Origin of the Infinity Symbol

Date: 20 Jan 1995 17:47:00 -0500
From: Betty Thompson
Subject: math symbol

I need to find the origin of the math symbol for infinity that is 
used today.  It looks like an 8 lying on its side.

Betty Thompson
Taylor Public Library
Taylor, TX 76574
thompson_be@mailserver.capnet.state.tx.us

Date: 24 Jan 1995 00:41:39 GMT
From: Dr. Math
Subject: Re: math symbol

Hello there!

I looked this one up in a book called "A History of Mathematical
Notations" by Florian Cajori.  He credits the English mathematician, John
Wallis, with inventing the modern notation for infinity.  And I quote:

"Cum enim primus terminus in serie Primanorum sit 0, primus terminus in
serie reciproca erit [infinity symbol] vel infinitus."

I don't read Latin, but I think that what he was trying to do is give a
definition of infinity, and then introduce his new symbol.  It looks like
he was talking about sequences and all that stuff.  He alludes to the
fact that if a sequence goes to zero, then the sequence of reciprocals
will go to infinity.

The work which he wrote this in was called "Arithmetica infinitorum,"
which was published in 1655.  This notation also appears in his book "De
Sectionibus Conicis."