With the best intentions, but also with a hint of subversion, Adam Block makes you feel insignificant.

Block is the manager of the public observing programs at the Mount Lemmon SkyCenter on the tiptop of the Catalina Mountains north of Tucson, Ariz. It’s a bureaucratic title for an existential task: His job is explaining to earthbound visitors how they fit into a universe so vast that … well, here’s one example:

On an easel at the far end of a conference room, Block placed a photo of the sun. It was about 12 inches across. Then he picked up a small pebble — small enough, he said, that 100 such pebbles could fit in a line across the photo.

Then, pebble in hand, he began walking away from the photo. Crossing the room, he had to turn down a hallway before he’d paced off the necessary 60 feet.

This distance, he said, raising his voice to be heard, is how far away we are from the sun. The pebble is the Earth and represents how tiny we are.

Just as we were starting to feel like the dust on Neil Armstrong’s moon boot, Block returned and said, smiling almost reverently at the stone, “And everything that has ever happened on Earth has happened on this pebble.”

With that, Block struck that tightrope balance between the cosmic and the earthbound, a thread that continued throughout the evening.

The class is offered almost every clear night, year-round, atop the “sky island” of the University of Arizona’s Steward Observatory on Mount Lemmon. Far above Tucson’s lights, visitors can see deep into the universe by peering through powerful telescopes or top-quality binoculars.

Nothing will jump out at you at first, he said, as we began scanning the night sky. But wait. “It is the subtlety that makes things sublime.”

Old light, but new to us

The sky is more crowded than it appears, and too immense to easily grasp. Yet it can be measured. Stars’ distances are tracked in terms of how long it takes their glow to reach Earth while moving at the speed at which light travels. That’s about 186,000 miles per second, or 671 million miles per hour. We can’t even sneeze that fast.

That’s humbling, yet kind of cool. Late last winter, we contemplated such facts as Block guided us through the night sky from the North Star to the Orion Nebula. Technically, the program lasts five hours. Astronomically, it’s lasted for millions of years.

Take the constellation of Orion, the hunter. His “belt” of three stars makes it one of the more familiar sights in the sky. Two stars above mark his shoulders; two below, his feet. In between, emptiness.

But Block had a surprise.

Leading us to the powerful 32-inch Schulman telescope, he showed us, in what might be Orion’s right pocket, a brilliantly striated cloud of gases that glowed scarlet, lavender, saffron and slate.

In astronomer-speak, it’s an immense interstellar molecular cloud. To ordinary stargazers like us, it was … heavenly. The light that we were seeing started its journey toward Earth about 1,500 years ago — about the time King Arthur was assembling his Round Table.

Think of all that’s happened since then.

Earth isn’t so bad, either

Block himself holds his own with the stars. Geeky-smart, he recently was honored for his work in “bringing the cosmos to the people.” The astrophotographer’s images are regularly featured on NASA’s “Astronomy Picture of the Day” (apod.nasa.gov/apod/astropix.html).

The SkyNights program is his baby. It’s offered almost nightly throughout the year, canceled only for overcast skies or special events. Reservations are necessary, and best made months in advance. (Do so at skycenter.arizona.edu.) Tickets are $60 for adults and $30 for ages 7-17, and includes what was described as a “light dinner” but was a hearty array of food that Block brings up from a local Costco.

Getting to the site is an education in itself, a 25-mile winding drive 6,000 feet up Mother Earth. (Dress warm; even summer nights can be chilly.)

The climb encompasses six vegetation zones — like driving from Mexico’s deserts into the fir forests of Canada. Give yourself plenty of time to pause at the many turnouts with explanatory markers.

Arriving at the observatory itself was almost anticlimactic, with its few sheds and what appeared to be five large white mushrooms amid the pines. These are the observatories, used by astronomers from around the world.

That we were among them is a privilege, Block said. “Most of humanity have not seen the universe as clearly as we are able to.”

The research done at the center is the ultimate night job, of which we were reminded when it was time to leave.

In what proved a not-as-tricky-as-it-sounded maneuver, we drove the first several hundred feet with our headlights turned off. Any artificial light, however brief, could interfere with an astronomer’s work.

We descended the mountain into Tucson’s grid of lights, feeling smaller. But wiser.