As Saint Augustine once reflected, “What then is time? If no one asks me, I know; if I wish to explain it, I do not.” Perhaps we can only trace its elusive shadow in the drifting dreams of the past.
The last time I truly pondered this question was in my second year of high school physics. The teacher was explaining the time dilation of Einstein’s theory of relativity, how a moving clock slows within the fabric of spacetime. A few lines of calculation, a delay of mere microseconds, left me astonished. For a long time afterward, I kept thinking about the mystery of time, unable to grasp even its outline. In those innocent years, I was caught in the endless tide of tests and lessons, chasing grades and expectations without pause. I imagined the distant college entrance examination and the life that followed, yearning for a future that felt unreachable. To me then, time was like a mussel resting in a flowing river, unmoved to the eye, silent yet unceasing.
It feels almost sentimental to realize that four years had passed before I thought of the question again. One morning in autumn, under the gentle sunlight, I was hurrying to class. The plane-tree leaves were drifting down in soft golden spirals. Watching them fall, I felt a sudden ache in my chest, a quiet sorrow, as if the line “Spring flowers once bloomed, and now autumn leaves fall” had come alive before me. I remembered my younger self in that old classroom: the passing of my great-grandmother, the mock exams, the college entrance test, and the friends who once shared my days. “Pleasant scenes seldom last; grand gatherings must end. The Lanting is gone, its waters and woods turned to dust.” More than a thousand days and nights had passed, filled with love, loss, laughter, and pain. All those memories now flicker like film upon a screen. I have been carried by time to a distant city, and only now do I realize how swiftly it has flown, so fast that I can scarcely hold on.
What has gone has truly gone, and what comes will surely arrive. Beyond the silence and the changes of the world, what remains is the faint sweetness that follows bitterness, the aftertaste of years steeped like coffee—dark, deep, and strangely comforting.
Time is both rational and emotional. It can be clear and cold enough to strip away desire, and yet tender enough to bring tears to one’s eyes.
I still remember Christopher Nolan’s Interstellar, where the secret of time unfolds through the imagination of higher dimensions. If a point is the zero dimension, a line the first, a plane the second, and a solid the third, then the fourth is formed when all these are joined together: the dimension of time. Countless solids weave the fabric of spacetime, each higher dimension guiding the one beneath it. To glimpse the fifth dimension, one must first come to understand the enigma of time.
So what is time? I cannot define it. As the poet Yan Shu once wrote, “Helplessly the flowers fall, yet familiar swallows return.” When I am joyful, when I am surrounded by the love of family and the warmth of beauty, time flows gently, like water through my fingers, like a breeze upon my cheek. But when sorrow visits me, when I try to feel time’s weight and form, it seems unchanged—eternal, distant, indifferent. Where does it come from? When we look upon the vastness of the universe, we see that the Earth’s orbit around the sun marks a year, its rotation a day, divided further into hours and seconds, into ever smaller fragments. Without energy or motion, time and space lose meaning. Where there is motion, time is its measure. Perhaps life is the same. Perhaps time does not truly exist. Perhaps we are only burning our finite energy in the brief span of our being, striving to make the world a little more radiant before it dims.
People often long for the past, perhaps because its soft haze blurs the arrow of time, creating a dreamlike beauty like that of the Peach Blossom Spring, untouched by decay. The fragments of memory flicker like black-and-white film across the sky, each frame a glimmer of fragile light. We also yearn for the future, perhaps because rebirth after hardship awakens new strength, or because we delight in walking along the flowered path toward what awaits, smiling as we open the sealed boxes of destiny. Yet time can also feel absurd, binding us to our fate in ways that seem strange yet inevitable.
Looking back, I find time both real and illusory, wandering between emptiness and the present moment. It is elusive, like a figure neither good nor evil, guiding us through mist and confusion toward a single spark of hope. The years blaze and vanish like morning dew. To remember or to forget, both are acts of devotion. Today’s joy is fleeting; tomorrow remains unknown.
And so, after all this thought and memory, I still cannot answer the question. What is time?