What Has SETI Ruled Out in the Search for Alien Civilizations?

[Drakkith]

The books main point is that we; The Earth itself is probably the only world to get as advanced and complex as can be, as in one of a kind. Dave

I personally don't believe this. The results of the Kepler mission have proven extremely fruitful so far. I can't see Earth being "one of a kind".

 

[mjacobsca]

The Kepler mission has proved that planets are extremely common, and rocky planets probably are as well. The Rare Earth theory does not disagree with this. The Rare Earth Theory even says that life is probably common. However, it lists numerous variables that pose enormous challenges to complex life, none of which Kepler has ruled out. I recommend you check out the theory to see some of the other concepts that it covers.

 

[Drakkith]

The Kepler mission has proved that planets are extremely common, and rocky planets probably are as well. The Rare Earth theory does not disagree with this. The Rare Earth Theory even says that life is probably common. However, it lists numerous variables that pose enormous challenges to complex life, none of which Kepler has ruled out. I recommend you check out the theory to see some of the other concepts that it covers.

I don't disagree with the challenges to life and all that, I simply disagree with Earth being one of a kind. We'll have to wait and see what happens in the future, and I am excited about it!

 

[spark802]

HI Again, i like the fact that u are optimistic Drakkith,

I Want to borrow your quote Drakkith "It's not about what's possible, it's about what's probable"

I've read Brownlee and Wards book a couple of times over and i ask; is there other life out there? Probably.

I then ask; is a twinlike planet for the Earth possible? Remember all the criteria that has to be met.

We need a moonlike sattelite to keep us locked in axial tilt. Early life needed tidal pools also our moon is involved. We need a Jupiter like planet to act as a attractor to sweep up debris otherwise destined to impact here. We know we can survive some big impact events as long as they are rare. We need interior convection and plate tectonics/ vulcanism. Vulcanism releases gases that help retain warmth and regulate the atmosphere.

We need a strong magnetic field and the properties of ozone. We need the Earth's mass as it is to keep the atmosphere intact. We need to keep some fresh H2O locked up as ice.

All of this has to happen over a very long period. And luck/happenstance can't hurt.

We need to dodge the odd cosmic bullet...

Are "Earths" possible twice? Or many times over?

I am not a religious person but we could be it...

Dave

 

[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,

http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html]

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