Why A Rock Is Heavy

An Amazing Fact About Matter
By Jim Hartsell, Dec. 30, 2006                            Back to home page

Hold a one-pound rock in your hand.
Why does it feel heavy? You won't believe the reason why!

Matter is made up of atoms that have a nucleus of protons and neutrons, with electrons in orbit around the nucleus. Protons and neutrons are each made up of three quarks. So, matter consists of quarks and electrons.

In one pound of any material (my calculations are below):

Total weight of electrons = .0087 ounce (1/115 ounce).

Total "at rest" weight of quarks = .23 ounce (less than 1/4 ounce).

Total weight of quarks and electrons in one pound = .239 ounce.


It is well known from Einstein's Relativity that when a particle with mass moves faster and faster, it's mass increases. The quarks are whizzing around in the proton and neutron so fast, that ...

The "missing" 15.761 ounces are from the kinetic energy of the quarks!
It is the extra mass taken on by the quarks from the speed they are traveling.

98.5% of the weight of matter is from the energy of motion of the quarks inside protons and neutrons.
In the 2006 Special Edition of Scientific American, "The Frontiers of Physics", there is an article "The Mysteries of Mass" by physicist Gordon Kane. It says "... nearly all the mass of protons and neutrons is from the kinetic energy of their constituent quarks (the remainder is from the quark's rest mass). Thus, almost all the familiar matter around us comes from the energy of motion of quarks in protons and neutrons." My number is 98.5% relativistic mass.

Quarks and electrons are dimensionless points. Their size is zero. Yet they have a tiny bit of mass (I assume with infinite density). Since an atom is all quarks and electrons, an atom is all empty space. But with all the dimensionless points whizzing around, it acts like a hard lump of matter.

100,000 atoms can fit in the width of a human hair.



CALCULATIONS (Feel free to check me.)

The sum of the mass of the three quarks in a proton is about 1/70 the mass of a proton. For our purposes, we can assume for every proton there is one neutron and one electron. Protons have 2 up and 1 down quarks. Neutrons have 1 up and 2 down quarks.
Proton mass = 938.3 MeV/c2. Neutron mass = 939.6 MeV/c2.
(Since E = Mc2, Mass = E/c2. Energy is in millions of electron volts.)
Average mass between a proton and neutron = 938.95 MeV/c2.
Up quark mass = 1.5 - 4 MeV/c2. Let's assume 3 MeV/c2.
Down quark mass = 4 - 8 MeV/c2. Let's assume 6 MeV/c2.
A proton and neutron together have 3 up and 3 down quarks. Average quark mass of the 6 quarks in a proton-neutron pair = (3x3 + 3x6)/6 = (9 + 18)/6 = 4.5 MeV/c2. So, we can assume the total 3-quark mass in a proton or neutron = 13.5 MeV/c2.
(At www2.slac.stanford.edu/wc/theory/quarks.html, it says 20 MeV/c2. They must have taken the high values for quarks in a neutron: 4+8+8=20 MeV/c2. Let's stick with the mid-values.)
Therefore, 938.95 / 13.5 = 69.55, or about 70.
PROTON/NEUTRON MASS IS 70 TIMES MORE THAN THE SUM OF THEIR CONSTITUENT QUARKS. Thus, 3-quark mass is 1/70 the mass of a proton/neutron. Electron mass is negligible, so in 1 pound of material, 16 oz./70 = .228 ounce of quarks.

The mass of an electron is 1/1836 the mass of a proton.
Looking it up in physics books, proton mass is 1836 times electron mass. Since a neutron is a proton plus an electron, for our purposes here we can say that an atom is all protons and electrons. Thus, the sum of all protons is 1836 times the mass of all electrons in the atom. In one pound of material, 16 oz./1836 = .00871 ounce of electrons.


1 keV/c2 = 1.783 x 10-33 kg
1 MeV/c2 = 1.783 x 10-30 kg
1 BeV/c2 = 1.783 x 10-27 kg
mass of up quark = .56 x mass of down quark
proton mass = 1.6726 x 10-27 kg
neutron mass = 1.6749 x 10-27 kg