STOCKHOLM (AFP) - Dr Peter Higgs of Britain and Dr Francois Englert of Belgium won the Nobel Prize for Physics on Tuesday for conceiving of the tantalising "God particle" which confers mass.
Dr Higgs, 84, and Dr Englert, 80, were honoured for theorising a particle - discovered last year after an agonising quest - that explains why the Universe has substance.
"This particle originates from an invisible field that fills up all space. Even when the Universe seems empty this field is there," the jury said in a statement.
"Without it, we would not exist, because it is from contact with the field that particles acquire mass." The University of Edinburgh posted a statement from Dr Higgs saying he was "overwhelmed" by the honour.
"I hope this recognition of fundamental science will help raise awareness of the value of blue-sky research," he said.
Known as a boson, the discovery was popularly dubbed the "God Particle" on the grounds that it is everywhere yet bafflingly elusive.
Without it, say theorists, we and all the other joined-up atoms in the Universe would not exist.
The presumed particle was discovered last year by a mega-scale physics lab near Geneva operated by the European Organisation for Nuclear Research (CERN), after a decades-long search.
"As an achievement, it ranks alongside the confirmation that the Earth is round or Man's first steps on the Moon," Canadian particle physicist Pauline Gagnon told AFP.
Dr Higgs and Dr Englert, the latter of the Free University of Brussels, received the world's most prestigious award for excellence in physics nearly a half century after they and others set down the conceptual foundations.
"Their work has helped shape our fundamental understanding of the world around us," said John Pethica, vice-president of Britain's Royal Society.
The history of the discovery dates back to 1964, when six physicists, working independently in three groups, published a flurry of papers.
The first were Belgians Robert Brout, who died in 2011, and Englert, who proposed a mechanism by which a mass-giving field of particles invaded the early Universe, which until then was filled only with massless particles.
Englert told reporters in Brussels Tuesday that his reaction at getting the prize was joy mixed with more complex emotions.
"There is regret too that my colleague and friend, Robert Brout, is not there to share it," he said.
Englert's and Brout's results were followed by Dr Higgs, who was the first to suggest that mass could only occur through the existence of a hitherto unknown particle.
Because of this, the particle has been named after him, although Dr Higgs has always been swift to acknowledge vital contributions from others.
At the heart of the search for the "Higgs," was a drive to fill the so-called Standard Model, a conceptual framework of the fundamental particles of matter.
The model, designed in the 1970s, failed to explain why some particles have substance, and others, such as light, have none.
The answer, according to the theories, lies in an invisible field of bosons, or force carriers, that was created after the Big Bang.
Fundamental particles travel through this field. Some interact with the Higgs to a greater or lesser degree, which thus confers mass, while others do not.
On July 4 last year, physicists at CERN announced to rousing applause that they had found an elementary particle "consistent with" the Higgs boson.
CERN director general Rolf Heuer, in a statement on Tuesday, gave the biggest sign yet that the presumed particle is indeed the right one.
"The discovery of the Higgs boson at CERN last year, which validates the Brout-Englert-Higgs mechanism, marks the culmination of decades of intellectual effort by many people around the world," he said.
Later he told staff at CERN that it was "a great day for particle physics", assuring his co-workers that they, too, deserved praise: "I'm really proud of you guys." The London-based Institute of Physics, where Dr Higgs is an honorary fellow, hailed the work on the Higgs boson, saying it had led to a very exciting and productive period in physics research.
"It has been a long journey but one that has inspired a generation to engage with the subject," said Frances Saunders, president of the institute.
"With the existence of the Higgs boson confirmed... we can now move on to the next challenges to our understanding such as the phenomena of dark matter and quantum gravity." In line with tradition, the laureates will receive their prize at a formal ceremony in Stockholm on December 10, the anniversary of prize founder Alfred Nobel's death in 1896.
The pair will share the prize sum of eight million Swedish kronor (S$1.55 million), reduced because of the economic crisis last year from the 10 million kronor awarded since 2001.