Here are some numbers.

My mother had me when she was 21 years old.

I had my daughter when I was 38.

For most of their lives, my mother lived six blocks away from her mother, who was 35 years old when my mother was born.

Since I turned 17, I have never lived closer than 70 miles from my mom.

This past fall I flew 800 miles to be at the wedding of a girl I love like my own daughter.

I left my own daughter behind, in the care of my mother. For four days we were those same 800 miles apart.

There is twice as much space time between me and my daughter, as there was time space between my mother and me. Two generations, not one.

It was 40 feet from my daughter’s room to mine, in the condo that we lived in when she was born. From the day we brought her home from the hospital she refused to co-sleep, wouldn’t rest unless she could put that space between us. Forty feet, when she’d rolled and twisted underneath my heart, inside my body, caged by my ribs.

I looked at her in those early days and felt — love, pride, awe, fear, but not knowing. Not known. I had imagined a child would be many things. Not on my list, that she (her pulse inside mine, however briefly, an echo and an answer) would be a stranger.

A stranger to me, and I to her, and so we still are.

Strangers who like one another. Strangers who enjoy spending time together. But strangers, always. We love who we think the other is. We love the assumptions because we have to love something and we can’t know the truth.

I was reading last week about encouraging older children — she is so much older, in a week, than she was in a month last year — to write about this time, to draw about it, because they’ll remember. I say to myself, ten times a day, when we talk about someone we know being sick or something we can’t do anymore: She needs you to be calm.

She needs you to tell her how to feel about this, that’s how we learn. Human psychology, all of it, is based on projection. We do lessons at the dining room table. We do crafts, go on nature walks, I’ve been dealing with health problems for decades and sometimes I wish she had a mother who didn’t need to sit on the bathroom floor for 20 minutes in the morning and breathe until she can manage getting some toast and coffee and feeding the cats.

My mother tells me, “She doesn’t even see that.” But I don’t know what she sees. I don’t know if she’ll need me to tell her about the spring we stayed inside, about the months she didn’t see her friends. I hate that she has lost half of her kindergarten year. I barely remember kindergarten. It’s the hardest thing to reckon with: You don’t get to choose what your children remember, or how they remember it.

It’s the hardest thing to reckon with, as a mother, as a daughter: Our children don’t belong to us. We belong to them. We only think of our ownership because we are large and they are small. We are old, and they are young. We think once claimed is claimed forever, that love imparts some unspoken wisdom, that we know. A mother knows. A mother is supposed to know.

A mother doesn’t know. A mother has no idea.

At her wedding, the girl I love like my own daughter caught my hands up in hers and I tried to tell her, stumbling a bit after two glasses of wine, how important she was to me. I work with a lot of kids; none of them invited me to their weddings, until her. When she was thousands of miles away in war zones working I would check on Facebook, make sure she’d been active in the past day. The past hour. She flew to Chicago for my daughter’s first birthday.

No matter how much time passes between us talking, she could call, in the middle of the night, say I need a shovel and an alibi. I’d go.

It’s not a phrase that had been invented, in the 21 years between my mother and me: Ride or die.

Of course you’d die for your child. That’s easy. It’s chemical, it’s instinct, it’s survival, it has to be. You love them before you know them, so that you keep them alive. Can you still love them, once everything that has ever happened to someone has happened to the both of you? Once you’ve happened to each other like a speeding train happens to a car stalled at the crossing, like a tornado happens to a town?

Are you ride or die, then?

What does it mean to ride? Does ride mean feed you, keep you safe, put you in a carseat and cut your grapes in half? That’s easy enough, for all our mommy-martyrdom. Is that all it means? Does it mean piano lessons? Does it mean until you’re 50? Are you ever done? There are people who are, who would be. Streets the world over are homes for children whose parents were done with them. The reverse, to be fair, as well.

I shudder at the very idea of I would do anything, forever: You are giving the gods a middle finger. Your future is out there waiting and it hears you. I shout it out just the same. Anything isn’t a hangnail, isn’t just showing up for a class play. Sometimes it’s involuntary commitment to a mental institution.

I don’t question love. What’s the use? But I question time space. I question years and miles. Not if they exist, but what they mean. What they might mean to me and mine. What I get to call mine: the girl I love like a daughter is not my daughter, feelings don’t give you rights, and all the love I bear my child, who knew my voice before she had a name, doesn’t obligate her to anything. I will keep saying this until I believe it the way I believe gravity: She does not owe me.

We are commanded by every deity we have ever invented to love the stranger. We think it means the scraggly homeless man who screams obscenities behind the trash cans in the alley, the twitching pale hitchhiker who needs a ride in the rain. I’ve begun to think it’s something else: Everyone is a stranger. The faces across the breakfast table, every single morning come ruin or rapture, the faces that need feeding and washing and kissing before school. Something happens and we say, how could I not have known?

How could you have, ever, known?

Does any of this make sense? I’m trying to say we don’t make sense to each other, mothers and daughters, and I’m trying to say I think it’s all right, that the chasm isn’t as important as the bridge we’re stringing across it, which will hang there until it’s needed. It’s 21 years and 70 miles wide, that bridge, between my mother and I. It’s two floors, in the house my daughter and I inhabit now, and 38 years, and a single breath when I hear her stir in her bed, in her warm safe bed at night.

My grandmother died at 91. My mother-in-law, two years ago. My daughter asked me, after her Nana’s funeral, how long do people live? How much time will there be, between us?

I didn’t have an answer for her.

All I had were numbers.

I hope that someday she’ll tell me what they mean.

A.