Newton's First Law and the Quiet Physics of Love

What if the heart, too, obeys the laws of motion?

There’s a strange comfort in science when it mirrors something personal. It feels like the universe leaving breadcrumbs—tiny reminders that human nature is not as unpredictable as we sometimes believe. That our deepest shifts, even in love, might follow patterns older than our wounds.

I was flipping through my timeline on Facebook last night—half scrolling, half ignoring life—when I stumbled on a short clip. The speaker casually mentioned Newton’s First Law of Motion, and I almost kept scrolling. But then I heard it again: “An object in motion stays in motion unless acted upon by an external force.” And something about the way those words landed… stopped me. I wasn’t thinking about physics in that moment. I was thinking about people—how they move, how they stay, and more painfully, how they sometimes stop. It suddenly made sense in a way I hadn't expected. Not in a classroom kind of way—but in the way that hits you in the chest when you’re trying to make sense of someone who changed. Or pulled away. Or quietly stopped showing up the way they once did.

Sir Isaac Newton once said, “An object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity—unless acted upon by an external force.” It is called the law of inertia, and while it was meant for matter and motion, I have come to believe it describes many hearts just as clearly.

People do not simply wake up one morning and change.
They do not suddenly stop loving, stop trying, stop reaching across the space between two souls unless something has slowly, or sharply, intervened. In fact, most people stay exactly as they are—steady in their affection, consistent in their effort, faithful to their emotional rhythm—until something shifts the conditions around them.

It is easy, perhaps too easy, to look at someone you once knew deeply and say they have changed. That they have grown cold. Detached. Silent. That the warmth that once flowed so naturally from their presence has somehow gone missing. But before we name it a lack of interest or label them emotionally absent, we might need to remember Newton. Because motion rarely halts without cause. Hearts rarely harden without a reason.

Inertia means that once something is in motion—like love, like daily calls, like random acts of tenderness, kindness, and commitment—it will keep moving unless something external applies force. And in relationships, these “forces” are often not loud or dramatic. They can be as subtle as repeated silence when someone shares a vulnerable thought. As invisible as criticism replacing curiosity. As unnoticed as appreciation fading into assumption.

A partner who once gave freely may begin to hesitate—not because they are tired of giving, but because they are no longer received in the way that nourishes the act. They may find their affection landing in a space that no longer feels safe. Their attempts at connection might now echo into indifference. And over time, like a pendulum that no longer has momentum, their motion slows. Not from laziness. Not from cruelty. But from being acted upon.

There are seasons when people stop because something around them told them to. Not in words. Not in commands. But in feeling. In tone. In how they were made to feel in their giving.

And sometimes, the force isn’t even negative. Sometimes, the one they loved changed too—became distant, colder, more distracted. Maybe unintentionally, maybe protectively. But the landscape changed. And as Newton said, so did the motion.

We often assume emotional distance is the evidence of emotional absence. That because someone no longer shows up the way they used to, it must mean their heart is no longer present. But just like an object cannot move against resistance forever, a person cannot keep extending what is not met, what is not held, what is not mirrored.

This is not an excuse for withdrawal. It is an invitation to look at the full picture. To see change not just as a decision made in isolation, but often as a response to a shift in the emotional atmosphere.

Love, like all motion, is sensitive to its surroundings.

So if you’ve found yourself wondering what happened to the person who once loved you so openly, perhaps begin by asking what happened to the environment that held their love. Did it remain open? Receptive? Safe? Or did something slowly press back against their motion?

Newton was not a counselor. But his law of inertia might be one of the most profound insights into the emotional life of relationships. It reminds us that people often do not change from the inside out—but from the outside in. That many who have pulled away were once moving toward us with great energy—until something acted upon their motion.

And if we can understand this, not with blame but with tenderness, we may find our way back to each other. We may learn how to be the kind of force that restores motion, not interrupts it.

Not all hearts are lost. Some are simply paused. Waiting for a space gentle enough to move in again.