in the video below, physicist Brian Greene
traces the early development of String Theory

he notes that at one point excitement spiked
as String Theory was seen as a possible
Theory of Everything

Greene says,
"What's really exciting about this is that it offers an amazing possibility. If we could only master the rhythms of strings, then we'd stand a good chance of explaining all the matter and all the forces of nature, from the tiniest subatomic particles to the galaxies of outer space. This is the potential of string theory, to be a unified 'Theory of Everything.'

But, at first sight, in our enthusiasm for this idea, we seem to have gone too far. Because we didn't produce just one string theory, or even two—we somehow managed to come up with five."

Five String Theories? That was four too many!
Greene says that String Theory went through
"a kind of doldrums"

this video ends with a reference to
the breakthrough that occurred in 1995

it was then that physicist Ed Witten, whom Greene
describes as possibly Einstein's successor,
blew everyone out of the water with what
has come to be known as M-Theory



the above video is a brief excerpt from NOVA's
The Elegant Universe,it can be seen in full here