The sun is radiating energy and heat into space and thus loosing its mass day by day. Possibly the energy supply (on which our earth is reliant) from the sun may discontinue in future or after a period of few million years. At last, it may cause uninhabitable conditions on the earth.
The fact that life has an enormous capacity to adapt itself to the changing environments can not help in the long run. The shrinkage of mass may a reduction of the radiation of sun to a tiny fraction of its present amount, transforming our ocean into ice and our atmosphere into liquid air. Consequently, there will be no procession of life on the earth in its present form.
Moreover, the sun decreases in weight by loss of its matte, its gravitational attraction is proportionately diminishing. Therefore, on amount of its decrease in gravitational pull, our planet, like others, is slowly moving away from the sun. This slow recession from the sun may, at some stage, cause collision of the sun with any other body in the universe.
Beyond the normal course of events, the possibility of variety of “accidents” as Sir James Jeans termed them can not be ruled out. The sun may run into another star; any of the stars in the space may wander into the solar system and upset the moments of planets to a fatal extent; any asteroid (a minor planet revolving between the orbits of Mars and Jupiter) may hit any other asteroid.
Although it is believed that the likelihood of such accidents is extremely small, still such a possibility can not be altogether ruled out.
It is observed that some new stars (nova, as they are technically called) burst out suddenly into a terrible brilliance and either fade away or continue to shine as ordinary stars.
Almost all the stars are in danger of bursting into new stars. The sun is star. It has been calculated that the sun is likely to become a nova in the next million years. This sudden bursting up of the sun into a nova will emit tremendous heat and light which will scorch all life on the earth.
In the normal course of events, i.e. if no accident happens, our earth may survive of thousands of millions of years. Sir James Jeans’s states: “looked at in terms of space, the message of astronomy is at best one of melancholy, grandeur and oppressive sadness. Looked at in terms of time, it becomes one of the almost endless possibility and hope.
As inhabitants of the universe we may be living, near its end rather than its beginning; for it seems likely that most of the universe had melted into radiation before we appeared on the scene. But, as inhabitants of the earth, we are living at the beginning of time.
We have come into being in the fresh glory of the dawn, and a day of almost unthinkable length stretches before us with unimaginable opportunities for accomplishment.
We seem to discern that the main message of it is one of the hope to the race and of responsibility, because we are drawing plans and laying foundations for a longer future than we can well imagine on our earth.