Bullwinkle Unbound

"Jim Greenfield" wrote in message
om...
(George G. Dishman) wrote in message
om...
(Jim Greenfield) wrote in message
. com...
I then
suggested that a piece of rock subject to this type of experiment in a
valley should give a different result from an identical piece at the
mountain top-- silence........

Erm, well, yes, I can undertsand that. How do you propose
to store the energy? Is it a springy piece of rock? Why
would it matter where you do the experiment?

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring. Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Thanks George

Pleasure.

George

"George Dishman" wrote in message ...
"Jim Greenfield" wrote in message
om...
(George G. Dishman) wrote in message
om...
(Jim Greenfield) wrote in message
. com...
I then
suggested that a piece of rock subject to this type of experiment in a
valley should give a different result from an identical piece at the
mountain top-- silence........

Erm, well, yes, I can undertsand that. How do you propose
to store the energy? Is it a springy piece of rock? Why
would it matter where you do the experiment?

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Compessing the spring required (work) energy input as well. If gravity
is used to perform the compression, a larger piece of rock is needed
at the top of the mountain than in the valley, as gravity is less at
the higher level. But the same amount of energy (mass) is stored in
the spring (if the calorific thing is correct). I think this shows
that potential (gravitational) energy SHOULD contribute mass to the
higher rock, and R&B's individual masses would be greater at distance
due to the increased potential (for gravity to accellerate them)

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring. Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Don't you mean "work is force times distance"- tension in the rope is
equivalent to tension in the spring, is to tension in the mountain
supporting the rock

,......and think about bringing opposing magnetic poles close- work is
done, but if I lock them in proximity, and then do the "calorific mass
equivalence test", will I see an increase in the mass of the magnets?)

Jim G

"Jim Greenfield" wrote in message
om...
"George Dishman" wrote in message
...
"Jim Greenfield" wrote in message
om...
(George G. Dishman) wrote in message
om...
(Jim Greenfield) wrote in message
. com...
I then
suggested that a piece of rock subject to this type of experiment
in a
valley should give a different result from an identical piece at
the
mountain top-- silence........

Erm, well, yes, I can undertsand that. How do you propose
to store the energy? Is it a springy piece of rock? Why
would it matter where you do the experiment?

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Compessing the spring required (work) energy input as well.

That was the point, the spring was compressed but the rock
wasn't. You can nitpick that everything is compressible to
some degree but I took it that you changed from a spring to
a rock to indicate it was non-compressible.

If gravity
is used to perform the compression, a larger piece of rock is needed
at the top of the mountain than in the valley, as gravity is less at
the higher level. But the same amount of energy (mass) is stored in
the spring (if the calorific thing is correct).

The force compressing the spring is due to gravity so the
source of the energy is the gravitational field, not the rock.

I think this shows
that potential (gravitational) energy SHOULD contribute mass to the
higher rock, and R&B's individual masses would be greater at distance
due to the increased potential (for gravity to accellerate them)

The "potential for gravity to accellerate them" also suggests
the energy is in the gravitational field, not in the rock.

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring. Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Don't you mean "work is force times distance"-

'work done' is another phrase meaning energy. If you press on
a spring it gets shorter. The end moves against a force so work
is done and energy transferred from whatever creates the force
into the spring. When you press on a rock in comparison, there
is no significant energy stored.

tension in the rope is
equivalent to tension in the spring, is to tension in the mountain
supporting the rock

If the tension is "in the mountain supporting the rock", then
it would be the mass of the mountain that would increase, not
that of the rock.

,......and think about bringing opposing magnetic poles close- work is
done, but if I lock them in proximity, and then do the "calorific mass
equivalence test", will I see an increase in the mass of the magnets?)

No, the energy is stored in the magnetic field, not in the
magnets. I believe the mass of the system would change but
not that of the magnets.

Incidentally, a small technical note: gravitational effects
are a result of what is called the "stress-energy tensor" so
in fact pressure creates gravitational effects as well as
mass. I don't know GR well enough to comment further but I
thought I would mention it in case just to be complete. I
don't think it affects our discussion.

George

"George Dishman" wrote in message ...
"Jim Greenfield" wrote in message
om...
"George Dishman" wrote in message
...
"Jim Greenfield" wrote in message
om...
(George G. Dishman) wrote in message
om...
(Jim Greenfield) wrote in message
. com...

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Compessing the spring required (work) energy input as well.

That was the point, the spring was compressed but the rock
wasn't. You can nitpick that everything is compressible to
some degree but I took it that you changed from a spring to
a rock to indicate it was non-compressible.

Compression of the rock is not the issue: it is comparison of the
different energies- that stored in the spring due to compression, and
that (equal amount) of energy expended by lifting the rock against
gravity.

If gravity
is used to perform the compression, a larger piece of rock is needed
at the top of the mountain than in the valley, as gravity is less at
the higher level. But the same amount of energy (mass) is stored in
the spring (if the calorific thing is correct).

The force compressing the spring is due to gravity so the
source of the energy is the gravitational field, not the rock.

Maybe- but gravity has contributed indirectly mass to the spring (if
the calorific experiment re increased mass due to the stress is
correct). Gravity has increased the mass of the spring, but did the
increase come from the rock or the gravitational field?

I think this shows
that potential (gravitational) energy SHOULD contribute mass to the
higher rock, and R&B's individual masses would be greater at distance
due to the increased potential (for gravity to accellerate them)

The "potential for gravity to accellerate them" also suggests
the energy is in the gravitational field, not in the rock.

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring. Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Don't you mean "work is force times distance"-

'work done' is another phrase meaning energy. If you press on
a spring it gets shorter. The end moves against a force so work
is done and energy transferred from whatever creates the force
into the spring. When you press on a rock in comparison, there
is no significant energy stored.

As above, I was lifting the rock, not compressing it.

tension in the rope is
equivalent to tension in the spring, is to tension in the mountain
supporting the rock

If the tension is "in the mountain supporting the rock", then
it would be the mass of the mountain that would increase, not
that of the rock.

Hasn't the mountain just become the equivalent of the mechanism
restraining the stressed spring?

,......and think about bringing opposing magnetic poles close- work is
done, but if I lock them in proximity, and then do the "calorific mass
equivalence test", will I see an increase in the mass of the magnets?)

No, the energy is stored in the magnetic field, not in the
magnets. I believe the mass of the system would change but
not that of the magnets.

If released, these magnets would behave very much like the spring. The
increased mass of the spring then must be due to the forces between
the iron atoms (obviously) in the spring, but outside the iron in the
case of the magnets?

Incidentally, a small technical note: gravitational effects
are a result of what is called the "stress-energy tensor" so
in fact pressure creates gravitational effects as well as
mass. I don't know GR well enough to comment further but I
thought I would mention it in case just to be complete. I
don't think it affects our discussion.

It might.If pressure contributes to increased gravity, and gravity
produces pressure, we have the makings of a perpetual motion machine,
or a black hole!?

Merry Christmas, George
(and I get to open my presents a day before you!!!)

"Jim Greenfield" wrote in message
om...
"George Dishman" wrote in message
...
"Jim Greenfield" wrote in message
om...
"George Dishman" wrote in message
...
"Jim Greenfield" wrote in message
om...
(George G. Dishman) wrote in message
om...
(Jim Greenfield) wrote in message
. com...

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased
gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Compessing the spring required (work) energy input as well.

That was the point, the spring was compressed but the rock
wasn't. You can nitpick that everything is compressible to
some degree but I took it that you changed from a spring to
a rock to indicate it was non-compressible.

Compression of the rock is not the issue:

OK thanks for clearing that up.

it is comparison of the
different energies- that stored in the spring due to compression, and
that (equal amount) of energy expended by lifting the rock against
gravity.

When something pushes against the spring, the energy goes
into the spring. When you lift a rock against gravity, the
similarity suggests the energy is stored in the gravitational
field. The rock is just like putting a rigid handle on the
end of the spring.

If gravity
is used to perform the compression, a larger piece of rock is needed
at the top of the mountain than in the valley, as gravity is less at
the higher level. But the same amount of energy (mass) is stored in
the spring (if the calorific thing is correct).

The force compressing the spring is due to gravity so the
source of the energy is the gravitational field, not the rock.

Maybe- but gravity has contributed indirectly mass to the spring (if
the calorific experiment re increased mass due to the stress is
correct).

Gravity plays no part, it is just the energy stored in the
spring that contributes. Imagine compressing the spring in
deep space a well away from any large masses.

Gravity has increased the mass of the spring, but did the
increase come from the rock or the gravitational field?

You are confusing the source and destination. Imagine instead
the spring was compressed by putting it in a 'G clamp' and
turning the screw. Gravity plays no part put the mass of the
spring still increases.

You are imagining using a rock to compress the spring. Gravity
acting on the rock produces energy which is passed into the
spring but this picture doesn't differentiate between the rock
and field as the source.

I think this shows
that potential (gravitational) energy SHOULD contribute mass to the
higher rock, and R&B's individual masses would be greater at distance
due to the increased potential (for gravity to accellerate them)

The "potential for gravity to accellerate them" also suggests
the energy is in the gravitational field, not in the rock.

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring.
Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Don't you mean "work is force times distance"-

'work done' is another phrase meaning energy. If you press on
a spring it gets shorter. The end moves against a force so work
is done and energy transferred from whatever creates the force
into the spring. When you press on a rock in comparison, there
is no significant energy stored.

As above, I was lifting the rock, not compressing it.

OK, I was just clarifying the jargon.

tension in the rope is
equivalent to tension in the spring, is to tension in the mountain
supporting the rock

If the tension is "in the mountain supporting the rock", then
['tension' should be 'compression' btw]
it would be the mass of the mountain that would increase, not
that of the rock.

Hasn't the mountain just become the equivalent of the mechanism
restraining the stressed spring?

No, the mountain is the equivalent of the spring. The rock, which is
not itself compressed, is the mechanism compressing the mountain.

,......and think about bringing opposing magnetic poles close- work is
done, but if I lock them in proximity, and then do the "calorific mass
equivalence test", will I see an increase in the mass of the magnets?)

No, the energy is stored in the magnetic field, not in the
magnets. I believe the mass of the system would change but
not that of the magnets.

If released, these magnets would behave very much like the spring.

Yes.

The
increased mass of the spring then must be due to the forces between
the iron atoms (obviously) in the spring, but outside the iron in the
case of the magnets?

A compressed spring between two rocks pushes them apart. The
magentic field pushes the magnets apart, so the field is the
equivalent of the spring and the magnets are the equivalent
of the rocks. Don't confuse the roles just because the
magnets and the spring are all made of iron ;-) It is the
spring that increases in mass when compressed and the energy
is stored in the magnetic field, not the magnets. Do you know
about the 'flyback' voltage you can get from a coil?

Incidentally, a small technical note: gravitational effects
are a result of what is called the "stress-energy tensor" so
in fact pressure creates gravitational effects as well as
mass. I don't know GR well enough to comment further but I
thought I would mention it in case just to be complete. I
don't think it affects our discussion.

It might.If pressure contributes to increased gravity, and gravity
produces pressure, we have the makings of a perpetual motion machine,

Nope.

or a black hole!?

Possibly, but someone who understands GR would need to answer
that one, what is the role of pressure in the Schwarzschild
solution. However, things called 'geons' have also been
considered. AIUI, these are 'particles' that are held intact by
the gravitational effect of the energy in their own gravitational
field and nothing else. Of course they are entirely theoretical
at the moment but an interesting prediction of GR nonetheless.

http://www.lns.cornell.edu/spr/1999-12/msg0019961.html

Merry Christmas, George

Merry Christmas to you too Jim.

(and I get to open my presents a day before you!!!)

On the 24th? Or are you just close to the dateline?

best regards
George