[Sabertooth]

Would an Earth-like planet require a Sol-like solar system?

Would that Sol-like system course placidly on the galactic periphery, as ours does? Wouldn't that exclude a big chunk of the 400 billion stars in the Milky Way as candidates?

Would there be lots of circular orbits, and friendly gas giants sucking up space debris along the perimeter?

Would an Earth-like planet exist in what is basically a binary planetary system, as is ours with our Moon?

[petuniasevan]

Yeah, it wouldn't be a great neighborhood in a globular cluster, huh? Lotsa traffic! (Even if you could scrape together the heavy elements to MAKE a planet)

Or how about orbiting a red dwarf sun REALLY close-in for that needed warmth? OOPS! Stellar flare! Sorry, life-forms; it's barbecue day!

How about a nice white-hot star and an orbit like Saturn's? Okay...uh-oh! Star core out of fuel already! %&#* proton hog...BOOM!

As for a Sol-like solar system: consider that Jupiter "eats" a lot of comets, asteroids, and assorted space debris. Without a Jupiter, that Earthlike planet is likely to resemble Mercury.

[Virginia-American]

Personally, I'm hoping that someday we can detect oxygen-rich atmospheres - IMO, a sure sign of life.

[tophat9000]

I would call Earth-like surface livable with out pressure suit.. free standing liquid water ... farmable