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Golden Boar science forum Guru
Joined: 17 May 2005
Posts: 651

Posted: Sun Apr 23, 2006 5:46 pm Post subject:
Re: About mass  the resistance to movement



PD wrote:
Quote:  Golden Boar wrote:
PD wrote:
Golden Boar wrote:
PD wrote:
Golden Boar wrote:
Old Man wrote:
"Golden Boar" <goldenboar@hotmail.com> wrote in message
news:1145553961.100384.313320@v46g2000cwv.googlegroups.com...
... An object moving through the air will experience drag. As
the speed of the object increases, the drag it experiences will
increase as well.
It is similar with a particle moving through spacetime. As it's
speed is increased, the resistance to movement is also
increased ...
Erroneous analogy, sloppy language. "resistance" implies energy
loss. In the case of a particle in free space, there is no "resistance
to movement". The energy and momentum of the particle are
conserved. Under acceleration, the particles momentum increases,
but it's mass is invariant.
Mass is resistance to movement. Are saying is that a particle in free
space has no mass? According to special relativity, as the speed of a
particle increases, so does it's mass. Rest mass is said to be
invariant, but has anyone actually brought anthing to rest?
There is no "résistance" to acceleration, no loss of energy.. The
work energy required to accelerate the particle goes to the
relativistic kinetic energy of the particle.
Yes there is, it is called mass. If there was no resistance to
acceleration, then an object given an initial acceleration would
continue to accelerate indefinitely.
That's not what mass does.
The time that an object accelerates is set not by the mass, but by the
time the net force is available. That's what F=ma means. When F stops,
so does a. The mass has nothing to do with it.
The equation is F=ma not F=a.
:>)
Here m is constant. If F increases, so does a. If F goes to zero, then
a goes to zero. For a given nonzero value of F, no value of m can make
a go to zero.
I am not saying that it can. What gave you that impression?
What the mass does it is tell you the proportion of acceleration to the
force. E.g. if m = 7, then you will get 1 part acceleration for 7 parts
force applied. If m = 21, then you will get 1/3 part acceleration for 7
parts force applied. That's all it means.
In other words, the mass is resisting acceleration.
If you like. But again, there is no value of m that will cancel that
force. There is no value of m that will stop acceleration from
happening further if F is still there.
Reist does not mean stop.
If the force is there indefinitely, then the acceleration will be there
indefinitely. There is a caveat. F=ma is a formula that only works at
low speeds, if m is taken to be the rest mass of an object. There are
two ways to fix this to be more general. The antiquated way is to say
that m increases as the speed increases, so that m is no longer the
rest mass. The better way to fix this is to write the equation as
Newton originally described it: F = dp/dt. Here, p = (gamma)(beta)m*c
for an object of nonzero rest mass. In this form, the law works
perfectly instead of as a lowspeed approximation.
Does this help?
PD
And what does the Lorentz factor do, if not change the value of m?
It is part of the *momentum*. Newton's 2nd law as he described it is
F=dp/dt
and p is (gamma)(beta)m*c.
That (gamma) is the Lorentz factor you talked about, and m doesn't
change.
The lorentz factor is used to alter time, length, and mass. In the
above equation it is used to alter the mass.
Actually, this interpretation of "mass" is now considerably out of
date. Mass is taken these days to mean the invariant quantity m, not
the "relativistic mass" (gamma)*m.
What have you been reading that gave you bad information about this?
It's common sense. The Lorentz factor is used in calculating the
relativistic mass. Here we have the Lorentz factor and a mass, what
else would it be applied to?
"Relativistic mass" is an old term that was meant only to bridge the
gap between a Newtonian way of thinking and a relativistic way of
thinking.
Rest mass does not exist, as energy packets cannot be brought to rest.
F=ma doesn't apply to "energy packets", if you mean by that what I
think you do.
As you pointed out, the correct equation is not F=ma. By energy packet,
I mean the total energy of an object, be it a particle or a planet. I
use the term 'energy packet' because I have come to realise that rest
mass does not exist.
And how do you arrive at that conclusion?

You answer this question yourself in a later post, which I will address
there.
Quote: 
It is true that the particles momentum, p, is not linear WRT to
its velocity, v. For a given change in the particle's momentum,
delta_p, the change in its velocity, delta_v, is such that
delta_v / delta_p => 0 as v => c
No "resistance" involved: as it's inertia increases without limit,
the particle's velocity approaches c.
[Old Man] 


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Golden Boar science forum Guru
Joined: 17 May 2005
Posts: 651

Posted: Sun Apr 23, 2006 7:54 pm Post subject:
Re: About mass  the resistance to movement



PD wrote:
Quote:  Golden Boar wrote:
PD wrote:
Golden Boar wrote:
When people think of mass, they think of something they can reach out
and touch, but this idea is wrong. Mass is the resistance of an energy
packet to a change in its spacetime coordinates, or , more simply, mass
is resistance to movement.
Actually this is not a particularly inclusive definition of mass. For
example, two colliding photons do not have any resistance to movement,
nor do they have invariant mass individually, but together they *do*
have invariant mass, as evidence by the positronelectron pair that
emerges from the collision and bears the same invariant mass.
Just because the 2 photons can be converted to mass, does not mean that
the photons have mass. You cannot say that 2 photons have mass but a
single photon does not, as that is complete and utter nonsense. So lets
think about this for a second.
Actually, yes you can say two photons have mass but a single photon
does not. Invariant mass is a property of a *system* of objects, and it
is nonadditive; that is, the mass of the system is not necessarily the
sum of the masses of the parts of the system. You may not like this,
but it is true nonetheless.

At one point can you say that the photons gained that mass? Before,
during or after the interaction?
Quote: 
We have 2 energy packets moving towards eachg other, neither of them
feeling any resistance. They then collide with each other. At the
moment they collide, have they felt a resistance to their motion in any
way? If not, then they passed right through each other without any
effect.
I'm not sure what you mean "felt a resistance". Do you mean have they
interacted? Yes. Do they slow down? No.

What I am trying to understand is how that interaction works.
Quote: 
A photon travels through the vacuum of spacetime at the constand speed
of c, the speed of light. All other particles travel through this
vacuum at less than c. This is becuase they have mass, or to put it
more correctly, they have a resistance to movement.
Since mass is the resistance to movement, this explains why there is no
negative mass.
And actually, invariant mass *can* be negative. It's not compatible
with *your* definition of mass, but as I said, your definition is not
particularly inclusive.
Can you give any experimental proof of negative invariant mass?
Sure. Measured resonances in particleparticle scattering have mass
distributions with tails that dip into negative values.

I dont understand what this means, could you explain it in layman
terms?
Quote: 
Relative mass
An object moving through the air will experience drag. As the speed of
the object increases, the drag it experiences will increase as well.
It is similar with a particle moving through spacetime. As it's speed
is increased, the resistance to movement is also increased.
Since a photon's speed is constant, there is no change in its
resistance.
What resistance does a photon have at all? If it has a finite
"resistance" as you've defined it, then a photon should be capable of
being accelerated, since what you're invoking is the mass as defined by
Newton's 2nd law: F=ma.
I did not say that a photon has resistance.
You asked me above if photons encounter resistance in any way when they
collide, presuming that if they don't, then they would pass through
each other without interacting. Well, they do interact. What does that
mean to you?

I am thinking along the lines that the interaction is really the
photons being forced to somehow slow down, which in turn causes them to
gain a finite amount of mass, which means they are no longer photons.
They also pickup an electric charge during the process.
Yes, I said a finite amount of mass, see my new thread "Proof that
photons are not massless!" I came up with the idea as I was answering
this question.
Quote: 
Questions
How do we know that an object at rest has mass if we have never brought
an object to rest?
Consider the value of a linear extrapolation.
Any experimental proof?
Do you require proof of absolute zero (temperature), though it has
never been achieved? (The latter being forbidden by the 3rd law of
thermodynamics.)

If you were to tell me that someting has a temperature of absolute
zero, then damn right I would require proof, wouldn't you?
The fact that a temperature of absolute zero is forbidden, implies that
rest mass is also forbidden, since nothing can be brought to rest. To
use rest mass is therefore illogical.
Quote: 
Recent ideas about the vacuum suggest that it is not empty after all,
but filled with virtual particles, quantum fluctuations, etc. Could
these act like air molecules causing drag, to give rise to an increase
in relative mass?
When an object approaches the speed of light, time runs slower for that
object.
Not sure what you mean by that. Be *very careful* about overly shallow
popularizations of SR here.
Could a particle capture virtual particles and therby increase in mass.
The faster the particle was moving, the more virtual particles it would
come into contact with.
Interesting guess, but that's not what happens.

Then can you tell me what does happen?
Quote: 
Does this mean that a photon does not travel through the time
dimension? If so, could it be that travelling through the time
dimension gives an object mass?
PD 


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Golden Boar science forum Guru
Joined: 17 May 2005
Posts: 651

Posted: Sun Apr 23, 2006 8:01 pm Post subject:
Re: About mass  the resistance to movement



Materion wrote:
Quote:  Golden Boar wrote:
When people think of mass, they think of something they can reach out
and touch, but this idea is wrong.
Yes, you are right. Something you can reach out and touch is what we
call *matter*, not *mass*.
Mass is the resistance of an energy
packet to a change in its spacetime coordinates, or , more simply, mass
is resistance to movement.
Well, I should say mass is a coefficient characterizing the inertia of
an energy packet (resistance to change of motion).
...
Relative mass
An object moving through the air will experience drag. As the speed of
the object increases, the drag it experiences will increase as well.
It is similar with a particle moving through spacetime. As it's speed
is increased, the resistance to movement is also increased.
Since a photon's speed is constant, there is no change in its
resistance.
That seems to me a bit confusing. Maybe it is useful to reformulate it
replacing *resistance to movement* by *resistance to change of
movement*.

I did actually mean 'resistance to a change in motion'.
Quote: 
Questions
How do we know that an object at rest has mass if we have never brought
an object to rest?
Mass being the resistance to change of motion, it is unnecessary to
bring it at rest in order to measure its mass.

The point I was trying to make is that an object cannot be brought to
rest, and therefore the concept of rest mass does not make any sense.
Quote: 
Recent ideas about the vacuum suggest that it is not empty after all,
but filled with virtual particles, quantum fluctuations, etc. Could
these act like air molecules causing drag, to give rise to an increase
in relative mass?
This is a suggestive idea, with similarities for the Higgs field.
Another suggestive phenomenon in that trend is the effect of chattering
collisions on the selfdiffusion of particles.

I'd never heard of this before. I was just thinking out loud. I'll
definitely have to look into this.
Quote: 
A chattering collision is a collision where the particles collide more
than once in the collision process. When the particles have structure
(non spherical and non pointlike particles), the particles may collide
successively at different points of the structure before separating.
The number of *chatters* depends on the mutual configuration and on the
spinning frequency of each particle. These processes are quite
complicated to analyze and research in this field is therefore
embryonic. I could recommend A. Mukoyama and Y. Yoshimura :
Hundreds of collisions between two hard needles (1997,
http://www.iop.org/EJ/abstract/03054470/30/19/009).
Effect of chattering collisions on the selfdiffusion coefficient of a
dilute gas composed of infinitely thin hard needles (2001 :
www.iop.org/EJ/abstract/03054470/34/19/307).
However, some simple things may be said about chattering collisions for
particles with a simple structure. For freely spinning rectilinear
particles, like needles or arrows, the duration tc of the chattering
process is proportional to the angular spinning frequency omega: tc ~
omega. If we shoot an energetically spinning needle through a
background field of all pervading needles, the needle travels at
constant speed from chattering collision to chattering collision,
experiencing an inertial effect of mean duration tc at each collision.
The duration tc then denotes a measure of that inertial effect, which
we could suggestively denote by m.
The question is then, how do omega and m relate? A solution may be
given if we realize that the energetically spinning needle traces a
nearly helical surface. The interaction points between the chattering
spinning needle and background needle are therefore localized on that
helical surface and outline a Brownian path on that surface. The
chattering process ends when the path runs out of the surface.
Therefore tc=m is also :
 proportional to the length of the needle, which we suggestively
denote by h.
 inversely proportional to the mean area per unit time that these
points delimitate on the helical surface = square of separating
velocity, which we suggestively denote by c^2.
With our very suggestive notation , we then have for the inertial
effect of spinning needles colliding with background needles :
h * omega / c^2 = m.
When an object approaches the speed of light, time runs slower for that
object. Does this mean that a photon does not travel through the time
dimension? If so, could it be that travelling through the time
dimension gives an object mass?
What do you mean by travelling through time? If that means running
through a sequence of processes or periods, then there is no difference
between a massless and a ponderable object. Louis Savain has some
thoughtful ideas about timetravelling :
http://www.rebelscience.org/Crackpots/notorious.htm

Idid not mean timetravel. If for an object, time slows down as it
speed it increased towards c, then I just thought it logical that at a
speed of c, we would get t=0.
Quote: 

Arjen Dijksman
*the mass of a body is a measure of its energycontent* (Einstein,
1905).
More on inertia at http://materion.free.fr 


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PD science forum Guru
Joined: 03 May 2005
Posts: 4363

Posted: Sun Apr 23, 2006 8:14 pm Post subject:
Re: About mass  the resistance to movement



Golden Boar wrote:
Quote:  PD wrote:
Golden Boar wrote:
PD wrote:
Golden Boar wrote:
When people think of mass, they think of something they can reach out
and touch, but this idea is wrong. Mass is the resistance of an energy
packet to a change in its spacetime coordinates, or , more simply, mass
is resistance to movement.
Actually this is not a particularly inclusive definition of mass. For
example, two colliding photons do not have any resistance to movement,
nor do they have invariant mass individually, but together they *do*
have invariant mass, as evidence by the positronelectron pair that
emerges from the collision and bears the same invariant mass.
Just because the 2 photons can be converted to mass, does not mean that
the photons have mass. You cannot say that 2 photons have mass but a
single photon does not, as that is complete and utter nonsense. So lets
think about this for a second.
Actually, yes you can say two photons have mass but a single photon
does not. Invariant mass is a property of a *system* of objects, and it
is nonadditive; that is, the mass of the system is not necessarily the
sum of the masses of the parts of the system. You may not like this,
but it is true nonetheless.
At one point can you say that the photons gained that mass? Before,
during or after the interaction?

No, they did not *gain* the mass. The two photon system has a mass as
long as those two photons are in existence, even though the individual
photons do not have a mass, and even though there is *nothing else*
present in the system that contains that mass. Again, mass is NOT the
sum of the masses of the components of the system.
Quote: 
We have 2 energy packets moving towards eachg other, neither of them
feeling any resistance. They then collide with each other. At the
moment they collide, have they felt a resistance to their motion in any
way? If not, then they passed right through each other without any
effect.
I'm not sure what you mean "felt a resistance". Do you mean have they
interacted? Yes. Do they slow down? No.
What I am trying to understand is how that interaction works.

See my responses to John (ma1ibu) elsewhere in this thread. If that
doesn't make any sense to you, then you're trying to leap too far ahead
without benefit of the basics  sort of like attempting brain surgery
without any training in anatomy.
Quote: 
A photon travels through the vacuum of spacetime at the constand speed
of c, the speed of light. All other particles travel through this
vacuum at less than c. This is becuase they have mass, or to put it
more correctly, they have a resistance to movement.
Since mass is the resistance to movement, this explains why there is no
negative mass.
And actually, invariant mass *can* be negative. It's not compatible
with *your* definition of mass, but as I said, your definition is not
particularly inclusive.
Can you give any experimental proof of negative invariant mass?
Sure. Measured resonances in particleparticle scattering have mass
distributions with tails that dip into negative values.
I dont understand what this means, could you explain it in layman
terms?

It would take some effort. Since it is a substantial topic, I suggest
you create a new topic with the title "How is the mass of a shortlived
particle measured?" I will look for it there.
Quote: 
Relative mass
An object moving through the air will experience drag. As the speed of
the object increases, the drag it experiences will increase as well.
It is similar with a particle moving through spacetime. As it's speed
is increased, the resistance to movement is also increased.
Since a photon's speed is constant, there is no change in its
resistance.
What resistance does a photon have at all? If it has a finite
"resistance" as you've defined it, then a photon should be capable of
being accelerated, since what you're invoking is the mass as defined by
Newton's 2nd law: F=ma.
I did not say that a photon has resistance.
You asked me above if photons encounter resistance in any way when they
collide, presuming that if they don't, then they would pass through
each other without interacting. Well, they do interact. What does that
mean to you?
I am thinking along the lines that the interaction is really the
photons being forced to somehow slow down, which in turn causes them to
gain a finite amount of mass, which means they are no longer photons.
They also pickup an electric charge during the process.

No, this doesn't happen. The experimental results are inconsistent with
that "model".
Quote: 
Yes, I said a finite amount of mass, see my new thread "Proof that
photons are not massless!" I came up with the idea as I was answering
this question.

OK.
Quote: 
Questions
How do we know that an object at rest has mass if we have never brought
an object to rest?
Consider the value of a linear extrapolation.
Any experimental proof?
Do you require proof of absolute zero (temperature), though it has
never been achieved? (The latter being forbidden by the 3rd law of
thermodynamics.)
If you were to tell me that someting has a temperature of absolute
zero, then damn right I would require proof, wouldn't you?
The fact that a temperature of absolute zero is forbidden, implies that
rest mass is also forbidden, since nothing can be brought to rest. To
use rest mass is therefore illogical.

Not necessarily. Absolute zero is an *asymptote*, which means you can
get as close as you want to it, but you can't get right on it.
Mathematically, it's a little like the series
1 + 1/2 + 1/4 + 1/8 + .... Here, the infinite sum is *exactly* 2 and we
know that it's 2, even though the sum of any finite number of terms
will be shy of 2.
For temperature, this does not negate the fact that absolute zero as a
strict limit exists and is well defined, even though there is no
physical system that sits at absolute zero.
Likewise, a rest mass exists and is perfectly welldefined, even though
no single particle will ever be found completely at rest. It is not
illogical to use and to calcluate with.
Quote: 
Recent ideas about the vacuum suggest that it is not empty after all,
but filled with virtual particles, quantum fluctuations, etc. Could
these act like air molecules causing drag, to give rise to an increase
in relative mass?
When an object approaches the speed of light, time runs slower for that
object.
Not sure what you mean by that. Be *very careful* about overly shallow
popularizations of SR here.
Could a particle capture virtual particles and therby increase in mass.
The faster the particle was moving, the more virtual particles it would
come into contact with.
Interesting guess, but that's not what happens.
Then can you tell me what does happen?

Only in a rough sketch. Unfortunately, this is not a topic that can be
learned in detail without doing a lot of prerequisite work to do the
basics. There is, unfortunately, no shortcut.
PD
Quote: 
Does this mean that a photon does not travel through the time
dimension? If so, could it be that travelling through the time
dimension gives an object mass?
PD 


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Materion science forum beginner
Joined: 06 Apr 2006
Posts: 9

Posted: Mon Apr 24, 2006 7:23 pm Post subject:
Re: About mass  the resistance to movement



Golden Boar wrote:
Quote:  Materion wrote:
Mass being the resistance to change of motion, it is unnecessary to
bring it at rest in order to measure its mass.
The point I was trying to make is that an object cannot be brought to
rest, and therefore the concept of rest mass does not make any sense.

Rest (zero velocity wrt another object) being a relative notion, you
can say indeed that an object is never at rest, but you can also say
the contrary: every object is at rest with respect to its own
referential (not necessarily inertial). For example, a photon A,
following another photon B on the same path, is at rest wrt that photon
B. The remanent energy content of the photon in that framework divided
by c^2 is called *rest mass*. I admit the denomination *rest mass* is
not a very good choice. However, the concept *rest mass* makes sense in
the light of Einstein's definition : the mass of a body (or a photon)
is a measure of its energy content.
Quote:  Another suggestive phenomenon in that trend is the effect of chattering
collisions on the selfdiffusion of particles.
I'd never heard of this before. I was just thinking out loud. I'll
definitely have to look into this.

Well, I also have never heard anyone calling attention on the analogy
between chattering collisions and inertia. We'll have to make up our
minds for ourselves on this phenomenon;)

Arjen Dijksman

Materion physics, the search for a satisfactory explanation of natural
phenomena at http://materion.free.fr 

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