Big Bang: Spectacular cosmic discovery hailed
17 March 2014 Last updated at 23:40 GMT
Scientists say they have extraordinary new evidence to support a Big Bang Theory for the origin of the Universe.
Researchers believe they have found the signal left in the sky by the super-rapid expansion of space that must have occurred just fractions of a second after everything came into being.
It takes the form of a distinctive twist in the oldest light detectable with telescopes.
The BBC's science editor David Shukman reports.