Hello,

Does Newton's third law, that says that every force has an equal and
opposite counter force, still applies in Special Relativity?
From Principia, by Isaac Newton (translated by Andrew Motte) page

Hello,

Does Newton's third law, that says that every force has an equal and
opposite counter force, still applies in Special Relativity?

equations are technically in contradiction.

Maxwell's equations and Newton's Laws are in logical
contradiction. Newton's Laws were stated in the present tense as
though forces are instantaneous, but in actuality forces propagate at
a finite speed. I think this contradiction preceded special
relativity. I suspect that this contradiction lead to relativity.
Special relativity started as a means of modifying Newton's Laws so
that there is no logical contradiction.

Darwin123 wrote:

Newton and Maxwell's

equations are technically in contradiction.

Maxwell's equations and Newton's Laws are in logical
contradiction. Newton's Laws were stated in the present tense as
though forces are instantaneous, but in actuality forces propagate at
a finite speed. I think this contradiction preceded special
relativity. I suspect that this contradiction lead to relativity.
Special relativity started as a means of modifying Newton's Laws so
that there is no logical contradiction.

Newton's Laws are not Lorentz Invariant. Therefore they are wrong.

Bob Kolker

On Apr 6, 11:29 am, "Robert J. Kolker" <bobkol...@comcast.net> wrote:



Darwin123 wrote:

Newton and Maxwell's

equations are technically in contradiction.

    Maxwell's equations and Newton's Laws are in logical
contradiction. Newton's Laws were stated in the present tense as
though forces are instantaneous, but in actuality forces propagate at
a finite speed. I think this contradiction preceded special
relativity. I suspect that this contradiction lead to relativity.
Special relativity started as a means of modifying Newton's Laws so
that there is no logical contradiction.

Newton's Laws are not Lorentz Invariant. Therefore they are wrong.

Bob Kolker

       I was pointing out WHY Newton's Laws are not consistent with
special relativity. In particular, Newton's Laws are not Lorentz
invariant. However, I don't think this is immediately obvious even to
somebody with a mathematical background. I myself was a little
confused on this point for a while. There is no explicit constraint on
the form of the force laws in Principia. If a force law is Lorentz
invariant, can't one simply use Newtons Laws to calculate the results?
The answer is that there is no Lorentz invariant force law that is
consistent with Newton's Laws.
     A nonmathematical way to show that Newton's Laws are not
consistent with special relativity is simply to look carefully at the
sentences in Principia. They are all in present tense. In other words,
only instantaneous forces are allowed in Principia. Therefore, one
can't have a "force field" with a "finite propagation velocity."
      The question was at heart historical, although phrased in an
offensive way. I interpreted his question as meaning this, aside from
the jealous attacks on Einstein. The question is, "Why in the days
before Einstein didn't scientists merely modify the force laws
describing the Michaelson Morley experiment in such a way as to
explain the experimental results?"
     I conjectured that the reason is that Newton's Laws and Maxwell's
equations are logically inconsistent. I pointed out where the
inconsistency is in Principia. There are several statements made both
by H. A. Lorentz and A. Einstein that pointed me to that conjecture,
but I honestly can't be 100% sure that this is relevant.
     I see ad hominum statements as a cry for help. Calling Einstein
stupid is a desperate plea by a scientific illiterate clarification on
a misunderstood point that irritates his or her learning disability. I
try relieve the inner conflict by providing a historical conjecture
that will help him or her make sense of a world that is beyond their
feeble comprehension.

On Apr 7, 3:08 am, Darwin123 <drosen0...@yahoo.com> wrote:



On Apr 6, 11:29 am, "Robert J. Kolker" <bobkol...@comcast.net> wrote:

Darwin123 wrote:

Newton and Maxwell's

equations are technically in contradiction.

Maxwell's equations and Newton's Laws are in logical
contradiction. Newton's Laws were stated in the present tense as
though forces are instantaneous, but in actuality forces propagate at
a finite speed. I think this contradiction preceded special
relativity. I suspect that this contradiction lead to relativity.
Special relativity started as a means of modifying Newton's Laws so
that there is no logical contradiction.

Newton's Laws are not Lorentz Invariant. Therefore they are wrong.

Bob Kolker

I was pointing out WHY Newton's Laws are not consistent with
special relativity. In particular, Newton's Laws are not Lorentz
invariant. However, I don't think this is immediately obvious even to
somebody with a mathematical background. I myself was a little
confused on this point for a while. There is no explicit constraint on
the form of the force laws in Principia. If a force law is Lorentz
invariant, can't one simply use Newtons Laws to calculate the results?
The answer is that there is no Lorentz invariant force law that is
consistent with Newton's Laws.
A nonmathematical way to show that Newton's Laws are not
consistent with special relativity is simply to look carefully at the
sentences in Principia. They are all in present tense. In other words,
only instantaneous forces are allowed in Principia. Therefore, one
can't have a "force field" with a "finite propagation velocity."
The question was at heart historical, although phrased in an
offensive way. I interpreted his question as meaning this, aside from
the jealous attacks on Einstein. The question is, "Why in the days
before Einstein didn't scientists merely modify the force laws
describing the Michaelson Morley experiment in such a way as to
explain the experimental results?"
I conjectured that the reason is that Newton's Laws and Maxwell's
equations are logically inconsistent. I pointed out where the
inconsistency is in Principia. There are several statements made both
by H. A. Lorentz and A. Einstein that pointed me to that conjecture,
but I honestly can't be 100% sure that this is relevant.
I see ad hominum statements as a cry for help. Calling Einstein
stupid is a desperate plea by a scientific illiterate clarification on
a misunderstood point that irritates his or her learning disability. I
try relieve the inner conflict by providing a historical conjecture
that will help him or her make sense of a world that is beyond their
feeble comprehension.

Darwin123, you have not explained the most important part.

The reason I was confused over this is because of the conservation of
momentum. Assume you're right, and the third law doesn't hold. Observe
this. Momentum is conserved in Special Relativity. Momentum remains a
constant. Force is the change of momentum over time. Therefore, the
total force must always be zero. But that would mean that for every 2-
body system, Newton's third law WILL hold. So how do you explain that?

Ram.

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"Robert J. Kolker" <bobkol...@comcast.net> wrote in messagenews:pPqdnTx62_sicWXanZ2dnUVZ_oWdnZ2d@comcast.com...| Darwin123 wrote:

| Newton and Maxwell's
| > equations are technically in contradiction.
|
| >     Maxwell's equations and Newton's Laws are in logical
| > contradiction. Newton's Laws were stated in the present tense as
| > though forces are instantaneous, but in actuality forces propagate at
| > a finite speed. I think this contradiction preceded special
| > relativity. I suspect that this contradiction lead to relativity.
| > Special relativity started as a means of modifying Newton's Laws so
| > that there is no logical contradiction.
|
| Newton's Laws are not Lorentz Invariant. Therefore they are wrong.
|

Newton's Laws are not Lorentz Invariant. Therefore they are right, crank.

On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:
The reason I was confused over this is because of the conservation of
momentum. Assume you're right, and the third law doesn't hold. Observe
this. Momentum is conserved in Special Relativity. Momentum remains a
constant. Force is the change of momentum over time. Therefore, the
total force must always be zero. But that would mean that for every 2-
body system, Newton's third law WILL hold. So how do you explain that?

Newton's 3 laws of motion can be summarised as "momentum is conserved",
with a definition of force thrown in for good measure. Sounds nicely
compatible with special relativity (given some care in what the derivative
in the rate of change of momentum in the definition of force is taken
w.r.t.).

What is incompatible between Newton and SR are: (a) Newton's definition of
mass, as the quantity of matter, vs SR magnitude of the energy-momentum
4-vector, (b) Newton's definition of momentum, and (c) if you include it
as part of Newtonian dynamics, Newton's law of universal gravitation.

In SR, there are no separated 2-body systems with forces. If the 2 bodies
are separated, and there is a force acting between them, it's mediated by
a field, and this field can transport energy and momentum. For 2-body
systems where the bodies only interact when in contact, Newton's 3rd will
be fine. For separated 2-body+field systems, it'll work too, if you assume
that you can exert a force on a field, defined by Newton's 2nd.

I don't think a field, or even a little piece of a field, can be

The reason I was confused over this is because of the conservation of
momentum. Assume you're right, and the third law doesn't hold. Observe
this. Momentum is conserved in Special Relativity. Momentum remains a
constant. Force is the change of momentum over time. Therefore, the
total force must always be zero. But that would mean that for every 2-
body system, Newton's third law WILL hold. So how do you explain that?

On Mon, 7 Apr 2008, Darwin123 wrote:
On Apr 7, 4:41 pm, "Timo A. Nieminen" <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:

Rather, one would use Maxwell's equations (etc) to obtain the same result
as Newton's laws (see further below), in an appropriate limit.
Key qualifier: In the appropriate limit. Maxwell's equations are

Probably the best way to approach this would be via Lagrangian field
theory, given that we know the equivalence between the Lagrangian
formulation of classical dynamics and Newtonian mechanics.
Yes, there are relativistic Lagrangians which describe a charged

On Apr 7, 4:41 pm, "Timo A. Nieminen" <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:
The reason I was confused over this is because of the conservation of
momentum. Assume you're right, and the third law doesn't hold. Observe
this. Momentum is conserved in Special Relativity. Momentum remains a
constant. Force is the change of momentum over time. Therefore, the
total force must always be zero. But that would mean that for every 2-
body system, Newton's third law WILL hold. So how do you explain that?

Newton's 3 laws of motion can be summarised as "momentum is conserved",
with a definition of force thrown in for good measure. Sounds nicely
compatible with special relativity (given some care in what the derivative
in the rate of change of momentum in the definition of force is taken
w.r.t.).

What is incompatible between Newton and SR are: (a) Newton's definition of
mass, as the quantity of matter, vs SR magnitude of the energy-momentum
4-vector, (b) Newton's definition of momentum, and (c) if you include it
as part of Newtonian dynamics, Newton's law of universal gravitation.

In SR, there are no separated 2-body systems with forces. If the 2 bodies
are separated, and there is a force acting between them, it's mediated by
a field, and this field can transport energy and momentum. For 2-body
systems where the bodies only interact when in contact, Newton's 3rd will
be fine. For separated 2-body+field systems, it'll work too, if you assume
that you can exert a force on a field, defined by Newton's 2nd.

I don't think a field, or even a little piece of a field, can be
thought of as a body in the Principia sense.

Fields obey the laws of
vector addition, while bodies do not.
[cut etc]

Principia is a complete
description of the dynamics of bodies.

One can not use Newtons Laws to describe the behavior of light,
as known in the nineteenth century. If you apply Newton's Third Law to
the electromagnetic field, you get a result that indeed conserves
momentum but doesn't describe diffraction.

The real electromagnetic
field obeys the law of superposition. Therefore, one can't consider
the electromagnetic field a body. But more important, you can't
consider the Third Law of motion to be exactly equivalent to
conservation of momentum.
We can wrangle about whether or not the third law is the same as
momentum conservation.

I just know that H. A. Lorentz was concerned
about the contradictions between mechanics and electromagnetic theory.
He said so.
Obviously, there is some type of gap between Maxwell's equations
and Principia. I am proposing that it shows itself in the language
and diagrams of Principia. Principia seems to contradict Maxwell's
equations. There is no "field" in Principia and no "body" in Maxwell's
equations. Modern physics uses hybrid concepts that were not available
to either Einstein or Lorentz. In fact, they helped develop these
hybrid concepts.
I am not sure of all this. Relativity is an advocation of mine. I
am a physicist working in an unrelated area. If you know how Principia
and Maxwell's equation are compatible, please describe Maxwell's
equations in terms of Newton's Three Laws.

On Apr 7, 8:37 pm, Timo Nieminen <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, Darwin123 wrote:
On Apr 7, 4:41 pm, "Timo A. Nieminen" <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:

Rather, one would use Maxwell's equations (etc) to obtain the same result
as Newton's laws (see further below), in an appropriate limit.

Key qualifier: In the appropriate limit. Maxwell's equations are
still considered more accurate than Newton's Laws. There is no way to
extract a force law consistent with both Maxwell's equations and
Newton's Laws at the same time. As a special limit, sure.

On Mon, 7 Apr 2008, Darwin123 wrote:
On Apr 7, 8:37 pm, Timo Nieminen <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, Darwin123 wrote:
On Apr 7, 4:41 pm, "Timo A. Nieminen" <t...@physics.uq.edu.au> wrote:
On Mon, 7 Apr 2008, ram.rac...@gmail.com wrote:

Rather, one would use Maxwell's equations (etc) to obtain the same result
as Newton's laws (see further below), in an appropriate limit.

    Key qualifier: In the appropriate limit. Maxwell's equations are
still considered more accurate than Newton's Laws. There is no way to
extract a force law consistent with both Maxwell's equations and
Newton's Laws at the same time. As a special limit, sure.

Sure there's a way. See, e.g., Jackson pp 105-108. Once you have the
canonical energy-momentum tensor, you know what the momentum and energy
density of the field is (assuming one can identify the integrands in the
relevant conservation laws with the density of the conserved quantities).
Maxwell's equations tell you how the energy and momentum moves from one
place to another in the field, the Lorentz force tells you the forces
involved in the interaction with matter, and, given that the force
exterted by the field is indeed equal to the rate of loss of momentum of
the field, how can this _not_ be consistent with Newton's laws? Of
course, not consistent with Newton's definition of momentum.

--
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E-prints:http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
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