When you step outside at night and look to the sky, what do you see: black velvet accented by hundreds of stars , or a bluish glow dotted by a few lights that turn out to blink or dart across the sky?

As artificial lightning shines over human settlements, stars fade. Only one in five North Americans can see the Milky Way at night, and 99% of Americans experience light pollution, according to a 2016 study . That's a stark difference from the way humans lived for millennia, E.C. Krupp, director of the Griffith Observatory in Los Angeles who studies how people have related to the heavens over millennia, told Space.com.

"Most of us are living in an urban environment where we not only don't see the night sky, we actually are kind of oblivious that it even exists," Krupp said. "It takes work to re-immerse oneself into the perspective of our ancestors, not only our ancient and prehistoric ancestors, but frankly, just our historic ancestors, because it wasn't like this a little over 100 years ago."

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"Artificial lighting has been an extraordinary blessing to human beings but at the same time has divorced us from the night sky, not only by polluting it extraordinarily with unnecessary light but also just by distracting us," Krupp said. "We are occupied with other things."

But awareness of that separation has been increasing over recent decades, he said, with a small movement focused on preserving dark skies. (The International Dark-Sky Association, which is holding its annual International Dark Sky Week beginning today , April 19, is one leader of that movement.)

"Our emotional response to the night sky, to its beauty, to its apparent order, although that's an accident of where we happen to be in the cosmos — those things to which our brains are responding are in fact extraordinarily pleasurable, and you really don't want people to miss it," Krupp said. "We can see that that engagement with the sky has been one of the things that has propelled our inquiries about everything and in fact our mastery of technologies and our ability to modify our behavior."

Krupp said that connection between the sky and the human brain is rooted in our tendency to look for patterns — particularly those that might connect to, say, agricultural cycles. "Patterns in the sky have the advantage that they're out of reach, so nobody can mess with them," he said. "They're visible to all and they also are synchronized with things that make a difference to us here on the Earth."

That connection made paying attention to the night sky a survival tool for millennia that it no longer is, Krupp said. But even as technology has disconnected humans from the night sky, it has also offered new connections to replace those, particularly through the space images and news stories that flood the internet.

"More people than ever have a better appreciation than ever of the scale and the strangeness and the absolute glory of what we see in outer space," Krupp said, even though all the images that delight us so much are rarely raw footage but instead tweaked to be more accessible to us.

"This is a transformation for the benefit of our eye and brain," he said. "If you went out in space, it wouldn't look like that. But that's the point. We're making the universe into something heroic, just as our ancestors did, and we're just doing it in a different way."