The original Drake equation:
Can be rewritten as
I'm impressed someone else is familiar with the Drake equation. Carl Sagan used it, and I even saw him calculate it once on
Cosmos. If I remember, the number is surprisingly low, and some factors involved in the equation are based on assumptions, which slightly diminishes the quantitative aspect of it. But I still like it, and highly respect Drake for coming up with it.
Arthur C. Clarke made a small speech in
Stanley Kubrick: A Life in Pictures that will always stay with me. I don't remember it verbatim, but I'll see if I can get the general gist of it down:
"Behind every man now alive stand thirty ghosts, for that is the ratio by which the dead outnumber the living. Since the dawn of time, roughly a hundred billion human beings have walked the planet Earth. Now this is an interesting number, for by a curious coincidence there are approximately a hundred billion stars in our local universe, the Milky Way. So there is enough space in just our Galaxy for everyone living, and everyone who has ever lived, to have their own world." - Arthur C. Clarke
To think that there is not life out there somewhere is somewhat presumptuous. Probability-speaking, it's less likely that there isn't life out there, when you think about it.
EDIT:
It is in theory infinitely expanding and if that theory is true, which it probably is, then we are all going to die eventually because the temperature will eventually reach absolute zero which is the temperature at which molecules stop moving. This is called heat death and it is inevitable. This of course if we survive the destruction of life on our planet by our sun. Yup, the long term future looks bleak for all life.
It's still debated if Absolute Zero could be even reached. I believe we've come close to 0.0 K, but never got to it. We also don't know what would happen if we ever did. If electrons stopped moving, it's possible the matter would just fall apart. But, taking magnetic force into account, it could be highly dangerous. There are many possibilities! Although, new suns are being formed every day, so it's not like the Universe will become a barren wasteland of giant rocks. Not to mention the rate at which the Universe is expanding is diminishing, if I remember.
Now, Heat Death (the theory) assumes that Entropy will continue to the logical extreme, but doesn't take into account random chance. It's kind of like the absolutist theories, but applied to the inverse. In that sense, Heat Death is rather hard to believe. I was always a fan of the Big Crunch myself (a nice, almost epic closure), but I think that's basically been proven wrong, right? But still, who wouldn't want to become a Black Hole Singularity? haha
Or you know, God could save us all.
I kinda doubt that. :-)