How many atoms are there in (and on) the Earth?

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

23 August 2020

The name of the Internet search engine, Google, was coined as a corruption of the word googol. A googol is a very large number: the digit 1, followed by 100 zeros! Perhaps the founders had a vision of having googols of visitors to their site…or to make googols of money. We may never know!

But who needs such a large number as a googol? What on Earth would they be counting? It turns out that there is nothing in or on the Earth that comes in such a large number.

The mass of our planet is about 6,000,000,000,000,000,000,000,000kg; that is 6 followed by 24 zeroes or six million, million, million, million kilograms! But that’s very, very small compared to a googol: it is 76 zeroes short!

We may take this further and try to count all the atoms that make up our planet. The top five, most abundant elements account for over 95 per cent of the Earth’s mass. They are: Iron (32per cent), Oxygen (30pc), Sulfur (15pc), Magnesium (15pc) and Silicon (3pc).

These atoms have similar average mass. A kilogram of each of the elements has about 100,000,000,000,000,000,000,000,000 atoms. This is a number with 26 zeroes.

If we multiply this number by the mass (kilograms) of the planet, we get a rough idea of how many atoms there are in the Earth. The calculation is easy: we simply add the 24 zeroes in the mass to the 26 in the number of atoms per kilo. The answer is 50 zeroes.

That is, the total count of all the atoms that make up the entire planet Earth is a number that has 50 zeroes. Still; this is very small compared to a googol!

You might be tempted to think that we are half-way there; after all, a googol has 100 zeroes while number of atoms in the Earth has 50 zeroes. But you would be very wrong!

Think about it this way: the number one thousand (1,000) has 3 zeroes and one million (1,000,000) has 6. Now, 3 is a half of 6; but is one thousand a half of one million? Of course not!