Survey: Why haven't we discovered aliens yet? Is humanity doomed?

[mckitterick]

If you're reading my blog, you're probably someone familiar with the Fermi Paradox: If our galaxy is billions of years old, and stars like ours are common, and especially now that we believe all stars have planets and Earth-like planets are common, why the heck haven't we been visited by other aliens yet? Stars much older than ours abound, and we

Comments

[nojay]

Stars much older than ours will tend to be the product of a single supernova event and hence any planetary accretion disc around them will be poor in metals such as iron. Technology development by an intelligent race in such an environment would be trickier, perhaps.

Stars much younger than ours probably don't have planetary bodies that can sustain complex life "as we know it". It took well over a billion years after the Sun formed for Earth to cool down to the point where liquid water could exist and another couple of billion years before vertebrate life evolved.

There's also the Galactic orbit -- Earth's sun seems to have avoided entering closer to the Galactic core over the past dozen or so go-arounds. It is believed the core areas have much higher radiation densities due to particle interactions and the black hole posited to be at the centre and that radiation could kill off nascent lifeforms on less fortunate planets over time.

[mckitterick]

True - so you're suggesting that we stick with Sol's generation of stars, and those that haven't passed too close to the galactic core, to look for advanced life?

That DOES narrow it down quite a lot! Still, there ought to be thousands, nay, MILLIONS of civilizations out there like ours, unless... .

[ext_1269766]

The extra lines in the Drake Equation posited by the "Rare Earth" hypothesis- location of the star and planetary system in the galactic "habitable zone"; a planet with a large satellite; chemical makeup that makes plate tectonics possible; and a Jovian planet that A) sweeps up asteroidal debris and B) doesn't go rogue and sweep up inner planets on its way to becoming a "hot Jupiter"- may make intelligent life more rare, and may be a part of the solution to the Fermi paradox.