According to relativity, the difference between relativistic (or kinetic) mass and rest (or invariant) mass is
velocity. If you travel at near-c, your mass increases as a result of an increase in velocity. Had you stayed
on Earth, your mass would have remained more or less the same: what relativists call ‘rest’ mass.
Fortunately, Baez’s Physics FAQ clarifies the differences between these qualifiers ‘once and for all’:

The invariant mass of a particle is independent of its velocity v, whereas relativistic
mass increases with velocity… At zero speed, the relativistic mass is equal to the
invariant mass… For example, when physicists quote a value for ‘the mass of the
electron’ they mean its invariant mass… The invariant mass is therefore often called
the ‘rest mass’ ” 

Relativists are in effect saying that, since the Earth moves at a certain velocity with respect to Jupiter,
your body can be regarded as part of the mass of the Earth. Hence, your dynamic mass with respect to
Jupiter is variable (relativistic mass) whereas your stationary, velocity-free mass with respect to Earth is
not (rest or invariant mass).

But this is not altogether true. Relativists are insinuating that your weight on Earth is a measure of your
‘rest’ or 'invariant' mass, meaning the mass that doesn’t change, because it purportedly doesn’t move,
meaning quantity of matter’ (wink, wink, nudge, nudge). What else can the concept ‘rest’ mass refer to if
not ‘quantity of matter?’ What does the word ‘rest’ refer to from a conceptual point of view if not to a still
image? What do relativists really mean, if not quantity of matter, when they say:

“ The rest mass or invariant mass is an observer-independent quantity.” 

When an object is standing absolutely still, for instance in a photograph, in a single frame of the
Universal Movie, the quantity of matter (i.e., the number of indivisible particles that comprise it) at that
instant has to be fixed (invariant). We are not weighing it or applying any force to measure its inertia. We
are just staring at an object frozen in time. From a conceptual point of view, it has to be constituted by a
certain number of fundamental particles (if as quantum argues particles underlie matter and there is an
indivisible unit of matter). However, not a single m in any equation of Mathematics, whether relativistic,
quantic, or classical, represents the unfathomable notion of quantity of matter. The mass that every
mathematician from Newton onwards used has always been a dynamic quantity known as inertia, a
concept that embodies motion. The way in which we determine inertia is by applying a force to the test
object. Do relativists measure the invariant mass of the electron by counting the number of its
subcomponents? No. They calculate the mass of the electron after taking measurements of parameters
such as force and energy, all of which embody motion.  Then, they compare this measurement against
the variable known as Le Grand.

So, which parameter is it that changes when your weight varies between two static locations (e.g., resting
on a mountain versus resting in the valley)? Is it velocity or the quantity of matter? We know that inertia
has changed because so says the scale and because it now takes a different amount of force to dislodge
you from your position. But which of the constituents of inertia changed?

The change in inertia would seem to be a result of neither velocity nor quantity of matter. What has
changed is the separation between you and the center of Earth or other objects in your vicinity. It isn’t
(dynamic) distance-traveled that has changed. It is just (static) distance. The change in inertia has to do
with gravitational force, and force has two components, one of which is mass (f = m a). This takes us back
to square one. Relativists invoke the word mass to explain why mass changed. (Actually, gravitation is not
a result of force, but of tension.)

Therefore, the problem with relativistic mass is that the explanation is circular. Relativistic mass has a
velocity and a quantity of matter component. Relativists ask you to believe that if you travel at just below c,
your mass increases as a result of velocity. We have no trouble understanding and accepting this
argument. The Vikings already knew that they would have to rush the castle door if they wanted to break it
down. Relativists have not discovered anything new under the Sun. They are just rephrasing the
centuries-old wisdom. It is the other predicament that is unclear, the notion that relativistic mass without
velocity is equal to rest or invariant mass. What is ‘rest’ mass without velocity if we need velocity to
determine rest mass? We need to apply a dynamic force to measure the mass (i.e., inertia) of an object ‘at
rest.’ Force requires acceleration and acceleration embodies velocity.

Relativists insinuate and would like you to think that velocity-free mass is equivalent to quantity of matter.
They attempt to convince you that rest mass is mass without motion (i.e., only quantity of matter):

“ [Rest mass] is just that part of the energy of a body which is not kinetic energy. Mass
is independent of velocity whereas energy is not.” 

However, Taylor and Wheeler just finished knocking down such a preposterous idea. This leaves only one
other possibility. Relativistic mass is simply faster moving mass than rest mass. A couch potato staring at
a TV already has velocity embodied in the gravitational acceleration of Earth.

Does this mean that there is no difference between rest and relativistic mass?

Actually, yes, there is no difference. If you stand absolutely still on the surface of the Moon, your ‘rest’ mass
will be lower than if you stood absolutely still on the surface of Earth. The reason for this is that the Earth is
a larger celestial object than the Moon. Irrespective of where you stand 'still,' you are necessarily farther
away from the center of Earth than from the center of the Moon. The issue of rest versus relativistic mass is
just a matter of degrees (Fig. 1). It doesn’t address any fundamental question of Physics. The differences
simply come down to weight at different gravitational potentials.
 Adapted for the Internet from:Why God Doesn't Exist
 Rest mass is another way relativists have of saying relativistic mass
 Fig. 1   Rest versus relativistic mass

In order to have true, genuine, unadulterated rest mass (i.e., velocity-free mass) we have to deal with
units of matter. If invariant mass is that which doesn’t change irrespective of location, then this term can
refer only to the quantity of matter of an object. However, under this ‘amount of substance’ proposal, we
would not say that 1 gram of mass moved. We would say that 100 units of matter moved. Now there is no
ambiguity in the relativistic versus rest mass debate. If an object travels at near-c and a relativist alleges
that mass increases, from a conceptual point of view, either the number of units comprising it or the speed
of the entire object increases. It can be no other. So which is it going to be?

Taylor and Wheeler answer that the number of units don't increase:

" The concept of `relativistic mass' is subject to misunderstanding... it makes
increase of energy of an object with velocity or momentum appear to be
connected with some change in internal structure of the object." 

Relativists may insist that mass and weight are two different concepts. Weight is affected by its location
with respect to the center of Earth. Mass is not. For example, if Le Grand Kilo is taken to the top of Mount
Everest, its weight changes, but not its internal physical structure. What we did was affect its velocity
component (or potential energy). Or perhaps we changed its relativistic or kinetic mass. Who knows?

This argument has no merit whatsoever. The concept mass embodies both quantity of matter AND velocity
taken as a whole. Inertia is a parameter that is specified without regard to its individual components. The
stupid mathematicians have never devised a method to separate these factors and never will. It is not in
their interest to do so. Quantity of matter is a concept that would irrevocably destroy all contemporary
religions of Mathematical Physics. Hence, whenever the weight of an object is measured anywhere on
Earth, we have measured its mass and still have no clue regarding how much matter it contains or what
its composition is. When the object changes locations, its weight changes but so does its mass because
we determine its mass by measuring its weight. The mathematicians assume that the quantity of matter of
the object remained constant and that what changed was its velocity or distance or energy or whatever,
but they have never figured out a way to isolate quantity of matter! Using the mathematical methods and
definitions in effect today, we cannot say that the mass of the object did not change because, in fact, it did.

Relativists may argue for another two hours that what changed is the distance or the velocity and not the
structure or composition of the test object.

However, we never established the internal structure of the object to begin with! Relativists cannot tell us
how many units of matter an object has before we start the experiment. So, what are relativists referring to
when they say that the internal structure or composition of the object didn’t change? Do they, perchance,
count the number of atoms in Le Grand to come up with the kilo before they take it up the mountain? Do
they determine the mass of the top quark by counting its subcomponents or analyzing its internal
architecture? No. They determined the mass of the top quark by accelerating a particle, smashing it to
pieces, and comparing the weight of the debris (actually the ‘energy’ needed to accelerate the quark) to a
pre-established standard. What is this pre-established standard? Why non other than Old Unfaithful: Le
Grand Kilo! Any way we look at it, we cannot remove velocity from mass if we are going to determine
mass through measurement. There is no such monster as rest mass except in the minds of the stupid
morons of Mathematical Physics!

If, instead, we were privy to the unit of matter, it would be a piece of cake just to aggregate these particles
to express the mass of any object. We could just say that Object A is made of one trillion units of matter
and thus put the relativistic debate on a sound footing. Even a baby understands that a bigger beach
castle requires more sand. It would now be easy to explain whether the SR equation ‘predicts’ that inertia
increases as a result of speed or of more matter. The question before us would be simple. Were more
particles created from the void or does the object just exert more pressure because it is moving faster?
This is what people really want to know. The mathematicians can save themselves the trouble of
explaining what the observer measured because this argument implicitly assumes motion and brushes
aside the crucial ‘quantity of matter’ component. By introducing ad hoc qualifiers such as relativistic and
invariant, the idiots of relativity have not resolved anything. They have simply divided the old concept of
inertia into two more unnecessary categories just to accommodate their theories and to confuse
themselves and their audience. No madam! Yours is not relativistic mass. It is definitely inertial mass! Now please be so kind as to reimburse me for the scale you flattened in my shop!
 Relativistic mass is simply faster moving mass than rest mass. Rest mass embodies the velocity implied by gravitational acceleration (9.8 m/sec2). Relativists cannot sift quantity of matter from rest mass because they determine mass through measurement and not by counting particles. Measurement is a dynamic activity!   ________________________________________________________________________________________