In December 1995, Robert Williams, then director of the Space Telescope Science Institute, used a significant share of his discretionary Hubble time for an unusual experiment: pointing the telescope at a dark, seemingly empty patch of sky for ten consecutive days.

The nothing was a small, unremarkable square of sky near the handle of the Big Dipper, chosen precisely because it looked empty. No bright stars or conspicuous nearby galaxies, nothing anyone had a reason to examine more closely. That was the whole point. And it very nearly didn’t happen.

The gamble that almost didn’t happen

Hubble time is scarce, and committees guard it. Pointing the telescope at a deliberately blank patch for a hundred hours was not the kind of proposal that sailed through review. Robert Williams, then director of the Space Telescope Science Institute, knew that. So he used his director’s discretionary time. “The telescope allocation committee would never have approved such a long, risky project,” Williams later recalled. “But as director, I had 10 percent of the telescope time, and I could do what I wanted.”

Not everyone thought he should. Some senior astronomers considered it a poor use of a rare resource. “Scientific discovery requires risk,” Williams said, and he was ready to pay for the bet: “And I was at a point in my career where I said, ‘If it’s that bad, I’ll resign. I’ll fall on my sword.'”

He didn’t have to. The astronomer Robert Kirshner, who had been among the skeptics, later put his change of mind plainly: “Bob was right, I was wrong. The use of that discretionary time was a courageous thing.”

What came back

Over ten consecutive days, from December 18 to 28, Hubble took 342 separate exposures of that one spot, gathering more than a hundred hours of light through four filters. When the exposures were combined, the empty square turned out to be crowded. The Hubble Deep Field showed roughly 3,000 galaxies. Almost every smudge was a galaxy rather than a nearby star, many containing billions of stars.

Williams’s verdict was typically understated: “It turned out to be a neat image. Really.”

The size of the area is the part that stops people. NASA has described the patch as roughly the size of a pinhead held at arm’s length against the sky. And because some galaxies are so far away, their light had been traveling for about 10 billion years before it reached the camera, making the image a look far back in time.

Why a dark patch of sky is never really empty

Here is the part I find most interesting. The spot was chosen because it was ordinary. That carries a heavy implication: this crowd of galaxies isn’t a lucky find in a rich corner of the sky.

NASA notes the field is thought to represent the typical distribution of galaxies in space. Point Hubble at another carefully chosen blank sliver and you would expect a broadly similar result. The darkness you see is not emptiness.

Kirshner had a vivid way of describing those distant, ancient galaxies. Speaking of the young galaxies in the field, he said: “When the galaxies were young, they were very irregular, they were having collisions, they were erupting, they were having adolescent outbursts.” Many early galaxies were messier and more violent than the tidy spirals we tend to picture.

What the Deep Field changed

The image did more than settle Williams’s bet. It started a habit.

The Hubble Deep Field South followed in 1998, then the deeper Ultra Deep Field in 2004 and the eXtreme Deep Field in 2012. Later, Webb’s infrared deep fields carried the same idea farther back.

The Deep Field also reset the math of the whole sky. For years, estimates of the number of galaxies in the observable universe sat around 100 to 200 billion, drawing heavily on deep Hubble observations. Then in 2016, a team led by Christopher Conselice at the University of Nottingham modeled galaxies too faint to detect directly and put the total at about two trillion, at least ten times higher. Conselice’s reaction: “It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied.”

That two-trillion figure needs care. It was a model-based estimate of galaxies inferred below observational limits, not a direct census, and the total depends on how astronomers define and extrapolate the faintest galaxies. Read it as a striking estimate, not a fixed count. The broader point holds: vast numbers of galaxies remain too faint for direct study.

Come back to the pinhead. Hold it up, cover that scrap of sky, and you’ve hidden about three thousand galaxies from view, each a system of stars, some so far away their light is older than the Sun. Multiply that speck across the whole dome of the night and the number stops meaning anything you can feel.

What Williams bought with those ten contested days was a corrected sense of proportion, and our old one was off by a very large factor.