Time travel can feel like a far-fetched sci-fi concept, but technically, you’re already time traveling right now—moving into the future one tick of the clock at a time. According to relativity theory, time isn’t absolute; it’s like a malleable piece of clay that can be stretched or compressed depending on the circumstances. Higher gravity and speed can actually slow down time compared to places where gravity and speed are lower.

This phenomenon isn’t just theoretical; it has been proven through various experiments. For example, when scientists synced two atomic clocks and placed one at sea level and the other on a mountain, they found that the sea-level clock ticked slightly slower. Likewise, atomic clocks on fast-moving jets also ticked slower than those at rest. So, the idea of traveling into the future isn’t all that exotic—if you could speed yourself up to a significant fraction of the speed of light or hang out near an intense gravitational field, you could potentially travel decades into the future in just a few months, or even less.

But the real kicker is how one could travel back in time. While hopping to the future seems easier in theory, returning to your starting point isn’t straightforward. To move backwards in time, you need more than just slowing time down; you’d need to reverse it.

To understand this better, let’s delve into light cones. Space-time has four dimensions: three spatial ones and one for time. Picture a three-dimensional graph where the horizontal axes are spatial dimensions, and the vertical axis is time. So, when you map an object’s movement, you get what’s called a world line. If you flash a light at a point (Event A), it creates a cone of potential future events. A corresponding past cone includes all past events that could affect Event A. Points outside this cone are disconnected from Event A, meaning they can’t affect it.

When Einstein’s general relativity equations come into play, things get even wilder. The space-time inside a black hole, for instance, can theoretically allow for time travel. However, an event horizon—a boundary beyond which nothing can escape, not even light—poses a significant barrier. Once you cross it, there’s no coming back.

But what if we could bypass the event horizon? Enter the concept of a rotating black hole or a naked singularity, a solution proposed by physicist Ezra Newman in 1965. If a black hole spins fast enough, its event horizon could disappear, exposing the singularity. This singularity warps space-time to such an extent that future world lines could loop into past light cones, potentially allowing for time travel.

Nevertheless, there are some catches. Firstly, reality doesn’t always align with theoretical physics. High-speed rotating black holes, or naked singularities, might not exist. Secondly, even if they did, the math only works for particles with negligible mass, not larger objects like humans.

So, while the idea of traveling back in time remains tantalizingly on the edge of possibility, it’s not something we can count on—at least not yet.