When I was younger, my grandmother, Doris, said that she and my grandfather, Big Jack, were like ships passing in the night. Big Jack, who liked to watch the news in his favorite straight-back chair and eat microwave popcorn, never went to bed before midnight. Doris, on the other hand, was an early riser. She was up and having coffee before even the earliest of early birds. And she started waking even earlier the older she got.

I had a mental image of this “ships passing in the night” metaphor. Mostly, I pictured them passing each other on the red-carpeted stairs — Big Jack on his way to bed, Doris on her way down to start the day (even if it was, technically, the middle of the night).

This usually meant that no matter what time of day or night I called my grandparents’ house, someone was awake to answer the phone. There was comfort in that. If I woke up from a bad dream several hundred miles away in my home state of Virginia, I would sometimes actually picture either Big Jack sitting in his chair or Doris on her sofa, one of them keeping watch throughout the night.

Many years later, once I was grown and married, I was alone in Florida while my husband was on his first deployment and I had a newborn baby. The world had just witnessed the events of 9/11, and I found myself unable to go to sleep most nights. My new Navy-wife friend at the time had the opposite problem: she’d fall asleep, but then she’d wake up too early.

During those tense few months, when the world was on edge and our husbands were overseas, this friend and I would call each other at night and jokingly say, “You keep watch while I sleep, and then I’ll keep watch while you do.” We didn’t really mean it. Neither of us was truly keeping watch of anything besides our own homes and babies, but there was in fact comfort in knowing that someone, somewhere was awake while I was trying to sleep.

This summer, after my husband retired from his 20- year career as a Navy pilot, he began working as a helicopter pilot for LifeFlight, Maine’s critical care transport provider. This meant that for the first time in his life, besides the random military night flights or duty here and there, Dustin would have a night shift on a rotating schedule.

I was at first enthralled and stressed by the idea: When would he sleep? How would he adjust? Would he get tired?

Then, one night as I lay in our bed unable to go to sleep and watching the clock tick ever closer to morning, I heard the whop-whop-whop of a helicopter flying overhead. I ran to the window and saw that it was Life- Flight. That meant it was Dustin en route to or from the hospital. Suddenly the sound seemed less like another noise and more like a reminder that somewhere out there, my husband had the watch and I could go to sleep.

As you can probably tell by now, I’m someone who does not fall asleep easily. While people like my husband — people who fall instantly asleep when needed — cherish darkness and quiet by 9 p.m., I like to fall asleep with the lights and television on. And this goes all the way back to when I was a child and thought about my grandparents’ ships passing in the night. I like to think I’m not alone in this.

“Everything feels worse at night” was something that my mom liked to say to explain my feelings about nighttime. We feel vulnerable and trapped because it seems like the world shuts down and we are alone. Who would be there if we needed them?

The truth, of course, is that every night while all of us sleep, thousands of workers keep watch while we cannot. They are policemen, doctors, nurses, plumbers, electricians, dispatchers, firemen — the list goes on. In fact, there is a whole other world that comes to life when the daytime world (and those with healthy sleep/wake schedules) turns out the lights.

I’ve always been fascinated by this (obviously), and so this year, I plan to better understand the nighttime world that most of us never see and the people who keep watch while we (just me?) are staring at our ceiling. I begin next week, when I spend a night with the Bangor Police Department keeping watch of the streets while the rest of the city sleeps.