The secrets of the universe could be locked away under the number 73
The known boundaries of space could be expanding at a speed nine percent faster than scientists believed was possible under the existing laws of physics.
The groundbreaking discovery comes off the back of observations made by the European Space Agency’s (ESA) Gaia mission, which scans billions of stars in the Milky Way.
Earlier in April Cristina Martínez-Lombilla, of the Instituto de Astrofísica de Canarias in Tenerife, claimed the Milky Way appears to be expanding faster than the speed of sound.
Astronomers studying Gaia’s treasure trove of data have now questioned one of the most fundamental principles in cosmology, the Hubble Constant.
The Hubble Constant, or Hubble’s Formula, is a mathematical value which represents the speed at which the universe is expanding.
The expansion or contraction of space expressed in this value is a valuable key to understanding how the universe began in the Big Bang and how it might end one day.
The latest set of information collected by Gaia narrowed Hubble’s value down to 73 km/s/Mpc – which means two galaxies a staggering 9.5 trillion kilometres away from each other will grow further apart at a speed of 73 kilometres per second.
One way scientists arrived at this number is by focusing on the redshifts of brightly lit supernovae whose light quite literally stretches as it moves through expanding space.
Professor Adam Riess, at the Space Telescope Science Institute in Baltimore who led the latest analysis, said: “The fact the universe is expanding is really one of the most powerful ways we have to determine the composition of the universe, the age of the universe and the fate of the universe.
“The Hubble constant quantifies all that into one number.”
But a problem has emerged because the number contradicts previously accepted calculations of Hubble’s value.
The previous calculations based on measurements of Cosmic Microwave Background, primordial light released in the Big Bang, suggested the rate of expansion is much slower.
According to NASA’s space boffins, who pinpointed Hubble’s Constant at 70.1 km/s/Mpc, there is a corresponding three percent uncertainty with this figure.
Dr Reiss said: “The cosmic microwave background is the light that is the furthest away from us that we can see.
“It’s been travelling for 13.7 billion years and it’s telling us how fast the universe was expanding when the universe was a baby.”
A team of cosmologists calculated Hubble’s Constant to be 73km/s/Mpc
Based on these calculations the universe was thought to be expanding at a rate of 67 km/s/Mpc.
The fact the universe is expanding is really one of the most powerful ways we have to determine the composition of the universe
The discrepancy means our universe is stretching and growing at a rate much faster than initially assumed.
Dr Reiss explained: “You can think of the universe growing just like a child growing, and you can think of the cosmic microwave background as a snapshot of what the child looked like at that time.
“We measure their height on a door and we mark the date. And then, the parents and the doctor and all the experts say gee, following normal growth charts, this child will reach a height of six foot two, or something like that, when they’re full grown.
“Now, it’s the present day, the child is full grown, this is our present universe, and so now we actually measure the expansion rate of the universe and it’s not six foot two as predicted, it’s something larger. In this case, it’s something faster, and that is becoming quite significant.”
Edwin Hubble’s revolutionary formula was gifted to the world in the 1920s and has become his second most recognised contribution to science after the Hubble Telescope, launched in his name in 1990.
According to NASA, the Constant “marked the beginning of the modern age of cosmology”.
But this is not the first time scientists are quarrelling over Hubble’s constant and the US space agency said the figure varied widely over the past decades between 50 and 100 km/s/Mpc.
Wendy Freedman of the Observatories of the Carnegie Institution of Washington, said in 1999 we are now entering an era of more precise cosmological measurements.
She said: “Now we can more reliably address the broader picture of the universe’s origin, evolution and destiny.”
The universe is expanding faster than initially assumed the new data suggests
And yet the cosmic formula is being challenged on a daily basis despite hopes more accurate measurements would eliminate such big discrepancies.
The nine percent difference also raised interesting questions about what could be causing the accelerated rate of expansion.
NASA’s experts proposed the idea the presence of dark matter, which makes up about 25 percent of the universe, is pushing the expansion rate outwards.
Scientists are hoping to settle the score once and for all five years from now with gravitational wave observations by the international LIGO Scientific Collaboration.