SPOILER ALERT: Do not read if you have not yet seen “Don’t Look Up.”At the beginning of Adam McKay’s “Don’t Look Up,” Michigan State astronomy grad student Kate Dibiasky (Jennifer Lawrence) discovers that a comet is heading toward Earth, and will cause an extinction-level-event for the entire planet in a little over six months: something she duly reports to her professor, Dr. Randall Mindy (Leonardo DiCaprio).