oomis This is the fourth of four lunar eclipses in a years time which is called a blood moon tetrad. A tetrad is very rare. I believe there have been only 7 tetrads in the last 2000 years. that sounds contradictory. Is a tetrad rare or not?
oomis This is the fourth of four lunar eclipses in a years time which is called a blood moon tetrad. A tetrad is very rare. I believe there have been only 7 tetrads in the last 2000 years. that sounds contradictory. Is a tetrad rare or not?