Scientists say they have extraordinary new evidence to support a Big Bang Theory for the origin of the universe.
They 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.
The signal takes the form of a distinctive twist in the oldest light detectable with telescopes.
The breakthrough was announced by an American team working on a project known as BICEP2, using a telescope at the South Pole.
The aim has been to try to find a residual marker for "inflation" - the idea that the cosmos experienced an exponential growth spurt in its first trillionth, of a trillionth of a trillionth of a second, says the BBC.
Speaking at a news conference to announce the results, Professor John Kovac of the Harvard-Smithsonian Center for Astrophysics, and a leader of the BICEP2 collaboration, said: "This is opening a window on what we believe to be a new regime of physics - the physics of what happened in the first unbelievably tiny fraction of a second in the Universe."
The signal is reported to be quite a bit stronger than many scientists had dared hope, which simplifies matters, reports the BBC. The sensational nature of the discovery means the BICEP2 data will be subjected to intense peer review.
Professor Richard Easther is the head of physics at Auckland University, whose work focuses on the physics of the very early universe.
He told Radio New Zealand's Nine to Noon programme the discovery is up there with DNA, or evolution, or the discovery of the atom.