Favorite numbers

(Photo by Carlos Andrés Reyes)

The New Year doesn’t have much appeal, numberwise. 2019 sort of looks like a prime number but is not, since it’s evenly divisible by three and by 673. Next year will be much more fun, with its pair of 20s and its eye-chart implications. Writers are sure to make quips along the lines of it being a “visionary year” and such, while some may note that the sum of its digits yields the lowest number that will be seen for another four generations.

Such numerological musings come naturally to astronomers, since ours is a science intertwined with digits. People sometimes wonder if any cosmic numbers repeat or stand out. Well, in our neighborhood we use millions a lot, because the Sun, which is nearly a million miles wide, is 93 million miles away.

More astronomically useful is the trillion. This is a million millions. There are about a trillion stars in our galaxy. And the light-year is equal to six trillion miles. But all those zeroes can make us long for smaller, simpler numbers that have power.


One of these is 37, a prime number known to all physicists. For starters, the fraction 1/137 is the value of the “fine structure constant” that shows itself everywhere in the cosmos, governing the way atomic particles and photons behave. And 37 pops up elsewhere, too. The numbers 111, 222, 333, 444, 555, 666, 777, 888 and 999 are all divisible by 37 and 111.

Like Peter the Great, who had his wife’s lover beheaded and kept that head in a bottle of alcohol in her bedroom for her to contemplate, nature can also be perverse, since there’s no rhyme or reason for the numbers that nature springs on us. Why does each cell in our body have 90 trillion atoms, roughly the same as the number of stars in our home galaxy cluster? Why is there exactly the same number of Earth/Sun distances in a light-year as there are inches to the mile? Why does the diameter of the Sun have the same numerals as the number of seconds in a day (864,000 versus 86,400)? We love such strange coincidences.

As for the largest useful number: Well, that’s no doubt the number of things in the visible universe – meaning the sum total of all subatomic particles such as electrons. That figure deserves a name, but doesn’t have one. Still, it’s easy to write. It is a one followed by 87 zeroes. If you write a trillion seven times and then multiply that a thousand times over, you’ll have it.

Want to know more? To read Bob’s previous columns, visit our Almanac Weekly website at HudsonValleyOne.com. Check out Bob’s new podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.

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