The chapter I read last night was on Newton, the discoverer of the universal gravitational constant. The book describes in a very entertaining way what kind of loony character Newton was. But it didn't describe how Newton figured out that constant, G.

So I looked up the article on gravitation in the 1995 Encyclopaedia Britannica. Sure enough, there was the explanation for how Newton figured out G. He made a guess at the density of the earth (turned out to be just about dead-on) and thus calculated the mass of the earth. That led him to a figure for G: 6.608 x 10^-11 meters cubed per second squared per kilogram. OK! I now knew how G had been derived by Newton.

But I saw that the units used for G in the Britannica looked funny. Not only that, a table at the end of the article showed the correct representation of units.

I checked the Britannica online version of the article and found that the error has been perpetuated. So I wrote the following letter:

Dear Sirs,

There is an error in the article on Gravitation. I first noted it today in the 1995 print edition of the Encyclopaedia. It still appears in the online edition.

In the online article, http://www.britannica.com/eb/article-61466, the phrase immediately following formula (7) reads:

which numerically comes close to the accepted value of 6.6726 x 10^-11 m^3 x s^-2/kg^-1

I've used the caret (^) to indicate a power. The phrase SHOULD read:

which numerically comes close to the accepted value of 6.6726 x 10^-11 m^3 x s^-2 x kg^-1

which jives with the description of the formula found in the table: http://www.britannica.com/eb/table?tocId=9115984:

G (in units of 10^11 cubic metres per second squared per kilogram)

Sincerely,

Steve Erbach

Neenah, WI

I then noticed a second error. That prompted this letter:

Dear Sirs,

After sending my first message this morning, I noticed a second error in the Britannica online article on Gravitation. In article http://www.britannica.com/eb/table?tocId=9115984, the phrase should be changed FROM:

G (in units of 10^11 cubic metres per second squared per kilogram)

TO:

G (in units of 10^-11 cubic metres per second squared per kilogram)

Sincerely, etc.

My 0.03 seconds in the sun...

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