When I first filled my backpack with books and hauled it around the neighbourhood, I figured it weighed at least 15 pounds, if not 20. I didn’t actually know, because I didn’t think I had any way of measuring.
I can be a little slow, but I eventually remembered I could calculate the weight of my pack by weighing myself with and without the pack, and doing a bit of subtraction.
It turned out the pack with the books weighed a mere nine pounds.
I didn’t believe it. Something must be off.
I tried again. The weight did go up this time—but only by 0.2 pounds.
A few weeks later, when I finally filled my pack with all my gear (and a few substitutes for things I didn’t have yet), it weighed 15.4 pounds, without water.
But here’s the weird part: it actually felt lighter than the 9.2 pounds of books.
I have developed several hypotheses to account for this odd phenomenon.
1. My scale is broken.
Of course, it would have to be broken in a strange sort of way, where it shows heavier things as lighter, and lighter as heavier.
On balance, this seems highly improbable.
2. A pound of books weighs more than a pound of anything else.
I figure it’s the densely-packed knowledge that does it.
Except, of course, that a pound is a measure of weight, so a pound of one thing can’t possibly weigh more than a pound of something else—as long as you’re using the same kind of pound, anyway. As it turns out, a pound of metal weighs less than a pound of most other things, but that’s only because metal is measured using a different kind of pound.
But as my scale wasn’t designed to weigh metals, I’m pretty sure it only deals in the one kind of pound, and the hypothesis is a dud.
3. Weight is relative.
As every pilgrim knows, a backpack that was feather-light in the mornings can feel like someone filled it with 100 pounds of lead (a mere 82.29 regular pounds’ worth, since lead is a metal) by the end of the day.
Or, as in the case of my books, the exact same amount of weight can feel heavier or lighter depending on how it’s distributed. I did make an effort, by stuffing a blanket in my pack, to keep the books closer to my back, but it would seem it’s still better to have items of varying weights than a bunch of heavy objects.
Absolute weight—the kind you measure on a scale—can’t be relative. That would be a contradiction in terms.
But when you’re carrying the weight on your back, the absolute is somewhat less important. Weight, like time, depends on how it’s experienced.