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In CUriosity, experts across the CU �鶹ӰԺ campus answer pressing questions about humans, our planet and the universe beyond.

This week, Jeremy Darling, professor in the Department of Astrophysical & Planetary Sciences, jumps into “What is the biggest thing in the universe?” And stay tuned for “What is the smallest thing in the universe?”

The vastness of space can be hard to wrap your head around.

Say you are an ordinary beam of light blazing through space at a speed of 186,000 miles per second. It would take you 8 minutes and 20 seconds to make it from the sun to Earth—an impressive distance of 94 million miles. It would take almost an entire day to travel between Earth and NASA’s Voyager 1 spacecraft, currently more than 15 billion miles from Earth.

That’s far, but nothing compared to the entirety of the Milky Way Galaxy, which contains something around 100 billion stars. Light crosses from one edge of this expanse to the other over a staggering 100,000 years.

 

  Previously in CUriosity

How do sea creatures make light?

And this distance is only the tip of a very, very big iceberg, according to Darling. He’s a cosmologist who studies large things, from the evolution of galaxies like the Milky Way to how black holes can bend space and time.

“I really like big questions,” he said. “It's amazing to me that a person can say something new about the universe after working on it for only a few years.”

Darling explained that the universe has a structure that goes way beyond individual galaxies. Just after the Big Bang, he said, the universe wasn’t completely homogenous. Some regions of space were a little denser with matter than others. Over time, those dense areas got denser, while the less dense areas became even more sparse—a bit like milk separating into curds and whey. Eventually, the cosmos formed a pattern like a web. Galaxies tend to cluster into long strands, or filaments, that surround relative empty patches of space known as voids.

“The filaments are the most massive structures in the universe, especially at the points where they meet, which are called clusters or superclusters,” Darling said.

So how big is one of these galactic clumps? The Milky Way sits in what scientists call the Laniakea Supercluster, named after the Hawaiian word for “immense heaven.” This supercluster boasts around 100,000 galaxies, some much larger than our own, and extends around 520 million light-years across. Put differently, light has been traveling across this expanse for almost as long as animals with backbones have lived on Earth.

In his own research, Darling has tracked the evolution of such superclusters. He’s developed new methods to, for example, observe galaxies falling out of voids and into the denser filaments.

But you might not want to get used to them, at least on cosmic time scales. The universe, Darling said, is expanding at an accelerating pace due to a mysterious force known as dark energy.

“Dark energy, if it keeps going, will start pulling stuff apart that we would have otherwise thought would remain together,” he said.

Even the biggest things in the universe, it turns out, are no match for time.