It is the business of a scientist to speculate, to hypothesize, to think of possible explanations—if not in public, then in the privacy of his own mind. In fact, a scientist cannot help doing so, any more than a writer can keep from thinking of fragments of plot or snatches of dialogue, or a musician can keep from hearing in his mind notes put together into themes and variations.
But when a nonscientist, a member of the general public, encounters scientific speculations, how can he tell whether there is something sound and possible in it or whether it is just nonsense?
It is quite likely that he cannot tell, simply because he lacks the necessary background, knowledge, and experience, any more than he can tell, when he lacks literary or musical talent of his own, whether some tentative literary or musical excursions bear promise of merit or not. He may know whether the writing or music sounds good and pleases him, but his personal taste is not the point at issue. I, for instance, am very fond of the works of Agatha Christie, and yet I strongly suspect they do not represent deathless prose.
In the same way, a scientific theory may please you and may seem in accord with your own feelings and beliefs, but your own pleasure is no proof of its possible validity.
What, then, does one do?
In the first place, one must consider the source. A recognized scientist is far more apt to produce a possibly fruitful piece of speculation than an unknown or an amateur is. Thus Francis Crick has speculated on life having originated on Earth through seeding (intentional or not) by extraterrestrial travelers; and Fred Hoyle has speculated that life can evolve in interstellar dust clouds or on comets and that the latter are the origin of earthly pandemics.