MadSci Network: Physics

Re: I was wondering exatly how many particles there are in the world?

Date: Mon Dec 7 16:44:20 1998
Posted By: Tye Morancy, Grad student/Teaching Asst. Physics and Radiology, UMASS Lowell/Radiation Tech. Harvard Univ. EH&S
Area of science: Physics
ID: 912569223.Ph


      That's a tough one, but I'm up for the challenge.  I'm assuming that 
you are looking for the number of particles, in the sense of "atoms", 
which make up our world.  This calls for us to first throw out some facts 
about the planet so that we can go about calculating a number which is 

      The earth is made up of five parts, or layers so to speak.  
          1) The Atmosphere, which is gaseous.
          2) The Hydrosphere, which represents that part of the earth 
             which is liquid water, such as the lakes, seas, and oceans.
          3) The Lithosphere, which is the uppermost crust of the earth,
             which is the layer that you are standing on.
          4) The Mantle, which is the layer of rock and metal beneath the
          5) The Core, which is the very hot center of the planet made of
             iron and crystals.

      I performed several calculations for each layer based on the 
materials in them, their thickness, volume, and density, which I will 
explain as we go.  So, let's take it in parts and see what we get for our 
final number of "particles".

      The atmosphere is the gaseous envelope which surrounds the solid and 
liquid body of the planet.  The atmosphere is about 700 miles thick and 
most of all the air is concentrated in the bottom 3.5 mile thickness.  The 
gases within it are mostly Nitrogen and Oxygen, which we breathe.  I 
calculated the volume of the air and then approximately how many atoms 
that turns out to be.  The number of atoms comes out to :

             1.112 x10^46 atoms

      The Lithosphere is made mostly of the cold, rocky crust of the earth 
which goes down below your feet to a depth of 60 miles.  This layer is 
made up of mostly 11 elements : oxygen, silicon, aluminum, iron, calcium, 
sodium, potassium, magnesium, titanium, hydrogen, and phosphorous.  These 
11 elements are all mixed up within different compounds in a crystal form, 
so that we can call them minerals.  Taking all of this and some other 
factors into consideration, we get :
             3.406 x10^42 atoms

      The Hydrosphere is the layer of water which covers about 71% of the 
earth's surface.  This layer is the combination of rivers, seas, lakes, 
underground water, and all the world's oceans. The average depth of the 
oceans is 12,447 feet and their combined mass is 1.35 quintillion tons.  
From this and other data we calculate :

             4.517 x10^46 atoms

      The Mantle is just below the Crust and is much more dense.  The 
Mantle is 1800 miles thick and is mostly solid, made up of iron and other 
minerals.  For this layer we calculate a value of :

             4.434 x10^43 atoms

      The Core is the center part of the earth and is actually divided 
into an outer core and inner core.  The outer core is 1380 miles thick and 
is 3 times more dense than the mantle above it.  This layer is made mostly 
of iron and a little bit of nickel.  From this we can calculate the number 
of atoms to be :

             1.672 x10^43 atoms

       The inner core is even more dense and is lies at the very center.  
This last layer is 800 miles thick and is solid iron.  The temperature is 
very high there and may be as hot as 12,000 degrees Fahrenheit.  Phew!!!
The number of atoms that I get for this last section is :

             9.003 x10^46 atoms

       So, now that we figured out all the pieces we can add them all up 
to get the total number of atoms or "particles", which make up the earth 
from the center all the way out to the edge of the atmosphere.  The total 
number of atoms which make up the earth is :

             1.1185 x10^46 atoms

       That is another way of saying 11,185 billion, billion, billion, 
billion, million atoms!  That's quite alot don't you think?!  The entire 
earth weighs 6 thousand, billion, billion tons!!!

       As a comparison, you could also look at the earth in terms of the 
number of nucleons instead of atoms.  Nucleons are the "particles" which 
make up the nuclei of atoms and most often are called either protons or 
neutrons.  They weigh pretty much the same as each other and are what make 
up the nucleus, which is where most of the mass of the atom sits.  Since, 
for every atom, there are at least 2 or more nucleons, our number should 
be much bigger.  If you could look at atoms with your eye you would see 
that they all have different numbers of nucleons (just look at a periodic 
table to see...).  A hydrogen atom has 2 of them, an iron atom has 56 of 
them, and something heavy like uranium, has about 238 of them.  The 
earth's center is where alot of the mass is, and it has all kinds of heavy 
elements like these.  So, if we take all of these differences under 
consideration, we can calculate the number of "particles" in terms of 
nucleons.  The number that we calculate is :

           3.5847 x10^51  nucleons

       That is another way of saying 3.6 million, billion, billion, 
billion, billion, billion nucleons!  The smaller we go in size of our 
particles, the bigger the number gets.  
I hope this helped you out...

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