Peter Backus. WHY I DON’T HAVE A GIRLFRIEND:
An application of the Drake Equation to love in the UK.
The Drake equation is used to estimate the number of highly evolved civilizations that might exist in our galaxy. The equation was developed in 1961 by Dr. Frank Drake at the National Radio Astronomy Observatory in Green Bank, West Virginia.
The equation is generally specified as:
G = R × fp × ne × fl × fi × fc × L
Using this equation Prof. Drake estimated that 10,000 communicative civilizations probabilistically exist in the Milky Way alone. Astronomers estimate that there are between 200 and 400 billion stars in the Milky Way. Let’s call it 300 billion. This makes the probability of a star chosen at random supporting life capable of interstellar communication 3.333e–08 or 0.000003%.
Another way to think about this is that this is probability of the conditions necessary for us to communicate with an alien civilization being satisfied. These seem like slim odds the best, but the probability is positive (There is a chance!) and this approach is widely accepted by astronomers (This isn’t science fiction!). The idea that there could be 10,000 civilisations that we are capable of communicating with is very exciting indeed.
While extraterrestrial civilizations maybe rare, there is something that is seemingly rarer still: A girlfriend. For me. What might the approach employed in the estimation of the number of alien civilizations tell us about the number of potential girlfriends for me? A somewhat less scientific question, I admit, but one of substantial personal importance.
The parameters are re-defined as follows with the values in parentheses:
G = The number of potential girlfriends.
R = The rate of formation of people in the UK (i.e. population growth).
fW = The fraction of people in the UK who are women.
fL = The fraction of women in the UK who live in London.
fA = The fraction of the women in London who are age-appropriate.
fU = The fraction of age-appropriate women in London with a university education.
fB = The fraction of university educated, age-appropriate women in London who I find physically attractive.
L = The length of time in years that I have been alive thus making an encounter with a potential girlfriend possible.
We can simplify the above specification by recognizing that the number of people who have ever lived in the UK is related to the population growth rate by
where T is the age of the UK. If we assume that R is constant over the period T than N = R × T. While this simplification is often used for the Drake Equation’s intended purpose, it isn’t a good assumption when adapting the equation for our purposes here. Instead we use N’, the population of the UK of 2007, where N’ = 60,975,000.
With this simplification we can re-specify the Drake Equation as:
G = N’ × fW × fL × fA × fU × fB
If we plug in the above values we get:
G = 60,975,000 × 0.51 × 0.13 × 0.20 × 0.26 × 0.05 = 10,510.
So, what this means is that there are 10,510 people in the UK that satisfy these most basic criteria for being my girlfriend. That is 0.017% of the UK and 0.14% of Londoners, which doesn’t seem so bad. On a given night in London, there is greater than 1 in 1000 chance that I will meet an attractive woman between the ages of 24 and 34 with a university degree. Of course this doesn’t take into account the fraction of these women that will find me attractive (depressingly low), the fraction of these women who will be single (falling with age) and, perhaps most importantly, the fraction of these women who I will get along with. Including such factors would greatly reduce the above figure of 10,510. A rough estimate puts the number of potential girlfriends accounting for these three additional criteria (1 in 20 of the women find me attractive, half are single and I get along with 1 in 10) at 26. That’s correct. There are 26 women in the UK with whom I might have a wonderful relationship. So, on a given night out in London there is a 0.00034% chance of meeting one of these special people, about 100 times better than finding an alien civilization we can communicate with. That’s a 1 in 285,000 chance. Not great.
Make of this what you will. It might cheer you up, it might depress you. I guess it depends on what you thought your chances where before reading this.
I would like to thank Ian L. Johnson and an anonymous volunteer referee for comments and suggestions concerning this paper. Others have applied the Drake equation in the same way. See: ‘Singles in SF’, ‘This American Life’, Raymond Francis’s paper and ‘The Big Bang Theory’. Links to all of these are available on my website.
Девушки = Зло
Девушки требуют времени и денег: Девушки = Время × Деньги. Известно, что Время = Деньги. Получаем: Девушки = (Деньги)2. Так как Деньги – это корень Зла, то Деньги = и, таким образом, Девушки = = зло.
Рассмотрим женщину как релятивистский объект. Представим себе ситуацию: она сказала, что придёт через 10 минут, а пришла через 30. На первый взгляд, это повод обидеться. Но давайте рассмотрим ситуацию глубже. Предположим, она сдержала своё обещание, то есть в её собственной системе отсчёта прошло 10 минут, однако в нашей системе отсчёта прошло 30 - значит, релятивистский γ-фактор равен 3. Зная его, находим скорость женщины - 282 тыс. км/с. Вот видите, как она к вам спешила! Впрочем, вопрос, что она делала за полмиллиарда километров от вас, остаётся открытым.
А.Г. Ваганов. Наука - баба веселая.