Why do we have only one sun and moon on planet earth , while there are more than one sun on other planets ? Is there a possibility that one day in the future we might have another sun or moon on planet Earth ?
I'm asking for the sake knowing . These questions came into my mind today when i was reading one Astronomy book . I'm really interested in these questions and believe that there no which is foolish . I will quote from Einstein who say " The most important thing is never to stop questioning " .
Daveb's answer is actually the correct one, although phrased somewhat jokingly.
It turns out that there is no reason why it must be the case that there is only one sun and one moon, but it also turns out that both features lead to great stability of the Earth's biosphere, which is of course conducive to life. In a double star system, for example, general system dynamics are much more complicated than in a single star system, and often have highly eccentric orbits, or those which are otherwise outside the habitable zone.
The chance of the Earth acquiring an extra moon is basically zero. The Earth's current moon was formed by a collision with a mars-sized object, and we know that there are no objects in the solar system with that mass which could potentially impact us. We could, I suppose, capture a small asteroid at some time in the future, but certainly something orders of magnitude smaller than the moon (the kind of thing which would be only visible as a bright star in the night sky).
With regards to acquiring another sun, this is even less likely. It certainly is possible that sometime in the future the sun will interact gravitationally with another star, perhaps forming a bound system. However, in this event, the Earth will almost certainly be flung out into interstellar space.