When did we first realize that more than four dimensions may exist?

[Ivan Seeking]

I was reviewing the history of String Theory, and I was wondering if anyone can tell me the history of our interpretation of dimensions. When did we first realize that more than four dimensions may exist, and when did we first land on the head count of 10 or 11 as the correct number? I couldn't find the year that these hypotheses were first suggested.

 

[meteor]

When did we first realize that more than four dimensions may exist ?

The first theory that proposed more than 4 dimensions I think that is Kaluza-Klein theory, discovered by Kaluza in 1919, and published by him in 1921.It has 5 dimensions, 4 of space and one of time. Then Einstein spent 30 years trying to unify electromagnetism and gravity with this theory, without success

and when did we first land on the head count of 10 or 11 as the correct number?

11-dimensional supergravity was discovered in 1978 by Cremmer, Julia and Scherk.
The first string-related theory using 10 dimensions was Type I Superstring theory, discovered by Schwarz and Green in 1980. They used the Green-Schwarz mechanism to achieve anomaly cancellation

 

[meteor]

This recent paper,
"The many dimensions of Dimension"
http://arxiv.org/abs/physics/0402105
says that in 1914, Nordstrom tried to unify scalar gravity and electromagnetism in a theory with 5 dimensions

Here's a biography of Gunnar Nordstrom
http://www.physics.helsinki.fi/~tfo_www/nordstrom/