Gravity. Score decreases over time, so interesting news bubble up, and older/no-longer-relevant news gradually decline. (= gravity* 1.8 timebase* 120 fron

Gravity. Score decreases over time, so interesting news bubble up, and older/no-longer-relevant news gradually decline. (= gravity* 1.8 timebase* 120 front-threshold* 1 nourl-factor* .4 lightweight-factor* .17 gag-factor* .1) (def frontpage-rank (s (o scorefn realscore) (o gravity gravity*)) (* (/ (let base (- (scorefn s) 1) (if (> base 0) (expt base .8) base)) (expt (/ (+ (item-age s) timebase*) 60) gravity)) (if (no (in s!type 'story 'poll)) .8 (blank s!url) nourl-factor* (mem 'bury s!keys) .001 (* (contro-factor s) (if (mem 'gag s!keys) gag-factor* (lightweight s) lightweight-factor* 1)))))