Probably a long melancholic story starting with a general freezing over of our planet, prompted by the dimming of the Sun.
This phase may last a few hundred thousand years, then the explosion and the departure through space of our pebble, to be eventually caught by the gravity field of a far distant star.
An uninspiring solution to our magnificent story.
What is more interesting however, is WHEN will all this happen. And, not in absolute time, but in the time frame containing the two above mentioned happenings: the end of Sun and the beginning of the interstellar trip of the Earth.
Time? What time? Newtonian mechanics does not envisage such two distinct events, nor a time lag between the explosion of the Sun and our departure for the outer space. A potential field is there or is not there. No question of shrinking or expanding over a given time bracket. The moment the Sun is out, that very moment we are off. That’s it!
Yet, things have changed since Sir Isaac’s apple. Relativity brought us new concepts. These days, space bends around objects, and nothing travels faster than light. Nothing: not even gravity waves.
But is gravity a wave? And if it were, would it behave like a light wave? True, the equation describing a gravity field is very similar to the one describing a magnetic field, but does this make gravity an electromagnetic phenomenon?
Physicists have been working on the concept of gravity waves for a few years now, they know they extend to infinity but they also experienced that they are so week that it seems impossible to convincingly detect them yet.
What they did find however, is a way to accommodate in their equations the rectilinear attraction of Newtonian gravity, and warp it to the space-time envisaged by Einstein. In other words, they built the house before they found someone to live in it. Which is a common occurrence in theoretical physics. Think of the neutrino, think of Higgs boson or even of Marie Curie radiations, all suspected and confirmed well before their actual discoveries.
Thus, the undetected gravity waves do exist and, since they exist, they cannot go faster than the velocity of light. Well, the Sun’s light takes eight minutes to reach the Earth therefore...
No one can seriously imagine what will happen when the light of our Sun goes out. But I can tell you for certain that whomever inhabits this planet at that time, will have an eight minutes respite before it spins out of orbit, lock stock and barrel, into the freezing sidereal abysm.
Isn't this one a happy news?