There is a brand new satellite above called Kepler, and orbiting with it is a whole new wave of science rhetoric. Kepler has rejuvenated the question that really needs no rejuvenation: the perennial question about whether another Earth-like planet exists which could harbor life.

Kepler's whole purpose is to pick up the very slight dimming of stars as tiny orbiting planets move in front of them. With enough data one can estimate the size and orbit of those planets. The hope is to find "earthlike" planets, something up until now we have been unable to detect.

But what exactly does "earthlike" mean?

Well, what "earthlike" means, compared to what it implies, are two vastly different things. According to the Kepler team it is simply defined as a rocky planet that abides somewhere in what is called the "habitable zone" around its star. That would be an orbit which allows it to have water in its liquid state; not too far from its sun so as to freeze its water, not so close so as evaporate it all away.

But the more popular understanding of "earthlike" heavily implies a duplicate earth: A big blue planet with continents and oceans and clouds - and life.

We all know that if Kepler does find a planet roughly the same size as Earth and orbiting in the habitable zone, that many in the popular press and some scientists will leap onto that to quickly conclude that life must be there. It will be an unfounded conclusion which will make headlines everywhere.

But before readers here jump on that inevitable Bandwagon of Life we should ask some questions - and lots of them. Here is a very small check list.

Is the planet's star the correct type of star, not too big, not too small? Is the parent star alone or does it have some orbit-disrupting partner? Does the planet have the just-right size to hold on to a just-right atmosphere? Does the planet have any water at all? Does it have giant planets perfectly placed in outer orbits and locked there, protecting it from life-destroying bombardment? Is the planet's orbit nearly circular, if not perfectly circular? Does it have a life-giving, perfectly placed moon to keep it steady? Has it cooled to a solid rock or is it alive with plate tectonics?

The list is endless. But if you want a home for life, especially complex life, you had better have the perfect planet, not just a rock in the right place. But there is one more thing, one more very important thing. Even if a newfound planet were an exact doppelgänger of Earth in every way, it doesn't follow that life must be there. But that's a subject for next time.