Comparison Between Two Isolated Systems

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Discussion Overview

The discussion revolves around the comparison of two isolated systems, A and B, each containing a box of matter and antimatter that will annihilate under specific gravitational conditions. Participants explore the implications of energy expenditure related to the escape velocity of the planets in each system and how this affects the energy balance between the two systems when the annihilation occurs.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the energy converted from mass to electromagnetic radiation during annihilation should be the same in both systems, despite differing energy expenditures to push the boxes into space.
  • Others question the assumption that the energy proportions between the two systems remain the same, emphasizing that the kinetic energy imparted to the boxes must come from the systems themselves.
  • A later reply suggests that the energy difference at the start of the experiment is due to the greater mass of the planet in system B, which should remain constant throughout the process.
  • Some participants argue that the kinetic energy does not leave the system but is transformed into gravitational potential energy, raising questions about the fate of this energy once the boxes are far from the planets.
  • There is speculation about the potential benefits of the gravitational potential energy for the civilization on the planet after the boxes are removed.
  • Concerns are raised about how the gravitational influence of the planets might affect the radiation produced by the annihilation events.

Areas of Agreement / Disagreement

Participants express differing views on whether the energy proportions between the two systems can remain the same given the differing energy expenditures. The discussion remains unresolved, with multiple competing perspectives on the implications of energy transformation and conservation.

Contextual Notes

There are unresolved questions regarding the definitions of energy within the systems, the role of kinetic energy, and how gravitational potential energy is accounted for in the context of the experiment.

J. Richter
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If we think of two isolated systems, A and B, existing side by side, the proportion of the energy between those systems should always stay the same.

Here is a thought, that I would like some comments on:

System A contains a planet, and the advanced civilisation on this planet, have created a box with matter and antimatter ready to annihilate. Some electronic in the box will carry out this annihilation automatically, let’s say when the strength of the surrounding gravity field decreases below a certain limit.
Now, they are pushing this box out in the universe with the exact escape velocity of this planet.


The situation mentioned above, also happens in system B. The two systems are completely identical, except that the planet in system B has more mass, yet the same size.

So it is more “expensive” for the civilisation in system B, to push the box out in space, because of the higher escape velocity of this planet. It takes more energy.


Sometime in a very far future, the boxes will reach the decreased value of gravity that makes the matter and antimatter annihilate.

The two boxes will explode at exactly the same very low strength of gravity, and at very low speeds.

So, (that portion if not all) of the energy that is being converted from mass to electromagnetic radiation when the matter and antimatter annihilates, must be the same in the two systems.

How can the proportion between the energy in these two systems still be the same, as the civilisation in system B did spend more energy, pushing the box out in space?

Where and how in the two systems do we now see a change, that reflects and equalizes the two civilisations different use of energy, so that the proportion of the energy between system A and B will stay the same?
 
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J. Richter said:
So, (that portion if not all) of the energy that is being converted from mass to electromagnetic radiation when the matter and antimatter annihilates, must be the same in the two systems.
OK, this is the energy contained in the boxes, not the energy of "the system".
How can the proportion between the energy in these two systems still be the same, as the civilisation in system B did spend more energy, pushing the box out in space?
Who said they were the same? Where does the energy to impart KE to the boxes come from? And when KE is given to the box, does that energy leave "the system"?
 
Doc Al said:
OK, this is the energy contained in the boxes, not the energy of "the system".

Who said they were the same? Where does the energy to impart KE to the boxes come from? And when KE is given to the box, does that energy leave "the system"?

The boxes is not isolated systems themselves, so the energy contained in the boxes are part of the energy of the systems.

When the experiment starts there is a difference between the energy in system A and B, because the planet in system B has more mass. That difference should always be the same.

The energy of KE is not leaving. What appears to be leaving, (and is probably not), is the extra energy the civilisation in system B used, to carry out this experiment.
 
J. Richter said:
When the experiment starts there is a difference between the energy in system A and B, because the planet in system B has more mass. That difference should always be the same.
What makes you think it changes?
The energy of KE is not leaving. What appears to be leaving, (and is probably not), is the extra energy the civilisation in system B used, to carry out this experiment.
That energy isn't lost, just transformed into increased gravitational PE.
 
Doc Al said:
That energy isn't lost, just transformed into increased gravitational PE.

Increased gravitational PE between the planet and the box, yes.
When the box is gone, or part of it, what happens to the PE?

Who can now benefit from the PE?
 
J. Richter said:
Increased gravitational PE between the planet and the box, yes.
When the box is gone, or part of it, what happens to the PE?
Since the box is "infinitely" far from the planet, you don't have to worry about PE any more.
Who can now benefit from the PE?
I suspect the folks back on the planet are quite happy to have given up energy (on the planet) to send that box sailing away before it exploded.

But interesting question about how the radiation created by the annihilation would be affected by the gravity of the planet.
 

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