A Matter of Perspective

Every now and again, I like to take a deep breath and regain some perspective.

When I was in graduate school, we were presented with a little cautionary tale about perspective. There was this graduate student, you see, a brilliant young man, who decided to tackle some of the Big Questions in cosmology for his PhD thesis.

He breezed through his classes and dazzled all his professors. His thesis defense was barely a formality, and all of his committee professors nodded and smiled as he spoke. They asked few questions, challenged nothing: he had enchanted them with his charm and fierce intelligence. At the end of his presentation, and after the last question from his committee, an old Professor Emeritus at the back of the room harrumphed and spoke up.

“Well, how big is it?” he asked.

The student paused, puzzled. The other professors craned their necks to stare at the old man, then rolled their eyes. Clearly the old fool, long past his prime, hadn’t followed a word of the presentation. He’d probably just awakened from a little snooze. But the student had been brought up to be polite to his elders.

“I’m sorry, sir, but I don’t understand. How big is what?”

“The universe!” the old man snapped irritably. “The universe, of course. You’ve just given us a grand theory on how absolutely everything in the universe works, and right there, and there, and there you have all the relevant physical constants. Surely you’ve made an estimate of the total size?”

The young man blinked several times, and said, “Why, no, that never occurred to me!”

He picked up his whiteboard marker and began to scribble in the arcane language of physical cosmology. A few moments later, he put down the marker and stared at the board in silence. Then he turned without a word and walked out of the room.

The other professors colored as they stared at what the student had written, and one by one, they quietly stood and left. Plain for all to see was the conclusion of this elaborate, but obviously wrong theory: that the entire universe was smaller than a basketball.

For us graduate students, the lesson was clear: always do rough estimates — “reality checks.” They’re quick, they’re easy, and they will save your academic ass. I’ve found that they save your practical ass as well.

Suppose you need to know the number of grains of sand on all the beaches of the world. Hard question, right?

But here’s an easier question: how many grains of sand would there be if the whole surface of the world were covered with sand, say, three meters deep? The earth is around 4000 miles in radius, which is about 6500 km. Surface area of a sphere is 4*pi*radius2, so we get about 530 million square kilometers, times 0.003 kilometers deep, for a grand total of 1.6 million cubic kilometers of sand. A grain of sand is at least a tenth of a millimeter across, let’s say, or one ten-millionth of a kilometer — ten million, or 107, grains lined up end-to-end in one kilometer, or 1021 grains packed in one cubic kilometer. We had 1.6 x 106 cubic kilometers of sand on the surface of the earth, so we have a grand total of no more than 1.6 x 1027 grains of sand on all the beaches of the earth.

Of course, the answer is much less than that. The earth isn’t covered by a ten-foot-deep layer of sand, and a tenth of a millimeter is pretty fine sand. But this simple calculation took me only a minute or two, and now I’ve got a “reality check” for my more elaborate calculation, which might take weeks or even years to finish. If I get an answer bigger than this reality check at any point, I know I’ve made a huge mistake. And if someone else gives some answer that’s bigger than this, I know they’re spinning bullshit.

Counting grains of sand is not very useful. But the same principle applies when someone tries to sell you something that will “save you money.” Or when someone tries to tell you that a sitting president has spent more taxpayer dollars in four years than all the past presidents combined. Simple “reality checks” are a quick way to call bullshit on those who are trying to take advantage of you.

Reality checks of this sort give you perspective: broad outlines about how the world really works.

Here are a few points of perspective that have been passing through my mind lately, as we move into the mind-bending prevarication and fear-mongering of a presidential election season in the United States.

In 250,000 years, there will be no more humans on the earth. If we don’t drive ourselves into extinction first, “we” won’t be human any more — either way, no more humans. Why do I say this? Because 250,000 years ago, there were no humans on the earth. Even 100,000 years ago, Homo Neanderthalensis was the dominant erect primate, and Homo Sapiens Sapiens was just getting started on his path to world domination. In another 100,000 years, we’ll doubtless be on our way out as a species, and in 250,000 we’ll have joined the dinosaur and the loon.

In 5000 years, our entire civilization will be forgotten, or studied only as “ancient history” from scraps and fragments. Why do I say this? Because our entire history of the world is only around 3000 years old. What we think of as “civilization” is itself no more than 10,000 years old. Asphalt vanishes within a decade or two. Concrete crumbles and steel rusts within a few centuries. Even stone, like that used in Medieval cathedrals or the pyramids of Egypt or the megaliths of Paleolithic Europe, erodes, etches, and breaks over the course of a few thousand years.

In another 300 years, there will be no United States of America. Why do I say this? Because 300 years ago there was no United States of America. Any survey of maps through history shows how fluid and ephemeral national boundaries are over the course of even fifty years. Nations and empires never endure unchanged for a thousand years; only a few have lasted more than a handful of centuries; many lasted a single generation or less. The US is beginning to show fracture lines, and has clearly peaked as a unified world power. I personally doubt it will celebrate a fourth centennial, in 2176, much less a fifth. It might not even reach 2076 intact.

In 100 years, we will no longer burn oil or petrofuels of any kind. Why do I say this? Because oil was first commercialized in the mid-1800’s — it’s only about 150 years old as a commodity. Yet we have just reached/passed peak global production, and are now on the downslope, which is always steeper than the upslope: from here, prices will rise on the whole. At some point well short of the next century mark, oil will become too expensive to burn.

In 50 years, us middle-aged curmudgeons will be dead, or drawing our last breaths of pure oxygen from a tube. The hot, randy, enthusiastic teens of today will be retiring with gray hair and wrinkled skin and pot bellies. The infants still in diapers will have just finished their mid-life crises.

I find these points of perspective useful (and calming) when deluged with all the panicked rhetoric about how the Roberts Court’s decision on Obromneycare has obliterated the boundary between federal and state governments. OMG! The world has come to an end!!!

Meh. Not so much.

In 5000 years, everything we’ve created will be completely forgotten: art, music, literature, laws, bridges, cities, monuments. In only 300 years, the Roberts Court will matter only to historians; whatever distant descendants I have will be living under a different form of government, probably something rebuilt after several bloody interstate wars and at least one descent into despotism — perhaps a Hunger Games sort of world, perhaps more like Ecotopia. In a mere 50 years, I’ll be beyond caring — my grandchildren will be thinking about stiff knees and retirement, and their grandchildren will be crawling around on the floor.

The only thing of lasting value that we pass on to future generations is the good earth: having lived upon it lightly enough that it can continue to serve as the mother of all life. We do this so that our descendants can live their own lives, and gradually forget about us. Just as we have gradually forgotten all those who came before us. Our greatest virtue is our ephemerality. Our invisibility. Our unimportance in the grand scheme of things.


We can be passionate about our politics, our religion, our art and music. But it’s useful to keep a little perspective on the matter.

This entry was posted in General.

4 comments on “A Matter of Perspective

  1. Alioth says:

    Beautiful post.

    There’s a line from Neal Stephenson’s book /Anathem/ that I like to keep in mind, about civilization “sloshing back and forth” over a large continental plain in the north of the world, as global warming peaked and receded and peaked again, and as the prices of the old cities’ scrap metal rose and fell. It’s a very vivid image, and what little I’ve learned about fluid dynamics only emphasizes how strange and incomprehensible the world of “sloshing” phenomena would look to a water molecule, or even to a bacterium. (Because bacteria are so small, swimming through water is as difficult to them as swimming through tar would be to us.)

    (The main character of /Anathem/ is of a monastic order that secludes the whole monastery for ten years at a time, and he’s just been dumped out into the regular world, accompanying some “hundreders” and even a “thousander” from yet more secluded orders. So he tends to take the long view, but is not so isolated that we non-monastic readers can’t relate to him.)


    • Thank you!

      Love Neal, but haven’t read Anathem. The one thing he does that annoys the crap out of me is when he ends the book at what is clearly chapter 19 of a 20-chapter story. But yes — as soon as you change your scale of reference, how much everything changes! 


  2. Tim Grote says:

    Great post! I was expecting something regarding the heath-care issue, and as you well hinted, given a dose of perspective. So true about keeping a ‘reality check’ so many engineers get lost in formulas and math, they forget the end goal. 

    Funny that Alioth brought up Anathem, I had the same thought as soon as you started bringing up millennia. 🙂


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