Science at Work: Elimination of Possibilities
The description in the left panel
of how it was concluded that Cygnus X-1 is a black hole
illustrates one way in which science works when one is on the frontiers of knowledge.
We cannot be absolutely
certain that Cygnus X-1 is a black hole because the evidence is indirect.
But we can have high
confidence that it is because a careful analysis of all other possibilities makes a black
hole the most plausible explanation.