Excerpt from “Climate Trek” by Mike Tidwell
THE EARTH SIDE OF THE SANDWICH
“As far as orbiting bodies go, Earth, with its palette of swirling white, fantastic greens, and deep-blue hues, is no less than extraordinary. We say this with a bit of hesitation, however, because our experience has been limited to very few such bodies in the Universe. The existence of other planets, other than the eight full-size planets, one dwarf planet (and as sometimes postulated 3 additional dwarf planets) in our solar system, some planet-sized moons orbiting Saturn and Jupiter, and a few faint planets detected orbiting neighboring stars, is entirely theoretical.
In a Universe so vast that the nearest and next-to-nearest stars to us are, respectively, four and seven light years away, it is impossible for us to know absolutely how common or uncommon Earth-like planets are in the universe. We can only note that with trillions upon trillions of possibilities in the stars, and finding nothing exceptional about our sun or the physical laws it obeys compared with the rest of the Universe, there is no reason for there not also to be trillions of Earth-like worlds as well. What might be the factors that are most responsible for the extraordinary nature of our little Earth?
Our Earth derives its uniqueness from the few comparisons available to us by two startlingly simple parameters: the distance it maintains from the sun, and a large-enough mass.
Critically, planet Earth lies at a proper enough distance from the sun for water to exist on its surface in all three of its phases—gas, liquid, and solid. Other bodies that orbit inside Earth’s orbital range, in the extra heat of the sun, are water-challenged, and they have little chance for liquid water and certainly no chance for the existence of solid water on their surfaces. Other bodies just beyond Earth’s orbital range quickly suffer temperatures far below the freezing point of water and surface water; in these bodies exists only as a rock-hard solid. All life forms that we know about require liquid water, so none of these situations is conducive to life. It is therefore unlikely that other bodies in our solar system will be found to harbor surface life. This is not to say, however, that life does not exist in the rest of the solar system. Quite to the contrary, nine other moons and planets within our solar system have been identified as good prospects for the existence of life. The form that life is expected to take in these places is single-celled and its location within them, subterranean. Furthermore, it is not expected that these life forms will have managed to populate the surface of these worlds, for the simple reason that none of these places maintain liquid water on their surfaces. It is, then, the just-so temperatures of Earth’s water that give Earth is its distinctive blue and white colors.
Another special characteristic about Earth, beyond a favorable distance from the sun, is its size, more precisely, in mass 5.98 x 1024 kg, in diameter 12,755 km, and in volume 1.08 x 1022 cubic kilometers. Importantly, Earth’s not-too-small size has allowed it to produce and hold enough interior heat to maintain over its lifetime a large molten interior covered by a relatively thin outer crust. Interestingly, this circumstance of sufficient mass has allowed our planet to recycle its surface, which for many reasons has sustained the diverse biosphere that we know and love. Certainly, without Earth’s not-to-small of a size life as we know it would be greatly diminished or perhaps even nonexistent.”
You will be able to read more in the soon to be published book
by Mike Tidwell