The universe is expanding faster than previously thought, and scientists are at a loss to explain it.
New data from the Hubble Space Telescope has measured the speed of the universe's expansion to a greater level of accuracy than ever before, and it's between 5 and 9 percent speedier than expected.
"A funny universe just got funnier," says astrophysicist Dr Brad Tucker of the Australian National University, which was involved in the research.
Since the Big Bang, the universe has not just gotten bigger -- the speed of its growth has accelerated.
"We thought we were close to understanding dark energy, but now we know we don't know the answer at all. There's a lot of work to do."
Dark energy is believed to make up 70 percent of the universe and dark matter 25 percent, while normal matter and energy -- the kind we can see and detect -- is only 5 percent.
Dark matter and energy have never been directly observed -- they don't interact with normal matter, except through gravity. But without them the universe's increasing rate of expansion doesn't make sense -- the laws of physics just don't add up.
Brad Tucker (Stuart Hay, ANU)
Astronomers used Hubble to measure 2700 stars and supernovae over two-and-a-half years, measuring the speed of the universe's expansion to an accuracy of 2.4 percent.
It means that despite being 13.8 billion years old, distances between cosmic objects will double in only 9.8 billion.
But the new, higher speed means what little scientists know about dark energy and matter just got relatively smaller.
"If this discrepancy holds up, it appears we may not have the right understanding," says study leader Adam Riess of the Space Telescope Science Institute.
So what could be behind it? Scientists have a few theories:
"Future studies using different techniques will hopefully shed light on exactly what is going on," says Dr Tucker.
The universe's accelerating expansion was only discovered in 1998. Before then, most thought it expansion was slowing down, and would perhaps one day even collapse in a 'big crunch'.
That could still happen, since it seems scientists have a lot to learn about dark energy.