[XorNot]

Isn't the point closer to, humans simply go "hey that seems to be taking a little long?" when a program doesn't halt, so why couldn't a machine? Basically a fairly obvious constraint on the solution space is "completes in less then N wall-clock time".

[roywiggins]

You can definitely detect a portion of halting machines this way, but it's probably a relatively small portion because the Busy Beaver numbers grow inconceivably quickly: the longest-running machines that halt can go practically forever, you'd need more time than the universe has negentropy left to detect them.