Almost 500 years ago we all believed that earth was the center of the universe and for the major period of our existence we have believed that earth is unique and so is our solar system, it is very recently that we have discovered that planets actually more common than we ever thought.
Possible world is necessarily true concept if and only if it is true not only in the actual world but in all possible worlds
We see Universe not as it is, But as it was once and existing ubiquitously.
The concept of a possible world leads to the theological problem of the existence of evil, arguing that an all-perfect God would actualize the best of all possible worlds.
It is very recently that we have discovered that planetary systems are very common across the galaxy , and many are even too bizarre to even exist .Luckily we have some promising planets for humans to Colonize and destroy too just like Earth. (sad, but True)
Before moving into that let’s peep into some factors which are considered before classifying a planet as habitable.
Goldilocks and The Bears
Remember that childhood tale of Goldilocks and the bears?, that’s exactly is the case with the planets, some are too hot, some are too cold, some has the most bizarre weather conditions.
Around almost every “normal” star, including our sun, we can draw a band of potential habitability: the right distance and temperature for liquid water to exist. The key, of course, is a planetary surface where the water could pool. Both stars and planets come in many types and sizes, and the interplay of these factors determines the extent and influence of this “habitable zone.”
A giant, hot-burning star’s habitable zone would be found at a much greater distance than that of a smaller, cooler stellar dwarf. And if we stick with the plan — hunting first for what we know — then small, rocky worlds are our best bet for finding evidence of life as we know it .
So the ideal candidate is an Earth-sized, rocky world nestled comfortably within its star’s habitable zone — though scientists’ understanding of what makes up a habitable zone continues to evolve.
A proposition is possibly true if and only if it is true in at least one possible world, perhaps distinct from the actual world.
There is a thesis that the existing world is the best world that God could have created.
Is it so? Let’s find out…
Kepler-442b’s status has been confirmed as an exoplanet that has almost the same size as Earth, and it happens to be almost the same size as Earth. The terrain is expected to be rocky, and Kepler-442b orbits inside the habitable region of the K-type-main-sequence star Kepler-442, which is located around 1120 light years away from our planet. The K-type-main-sequence stars tend to be much smaller as compared to the sun, and they also live longer, carving out a main sequence of around 15 to 30 billion years as opposed to the 10 billion years estimated for the sun.
Kepler-22b orbits around Kepler-22 and maintains an average distance of 15% less than the distance between the Sun and the Earth, however, the light radiating by Kepler-22 happens to be 25% less powerful than the luminosity of the Sun.
Given a suitable combination of a low stellar luminosity and a short average distance from its host star, the surface temperature and distance of Keper-22b are considered sufficiently habitable. Experts believe that the surface of Kepler-22b is not exposed to severe temperatures of greenhouse heating.
3. HD 40307g
Super-Earth” HD 40307g orbits comfortably inside the habitable zone of its parent star. It lies about 42 light-years away from Earth in the constellation Pictor. It is so close by that future telescopes may be able to peer at its surface. It orbits its parent star about 56 million miles (90 million kilometers) away, which is just over half of the Earth-sun distance of 93 million miles (150 million kilometers).
4. Gliese 667Cc
Another “super-Earth”, Gliese 667Cc is also close by Earth: about 22 light-years away in the constellation Scorpius. The planet is at least 4.5 times bigger than Earth, and takes 28 days to make an orbit around its parent star. GJ 667C — the parent star — is actually part of a triple-star system. The star is an M-class dwarf star that is about a third of the mass of Earth’s sun.
Kepler-186f is the first truly Earth-size exoplanet ever found in its host star’s habitable zone. The alien world, which lies 490 light-years from Earth, is just 10 percent bigger than our own planet and is almost certainly rocky.
What we can Expect in coming future?
Until and unless James Webb Telescope is up and running, we won’t be looking at an amazing breakthrough , though there are other possible worlds too , the newly found Trappist-b,c,d,e shows a great promise and the search continues.
But in the field of space exploration anything can happen.Who knows? where is out next home?
Possible world is actually necessity, possibility, contingency