Much Ado About Nothing

Today, I’d like to talk about some science a little farther away than the life sciences I’ve written about so far. Actually, it’s literally farther away – out in space. Outer space encompasses everything else in the universe outside of earth’s atmosphere, from the moon (a mere 250,000 miles away) to the Abell 2218 galaxy (a much farther distance of close to 13 billion light years), and everything in between. As I’m sure you are aware, that’s a pretty big area. No one really knows how large the universe is, or if it even has edges at all! (It’s possible that the universe is infinitely large.) The most distant galaxies seen by the Hubble space telescope are at about 13 billion light years away, and the visible horizon of the universe (that is, as far as we can detect) is about 15 billion light years away. Within that area, there are differences in the distribution of celestial objects. However, even with an uneven distribution, scientists have always observed that most of outer space has something in it. Even if it’s not filled with stars, space contains things like galaxies, black holes, gas and dark matter (that strange and mysterious material). At least, no one has ever found a significant region of space that is void of any of these objects – until August.

At the end of August, researchers from the University of Minnesota announced that they discovered a vast chunk of space with nothing in it. This area is 1 billion light years across – that’s 6 billion trillion miles of emptiness. If we assume that the Milky Way is 100,000 light years across, the void is 10,000 times larger. And it appears to be truly empty – no stars, no galaxies, no black holes, no gas and no dark matter. Nothing.

While scientists have observed other areas of space with nothing in it, the sheer size of this cosmic void has taken everyone by surprise. For example, there is a small cosmic void fairly close to Earth – only 2 million light years away. It’s called the South Pole Void, so named because it occupies the sky directly above the southern pole of the Milky Way galaxy. But the region discovered by the Minnesota team is roughly 1,000 times the volume of any other known void, including the South Pole void. That’s close to comparing the volume of the Great Lakes with the volume of the Atlantic Ocean. Sure, the Great Lakes are really large. But the Atlantic is much, much larger.

How on earth did these astronomers find something with nothing in it? To accomplish it, they relied on pictures from the National Radio Astronomy Observatory. The NRAO, headquartered in West Virginia, designs, builds, and operates some of the world’s most advanced radio telescopes. Unlike standard telescopes, which visualize light waves, radio telescopes “see” radio waves generated by interstellar objects. These radio waves provide a much clearer view of stars, galaxies, and planets because they can pass through much of the gas and dust in space without distortion, unlike visible light. And many celestial objects produce much stronger radio waves than they do visible light waves, so radio telescopes can see them in much greater detail. Lawrence Rudnick’s team studied radio pictures taken from the NRAO’s Very Large Array (VLA) telescope. Their careful study of the NVSS data showed a remarkable drop in the number of galaxies in a region of sky in the constellation Eridanus. Further study showed that, not only is the region devoid of galaxies, it is devoid of nearly all matter.

Scientists say that it is possible that this giant empty space is simply a fluke of nature. After all, with a virtually infinite area of space and a finite amount of matter to disperse in it, it’s possible to get a large area devoid of objects. However, the chance of that happening is pretty small, according to James Conlan, an astronomer at the National Radio Astronomy Observatory. Conlan, though not a part of the Minnesotan research team, is investigating this empty region of space further. He believes that even though further investigation may discover a few objects in this space, it will still be the largest least dense region of space ever discovered.

What causes such a large region of empty space? Brent Tully is an astronomer at the University of Hawaii who studies the near-Earth void. According to him, empty regions of space are likely caused by a gravity battle. Areas of space that are more densely packed with matter have bigger gravitational pull than areas that are packed less densely. Over time, dense space will pull matter away from less dense space. Of course, the effect will increase over time; as more and more matter gets added to the dense space, its gravity will increase, which will pull in more matter, which will increase its gravity, and so on. After billions of years, this could eventually lead to a hole in the universe – areas where there is simply nothing left.

It’s fascinating to learn that not only are there objects in space that are worth studying, it is also worth studying, well, nothing! According to retired NASA astronomer Steve Maran, "This is incredibly important for something where there is nothing to it."