It’s More Reasonable to Determine Physical Age by Health Checkups

We automatically become one year older on our birthday — a system that feels surprisingly bold when you stop to think about it.

After all, even among people who are supposedly the same age, some look remarkably youthful while others make you think, “Wait… we’re the same age?”

Different lifestyles, stress levels, sleep habits, diets, and exercise routines naturally lead to different rates of aging.

Yet society treats them as if they were the same age, as though “time” flowed equally for everyone.

But in reality, time is not such an equal or impartial thing.

We tend to imagine time as something that “flows on its own” or “moves forward at the same speed for everyone.”

However, if we look closely, what we call “time” is really just a label we attach to the changes happening in our bodies and minds.

For example, staring at a glass object doesn’t make you feel time passing — because its molecular structure barely changes, even over an eternity.

In other words, something everyone intuitively understands: a glass doesn’t age because it doesn’t change.

Time appears only where change exists.

Aging works the same way: the “speed” of physical aging differs depending on how much change has accumulated.

Your birthday is just a commemorative date. Your body doesn’t suddenly age on that day.

Aging is the accumulation of daily changes — the wear of blood vessels, the decline of cells, shifts in metabolism, fluctuations in hormones.

So in reality, it makes far more sense to say:

These reflect actual change. Determining age by birthday alone ignores the enormous individual differences in how people change.

Structurally speaking, without change, time does not arise.

Glass: no change → no time

Humans: different amounts of change → different “physical ages”

This structure is simple — and everyone has experienced it firsthand.

Yet because birthdays arrive equally for everyone, we fall into the strange illusion that people of the same age are somehow equivalent.

That’s why determining physical age through health checkups is far more reasonable.

Birthdays are just markers. Physical age is a measure of accumulated change. Time is a label we attach to that change.

Once you line these up, the conclusion becomes obvious:

Physical age should be determined not by birthdays, but by how much a person’s body has actually changed.

And the tool that measures that change is, quite naturally, the health checkup.

Improve your lifestyle, and you might even come back “younger” than last time.

Age, time, and change — these concepts all share the same underlying structure.

Which is why determining physical age by “amount of change” isn’t a joke at all, but a deeply reasonable idea aligned with the true nature of time.

And if this idea ever became mainstream, asking someone their age — or being asked your own — might make your heart beat just a little faster.