This is the equation of Frank Drake, penned in 1961. The equation is, simply put, a means by which one can determine the chances of there being other advanced civilisations in our galaxy, the Milky Way.
N is the number of civilisations in our galaxy and you reach that figure by multiplying all the other factors on the other side of the equation together. They relate to stars formed per year, the number of those stars that have planets, the number of those planets capable of forming life, the number of those planets that will actually form life, the percentage of which will be intelligent life, the percentage of which will then be able to communicate with us and, finally, the length of time each civilisation will roughly exist for.
Now, this equation in reality relies on gargantuan quantities of conjecture and speculation and data that we have that is, at best, a rough outline of a tiny part of the picture. But, even bearing this in mind, there are many astronomists who will take the figure N to be in the hundreds, thousands or even millions. It is very plausible to suggest that, with conservative estimates, N can be a healthy positive number. This model is but a simple one to hazard but a guess as to whether the concept of other intelligent communicative life exists in our galaxy (this is just one galaxy of countless others remember).
Of course, with other much more conservative inputs, the figure N can be determined at 1 or 2. So you have to take your pick for now. I like the former answer; what a mesmerically beautiful concept to feel that there are many, many other civilisations pottering along out there as well.
If that doesn’t make you smile, and keep your ego in check and you worries at bay a little, then here is reason number two:
Carl Sagan, the eminent and wonderful astronomer and NASA scientist (download his audiobooks or get the real books if you can), once calculated a rough value of the chances you had of landing on or near a planet if you were to randomly appear at any one point in the universe. He came up with a figure of 1 in 10 to the power of 33, that is;
1 : 1,000,000,000,000,000,000,000,000,000,000,000
Remember that is the chance of being on or near a planet, and I don’t know how many of us are capable of getting from near a planet to actually on it. So my point is this, there is a heck of a lot of space here and only a very little not space that we could conceivably be on. So what wonderful good news it is that you or I are actually here! Lucky, lucky us!