Recent content by YooperJohn

  1. YooperJohn

    An astronomer calculated that Earth's intelligent life is probably 'rare.' Here's what that means.

    The article stated "Once atmospheric CO2 drops below 10 parts per million, plants will die off ...." I believe this statement is in error by an order of magnitude. Green (photosynthetic) plant life on this planet dies off when atmospheric CO2 falls below 150 ppm... a much higher concentration...