Infinity Symbol

Date: 18 Apr 1995 15:43:43 -0400
From: Scott T Cramer
Subject: Q: name for infinity symbol

Dr Math,

I got your address from the WWW.  If this is appropriate, I'd
appreciate your reply.  My question is: What is the name for
the infinity symbol (the on-its-side figure eight)?
Or is there no name for it?  Thanks in advance.

Scott

Date: 19 Apr 1995 15:43:34 -0400
From: Dr. Ken
Subject: Re: Q: name for infinity symbol

Hello there!

Well, I thought I'd just write to let you know that we're working on your
question.  I'll have an opportunity to do more research on it a little bit
later, but here's what I think I remember:  the modern symbol for infinity
was an invention of some English mathematician, and I don't think it was
used as a symbol before that.  I'll have to check on that, though.  Anyway,
I've never heard of a name for it before; sometimes people call it "the
sideways 8" or "the infinity symbol" or things like that.  I'll let you know
what else I find out.

-Ken "Dr." Math

Date: 19 Apr 1995 17:01:04 -0400
From: Scott T Cramer
Subject: Re: Q: name for infinity symbol

Ken,

Thank you for your efforts in naming the infinity symbol.  I have also
posted the query to Usenet and have received a few replies of "lazy eight"
and one of "lemniscate".  I've looked in several math and symbol dictionaries
and all of them simply define the symbol as "infinity".  I managed to
find lemniscate, but its definition was that of an "algebraic curve"
which, although it looks (when plotted) like the infinity symbol,
doesn't seem to have much to do with the concept of infinity.

Your historical info sparked my interest too.  Any idea on when the
symbol was first used?  (Well, now I really am off on a tangent :-)

Anyway, thanks again.  It's strange how seemingly trival details
can gnaw away at one's attention.

Scott

From: Dr. Ken
Subject: Re: Q: name for infinity symbol
Date: 19 Apr 1995 19:23:59 -0400

Hey there.

I found this in Florian Cajori's "A History of Mathematical Notations":

     The sign [infinity] to signify infinite number was introduced by John
Wallis in 1655 in his "De sectionibus conicus" in this manner: "Esto enim
[infinity] nota numeri infiniti."  The conjecture has been made that Wallis,
who was a classical scholar, adopted this sign from the late Roman symbol
[infinity] for 1000.  

So that's as much as I find.  It goes on to say where the symbol was
subsequently used, and how it was used, and so on.  Hope this hits your
interest.

-Ken "Dr." Math     The Math Forum
 Check out our web site   http://mathforum.org/dr.math/   

From: Dr. Ian
Subject: Re: Q: name for infinity symbol
Date: 21 Nov 2001 11:47:00 -0400

Hi,

Jerry Jelincic has pointed out that according to 

  http://www.geocities.com/Paris/Rue/1861/etyindex.html   

the symbol introduced by Wallis may have been a variant of the Greek
letter omega, which to me seems more plausible than using the Roman
symbol for 1000.

Thanks, Jerry!

-Dr. Ian
 http://mathforum.org/dr.math/