Grains of Sand

So I’m entering my credits and debits at work today, a huge spreadsheet, into our accounting software, and I’m using a ruler to go line by line so I don’t mess anything up. Before long, I’m not looking at my data. I’m looking at the ruler. Specifically, the tiny lines demarcating the wood into sixteenths of an inch.

What would be a sixteenth of an inch long?

A single grain of sand? No … somewhere between two and three grains, I’d guess. More on the side of two than three. Before I know it, I’m satisfied that thirty-six grains of sand could be lined up on this ruler in the space of one inch. Call it idiot’s intuition.

Hey – can I use this to figure out that rhetorical question: how many grains of sand are on the beach?

Sure!

Well, I did some quick math, and noted this memory trick for geeks of all stripes – but particularly physics geeks – out there:

Simplify matters by saying that we just want to find the numbers of sand on the surface of the beach. So we’re looking for area.

If you could fit 36 grains of sand in a line an inch long, that’d be 432 grains of sand in a foot.

A square foot plane one-grain deep would hold 432 x 432 grains, or … 186,624 grains of sand.

186,624! That’s remarkably close to the physics constant c, the speed of light – 186,262 miles per second.

I figure you could round it downward a bit to 186,000. That’s the figure I always retain when thinking about c. (Which I really only do when reading a physics pop sci book or an SF paperback dealing with FTL travel.)

Anyway, all you need to do to calculate the number of grains of sand on a beach is –

(1) Find the square footage of the area of beach in question

(2) Multiply that figure by c

Want an example?

My house sits on a 50 x 100 foot lot. If I obliterate everything on it, house included, and fill it with a coating of sand one-grain deep, I will need … 50 x 100 x 186,000 … 930 million grains of sand!

Groovy, man, groovy!