There’s a common question most of us will ask at one time or another.

We ask it in expectation of birth and we ask it in expectation of death.

“Doctor, how much longer?”

The mother in labor may ask the doctor how much longer and perhaps decades later, the child echoes the question while his mother labors to take her final breath.

In both instances, families will assume similar postures as they stand around the bed looking at the patient. Their glances echo the question, “Is it time yet?”

They watch, wait and wonder, “How much longer?”

Doctors usually choose between two responses to this question.

Sometimes a doctor will give you her best guess. Guessing has its hazards as studies suggest that doctors frequently are too generous with their guesses. Usually, it’s sooner than most people want to believe.

But the truthful response, the one that no one wants to hear, including myself sometimes, is a simple: “I don’t know.”

They don’t know, because no matter what they think they know — no matter their experience — neither the end nor the beginning of life can be predicted with the accuracy we long for.

I’ve been present many times when family members have been able to extract some kind of guess from medical staff, only be to proven wrong. Though science sometimes can forecast the coming of death or life, we really can’t pinpoint when.

“When?” is the final question about death and life.

Yes, even life.

Today, as I write this, I’m on the other side of this guessing game. My wife and I are trying to predict the arrival of life. We’re expecting our first grandchild. It’s a boy, but we’re worried, as my daughter is 11 days past due.

So, we’re all standing around looking at my daughter.

When? We ask the doctor, when? How much time do we have? Do we have time to buy a pizza? Write a letter? File this column?

“How much time, doctor?”

When will it happen? When will this precious life emerge and take his first breath?

And you know what? Surprise, surprise. The doctor doesn’t know. I mean, you’d think the baby at least would be influenced by my editors, who must have this column on time.

When will life arrive? When will life be gone? No one can tell you that. The only choice we have in the meantime is what happens in the middle.

As illustrated by Linda Ellis’ 1996 poem, “The Dash,” there is a simple mark carved on every tombstone. It’s the dash between the year of your birth and the year of your death. We absolutely have no impact on either of those dates, but it’s the dash in between those dates that represents our lives and what we did with them.

So, the most appropriate question is not the one we often ask our doctors — the question of how much longer. The only viable question about life is the one we ask ourselves: Are we making a difference with the dash between our dates?