Helen of Troy is infamous for her pivotal role in the Trojan War after she left Sparta for her new lover, Paris of Troy. She was deemed the “most beautiful woman” in the world by Aphrodite, the goddess of love, who made her fall in love with Paris in return for him choosing Aphrodite as the most beautiful goddess.
Helen is said to have been so beautiful that she had “the face that launched a thousand ships” (in reference to the Trojan War and the massive navy of Greece). Using this statement, clever authors such as Isaac Asimov and W.A.H. Rushton invented the “Helen (H)” unit – an international, standardised measurement of beauty. As Helen launched a thousand ships, a milliHelen (mH) of beauty equates to the amount of beauty required to launch a single ship.
For example, according to The Iliad, the total number of ships that joined the expedition to Troy was 1186. This means that Helen had a beauty rating of 1.186 Helens – ergo, capable of launching more than one thousand ships.
The unit also goes both ways as negative Helen units are possible. For example, -1 mH would mean “beauty” (read: ugliness) that drives a single ship away. The units can be subdivided further, such as a picoHelen (10^-12) being the amount of beauty that “tosses an inflatable tube into the pool”.
Another interpretation of the Helen is the number of women that said woman is more beautiful than. For example, during Helen of Troy’s time (1100 BC), about 50 million women existed on Earth. Therefore, 1 Helen is amount of beauty sufficient to be greater than the beauty of 50 million women.
Finally, beauty is considered to be on a logarithmic scale of base 2. Simply put, for beauty to increase by 1H, the woman must be the most beautiful of double the number of women. In practical terms, the most beautiful woman who ever lived (using the cumulative female population of the world) has a beauty rating of 1.34H. The most beautiful of a dozen women would be 0.14H.