The cosmos contains vast numbers of stars and presumably vast numbers of planets orbiting those stars.But our home is not just another rock in an immense universe.earth is really a very special place. Firstly, the MiIky Way is a good galaxy to call home.Some galaxies emit indescribably enormous amounts of radiation from their centers due to voracious super -massive black holes. The radiation from some galaxy cores would not just sterilize a planet, it could destroy entire solar systems. Saggitarius A*, the central black hole in our galaxy , has a mass of "only"3.7 million Msun, 3000 times less than the most massive black holes. This indicates that Sag A*has consumed much less matter and emitted much less radiation than many of its heavier cousins. Our galaxy resides in a relatively placid group of about 30 galaxies .Within the local group, the Milky Way and Adromeda are the only major galaxies and all the others are much smaller. Thus it's likely that the Milky way has never suffered a collision with another major galaxy, at least so far. Our solar system is favourably positioned within our galaxy. We are far enough from the galactic center, 27,000 light- years, to avoid its hazards.As sedate as the Milky Way is compared with some galaxies, all galactic centers are dangerous places. The most massive black holes are in the center of galaxies,as is the most intense radiaton. Our solar system is in a very favourable neighbourhood in the suburbs, not too close and not too far. Astrophysicists call this the galaxy's GOLDILOCKS ZONE.
THE TOP TEN REASONS EARTH IS SPECIAL- 1. The milky way is a relatively placid galaxy. 2.The sun is in our galaxy's GOLDILOCKS ZONES. 3.Our solar system bagan at the right time. 4.our solar system has only one star. 5. our sun has a favorable mass. 6.jupiter protects earth. 7.our moon stabilizes earth's axis. 8. earth's magnetic field deflects the solar wind. 9. earth is in our solar system's goldilocks zone. 10. earth's gravity is favorable.
sources: Einstein for everyone by robert I.Piccioni