We live under the assumption that time flows in one direction—past to present to future. You wake up, drink your coffee, scroll on your phone, and move forward through the day. But what if time doesn’t work like that? What if linear time is just an illusion?
A recent study published by researchers at the University of Surrey suggests that physics doesn’t care which direction time moves. The equations governing motion—whether it’s a swinging pendulum or the orbit of a planet—work just as well forward as they do backward. In theory, time could flow in reverse, and we’d never know the difference.
The truth is that physics has never been great at explaining why time moves forward. Newton’s laws of motion, which describe how objects move, make no distinction between past and future—our idea of linear time. Schrödinger’s equation, the foundation of quantum mechanics, doesn’t enforce a direction for time either.
If you took a video of a planet circling a star and played it backward, the physics would be just as valid. So why don’t we see broken vases reassembling themselves or spilled coffee jumping back into the cup?
That’s where Markovian dynamics come in. Scientists use this theory to describe processes where each step depends on the last, like a domino effect. Once things start moving in one direction, they tend to keep going that way. For instance, the Big Bang created an expanding universe, and thus, the universe continues expanding.
But if physics doesn’t demand linear time, what does? Well, scientists think it might have to do with the universe’s expansion, which I mentioned before. The Big Bang sent everything outward, and as the universe grows, matter cools, clumps together, and forms the planets and stars we see today. This expansion is what gives time its one-way street.
But some physicists argue that even this isn’t absolute. One radical theory suggests that the Big Bang may have created two parallel universes, each experiencing time in opposite directions. In our universe, we remember the past and move toward the future. In the other, time might run the other way—but from their perspective, we’re the ones moving backward.
Of course, time reversal remains a thought experiment. The laws of physics say it’s possible—and scientists say they may have unlocked the secret to time travel. But reality suggests otherwise.
Still, imagining a world where time might be different is fun. A world where clocks tick backward, our coffee unspills, and Monday mornings never arrive. Maybe one day, science will figure out how to break free from linear time.
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