileo galilei did just that by using the lenses of his simple telescope to reveal our true
place in the cosmos. in the 1670s, the danish astronomer ole roemer discovered that light travelled at
a finite speed, a discovery that had a profound implication. it meant the further one looks out into the
universe, the further one looks back in time. and in 1964, by detecting the cosmic microwave
background, the afterglow of the big bang, we captured the oldest light in the universe and saw as far
back as its possible to see with light.

dark -- professor jim al-khalili tells the story of how we went from thinking we were close to a
complete understanding of the universe to realising we had seen almost none of it. today, our best
estimate is that more than 99 per cent of the cosmos is hidden in the dark, invisible to our telescopes
and beyond our comprehension. the first hints that there might be more out there than meets the eye
emerged from the gloom in 1846 with the discovery of the planet neptune. it was hard to find, because
there was precious little light to illuminate it. in the middle of the 20th century scientists discovered
dark matter - stuff that wasn't just unseen, it was fundamentally un-seeable. in the late 1990s scientists
trying to measure precisely how much dark matter there was in the universe discovered something
even more elusive out there - dark energy, a mysterious new force driving the universe apart that is
thought to make up a colossal 73 per cent of it.


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