Our ever-expanding universe may be expanding a lot faster than we previously thought, according to new scientific research on the Hubble constant, implying that something weird is happening in the universe that modern science may very well be incapable of explaining.
These findings, shared by NASA, were published on the pre-print publishing site arXiv and are set to be published in the peer-reviewed academic periodical The Astrophysical Journal.
What exactly is going on here?
An important part of understanding the universe is the fact that the universe is continuously expanding.
This idea was first discovered around a century ago by astronomer Edwin Hubble, who found other galaxies outside the Milky Way and found that they were constantly moving away.
Not only that, but the farther an object is from the Milky Way, the faster it seems to be moving.
Now, we have no idea how fast everything is moving, but understanding this could help us understand the rate of expansion, the consistent speed at which the universe expands in something that has become known as the Hubble constant. Knowing that can help tell us when it began.
To put it more simply, it could possibly be used to essentially tell us just how old the universe is.
So what's the problem?
Hubble himself was never satisfied with his findings, and decades later, most scientists are still scratching their heads.
There are a few reasons for this confusion.
First, there's the fact that the universe isn't just expanding. Rather, it has undergone two periods of what scientists have called cosmic acceleration.
The first was right after the Big Bang, but the second seems to have been around nine billion years later. It is this latter period that is still ongoing.
This was further elaborated upon in 1998 when scientists studied distant supernovae to prove the increasing cosmic acceleration.
That discovery alone was already groundbreaking, and in 2011, the scientists behind it, Adam Riess and Brian Schmidt, were awarded the Nobel Prize in Physics for it.
What is fuelling this acceleration?
The expansion is thought to be caused by dark energy. This force is widespread throughout the universe - in fact, it is thought to constitute a majority of energy in the universe.
But we also have no idea what dark energy actually is.
However, we have made considerable advancements in this field. In particular, Riess has led a scientific collaborative effort to study this using the Hubble Space Telescope called SHOES (Supernova, H0, for the Equation of State of Dark Energy).
But other recent research has revealed that the Hubble constant may be something considerably not constant.
To incredibly oversimplify such a complicated astrophysics issue, the rate of acceleration doesn't seem to add up to what was predicted.
Now, this new study has made more discoveries that could change everything.
The SHOES team utilized the Hubble Space Telescope to amass data from observations of multiple different objects that function as "cosmic milepost markers." These objects range from Cepheids, stars both in the Milky Way and other galaxies that brighten and dim periodically, and supernovae. When combined, this lets scientists create what has been called a "cosmic distance ladder" in order to measure cosmic acceleration.
“This is what the Hubble Space Telescope was built to do, using the best techniques we know to do it,” Riess explained.
“This is likely Hubble’s magnum opus, because it would take another 30 years of Hubble’s life to even double this sample size.”Adam Riess
Things are getting weird
The SHOES team came up with a new expansion rate for the universe, and it seems to be moving faster.
The Hubble constant astronomers had originally predicted was at 67.5 plus or minus 0.5 kilometers per second per megaparsec.
According to the SHOES team, though, it's at 73. And according to them, there is only a one-in-a-million chance that they're wrong.
Prior to this, while scientists had still struggled to find the Hubble constant, there was still a general understanding of the dynamic evolution of the universe.
These findings essentially turn the small gaps in that understanding into massive holes.
Why is this happening? Scientists don't know, and there's a chance that it might be that there are physics at work that we have yet to understand or maybe even discover.
Why do we care about the expansion of the universe?
This is a complicated question and the answers are even more complicated, but to oversimplify it, it could tell us, or give us clues about, the ultimate fate of the universe.
A prominent theory is that the universe will keep expanding, matter will become less dense as a result and soon all matter will just disintegrate in what is called the heat death of the universe.
Other theories exist too, such as the Big Crunch or Big Rip, but ultimately we have no idea what will happen.
To many, this is a scary thought, but to others, it is simply more challenges and avenues for science to explore.
Is there any way we can learn more?
Yes, but not with Hubble. That space telescope has been in use for over 30 years and has since long surpassed its expected lifespan.
But there's a new space telescope now, NASA's James Webb Space Telescope.
Set up farther out in space and with several tools and capabilities that make it far more advanced than its predecessor, the James Webb telescope is set to build on Hubble's work, taking closer and more detailed looks at the cosmic milepost markers.
And with that, hopefully, this and many of the other great mysteries of the greater cosmos can one day be solved.