The Odds of Contacting ET Are Nil, Despite That They Are Already Watching (cont.)
By Jim Elvidge
Given that we are assuming that our partner has a comparable level of technology, the best case is that there is a civilization out there somewhere pumping a megawatt of radio power into an Arecibo-sized telescope pointed directly at us, while we have our Arecibo-sized telescope pointed directly at them to receive it. In such case, we could actually detect a signal somewhere within 70,000 light years. Given that we are on the edge of the galaxy that has a 100,000 light year diameter, this may represent accessibility to about half of the stars in the galaxy, so we need to multiply our odds by .5.
The next question is to consider the odds that an "advanced technology" civilization even develops radio waves. Why would we even think that they would follow the technology path that we would? Maybe they don't have an ionosphere like we do (which causes the bending of radio waves) thereby eliminating the drivers for radio propagation research and development. Maybe ET modulates magnetic fields or seismic waves, maybe they got fully wired for broadband internet before discovering radio wave propagation, maybe they communicate via telepathy, or some form of communication that is completely unknown to us. So let's be generous and multiply our odds by another factor of .01.
Even then, what are the chances that we pick that 1 star of the hundred billion in the galaxy that built and uses an Arecibo dish at the exact same time that that they pick us out of the hundred billion stars in the galaxy? Let's give each SETI program a 50 year lifetime, equally split across those hundred billion stars, we would have to look at 228,000 stars an hour just to cover them all, which of course, we can't do. No matter how fast you scan the sky, you are ultimately only looking at one point per detector at any point in time. Turns out the odds of the right overlap are 1 in 100 billion. Factor in another 10-11.
Oh, by the way, what are the odds that we are using the same frequency as them? My head is starting to hurt. Another factor of 10-6?
And the total is 1.25ē10-22. For those who don't like scientific notation, how about .0000000000000000000000125.
So why is Stephen Hawking worried about us sending a message that gets intercepted by ET? Didnít anyone do the math?