The universe likes to play coy about its age, but astronomers believe they have a pretty good idea of the range. Now, a series of new studies has investigated the question using different methods – and they’ve come up with two different answers, separated by more than a billion years.
Currently, the most widely accepted age for the universe is around 13.8 billion years, but determining the age of … well, everything, is no easy feat. There are several key calculations that need to be done, and checked against each other. The problem is, these can be figured out in different ways, resulting in different answers.
Because the universe is expanding at an accelerating pace, the further away an object is, the faster it appears to be moving away from us. This is expressed as the Hubble constant, and it’s a key factor in figuring out the age of the universe. After all, if we can determine how fast objects are moving away from us, we can rewind that process to its logical beginning – the Big Bang.
A second method of figuring out the age of the universe is by mapping the oldest light we can detect. Known as the cosmic microwave background (CMB), this radiation was created when the universe was just 380,000 years old – a mere infant, in the grand scheme of things.
These two main techniques produce very different solutions to the problem, as demonstrated in the new studies. They each calculated different values for the Hubble constant, and came to their own conclusions accordingly.
In the first study, researchers from the University of Oregon set out to map the distance to dozens of galaxies. They recalibrated an existing tool for measuring distance, called the baryonic Tully-Fisher relation, which works independently to the Hubble constant.
Starting with Spitzer data of the distances of 50 galaxies, they used this to estimate the distances to another 95 galaxies. This then provides a new, supposedly more-accurate foundation for calculating the Hubble constant, and by extension, the age of the universe.
In this case, the Oregon team set the Hubble constant at 75.1 km (46.7 mi) per second per megaparsec. That means that a galaxy that’s one megaparsec (about 3.3 million light-years) away from Earth is whizzing away from us at 75.1 km every second.
From this, the team calculated that the universe is only 12.6 billion years old – that, you might notice, is much younger than the 13.8 billion years usually stated. It’s well beyond any margin of error that might be acceptable by the established calculations.
For the second study, researchers used the Atacama Cosmology Telescope (ACT) in Chile to measure the CMB in more detail. Images of the CMB always end up looking a bit like one of those magic eye pictures, with alternating splotches of color. These variations represent differently polarized light in the CMB. This time, the researchers measured the spacing between these variations to recalculate the universe’s age.
“We are restoring the ‘baby photo’ of the universe to its original condition, eliminating the wear and tear of time and space that distorted the image,” says Neelima Sehgal, a co-author on the study. “Only by seeing this sharper baby photo or image of the universe, can we more fully understand how our universe was born.”
In doing so, the researchers determined that the universe is 13.8 billion years old – in agreement with the accepted age. The Hubble constant, meanwhile, was found to be 67.6 km (42 mi) per second per megaparsec (/s/Mpc). This is also very close to the widely accepted value of 67.4 km (41.9 mi) /s/Mpc.
The fact that these figures line up with the generally accepted ones isn’t too surprising – both sets of data were found by analyzing the CMB, albeit in different ways.
The real problem though, is that the various studies disagree so wildly with each other, to the tune of a billion years. But they’re not the only ones – the battle lines are commonly drawn by the methods used. Whenever scientists measure the CMB they arrive at figures close to 13.8 billion years old and a Hubble constant of around 67 km/s/Mpc, and studying the motions of galaxies usually yields a younger age and a Hubble constant closer to 74 km/s/Mpc. Obviously something is amiss, and more research is needed to determine where the truth lies.
The first study was published in the Astrophysical Journal, while the second set of studies is currently available online at arXiv.
Sources: University of Oregon, Stony Brook University
