## Mathematicians Of The Day

### 4th August

On this day in 1539, Girolamo Cardan wrote to Niccolò Tartaglia in an attempt to understand why his calculations involving the square roots of negative numbers sometimes gave the correct answer. He said that his calculation was

On this day in 2014 Google released a Venn doodle.

*as subtle as it is useless.*On this day in 2014 Google released a Venn doodle.

Click on Ⓟ for a poster.

##### Born:

- 1805: William Rowan Hamilton Ⓟ
- 1834: John Venn Ⓟ
- 1843: Mauritz Dahlin Ⓟ
- 1893: Francis Murnaghan Ⓟ
- 1909: Saunders Mac Lane Ⓟ
- 1912: Aleksandr Aleksandrov Ⓟ
- 1939: Brian Sleeman Ⓟ

##### Died:

- 1812: Georg Klügel Ⓟ
- 1874: Otto Hesse Ⓟ
- 1906: Joseph Tilly Ⓟ
- 1920: Karl Rohn Ⓟ
- 1945: Gerhard Gentzen Ⓟ
- 1967: Archibald Macintyre Ⓟ
- 2009: James Wiegold Ⓟ

#### Quotation of the day

##### From William Rowan Hamilton

Time is said to have onlyone dimension, and space to havethree dimensions. ... The mathematicalquaternionpartakes ofboththese elements; in technical language it may be said to be "time plus space", or "space plus time": and in this sense it has, or at least involves a reference to,four dimensions.

And how the One of Time, of Space the Three,

Might in the Chain of Symbols girdled be.

Theorem of the day from Robin Whitty