Kate Becker
Kate Becker

I used to think that, if I tried hard enough, I would be able to imagine the fourth dimension of space.

"How hard can it be?" I thought. After all, imagining one spatial dimension is pretty easy: Just picture a line and you're done. Thinking in two dimensions is simple, too. Circles, squares and anything else you can put on a sheet of paper exist happily in the two-dimensional world. Three dimensions: No problem there. That's where we live every day.

Yet when it comes time to add just one more measly dimension, my mind can't bend to the challenge.

If it could, I would be able to imagine how space itself might curve along the invisible axis of the fourth dimension. I would have an instinctive grasp of what it would be like to live in a spherical universe, where a journey in any direction would ultimately bring you back home where you started, or a hyperbolic universe, contoured like a saddle on the back of that unimaginable fourth dimension.

As it is, I have to fall back on analogies. To picture a spherical universe, I can imagine a whole universe rising up from the surface of a balloon. If I want to see how the universe expands, I just inflate the imaginary balloon; to see the universe contract back to nothing, just let out all the air, and voila!


But the analogy isn't quite right. After all, what exactly is this universe rising up into? Why does it have a top and a bottom? These questions are artifacts of an imperfect analogy; the mental trade-off for thinking in three dimensions rather than four.

If I could think in four dimensions, I would feel in my bones how gravity warps space and time. I would know intuitively how light bends around a massive object and how a black hole drills a bottomless well into the fabric of the universe. Instead, I have to fall back on analogies (space as a rubber sheet, stretching under the weight of a heavy object) that just aren't up to the task.

These analogies never deliver the physical intuition I hope for -- the kind of "gut feeling" that we all have about how things work in our three-dimensional universe. And so, there is math, which allows us to perfectly describe four dimensions -- or 11, or 1,000, or a million -- and even make calculations and predictions about how they operate.

If only I knew the equation for the new dimension I'm about to enter: parenthood. Over the past months, I've tried to imagine what life will be like with the sudden introduction of this extra dimension. Along what new axis of care, anxiety and responsibility will my life now extend? Will entering the parenthood dimension be like opening a pop-up book, discovering wonders embedded in the "flat" world I thought I knew? Or will it be more like going to a 3D movie -- that is, basically like a regular movie, except that you look silly and by the end you always have a headache?

And yet the universe is full of creatures who live in the parenthood dimension: They walk among us! They try to explain what it is like there -- how they manage all those feedings, how they find time to sleep and shower, how the Diaper Genie works -- but these mechanical details can't capture what I most want to know: what it feels like.

So, I'll keep trying to imagine -- and in a few months, I won't have to imagine anymore. I will have entered the parenthood dimension. And that's a dimension from which there is truly no turning back.
