Brainers
Dr. Art's Math for "What About Meteors?"

The amount of material that has entered the Earth system in the past three billion years is equal to the annual rate times 3 billion years. We divide that amount by the total mass of the Earth to find the percentage. Annual inflow: (300 tons/day) x (365 days/year) = 109,500 = 1.1 x 105 tons/year Total inflow last three billion years: (1.1 x 105 tons/year) x (3 x 109 years) = 3.3 x 1014 tons Mass of Earth in tons: (6 x 1024 kg) X (1 pound/2.2 kg) X (1 ton/2,000 pounds) = 1.4 x 1021 tons Percentage of Earth's mass that has arrived in last 3 billion years: 3.3 x 1014 tons divided by 1.4 x 1021 tons = 2 x 10-7 = 0.0000002 Percentage is that ratio times 100 = 0.00002% DR. ART WAS WRONG! HE SAID LESS THAN 0.00001%. When he was writing the book, he made a mistake in his conversion figures. Still with 0.00002%, we can probably be comfortable saying Earth is essentially a closed system for matter. Back to "What About Meteors?"