Do you ever imagine if one moment in your life had been different?

We all can point to instances that have marked determinate shifts in our existence. What if you had attended a different school? Or moved to a different town? Or — on a smaller “Sliding Doors” scale — not missed that elevator?

While whimsical at times, this counterfactual consideration may lead to regret over the past, an exasperating reaction that helps nobody, and can seem unfaithful to the present. Sure, I could be living in Paris, but I would not have my husband, friends, job, etc.

If I find myself spiraling, I take a deep breath, remember one of my favorite theories in quantum mechanics and exhale.

According to the Many-Worlds Interpretation, “there are many worlds which exist in parallel at the same space and time as our own,” states the Stanford Encyclopedia of Philosophy. “…Every time a quantum experiment with different possible outcomes is performed, all outcomes are obtained, each in a different world, even if we are only aware of the world with the outcome we have seen. In fact, quantum experiments take place everywhere and very often, not just in physics laboratories: even the irregular blinking of an old fluorescent bulb is a quantum experiment.”

In other words: Countless versions of ourselves exist, stemming from all possibilities of all moments.

I was first introduced to this idea as a kid, when I read the excellent young-adult series “His Dark Materials” by Philip Pullman. I was entranced by the protagonists’ journeys to parallel worlds where life was subtly or entirely different. What if we had dæmons — visible souls who double as best friends? Or friendly mulefa rolling on seed pods? Or real-life witches?

When I learned that physics backs up fantasy, I was thrilled.

Since every event with multiple possible outcomes splits off from our world, there may be a reality in which you did not graduate from middle school — just as there may be a reality in which you attended Harvard. Wish you lived in Paris? Somewhere, sometime, you probably do — and that version of you wonders what it would be like to live in Wyoming.

While the Many-Worlds Interpretation means the worst possible realities co-exist alongside the best, it has always comforted me. The weight of events that we can and cannot control seems lifted. And yet, over the past few weeks, I have been thinking about the theory more often, as the political turmoil in the U.S. ratchets higher and higher. There is a different world in which our best selves are represented, but this version of us is all that we will ever experience.

We should strive for the best possible reality that we can achieve.