There are different ways to imagine of time’s passage. And this, in turn, involves different ways to imagine the human lifespan.
One popular way is to imagine time in linear terms. The river of time is a conventional metaphor, immortalized by Isaac Watts’ adaptation of Ps 90:
The busy tribes of flesh and blood,
With all their lives and cares,
Are carried downwards by the flood,
And lost in following years.
Time, like an ever-rolling stream,
Bears all its sons away.
On this view, we’re like rafters swept downstream by the current. We never see the same thing twice. Life is always in motion. We are facing into the future, while the past is rapidly receding behind us.
Life is a blur. We skim life. We see time passing us by on either side of the riverbank.
This metaphor captures the fleeting, ephemeral nature of time.
Another popular way is to imagine time in cyclical terms. The four seasons are a conventional metaphor. Spring represents birth and childhood; summer represents youth; autumn represents middle age, while winter represents old age and death.
Before the sun and the light and the moon and the stars are darkened and the clouds return after the rain (Eccl 12:2)
11for behold, the winter is past;
the rain is over and gone.
12 The flowers appear on the earth,
the time of singing has come,
and the voice of the turtledove
is heard in our land.
13 The fig tree ripens its figs,
and the vines are in blossom;
they give forth fragrance.
This captures the lifecycle. From a secular standpoint, this is cyclical in the sense that each spring represents the next generation. Taking the place of the older generation.
From a Christian perspective, the seasonal cycle represents birth, death, and rebirth. We are born. We live, we age, and we die. But that’s not the end. There’s the afterlife. The resurrection of the body.
Then there’s another, albeit neglected, metaphor–which was more familiar to folks in Bible times. And that is the mound or tell. This preserves the ancient cycle of settlement-abandonment-resettlement.
Thus says the Lord: Behold, I will restore the fortunes of the tents of Jacob and have compassion on his dwellings; the city shall be rebuilt on its mound, and the palace shall stand where it used to be (Jer 30:18; cf. Ezk 32).
This reflects a stratified view of time. A new city built atop the ruins of the last city. Deserted for a time. If you take a cross-section, you can see successive occupational levels. What’s lower is generally earlier, what’s higher is generally later.
This models the passage of time in both vertical and horizontal dimensions. The corporate dimension of life. The epochal nature of time.
Not just the lifecycle of individuals, but members of the same generation. Not just the diachronic aspect of time, but the synchronic aspect. Simultaneous lives. Interwoven lives. A group of individuals who grew, lived, aged, and died together at about the same time and place. A shared existence. A shared experience. Shared memories. A network of family and friends.
When contemporaries died off, they don’t merely die as isolated individuals. Relationships die. Their livelihood becomes obsolete. The world they knew becomes a lost world. Buried ruins.
In a sense, all of us reside in a cemetery. The living walk on the graves of the departed. We’re just one more level in a multi-storied existence. One generation stacked atop another.
It’s interesting to consider the extent to which heaven, the new Eden, and the New Jerusalem, will either combine or preserve different epochs.