Science tells us that matter is never really lost in the universe, that it just kind of changes form and continues forever as something else.

As far as I can tell, the theory is borne out every year at this time, when winter-weary homeowners get that spring-induced urge to throw open the doors and purge themselves of everything that has outlasted its usefulness and now serves only to clutter their lives.

So out to the curbside it goes, mountains of castoff household objects and odds and ends of things that have no discernible purpose in this world anymore except to be loaded onto a public works truck and hauled off to the dump during the city’s spring cleanup, which started in Bangor this week.

A trip through my neighborhood over the weekend, in fact, revealed enough sad-looking couches, tattered stuffed chairs and rolled up carpets to fill a warehouse. There in the mix were rusted bicycles and defunct lawn mowers, long-forgotten exercise equipment and busted TVs, battered barbecue grills and mangled microwaves that had cooked their last meals.

Yet considering that the city will haul away only stoves, washers, dryers, water heaters and furnaces, most of that other junk would seem destined to sit on public display at the curb until its surprised owners eventually get a knock on the door from the code enforcement people who tell them to get rid of the unsightly stuff or face a fine.

Since there is nothing more disheartening than having to bring junk back into the very house from which it was gratefully disgorged only a few days earlier, we should thank the picker patrol for helping to lighten our burdens.

Like crocuses and robins, they are the spring harbingers who arrive by truck, station wagon and van to roam the streets of their towns and others and winnow out the clogged waste stream. Before long, their vehicles are mounded high with stuff, an undifferentiated mass of miscellany that presumably will be carted off somewhere and be made useful again.

A few nails, a new knob or a handle, a bit of polish and paint and items that once were deemed worthless are transformed into functional objects again. The discriminating pickers can see the good in almost any sorry thing, from a discarded swing set that requires only swings to make it whole, to the ugly floor lamp that lacks a simple cord, to the three-legged chair that, with a 2-by-4 and a few screws can be made to stand proud once more. The pickers are, in a curious way, the ultimate conservationists. For them there is no such thing as obsolescence, only unrealized potential just waiting to be tapped and tapped some more.

Whenever the picker fleet rolls out of town, presumably to search for other curbside smorgasbords to plunder, I can’t help but wonder where all that stuff will wind up. Do they fill up their own houses with the roadside finds, or outfit their rustic hunting camps with our old toilets and decrepit dressers?

Actually, I think I have a pretty good idea where most of the stuff is bound. So do you, if you’ve ever wandered through a flea market, a junk barn in the country or a garage sale in summer and couldn’t resist buying things that were not much different from the very things you threw away in spring.

Nothing is lost forever, the scientists tell us, and the old becomes new again … and again … and again.