I'm seeing this in response to an input on swi prolog
% ... 1,000,000 ............ 10,000,000 years later
%
% >> 42 << (last release gives the question)
some sort of in joke I take it but no idea how to proceed?
It's humour that is referencing the Hitch Hiker's Guide the Galaxy. What it means is that your query consisted solely of a variable. This is certainly not what you intended. eg.
?- Foo.
Prolog has no way to unify the variable with any value, and cannot give you a meaningful answer. Though I believe SICStus prolog responds yes and that the variable has not been unified with any value.