SETI: What has it ruled out?

Drakkith

You are assuming a whole lot. There is no guarantee that most of that stuff is required in order for a planet like Earth to form. Or that what caused those things here on Earth are the only things that could cause it. For example, would there be a need for a Jupiter like object to sweep up debris if the amount of debris was much less than our own young solar system? Perhaps several smaller planets would be capable of having a similar effect of clearing debris. Does life really need tidal pools? Does a planet need a strong magnetic field and ozone if it's star puts out less radiation than our own sun?

spark802

Yes Drakkith you have some good points there.

Dave

Chronos

I think it fair to say earth has enjoyed fortuitous circumstances, but, given a jillion galaxies out there, each with hundreds of billions of stars, I am not convinced it is unique.

dodo

I have one question: how is it that a transmitter with a wider bandwidth gets a poorer reception from a distance? In the link quoted earlier,
I can't really see, to begin with, where the "Bt" (transmitter bandwidth) is used in the formula for the reception range.

P.S.: I think the idea is that the "Br" (receiver bandwidth) has to be at least as wide as the "Bt"; and that noise depends on this receiver's bandwidth. But I didn't quite understand (being a layman in physics) this "Nyquist noise" equation; maybe someone can provide a link, more related to antennas than the Wikipedia page.

dodo

For what is worth, there is an interesting initiative here:

http://setilive.org