The fact that our Universe's expansion is accelerating implies that dark energy exists. But could it be even weirder than we've imagined?

Since 1998, we've known our Universe isn't just expanding, but the expansion is accelerating. Could the Big Bang itself be the reason why?

The laws of nature are almost perfectly symmetric between matter and antimatter, and yet our Universe is made ~100% of matter only. But why?

Empty space itself, the quantum vacuum, could be in either a true, stable state or a false, unstable state. Our fate depends on the answer.

"Asking the question of, "Where did the entire universe come from?" is no longer a question for poets and theologians and philosophers. This is a question for scientists, and we have some amazing scientific answers to this question."

25 years ago, our concordance picture of cosmology, also known as ΛCDM, came into focus. 25 years later, are we about to break that model?

DESI, by mapping galaxies, has claimed they see evidence for dark energy evolving by getting weaker. But that's only one interpretation.

The Universe is expanding, and individual, bound structures are all receding away from one another. How, then, are galaxies still colliding?

"Asking the question of, where did the entire universe come from, is no longer a question for poets and theologians and philosophers. This is a question for scientists, and we have some amazing scientific answers to this question that have defied even the wildest of our expectations."

There are some 26 fundamental constants in nature, and their values enable our Universe to exist as it does. But where do they come from?

From the tiniest subatomic scales to the grandest cosmic structures of all, everything that exists depends on two things: charge and mass.

Dark matter doesn't absorb or emit light, but it gravitates. Instead of something exotic and novel, could it just be dark, normal matter?

Only 5% of the Universe is made of normal "stuff" like we are. Could there be dark matter or dark energy life, or even aliens, out there?

First discovered in the mid-1960s, no cosmic signal has taught us more about the Universe, or spurred more controversy, than the CMB.

In the year 2000, physicists created a list of the ten most important unsolved problems in their field. 25 years later, here's where we are.

Our Universe isn't just expanding, the expansion is accelerating. Instead of dark energy, could a "lumpy" Universe be at fault?

There was a lot of hype and a lot of nonsense, but also some profoundly major advances. Here are the biggest ones you may have missed.

DESI has allowed astronomers to create an unprecedented 3D map of the Universe representing 20% of the entire sky.

For nearly 60 years, the hot Big Bang has been accepted as the best story of our cosmic origin. Could the Steady-State theory be possible?

Two parts of our Universe that seem to be unavoidable are dark matter and dark energy. Could they really be two aspects of the same thing?

More than two years after JWST began science operations, our Universe now looks very different. Here are its biggest science contributions.

What are dark matter and dark energy? The large-scale structure of the cosmos encodes them both, with ESA's Euclid mission leading the way.

The most common visual depictions of the history of the Universe show the Big Bang as a growing tube with an "ignition" point. Why is that?

An in-depth interview with astronomer Kelsey Johnson, whose new book, Into the Unknown, explores what remains unknown about the Universe.

Today, the deepest depths of intergalactic space aren't at absolute zero, but at a chill 2.73 K. How does that temperature change over time?

In all directions, at great distances, the Universe looks younger, more uniform, and less evolved. Does that mean Earth must be the center?

It's possible to remove all forms of matter, radiation, and curvature from space. When you do, dark energy still remains. Is this mandatory?

In the expanding Universe, different ways of measuring its rate give incompatible answers. Nobel Laureate Adam Riess explains what it means.

The Universe isn't just expansion, but the expansion itself is accelerating. So why can't we feel it in any measurable way?

In all the Universe, only a few particles are eternally stable. The photon, the quantum of light, has an infinite lifetime. Or does it?