New light on dark energy changes the view of universe’s future

Findings back Einstein’s theory and raises new questions on universe’s expansion

Dark energy, the dominant energy form in the cosmos, continues to baffle astronomers. It turns out that the mysterious force is not what it seemed.

Findings of a new set of analyses published on Tuesday confirmed what scientists suspected.

Since the discovery of dark energy in 1998, the mysterious accelerative force powering the expanding universe has been considered a cosmological constant. Because scientists believe the strength of dark energy has remained the same throughout history.

That belief was upended early this year by an international research collaboration of more than 900 scientists, who found that the force pushing or pulling galaxies around was not constant but evolves over time. The same group of scientists published a broader set of analyses on Tuesday, confirming the earlier findings.

“The strong hint that dark energy is dynamical is the most important finding since the discovery of cosmic acceleration in 1998,” astrophysicist Mustapha Ishak-Boushaki of the University of Texas at Dallas said.

What do the findings mean?

It changes our understanding of the future since dark energy is the biggest component of the universe. “Its behaviour determines the universe’s fate,” an Associated Press report said, quoting David Spergel, an astrophysicist and president of the Simons Foundation. “If dark energy is constant, the universe will continue to expand, forever getting colder and emptier. If it’s growing in strength, the universe will expand so speedily that it’ll destroy itself in what astronomers call the Big Rip.”

There’s no reason to panic as it won’t happen in our life, and not in the near future. “If this is what’s going on, it won’t happen for billions of years,” Spergel said. “But we’d like to know about it.”

The findings have sent ripples through the scientific community. “It’s a time of great excitement, and also some head-scratching and confusion,” said Bhuvnesh Jain, a cosmologist at the University of Pennsylvania, told AP.

What happens next?

The analyses point to a possible explanation from an older theory. Physicist Albert Einstein’s groundbreaking theory of general relativity in 1915 predicted how the universe expanded and galaxies clustered across billions of years of cosmic history. The new findings attest to Einstein’s theory.

“Einstein’s theory of general relativity describes the motion of massive objects in a gravitational field that they create. It is one of the most successful physical theories that we have. The discovery of the accelerating universe, however, led to suggestions that maybe general relativity needs to be modified,” said University of Michigan cosmologist Dragan Huterer, co-leader of the working group that interpreted the DESI cosmological data.

What’s dark energy?

The Big Bang event 13.8 billion years ago has been expanding the universe. Dark energy, which makes up 68% of the universe, is described as a negative pressure that is pushing space outward.

Scientists say the fundamental background energy in space, also known as vacuum energy, could be equal to the cosmological constant since it remained unchanged throughout history. Constant is a mathematical term figure in Einstein’s theory of general relativity. When the Hubble telescope reaffirmed that the universe was expanding, Einstein removed the constant, calling it “my biggest blunder,” according to physicist George Gamow in a Nasa report.

Now, it seems Einstein was right. That’s what the new findings say.

How was the study carried out?

Scientists looked at distant, ancient galaxies to understand the evolution of the universe and the impact of dark energy. They used the Dark Energy Spectroscopic Instrument (DESI), which employs a telescope based in Tucson, Arizona, to create a three-dimensional map of the universe’s 11-billion-year history to find out how the birth of galaxies (a system of stars, stellar material and dark matter bound together by gravity).

The map that focused on the growth of the cosmic structure dispels the notion that dark energy is not a constant force; instead, it appears to be changing or weakening over time. If that’s true, dark energy is very different from what scientists thought.

“Dark energy seems to be dynamical and weakening. That changes the future of the evolution of the universe, which does not need to be accelerating forever in its expansion,” said astrophysicist Mustapha Ishak-Boushaki of the University of Texas at Dallas, co-leader of the working group.

What happens next?

“Dark energy is responsible for the accelerated expansion of the universe. The physical nature of dark energy is at present unknown,” Huterer said in a Reuters report. The new findings corroborate the standard cosmology model, including the theory of general relativity.

Scientists are now looking for more evidence of dynamic dark energy behaviour. More data and analyses over the next few years will determine whether this view of dark energy stands.

For life to exist in a universe, there must be stars [the sun is a star] to provide heat and energy to orbiting planets to sustain life. A changing dark energy would affect star formation, and stars are essential for life.