London, June 21 : A new analysis has found that variation in one of the fundamental constants of physics is not correct, and it is constant after all.
According to a report in New Scientist, the new analysis has found no significant variation in the electron-proton mass ratio, also known as mu, over the last 6 billion years, which is in contrast to a 2006 report that said the ratio may have decreased by 0.002% in the past 12 billion years.
For studying this constant, a team led by Michael Murphy of Swinburne University in Australia examined radio waves coming from a quasar, a giant black hole that glows brightly as it devours its surroundings, some 7.5 billion light years away.
The radiation from the black hole had passed through a galaxy containing clouds of ammonia gas.
This absorbs some parts of its spectrum, leaving a characteristic "fingerprint" that depends very sensitively on the ratio of the masses of the protons and electrons in the molecules.
When the radiation passed through the ammonia 6 billion years ago, the absorbed parts of the spectrum were the same as they would be today. That means the constant hasn't changed in that time.
This comes as a relief to many physicists, as the laws and constants of physics are generally thought to apply at all times and places in the universe.
"If we found mu - or any other constant - to vary, then that would be the end of the Standard Model," said Murphy. "We would have to come up with an entirely new theory of physics," he added.
According to Murphy, there is good reason to trust the new result.
The wavelengths at which the ammonia molecules absorb radiation depend more strongly on the proton-to-electron mass ratio than with other molecules, such as the molecular hydrogen that was used for the 2006 result.
"Our constraint is 10 times better than those previously obtained," said Murphy.